Mastering the surface strain of platinum catalysts for efficient electrocatalysis

Interface-rich porous Fe-doped hcp-PtBi/fcc-Pt heterostructured nanoplates enhanced the CC bond cleavage of C3 alcohols electrooxidation

Efficient CC bond cleavage and the complete oxidation of alcohols are key to improving the efficiency of renewable energy utilization. Herein, we successfully prepare porous Fe-doped hexagonal close-packed (hcp)-PtBi/face-centered cubic (fcc)-Pt heterostructured nanoplates with abundant grain/phase interfaces (h-PtBi/f-Pt@Fe1.7 PNPs) via a simple solvothermal method. The open porous structure, abundant grain/phase interface and stacking fault defects, and the synergistic effect between intermetallic hcp-PtBi and fcc-Pt make h-PtBi/f-Pt@Fe1.7 PNPs an effective electrocatalyst for the glycerol oxidation reaction (GOR) in direct glycerol fuel cells (DGFCs). Notably, the h-PtBi/f-Pt@Fe1.7 PNPs exhibit an excellent mass activity of 7.6 A mgPt-1 for GOR, 4.75-fold higher than that of commercial Pt black in an alkaline medium. Moreover, the h-PtBi/f-Pt@Fe1.7 PNPs achieve higher power density (125.8 mW cm-2) than commercial Pt/C (81.8 mW cm-2) in a single DGFC. The h-PtBi/f-Pt@Fe1.7 PNPs can also effectively catalyze the electrochemical oxidation of 1-propanol (17.1 A mgPt-1), 1,2-propanediol (7.2 A mgPt-1), and 1,3-propanediol (5.2 A mgPt-1). The in-situ Fourier-transform infrared spectra further reveal that the CC bond of glycerol, 1-propanol, 1,2-propanediol, and 1,3-propanediol was dissociated for the complete oxidation by the h-PtBi/f-Pt@Fe1.7 PNPs. This study provides a new class of porous Pt-based heterostructure nanoplates and insight into the intrinsic activity of different C3 alcohols.

Dual-Driven Activation of High-Valence States in Prussian Blue Analogues Via Graphene-Quantum Dots and Ozone-Induced Surface Restructuring for Superior Hydrogen Evolution Electrocatalyst

Electrochemical water splitting is a pivotal process for sustainable hydrogen energy production, relying on efficient hydrogen evolution reaction (HER) catalysts, particularly in acidic environments, where both high activity and durability are crucial. Despite the favorable kinetics of platinum (Pt)-based materials, their performance is hindered under harsh conditions, driving the search for alternatives. Due to their unique structural characteristic, Prussian blue analogs (PBAs) emerge as attractive candidates for designing efficient HER electrocatalysts. However, modulating their properties and functionalities is crucial to overcome their conductivity issue. Herein, a reconfiguration strategy for the dual-driven surface restructuring of the CoFe PBA involving graphene quantum dots (GQD) and UV/ozone is proposed. X-ray absorption spectroscopy (XAS) analysis revealed that dual-driven reconstruction plays a pivotal role in promoting the high-valence metal ions, effectively reducing charge transfer resistance-a key limitation in HER. The optimized CoFe PBA/GQD-UV exhibits remarkable electrocatalytic performance toward HER, with a low overpotential of 77 mV to reach a current density of 10 mA cm-2 with excellent durability for 12 h under an extremely high current density of 500 mA cm-2 in an acidic solution. This dual-combination strategy offering a new pathway to develop highly active electrocatalysts.

Modulating d-Orbital electronic configuration via metal-metal oxide interactions for boosting electrocatalytic methanol oxidation

Coordinating the interfacial interaction between Pt-based nanoparticles (NPs) and supports is a significant strategy for the modulation of d-orbital electronic configuration and the adsorption behaviors of intermediates, which is of critical importance for boosting electrocatalytic performance. Herein, we demonstrated a specific synergy effect between the ordered PtFe intermetallic and neighboring oxygen vacancies (Ov), which provides an "ensemble reaction pool" to balance the barriers of both the activity, stability, and CO poisoning issues for the methanol oxidation reaction (MOR). In our proposed "ensemble reaction pool", the deprotonation of methanol occurs on the Pt site to form the intermediate *CO, where the strain derived from the PtFe intermetallic could alter the d-orbital electronic configuration of Pt, intrinsically weakening the *CO adsorption energy, and Ov in CeO2 promote hydroxyl species (*OH) adsorption, which will react with *CO, facilitating the dissociative adsorption of *CO, thus cooperatively enhancing the performance of MOR. The X-ray absorption fine structure (XAFS) analyses reveal the electron transfer in CeO2 and then convert Ce4+ to Ce3+. The density functional theory (DFT) calculations revealed that introducing Fe induces strain could modify the d-band center of Pt, and thus lower the energy barrier of the potential-determining step. Meanwhile, the introduction of CeO2 can favor the *OH adsorption, speeding up the oxidation and removal of *CO blocked at the Pt site. Furthermore, the determined atomic arrangement and surface composition of PtFe intermetallic further guarantee the stability of MOR by suppressing less-noble metal into the electrolyte.

Strain engineering of PtMn alloy enclosed by high-indexed facets boost ethanol electrooxidation

Surface strain engineering has proven to be an efficient strategy to enhance catalytic properties of platinum (Pt)-based catalysts for electrooxidation reactions. Herein, the S-doped PtMn concave cubes (CNCs) enclosed with high index facets (HIFs) and regulatable surface strain are successfully fabricated by two steps hydrothermal method. The S element with electrophilic property can modify the near-surface of PtMn nanocrystals, altering the electronic structure of Pt to effectively regulate the adsorption/desorption of intermediates in the ethanol electrooxidation reaction (EOR). The PtMnS1.1 catalyst with optimal surface strain delivered extraordinary catalytic performance on EOR in acidic media, with a specific activity of 2.88 mA/cm2 and mass activity of 1.10 mA/μgPt, which is 4.1 and 2.2 times larger than that of state-of-the-art Pt/C catalyst, respectively. Additionally, the PtMnS1.1 catalyst also achieve excellent catalytic properties in alkaline electrolyte for EOR. The results of kinetic studies indicated that the surface strain and modified electronic structure can degrade the activation energy barrier during the process of EOR, which is beneficial for enhance the reaction rate. This work provides a promising approach to construct highly efficient electrocatalysts with tunable surface strain effects for clean energy electro-chemical reactions.

Interfacial Reactivity-Triggered Oscillatory Lattice Strains of Nanoalloys

Understanding the structure evolution of nanoalloys under reaction conditions is vital to the design of active and durable catalysts. Herein, we report an operando measurement of the dynamic lattice strains of dual-noble-metal alloyed with an earth-abundant metal as a model electrocatalyst in a working proton-exchange membrane fuel cell using synchrotron high-energy X-ray diffraction coupled with pair distribution function analysis. The results reveal an interfacial reaction-triggered oscillatory lattice strain in the alloy nanoparticles upon surface dealloying. Analysis of the lattice strains with an apparent oscillatory irregularity in terms of frequency and amplitude using time-frequency domain transformation and theoretical calculation reveals its origin from a metal atom vacancy diffusion pathway to facilitate realloying upon dealloying. This process, coupled with surface metal partial oxidation, constitutes a key factor for the nanoalloy's durability under the electrocatalytic oxygen reduction reaction condition, which serves as a new guiding principle for engineering durable or self-healable electrocatalysts for sustainable fuel cell energy conversion.

Synergistic Contribution of the Strain and Magnetic Field in Ferromagnetic NiMnIn Heusler Alloy Films for the Hydrogen Evolution Reaction

The external field-assisted hydrogen evolution reaction (HER), beyond modifying electrocatalysts themselves, has garnered significant research attention. However, achieving synergy between multiple fields to enhance the HER performance remains challenging and is not well-explored. Here, NiMnIn Heusler alloy thin films are fabricated using pulsed laser deposition on flexional Cu substrates. Due to the different adsorption free energy under tensile strain (TS) and compressive strain (CS), the most significant enhancement of the electrocatalytic HER activities for the NiMnIn film is observed in the 1.9% TS state, while the CS state of the NiMnIn film shows negative effects. Furthermore, when an external magnetic field is coupled to the 1.9% tensile-strained NiMnIn film, the total overpotential is reduced by 28.6% at a current density of -50 mA cm-2. This improvement is attributed to a synergistic effect that enhances the H adsorption stability and accelerates the H2 desorption process. This work demonstrates the effectiveness of combining multiple external fields and presents a promising strategy for advancing electrocatalysis.

A Library of Seed@High-Entropy-Alloy Core-shell Nanocrystals With Controlled Facets for Catalysis

High-entropy-alloy (HEA) nanocrystals hold immense potential for catalysis, offering virtually unlimited alloy combinations through the inclusion of at least five constituent elements in varying ratios. However, general and effective strategies for synthesizing libraries of HEA nanocrystals with controlled surface atomic structures remain scarce. In this study, a transferable strategy for developing a library of facet-controlled seed@HEA nanocrystals through seed-mediated growth is presented. The synthesis of seed@HEA core-shell nanocrystals incorporating up to ten different metallic elements, with control over the number of solid-solution HEA atomic layers is demonstrated. Epitaxial HEA growth on nanocrystal seeds with low-index and high-index facets leads to the formation of seed@HEA catalyst library with composition- and facet-dependent catalytic activities in both electrocatalysis and photocatalysis. In situ synchrotron X-ray absorption spectroscopy and density-functional theory calculations are employed to identify surface active sites of the HEA, rationalizing the high level of catalytic activities achieved. This work enables facet engineering in the multi-elemental chemical space and unveils the critical needs for their future development toward catalysis.

Exploring the Intrinsic Effects of Lattice Strain on the Hydrogen Evolution Reaction via Electric-Field-Induced Strain in FePt Films

Strain engineering has the potential to modify the adsorption process and enhance the electrocatalytic activity, especially in the hydrogen evolution reaction (HER). However, the introduction of lattice strain in electrocatalysts is often accompanied by a change in chemical composition, surface morphology, or phase structure to a certain extent, impeding the investigation of the intrinsic strain effect on HER. In this work, the FePt film was deposited on a Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) substrate to construct the FePt/PMN-PT heterojunction, and the continuously adjustable nonvolatile lattice strain is induced by the asymmetric electric field manipulation avoiding the aforementioned disturbance factors. HER experimental results demonstrate a drastic improvement in the overpotential of FePt with the largest tensile strain of 3000 ppm, and the observed variation of HER performance indicates an upward trend as the tensile strain increases. Density functional theory calculations reveal that the Gibbs free energy of FePt with the appropriate tensile strain is closer to zero, attributed to the downward shift of the d-band center. Our study provides an approach to continuously regulate the lattice strain with less interference factors, facilitating the exploration of the intrinsic strain effect on a wide range of catalysts.

Theoretical Prediction of Enhanced Hydrogen Evolution Reaction Electrocatalysts Based on Tantalum Phosphide

Ta-based transition metal catalysts have shown significant catalytic activity for the hydrogen evolution reaction (HER) in recent studies. However, the application of tantalum phosphide (TaP) in the HER has not been documented. Herein, a systematic study of TaP catalysts was performed through density functional theory (DFT). The performance of TaP (004) for the HER was predicted. Thermodynamic analyses of Ta-terminated and P-terminated surfaces with adsorbed hydrogen atoms were conducted, and the HER mechanism on TaP (004) surfaces was carefully investigated. Theoretical results revealed that TaP (004) exhibits excellent HER activity (ΔGH*=0.0456 eV), and both the Ta-terminated and P-terminated surfaces follow the Volmer-Heyrovsky mechanism under acidic conditions, with the Volmer step being the rate-determining step. A mixed surface strategy was also applied to explore the synergistic effects of Ta-terminated and P-terminated surfaces, which enhanced the HER activity. Additionally, the study screened dopants to assess their impact on the HER activity, revealing that doping with S, Ni, Co, Fe, and Cr could improve the HER performance.

2D Carbon-Anchored Platinum-Based Nanodot Arrays as Efficient Catalysts for Methanol Oxidation Reaction

Ultrafine Pt-based alloy nanoparticles supported on carbon substrates have attracted significant attention due to their catalytic potential. Nevertheless, ensuring the stability of these nanoparticles remains a critical challenge, impeding their broad application. In this work, novel nanodot arrays (NAs) are introduced where superfine alloy nanoparticles are uniformly implanted in a 2D carbon substrate and securely anchored. Electrochemical testing of the PtCo NAs demonstrates exceptional methanol oxidation reaction (MOR) activity, achieving 1.25 A mg-1. Moreover, the PtCo NAs exhibit outstanding stability throughout the testing period, underscoring the effectiveness of the anchoring mechanism. Comprehensive characterization and theoretical calculations reveal that the 2D carbon-anchored structure optimizes the electronic structure and coordination environment of Pt, restricts nanoparticle migration, and suppresses transition metal dissolution. This strategy represents a major advancement in addressing the stability limitations of ultrafine nanoparticles in catalytic applications and offers broader insights into the design of next-generation catalysts with enhanced durability and performance.

Construction of Pt─O Sites on Pt Nanoclusters in Silicalite-1 Zeolite for Efficient Catalytic Oxidation of Hydrogen Isotope Gases

The construction, use, and maintenance of tritium-related equipment will inevitably produce tritium-containing radioactive waste gas, and the production of efficient catalysts for tritium removal remains a difficult problem. Herein, silicalite-1 zeolite with entrapped Pt nanoclusters is skillfully post-oxidized at an appropriate temperature, building highly active Pt─O sites on the nanoclusters to achieve efficient oxidation of hydrogen isotopes at low temperatures. The designed Pt─O sites can directly participate in the oxidation reaction of hydrogen isotopes. Compared to the case without Pt─O sites, the presence of these sites significantly reduces the reaction energy barrier to 0.55 eV, enabling the catalyst to achieve a hydrogen conversion rate of 99% at a low temperature of 40 °C. Specifically, the O atoms consumed by the Pt─O sites in the reaction are replaced by O2 gas and this cycle repeats, which is consistent with the Mars-van Krevelen (M-K) theory. This ensures efficient catalytic oxidation of hydrogen isotopes, and provides an astonishingly high conversion rate of 99% in the nearly 34 days restart performance test. The results of this study provide insights into the strategic design of efficient catalysts for hydrogen isotope oxidation.

Understanding Pt Active Sites on Nitrogen-Doped Carbon Nanocages for Industrial Hydrogen Evolution with Ultralow Pt Usage

Engineering microstructures of Pt and understanding the related catalytic mechanism are critical to optimizing the performance for hydrogen evolution reaction (HER). Herein, Pt dispersion and coordination are precisely regulated on hierarchical nitrogen-doped carbon nanocages (hNCNCs) by a thermal-driven Pt migration, from edge-hosted Pt-N2Cl2 single sites in the initial Pt1/hNCNC-70 °C catalyst to Pt clusters/nanoparticles and back to in-plane Pt-NxC4-x single sites. Thereinto, Pt-N2Cl2 presents the optimal HER activity (6 mV@10 mA cm-2) while Pt-NxC4-x shows poor HER activity (321 mV@10 mA cm-2) due to their different Pt coordination. Operando characterizations demonstrate that the low-coordinated Pt-N2 intermediates derived from Pt-N2Cl2 under the working condition are the real active sites for HER, which enable the multi-H adsorption mechanism with an ideal H* adsorption energy of nearly 0 eV, thereby the high activity, as revealed by theoretical calculations. In contrast, the high-coordinated Pt-NxC4-x sites only allow the single-H adsorption with a positive adsorption energy and thereby the low HER activity. Accordingly, with an ultralow Pt loading of only 25 μgPt cm-2, the proton exchange membrane water electrolyzer assembled using Pt1/hNCNC-70 °C as the cathodic catalyst achieves an industrial-level current density of 1.0 A cm-2 at a low cell voltage of 1.66 V and high durability, showing great potential applications.

Electronic Structure Regulated Carbon-Based Single-Atom Catalysts for Highly Efficient and Stable Electrocatalysis

Single-atom-catalysts (SACs) with atomically dispersed sites on carbon substrates have attained great advancements in electrocatalysis regarding maximum atomic utilization, unique chemical properties, and high catalytic performance. Precisely regulating the electronic structure of single-atom sites offers a rational strategy to optimize reaction processes associated with the activation of reactive intermediates with enhanced electrocatalytic activities of SACs. Although several approaches are proposed in terms of charge transfer, band structure, orbital occupancy, and the spin state, the principles for how electronic structure controls the intrinsic electrocatalytic activity of SACs have not been sufficiently investigated. Herein, strategies for regulating the electronic structure of carbon-based SACs are first summarized, including nonmetal heteroatom doping, coordination number regulating, defect engineering, strain designing, and dual-metal-sites scheming. Second, the impacts of electronic structure on the activation behaviors of reactive intermediates and the electrocatalytic activities of water splitting, oxygen reduction reaction, and CO2/N2 electroreduction reactions are thoroughly discussed. The electronic structure-performance relationships are meticulously understood by combining key characterization techniques with density functional theory (DFT) calculations. Finally, a conclusion of this paper and insights into the challenges and future prospects in this field are proposed. This review highlights the understanding of electronic structure-correlated electrocatalytic activity for SACs and guides their progress in electrochemical applications.

Boosting Acidic Hydrogen Evolution Kinetics Induced by Weak Strain Effect in PdPt Alloy for Proton Exchange Membrane Water Electrolyzers

Strain engineering is an effective strategy for manipulating the electronic structure of active sites and altering the binding strength toward adsorbates during the hydrogen evolution reaction (HER). However, the effects of weak and strong strain engineering on the HER catalytic activity have not been fully explored. Herein, the core-shell PdPt alloys with two-layer Pt shells (PdPt2L) and multi-layer Pt shells (PdPtML) is constructed, which exhibit distinct lattice strains. Notably, PdPt2L with weak strain effect just requires a low overpotential of 18 mV to reach 10 mA cm-2 for the HER and shows the superior long-term stability for 510 h with negligible activity degradation in 0.5 M H2SO4. The intrinsic activity of PdPt2L is 6.2 and 24.5 times higher than that of PdPtML and commercial Pt/C, respectively. Furthermore, PdPt2L||IrO2 exhibits superior activity over Pt/C||IrO2 in proton exchange membrane water electrolyzers and maintains stable operation for 100 h at large current density of 500 mA cm-2. In situ/operando measurements verify that PdPt2L exhibits lower apparent activation energy and accelerated ad-/desorption kinetics, benefiting from the weak strain effect. Density functional theory calculations also reveal that PdPt2L displays weaker H* adsorption energy compared to PdPtML, favoring for H* desorption and promoting H2 generation.

Laser Irradiation Induced Electronic Structure Modulation of the Palladium-Based Nanosheets for Efficient Electrocatalysts

Palladium nanosheets (Pd NSs) are widely used as electrocatalysts due to their high atomic utilization efficiency, and long-term stability. Here, the electronic structure modulation of the Pd NSs is realized by a femtosecond laser irradiation strategy. Experimental results indicate that laser irradiation induces the variation in the atomic structures and the macrostrain effects in the Pd NSs. The electronic structure of Pd NSs is modulated by laser irradiation through the balancing between Au-Pd charge transfer and the macros-strain effects. Finite element analysis (FEA) indicates that the lattice of the nanostructures undergoes fast heating and cooling during laser irradiation. The structural evolution mechanism is disclosed by a combined FEA and molecule dynamics (MD) simulation. These results coincide well with the experimental results. The L-AuPd NSs exhibit excellent mass activity and specific activity of 7.44 A mg-1 Pd and 18.70 mA cm-2 toward ethanol oxidation reaction (EOR), 4.3 and 4.4 times higher than the commercial Pd/C. The 2500-cycle accelerated durability (ADT) test confirms the outstanding catalytic stability of the L-AuPd NSs. Density functional theory (DFT) calculations reveal the catalytic mechanism. This unique strategy provides a new pathway to design the ultrathin nanosheet-based materials with excellent performance.

Improved high-current-density hydrogen evolution reaction kinetics on single-atom Co embedded in an order pore-structured nitrogen assembly carbon support

Single-atom catalysis is a subcategory of heterogeneous catalysis with well-defined active sites. Numerous endeavors have been devoted to developing single-atom catalysts for industrially applicable catalysis, including the hydrogen evolution reaction (HER). High-current-density electrolyzers have been pursued for single-atom catalysts to increase active-site density and enhance mass transfer. Here, we reasoned that a single-atom metal embedded in nitrogen assembly carbon (NAC) catalysts with high single-atom density, large surface area, and ordered mesoporosity, could fulfil an industrially applicable HER. Among several different single-atom catalysts, the HER overpotential with the best performing Co-NAC reached a current density of 200 mA cm-2 at 310 mV, which is relevant to industrially applicable current density. Density functional theory (DFT) calculations suggested feasible hydrogen binding on single-atom Co resulted in the promising HER activity over Co-NAC. The best-performing Co-NAC showed robust performance under alkaline conditions at a current density of 50 mA cm-2 for 20 h in an H-cell and at a current density of 150 mA cm-2 for 100 h in a flow cell.

Greatly Enhanced Oxygen Reduction Reaction in Anion Exchange Membrane Fuel Cell and Zn-Air Battery via Hole Inner Edge Reconstruction of 2D Pd Nanomesh

Platinum group metals (PGM) have yet to be the most active catalysts in various sustainable energy reactions. Their high cost, however, has made maximizing the activity and minimizing the dosage become an urgent priority for the practical applications of emerging technologies. Herein, a novel 2D Pd nanomesh structure possessing hole inner reconstructed edges (HIER) with exposed high energy facets and overstretched lattice parameters is fabricated through a facile room-temperature reduction method at gram-scale yields. The HIER enhances the catalytic performance of Pd in electrochemical oxygen reduction reaction (ORR), achieving superior mass activity (MA) of 2.672 A mgPd -1, which is 27.8 fold and 23.6 fold higher, respectively, than those of the commercial Pt/C (0.096 A mgPt -1) and Pd/C (0.113 A mgPd -1) at 0.9 VRHE. Most significantly, in H2-air anion exchange membrane fuel cell (AEMFC) and Zn-air battery (ZAB) applications, this unique Pd catalyst delivers a much-outperformed peak power density of 0.86 and 0.22 W cm-2, respectively, compared with 0.54 and 0.13 W cm-2 of the commercial Pt/C catalyst, indicating a novel pathway in electrocatalyst designs through HIER engineering.

Bamboo-Like Carbon Nanotube-Encapsulated Fe2C Nanoparticles Activate Confined Fe2O3 Nanoclusters Via d-p-d Orbital Coupling for Alkaline Oxygen Evolution Reaction

The efficient anion exchange membrane water electrolysis is challenging with low cell voltage and long-term stability at large current density, due to the unstable anodic oxygen evolution reaction (OER). Fe-based electrocatalysts are potential candidates for the anodic OER. In Fe-based materials, iron oxides always show better stability in alkaline solution but lower OER activity. However, the catalysts in previous study are difficult to continuously and effectively activate iron oxides supported on carbon during electrocatalysis. Herein, a new class of electrocatalyst: bamboo-like carbon nanotubes (B-CNT)-encapsulated Fe2C nanoparticles (NPs) supported Fe2O3 nanoclusters (NCs), named Fe2O3/B-CNT@Fe2C is reported. Theoretical calculations and experimental results reveal that B-CNT-encapsulate Fe2C NPs activate Fe2O3 NCs by the d-p-d orbital coupling, thereby weakening the adsorption of OOH* intermediate during OER process. The electrolyzer based on the electrocatalyst requires only 1.48 V to reach 1.0 A cm-2 and shows a long-term stability at 1.0 A cm-2 for 1600 h, comparable to the best-reported values for the anion exchange membrane water electrolyzer (AEMWE).

Kirkendall Effect-Driven Reversible Chemical Transformation for Reconfigurable Nanocrystals

The potential universality of chemical transformation principles makes it a powerful tool for nanocrystal (NC) synthesis. An example is the nanoscale Kirkendall effect, which serves as a guideline for the construction of hollow structures with different properties compared to their solid counterparts. However, even this general process is still limited in material scope, structural complexity, and, in particular, transformations beyond the conventional solid-to-hollow process. We demonstrate in this work an extension of the Kirkendall effect that drives reversible structural and phase transformations between metastable metal chalcogenides (MCs) and metal phosphides (MPs). Starting from Ni3S4/Cu1.94S NCs as the initial frameworks, ligand-regulated sequential extractions and diffusion of host/guest (S2-/P3-) anions between Ni3S4/Cu1.94S and Ni2P/Cu3P phases enable solid-to-hollow-to-solid structural motif evolution while retaining the overall morphology of the NC. An in-depth mechanistic study reveals that the transformation between metastable MCs and MPs occurs through a combination of ligand-dependent kinetic control and anion mixing-induced thermodynamic control. This strategy provides a robust platform for creating a library of reconfigurable NCs with tunable compositions, structures, and interfaces.

Compressively Strained Fe3O4 in Core-Shell Oxygen Reduction Electrocatalyst Boosts Zinc-Air Battery Performance

Fe3O4 is barely taken into account as an electrocatalyst for oxygen reduction reaction (ORR), an important reaction for metal-air batteries and fuel cells, due to its sluggish catalytic kinetics and poor electron conductivity. Herein, how strain engineering can be employed to regulate the local electronic structure of Fe3O4 for high ORR activity is reported. Compressively strained Fe3O4 shells with 2.0% shortened Fe─O bond are gained on the Fe/Fe4N cores as a result of lattice mismatch at the interface. A downshift of the d-band center occurs for compressed Fe3O4, leading to weakened chemisorption energy of oxygenated intermediates, and lower reaction overpotential. The compressed Fe3O4 exhibits greatly enhanced electrocatalytic ORR activity with a kinetic current density of 27 times higher than that of pristine one at 0.80 V (vs reversible hydrogen electrode), as well as potential application in zinc-air batteries. The findings provide a new strategy for tuning electronic structures and improving the catalytic activity of other metal catalysts.

Rationally Designed L12-Pt2RhFe Intermetallic Catalyst with High CO-Tolerance for Alkaline Methanol Electrooxidation

It is a grand challenge to deep understanding of and precise control over functional sites for the rational design of highly efficient catalysts for methanol electrooxidation. Here, an L12-Pt2RhFe intermetallic catalyst with integrated functional components is demonstrated, which exhibits exceptional CO tolerance. The Pt2RhFe/C achieves a superior mass activity of 6.43 A mgPt -1, which is 2.23-fold and 3.53-fold higher than those of PtRu/C and Pt/C. Impressively, the Pt2RhFe/C exhibits a significant enhancement in durability owing to its high CO-tolerance and stability. Density functional theory calculations reveal that high performance of Pt2RhFe intermetallic catalyst arises from the synergistic effect: the strong OH binding energy (OHBE) at Fe sites induce stably adsorbed OH species and thus facilitate the dehydrogenation step of methanol via rapid hydrogen transfer, while moderate OHBE at Rh sites promote the formation of the transition state (Pt-CO···OH-Rh) with a low activation barrier for CO removal. This work provides new insights into the role of OH binding strength in the removal of CO species, which is beneficial for the rational design of highly efficient catalysts.

Structure-Activity Relationships in Oxygen Electrocatalysis

Oxygen electrocatalysis, as the pivotal circle of many green energy technologies, sets off a worldwide research boom in full swing, while its large kinetic obstacles require remarkable catalysts to break through. Here, based on summarizing reaction mechanisms and in situ characterizations, the structure-activity relationships of oxygen electrocatalysts are emphatically overviewed, including the influence of geometric morphology and chemical structures on the electrocatalytic performances. Subsequently, experimental/theoretical research is combined with device applications to comprehensively summarize the cutting-edge oxygen electrocatalysts according to various material categories. Finally, future challenges are forecasted from the perspective of catalyst development and device applications, favoring researchers to promote the industrialization of oxygen electrocatalysis at an early date.

Selective and durable H2O2 electrosynthesis catalyst in acid by selenization induced straining and phasing

Developing efficient electrocatalysts for acidic electrosynthesis of hydrogen peroxide (H2O2) holds considerable significance, while the selectivity and stability of most materials are compromised under acidic conditions. Herein, we demonstrate that constructing amorphous platinum-selenium (Pt-Se) shells on crystalline Pt cores can manipulate the oxygen reduction reaction (ORR) pathway to efficiently catalyze the electrosynthesis of H2O2 in acids. The Se2‒Pt nanoparticles, with optimized shell thickness, exhibit over 95% selectivity for H2O2 production, while suppressing its decomposition. In flow cell reactor, Se2‒Pt nanoparticles maintain current density of 250 mA cm-2 for 400 h, yielding a H2O2 concentration of 113.2 g L-1 with productivity of 4160.3 mmol gcat-1 h-1 for effective organic dye degradation. The constructed amorphous Pt-Se shell leads to desirable O2 adsorption mode for increased selectivity and induces strain for optimized OOH* binding, accelerating the reaction kinetics. This selenization approach is generalizable to other noble metals for tuning 2e‒ ORR pathway.

Growth Modulation of High-Entropy Alloys for Electrocatalytic Methanol Oxidation Reaction

High-entropy alloy (HEA) electrocatalysts have exhibited remarkable catalytic performance because of their synergistic interactions among multiple metals. However, the growth mechanism of HEAs remains elusive, primarily due to the constraints imposed by the current synthesis methodologies for HEAs. In this work, an innovative electrodeposition method was developed to fabricate Pt-based nanocomposites (Pt1Bi2Co1Cu1Ni1/CC), comprising HEA nanosheets and carbon cloths (CCs). The reaction system could be effectively monitored by taking samples out from the system during the reaction process, facilitating in-depth insight into the growth mechanism underlying the material formation. In particular, Pt1Bi2Co1Cu1Ni1/CC nanocomposites show superior methanol oxidation reaction (MOR) performance (mass activity up to 5.02 A mgPt-1). Upon structural analysis, the d-band center of Pt1Bi2Co1Cu1Ni1/CC is lower in comparison with that of Pt1Bi2/CC and Pt/CC, demonstrating the formation of a rich-electron structure. Both the uniformity of HEAs and the carbon-supported effect could provide additional active sites. These findings suggest that the strong electronic interaction within HEAs and additional active sites can effectively modulate the catalytic structure of Pt, which benefits the enhanced CO tolerance and MOR performance.

Stability of electrocatalytic OER: from principle to application

Hydrogen energy, derived from the electrolysis of water using renewable energy sources such as solar, wind, and hydroelectric power, is considered a promising form of energy to address the energy crisis. However, the anodic oxygen evolution reaction (OER) poses limitations due to sluggish kinetics. Apart from high catalytic activity, the long-term stability of electrocatalytic OER has garnered significant attention. To date, several research studies have been conducted to explore stable electrocatalysts for the OER. A comprehensive review is urgently warranted to provide a concise overview of the recent advancements in the electrocatalytic OER stability, encompassing both electrocatalyst and device developments. This review aims to succinctly summarize the primary factors influencing OER stability, including morphological/phase change and electrocatalyst dissolution, as well as mechanical detachment, alongside chemical, mechanical, and operational degradation observed in devices. Furthermore, an overview of contemporary approaches to enhance stability is provided, encompassing electrocatalyst design (structural regulation, protective layer coating, and stable substrate anchoring) and device optimization (bipolar plates, gas diffusion layers, and membranes). Hopefully, more attention will be paid to ensuring the stable operation of electrocatalytic OER and the future large-scale water electrolysis applications. This review presents design principles aimed at addressing challenges related to the stability of electrocatalytic OER.

Highly stable and active catalyst in fuel cells through surface atomic ordering

Shape-controlled alloy nanoparticle catalysts have been shown to exhibit improved performance in the oxygen reduction reaction (ORR) in liquid half-cells. However, translating the success to catalyst layers in fuel cells faces challenges due to the more demanding operation conditions in membrane electrode assembly (MEA). Balancing durability and activity is crucial. Here, we developed a strategy that limits the atomic diffusion within surface layers, fostering the phase transition and shape retention during thermal treatment. This enables selective transformation of platinum-iron nanowire surfaces into intermetallic structures via atomic ordering at a low temperature. The catalysts exhibit enhanced MEA stability with 50% less Fe loss while maintaining high catalytic activity comparable to that in half-cells. Density functional calculations suggest that the ordered intermetallic surface stabilizes morphology against rapid corrosion and improves the ORR activity. The surface engineering through atomic ordering presents potential for practical application in fuel cells with shape-controlled Pt-based alloy catalysts.

Ce-4f as an electron-modulation reservoir weakening Fe-O bond to induce iron vacancies in CeFevNi hydroxide for enhancing oxygen evolution reaction

Designing novel rare-earth-transition metal composites is at the forefront of electrocatalyst research. However, the modulation of transition metal electronic structures by rare earths to induce vacancy defects and enhance electrochemical performance has rarely been reported. In this study, we systematically investigate the mechanism by which Ce-4f electron modulation weakens the Fe-O bond, thereby altering the electronic structure in CeFevNi hydroxide to improve oxygen evolution reaction (OER) performance. Theoretical calculations and experimental characterizations reveal that Ce-4f orbitals function as electron-modulation reservoirs, capable not only of retaining or donating electrons but also of influencing the material's electronic structure. Moreover, Ce-4f bands optimize the Fe lower Hubbard bands (LHB) and O-2p bands, leading to weakened Fe-O bonds and the formation of cationic vacancies. This change results in the upshift of the d-band center at the active sites, favoring the reaction energy barrier for oxygen intermediates in the OER process. The synthesized catalyst demonstrated an overpotential of 201 mV at 10 mA cm-2 and a lifetime exceeding 200 h at 100 mA cm-2 under alkaline conditions. This work offers a proof-of-concept for the application of the mechanism of rare earth-induced transition metal vacancy defects, providing a general guideline for the design and development of novel highly efficient catalysts.

An Angstrom-Scale Protective Skin Grown In Situ on Perovskite Oxide to Enhance Stability in Water

The utilization of perovskite oxide as a catalyst for aqueous reactions is promising but challenging in stability. Here, we propose an in situ growth strategy that constructs an ultrathin protective skin on the Sr0.9Fe0.81Ta0.09Ni0.1O3-δ perovskite surface and thus effectively solves the stability issue. Using a spherical aberration-corrected transmission electron microscope, we observe the coexistence of an angstrom-scale (~7 Å) Fe2O3 protective skin and FeNi alloy nanoparticles. A number of alloy nanoparticles grow along with the skin and uniformly take root on the skin surface. Such a hierarchical structure can reconstruct the surface electronic structure and suppress the ion leaching of perovskite oxide in water. Benefiting from this unique structure, the catalyst has experienced a substantial increase (800 h, more than three orders of magnitude) in its stable operation time in water (for example, in a hydrogen evolution reaction). These results provide valuable insight into solid-solid phase transitions and have substantial implications for using structural defects at surfaces to modulate mass transport and transformation kinetics. Our strategy is sufficiently simple and can be used to subtly manipulate the catalyst structures to improve the performance of perovskite-based catalysts and potentially other oxide catalysts for a wide range of reactions.

Grain boundary engineering for efficient and durable electrocatalysis

Grain boundaries in noble metal catalysts have been identified as critical sites for enhancing catalytic activity in electrochemical reactions such as the oxygen reduction reaction. However, conventional methods to modify grain boundary density often alter particle size, shape, and morphology, obscuring the specific role of grain boundaries in catalytic performance. This study addresses these challenges by employing gold nanoparticle assemblies to control grain boundary density through the manipulation of nanoparticle collision frequency during synthesis. We demonstrate a direct correlation between increased grain boundary density and enhanced two-electron oxygen reduction reaction activity, achieving a significant improvement in both specific and mass activity. Additionally, the gold nanoparticle assemblies with high grain boundary density exhibit remarkable electrochemical stability, attributed to boron segregation at the grain boundaries, which prevents structural degradation. This work provides a promising strategy for optimizing the activity, selectivity, and stability of noble metal catalysts through precise grain boundary engineering.

Halogen Tailoring of Platinum Electrocatalyst with High CO Tolerance for Methanol Oxidation Reaction

The catalytic activity of platinum for CO oxidation depends on the interaction of electron donation and back-donation at the platinum center. Here we demonstrate that the platinum bromine nanoparticles with electron-rich properties on bromine bonded with sp-C in graphdiyne (PtBr NPs/Br-GDY), which is formed by bromine ligand and constitutes an electrocatalyst with a high CO-resistant for methanol oxidation reaction (MOR). The catalyst showed peak mass activity for MOR as high as 10.4 A mgPt -1, which is 20.8 times higher than the 20 % Pt/C. The catalyst also showed robust long-term stability with slight current density decay after 100 hours at 35 mA cm-2. Structural characterization, experimental, and theoretical studies show that the electron donation from bromine makes the surface of platinum catalysts highly electron-rich, and can strengthen the adsorption of CO as well as enhance π back-donation of Pt to weaken the C-O bond to facilitate CO electrooxidation and enhance catalytic performance during MOR. The results highlight the importance of electron-rich structure among active sites in Pt-halogen catalysts and provide detailed insights into the new mechanism of CO electrooxidation to overcome CO poisoning at the Pt center on an orbital level.

Compressive strain in Cu catalysts: Enhancing generation of C2+ products in electrochemical CO2 reduction

Elastic strain in Cu catalysts enhances their selectivity for the electrochemical CO2 reduction reaction (eCO2RR), particularly toward the formation of multicarbon (C2+) products. However, the reasons for this selectivity and the effect of catalyst precursors have not yet been clarified. Hence, we employed a redox strategy to induce strain on the surface of Cu nanocrystals. Oxidative transformation was employed to convert Cu nanocrystals to CuxO nanocrystals; these were subsequently electrochemically reduced to form Cu catalysts, while maintaining their compressive strain. Using a flow cell configuration, a current density of 1 A/cm2 and Faradaic efficiency exceeding 80% were realized for the C2+ products. The selectivity ratio of C2+/C1 was also remarkable at 9.9, surpassing that observed for the Cu catalyst under tensile strain by approximately 7.6 times. In-situ Raman and infrared spectroscopy revealed a decrease in the coverage of K+ ion-hydrated water (K·H2O) on the compressively strained Cu catalysts, consistent with molecular dynamics simulations and density functional theory calculations. Finite element method simulations confirmed that reducing the coverage of coordinated K·H2O water increased the probability of intermediate reactants interacting with the surface, thereby promoting efficient C-C coupling and enhancing the yield of C2+ products. These findings provide valuable insights into targeted design strategies for Cu catalysts used in the eCO2RR.

Polytypic metal chalcogenide nanocrystals

By engineering chemically identical but structurally distinct materials into intricate and sophisticated polytypic nanostructures, which often surpass their pure phase objects and even produce novel physical and chemical properties, exciting applications in the fields of photovoltaics, electronics and photocatalysis can be achieved. In recent decades, various methods have been developed for synthesizing a library of polytypic nanocrystals encompassing IV, III-V and II-VI polytypic semiconductors. The exceptional performances of polytypic metal chalcogenide nanocrystals have been observed, making them highly promising candidates for applications in photonics and electronics. However, achieving high-precision control over the morphology, composition, crystal structure, size, homojunctions, and periodicity of polytypic metal chalcogenide nanostructures remains a significant synthetic challenge. This review article offers a comprehensive overview of recent progress in the synthesis and control of polytypic metal chalcogenide nanocrystals using colloidal synthetic strategies. Starting from a concise introduction on the crystal structures of metal chalcogenides, the subsequent discussion delves into the colloidal synthesis of polytypic metal chalcogenide nanocrystals, followed by an in-depth exploration of the key factors governing polytypic structure construction. Subsequently, we provide comprehensive insights into the physical properties of polytypic metal chalcogenide nanocrystals, which exhibit strong correlations with their applications. Thereafter, we emphasize the significance of polytypic nanostructures in various applications, such as photovoltaics, photocatalysis, transistors, thermoelectrics, stress sensors, and the electrocatalytic hydrogen evolution. Finally, we present a summary of the recent advancements in this research field and provide insightful perspectives on the forthcoming challenges, opportunities, and future research directions.

Preserving surface strain in nanocatalysts via morphology control

Engineering strain critically affects the properties of materials and has extensive applications in semiconductors and quantum systems. However, the deployment of strain-engineered nanocatalysts faces challenges, in particular in maintaining highly strained nanocrystals under reaction conditions. Here, we introduce a morphology-dependent effect that stabilizes surface strain even under harsh reaction conditions. Using four-dimensional scanning transmission electron microscopy (4D-STEM), we found that cube-shaped core-shell Au@Pd nanoparticles with sharp-edged morphologies sustain coherent heteroepitaxial interfaces with larger critical thicknesses than morphologies with rounded edges. This configuration inhibits dislocation nucleation due to reduced shear stress at corners, as indicated by molecular dynamics simulations. A Suzuki-type cross-coupling reaction shows that our approach achieves a fourfold increase in activity over conventional nanocatalysts, owing to the enhanced stability of surface strain. These findings contribute to advancing the development of advanced nanocatalysts and indicate broader applications for strain engineering in various fields.

Atomic-scale strain engineering of atomically resolved Pt clusters transcending natural enzymes

Strain engineering plays an important role in tuning electronic structure and improving catalytic capability of biocatalyst, but it is still challenging to modify the atomic-scale strain for specific enzyme-like reactions. Here, we systematically design Pt single atom (Pt1), several Pt atoms (Ptn) and atomically-resolved Pt clusters (Ptc) on PdAu biocatalysts to investigate the correlation between atomic strain and enzyme-like catalytic activity by experimental technology and in-depth Density Functional Theory calculations. It is found that Ptc on PdAu (Ptc-PA) with reasonable atomic strain upshifts the d-band center and exposes high potential surface, indicating the sufficient active sites to achieve superior biocatalytic performances. Besides, the Pd shell and Au core serve as storage layers providing abundant energetic charge carriers. The Ptc-PA exhibits a prominent peroxidase (POD)-like activity with the catalytic efficiency (Kcat/Km) of 1.50 × 109 mM-1 min-1, about four orders of magnitude higher than natural horseradish peroxidase (HRP), while catalase (CAT)-like and superoxide dismutase (SOD)-like activities of Ptc-PA are also comparable to those of natural enzymes. Biological experiments demonstrate that the detection limit of the Ptc-PA-based catalytic detection system exceeds that of visual inspection by 132-fold in clinical cancer diagnosis. Besides, Ptc-PA can reduce multi-organ acute inflammatory damage and mitigate oxidative stress disorder.

Morphology Variation of Ternary PdCuSn Nanocrystalline Assemblies and Their Electrocatalytic Oxidation of Alcohols

Metal alloys not only increase the composition and spatial distribution of elements but also provide the opportunity to adjust their physicochemical properties. Recently, multimetallic alloy nanocatalysts have attracted great attention in energy applications and the chemical industry. This work presents the production of three ternary PdCuSn nanocrystalline assemblies with similar compositions via a one-step hydrothermal method. The shape variation of assembly units from nanosheets and nanowires to nanoparticles were realized by adjusting the percentage of Sn in metal precursors. Experimental data show that PdCuSn nanowire networks showed the best catalytic activity by virtue of their optimized morphological characteristics and microscopic electronic structure. With electrooxidation of methanol, ethanol, ethylene glycol, and glycerol at 30 °C, PdCuSn nanowire networks demonstrated catalytic activity of 1129, 2111, 2540, and 1445 mA mg-1, respectively. The catalytic activity for alcohol oxidation is attributed to the production of the electronic structure and morphology features that are most suitable. This is achieved by introducing the proper quantities of Cu and Sn components in the first stage of synthesis. This study would help with the construction of high-efficiency nanostructured alloy catalysts by regulating the electronic structure and morphology.

Engineering Asymmetric Strain within C-Shaped CeO2 Nanofibers for Stabilizing Sub-3 nm Pt Clusters against Sintering

Ultrafine noble metals have emerged as advanced nanocatalysts in modern society but still suffer from unavoidable sintering at temperatures above 250 °C (e.g., Pt). In this work, closely packed CeO2 grains were confined elegantly in fibrous nanostructures and served as a porous support for stabilizing sub-3 nm Pt clusters. Through precisely manipulating the asymmetry of obtained nanofibers, uneven strain was induced within C-shaped CeO2 nanofibers with tensile strain at the outer side and compressive strain at the inner side. As a result, the enriched oxygen vacancies significantly improved adhesion of Pt to CeO2, thereby boosting the sinter-resistance of ultraclose sub-3 nm Pt clusters. Notably, no aggregation was observed even after exposure to humid air at 750 °C for 12 h, which is far beyond their Tammann temperature (sintering onset temperature, below 250 °C). In situ HAADF-STEM observation revealed a unique sintering mechanism, wherein Pt clusters initially migrate toward the grain boundaries with concentrated stain and undergo slight coalescence, followed by subsequent Ostwald ripening at higher temperatures. Moreover, the sinter-resistant Pt/C-shaped CeO2 effectively catalyzed soot combustion (over 700 °C) in a durable manner. This work provides a new insight for developing sinter-resistant catalysts from the perspective of strain engineering within nano-oxides.

Selectivity switch via tuning surface static electric field in photocatalytic alcohol conversion

Photocatalysis has shown great potential in organic reactions, while controlling the selectivity is a long-standing goal and challenge due to the involvement of various radical intermediates. In this study, we have realized selectivity control in the photocatalytic conversion of alcohols via engineering the surface static electric field of the CdS semiconductor. By leveraging the Au-CdS interaction to adjust lattice strain, which influences the intensity of the surface static electric field, we altered the pathways of alcohol conversion. The increased intensity of the surface static electric field changed the activation pathways of the C-H/O-H bond, leading to the selective formation of targeted C/O-based radical intermediates and altering the selectivity from aldehydes to dimers. A wide range of alcohols, such as aromatic alcohol and thiophenol alcohol, were selectively converted into aldehyde or dimer. This work provides an effective strategy for selectively controlling reaction pathways by generating a surface electric field.

From Charge to Spin: An In-Depth Exploration of Electron Transfer in Energy Electrocatalysis

Catalytic materials play crucial roles in various energy-related processes, ranging from large-scale chemical production to advancements in renewable energy technologies. Despite a century of dedicated research, major enduring challenges associated with enhancing catalyst efficiency and durability, particularly in green energy-related electrochemical reactions, remain. Focusing only on either the crystal structure or electronic structure of a catalyst is deemed insufficient to break the linear scaling relationship (LSR), which is the golden rule for the design of advanced catalysts. The discourse in this review intricately outlines the essence of heterogeneous catalysis reactions by highlighting the vital roles played by electron properties. The physical and electrochemical properties of electron charge and spin that govern catalysis efficiencies are analyzed. Emphasis is placed on the pronounced influence of external fields in perturbing the LSR, underscoring the vital role that electron spin plays in advancing high-performance catalyst design. The review culminates by proffering insights into the potential applications of spin catalysis, concluding with a discussion of extant challenges and inherent limitations.

Defective Tungsten Oxides with Stacking Faults for Proton Exchange Membrane Green-Hydrogen Generation

Defects can introduce atomic structural modulation and tailor performance of materials. Herein, it demonstrates that semiconductor WO3 with inert electrocatalytic behavior can be activated through defect-induced tensile strains. Structural characterizations reveal that when simply treated in Ar/H2 atmosphere, oxygen vacancies will generate in WO3 and cause defective structures. Stacking faults are found in defects, thus modulating electronic structure and transforming electrocatalytic-inert WO3 into highly active electrocatalysts. Density functional theory (DFT) calculations are performed to calculate *H adsorption energies on various WOx surfaces, revealing the oxygen vacancy composition and strain predicted to optimize the catalytic activity of hydrogen evolution reaction (HER). Such defective tungsten oxides can be integrated into commercial proton exchange membrane (PEM) electrolyser with comparable performance toward Pt-based PEM. This work demonstrates defective metal oxides as promising non-noble metal catalysts for commercial PEM green-hydrogen generation.

Regioselective epitaxial growth of metallic heterostructures

Constructing regioselective architectures in heterostructures is important for many applications; however, the targeted design of regioselective architectures is challenging due to the sophisticated processes, impurity pollution and an unclear growth mechanism. Here we successfully realized a one-pot kinetically controlled synthetic framework for constructing regioselective architectures in metallic heterostructures. The key objective was to simultaneously consider the reduction rates of metal precursors and the lattice matching relationship at heterogeneous interfaces. More importantly, this synthetic method also provided phase- and morphology-independent behaviours as foundations for choosing substrate materials, including phase regulation from Pd20Sb7 hexagonal nanoplates (HPs) to Pd8Sb3 HPs, and morphology regulation from Pd20Sb7 HPs to Pd20Sb7 rhombohedra and Pd20Sb7 nanoparticles. Consequently, the activity of regioselective epitaxially grown Pt on Pd20Sb7 HPs was greatly enhanced towards the ethanol oxidation reaction; its activity was 57 times greater than that of commercial Pt/C, and the catalyst showed increased stability (decreasing by 16.3% after 2,000 cycles) and selectivity (72.4%) compared with those of commercial Pt/C (56.0%, 18.2%). This work paves the way for the design of unconventional well-defined heterostructures for use in various applications.

Facet-Controlled Synthesis of Unconventional-Phase Metal Alloys for Highly Efficient Hydrogen Oxidation

Facet control and phase engineering of metal nanomaterials are both important strategies to regulate their physicochemical properties and improve their applications. However, it is still a challenge to tune the exposed facets of metal nanomaterials with unconventional crystal phases, hindering the exploration of the facet effects on their properties and functions. In this work, by using Pd nanoparticles with unconventional hexagonal close-packed (hcp, 2H type) phase, referred to as 2H-Pd, as seeds, a selective epitaxial growth method is developed to tune the predominant growth directions of secondary materials on 2H-Pd, forming Pd@NiRh nanoplates (NPLs) and nanorods (NRs) with 2H phase, referred to as 2H-Pd@2H-NiRh NPLs and NRs, respectively. The 2H-Pd@2H-NiRh NRs expose more (100)h and (101)h facets on the 2H-NiRh shells compared to the 2H-Pd@2H-NiRh NPLs. Impressively, when used as electrocatalysts toward hydrogen oxidation reaction (HOR), the 2H-Pd@2H-NiRh NRs show superior activity compared to the NiRh alloy with conventional face-centered cubic (fcc) phase (fcc-NiRh) and the 2H-Pd@2H-NiRh NPLs, revealing the crucial role of facet control in enhancing the catalytic performance of unconventional-phase metal nanomaterials. Density functional theory (DFT) calculations further unravel that the excellent HOR activity of 2H-Pd@2H-NiRh NRs can be attributed to the more exposed (100)h and (101)h facets on the 2H-NiRh shells, which possess high electron transfer efficiency, optimized H* binding energy, enhanced OH* binding energy, and a low energy barrier for the rate-determining step during the HOR process.

Synergistic Modulation of Multiple Sites Boosts Anti-Poisoning Hydrogen Electrooxidation Reaction with Ultrasmall (Pt0.9Rh0.1)3V Ternary Intermetallic Nanoparticles

Promoting the hydrogen oxidation reaction (HOR) activity and poisoning tolerance of electrocatalysts is crucial for the large-scale application of hydrogen-oxygen fuel cell. However, it is severely hindered by the scaling relations among different intermediates. Herein, lattice-contracted Pt-Rh in ultrasmall ternary L12-(Pt0.9Rh0.1)3V intermetallic nanoparticles (~2.2 nm) were fabricated to promote the HOR performances through an oxides self-confined growth strategy. The prepared (Pt0.9Rh0.1)3V displayed 5.5/3.7 times promotion in HOR mass/specific activity than Pt/C in pure H2 and dramatically limited activity attenuation in 1000 ppm CO/H2 mixture. In situ Raman spectra tracked the superior anti-CO* capability as a result of compressive strained Pt, and the adsorption of oxygen-containing species was promoted due to the dual-functional effect. Further assisted by density functional theory calculations, both the adsorption of H* and CO* on (Pt0.9Rh0.1)3V were reduced compared with that of Pt due to lattice contraction, while the adsorption of OH* was enhanced by introducing oxyphilic Rh sites. This work provides an effective tactic to stimulate the electrocatalytic performances by optimizing the adsorption of different intermediates severally.

Biaxial strain induced OH engineer for accelerating alkaline hydrogen evolution

The sluggish kinetics of Volmer step in the alkaline hydrogen evolution results in large energy consumption. The challenge that has yet well resolved is to control the water adsorption and dissociation. Here, we develop biaxially strained MoSe2 three dimensional nanoshells that exhibit enhanced catalytic performance with a low overpotential of 58.2 mV at 10 mA cm-2 in base, and long-term stable activity in membrane-electrode-assembly based electrolyser at 1 A cm-2. Compared to the flat and uniaxial-strained MoSe2, we establish that the stably adsorbed OH engineer on biaxially strained MoSe2 changes the water adsorption configuration from O-down on Mo to O-horizontal on OH* via stronger hydrogen bonds. The favorable water dissociation on 3-coordinated Mo sites and hydrogen adsorption on 4-coordinated Mo sites constitute a tandem electrolysis, resulting in thermodynamically favorable hydrogen evolution. This work deepens our understanding to the impact of strain dimensions on water dissociation and inspires the design of nanostructured catalysts for accelerating the rate-determining step in multi-electron reactions.

Strain Engineering of Cd0.5Zn0.5S Nanocrystal for Efficient Photocatalytic Hydrogen Evolution from Wasted Plastic

The challenge of synthesizing nanocrystal photocatalysts with adjustable lattice strain for effective waste-to-energy conversion is addressed in this study. Cd0.5Zn0.5S (CZS) nanocrystals are synthesized by a simple solvothermal method, regulation of the ratio between N, N-dimethylformamide, and water solvent are shown to provoke expansion and contraction, inducing an adjustable lattice strain ranging from -1.2% to 5.6%. With the hydrolyzed wasted plastic as a sacrificial agent, the 5.6% lattice-strain CZS exhibited a robust hydrogen evolution activity of 1.09 mmol m-2 h-1 (13.83 mmol g-1 h-1), 4.5 times that of pristine CZS. Characterizations and density functional theory calculation demonstrated that lattice expansion increases the spatial distance between the valence band maximum and conduction band minimum, thus reducing carrier recombination and promoting charge transfer. Additionally, lattice expansion induces surface S vacancies and adsorbed OH groups, further enhancing redox reactions. This study focuses on the synchronous regulation of crystal structure, charge separation/transport, and surface reactions through lattice strain engineering, which providing a reference for the rational design of new photocatalysts for effective waste-to-energy conversion.

Freestanding Penta-Twinned Palladium Nanosheets

Control over the morphology of nanomaterials to have a 2D structure and manipulating the surface strain of nanostructures through defect control have proved to be promising for developing efficient catalysts for sustainable chemical and energy conversion. Here a one-pot aqueous synthesis route of freestanding Pd nanosheets with a penta-twinned structure (PdPT NSs) is presented. The generation of the penta-twinned nanosheet structure can be succeeded by directing the anisotropic growth of Pd under the controlled reduction kinetics of Pd precursors. Experimental and computational investigations showed that the surface atoms of the PdPT NSs are effectively under a compressive environment due to the strain imposed by their twin boundary defects. Due to the twin boundary-induced surface strain as well as the 2D structure of the PdPT NSs, they exhibited highly enhanced electrocatalytic activity for oxygen reduction reaction compared to Pd nanosheets without a twin boundary, 3D Pd nanocrystals, and commercial Pd/C and Pt/C catalysts.

Highly efficient semi-hydrogenation in strained ultrathin PdCu shell and the atomic deciphering for the unlocking of activity-selectivity

Excellent ethylene selectivity in acetylene semi-hydrogenation is often obtained at the expense of activity. To break the activity-selectivity trade-off, precise control and in-depth understanding of the three-dimensional atomic structure of surfacial active sites are crucial. Here, we designed a novel Au@PdCu core-shell nanocatalyst featuring diluted and stretched Pd sites on the ultrathin shell (1.6 nm), which showed excellent reactivity and selectivity, with 100% acetylene conversion and 92.4% ethylene selectivity at 122 °C, and the corresponding activity was 3.3 times higher than that of the PdCu alloy. The atomic three-dimensional decoding for the activity-selectivity balance was revealed by combining pair distribution function (PDF) and reverse Monte Carlo simulation (RMC). The results demonstrate that a large number of active sites with a low coordination number of Pd-Pd pairs and an average 3.25% tensile strain are distributed on the surface of the nanocatalyst, which perform a pivotal function in the simultaneous improvement of hydrogenation activity and ethylene selectivity. Our work not only develops a novel strategy for unlocking the linear scaling relation in heterogeneous catalysis but also provides a paradigm for atomic 3D understanding of lattice strain in core-shell nanocatalysts.

Molybdenum and Vanadium-Codoped Cobalt Carbonate Nanosheets Deposited on Nickel Foam as a High-Efficient Bifunctional Catalyst for Overall Alkaline Water Splitting

To address issues of global energy sustainability, it is essential to develop highly efficient bifunctional transition metal-based electrocatalysts to accelerate the kinetics of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, the heterogeneous molybdenum and vanadium codoped cobalt carbonate nanosheets loaded on nickel foam (VMoCoCOx@NF) are fabricated by facile hydrothermal deposition. Firstly, the mole ratio of V/Mo/Co in the composite is optimized by response surface methodology (RSM). When the optimized composite serves as a bifunctional catalyst, the water-splitting current density achieves 10 mA cm-2 and 100 mA cm-2 at cell voltages of 1.54 V and 1.61 V in a 1.0 M KOH electrolyte with robust stability. Furthermore, characterization is carried out using field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM-EDS), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations reveal that the fabricated VMoCoCOx@NF catalyst synergistically decreases the Gibbs free energy of hydrogen and oxygen-containing intermediates, thus accelerating OER/HER catalytic kinetics. Benefiting from the concerted advantages of porous NF substrates and clustered VMoCoCOx nanosheets, the fabricated catalyst exhibits superior electrocatalytic performance. This work presents a novel approach to developing transition metal catalysts for overall water splitting.

Gradient-concentration RuCo electrocatalyst for efficient and stable electroreduction of nitrate into ammonia

Electrocatalytic nitrate reduction to ammonia holds great promise for developing green technologies for electrochemical ammonia energy conversion and storage. Considering that real nitrate resources often exhibit low concentrations, it is challenging to achieve high activity in low-concentration nitrate solutions due to the competing reaction of the hydrogen evolution reaction, let alone considering the catalyst lifetime. Herein, we present a high nitrate reduction performance electrocatalyst based on a Co nanosheet structure with a gradient dispersion of Ru, which yields a high NH3 Faraday efficiency of over 93% at an industrially relevant NH3 current density of 1.0 A/cm2 in 2000 ppm NO3- electrolyte, while maintaining good stability for 720 h under -300 mA/cm2. The electrocatalyst maintains high activity even in 62 ppm NO3- electrolyte. Electrochemical studies, density functional theory, electrochemical in situ Raman, and Fourier-transformed infrared spectroscopy confirm that the gradient concentration design of the catalyst reduces the reaction energy barrier to improve its activity and suppresses the catalyst evolution caused by the expansion of the Co lattice to enhance its stability. The gradient-driven design in this work provides a direction for improving the performance of electrocatalytic nitrate reduction to ammonia.

Unveiling Atomic-Scaled Local Chemical Order of High-Entropy Intermetallic Catalyst for Alkyl-Substitution-Dependent Alkyne Semihydrogenation

High-entropy intermetallic (HEI) nanocrystals, composed of multiple elements with an ordered structure, are of immense interest in heterogeneous catalysis due to their unique geometric and electronic structures and the cocktail effect. Despite tremendous efforts dedicated to regulating the metal composition and structures with advanced synthetic methodologies to improve the performance, the surface structure, and local chemical order of HEI and their correlation with activity at the atomic level remain obscure yet challenging. Herein, by determining the three-dimensional (3D) atomic structure of quinary PdFeCoNiCu (PdM) HEI using atomic-resolution electron tomography, we reveal that the local chemical order of HEI regulates the surface electronic structures, which further mediates the alkyl-substitution-dependent alkyne semihydrogenation. The 3D structures of HEI PdM nanocrystals feature an ordered (intermetallic) core enclosed by a disordered (solid-solution) shell rather than an ordered surface. The lattice mismatch between the core and shell results in apparent near-surface distortion. The chemical order of the intermetallic core increases with annealing temperature, driving the electron redistribution between Pd and M at the surface, but the surface geometrical (chemically disordered) configurations and compositions are essentially unchanged. We investigate the catalytic performance of HEI PdM with different local chemical orders toward semihydrogenation across a broad range of alkynes, finding that the electron density of surface Pd and the hindrance effect of alkyl substitutions on alkynes are two key factors regulating selective semihydrogenation. We anticipate that these findings on surface atomic structure will clarify the controversy regarding the geometric and/or electronic effects of HEI catalysts and inspire future studies on tuning local chemical order and surface engineering toward enhanced catalysts.

Electronic-Structure Transformation of Platinum-Rich Nanowires as Efficient Electrocatalyst for Overall Water Splitting

Platinum (Pt) has been widely used as cathodic electrocatalysts for the hydrogen evolution reaction (HER) but unfortunately neglected as an anodic electrocatalyst for the oxygen evolution reaction (OER) due to excessively strong bonding with oxygen species in water splitting electrolyzers. Herein we report that fine control over the electronic-structure and local-coordination environment of Pt-rich PtPbCu nanowires (NWs) by doping of iridium (Ir) lowers the overpotential of the OER and simultaneously suppresses the overoxidation of Pt in IrPtPbCu NWs during water electrolysis. In light of the one-dimensional morphology featured with atomically dispersed IrOx species and electronically modulated Pt-sites, the IrPtPbCu NWs exhibit an enhanced OER (175 mV at 10 mA cm-2) and HER (25 mV at 10 mA cm-2) electrocatalytic performance in acidic media and yield a high turnover frequency. For OER at the overpotential of 250 mV, the IrPtPbCu NWs show an enhanced mass activity of 1.51 A mg-1Pt+Ir (about 19 times higher) than Ir/C. For HER at the overpotential of 50 mV, NWs exhibit a remarkable mass activity of 1.35 A mg-1Pt+Ir, which is 2.6-fold relative to Pt/C. Experimental results and theoretical calculations corroborate that the doping of Ir in NWs has the capacity to suppress the formation of Ptx>4 derivates and ameliorate the adsorption free energy of reaction intermediates during the water electrolysis. This approach enabled the realization of a previously unobserved mechanism for anodic electrocatalysts.