Engineering bunched Pt-Ni alloy nanocages for efficient oxygen reduction in practical fuel cells

Atomic layer deposition of Pt nanoparticles grown onto 3D B-doped graphene as an efficient ultra-low Pt loading catalyst layer for PEMFC

Proton exchange membrane fuel cell (PEMFC) with ultra-low Pt loading is highly desirable but confronts challenges of deficient activity and durability for practical application. Herein, we report a newly integrated catalyst layer based on 3D porous B-doped graphene (3D-PBG) with the atomic layer deposition of Pt (Pt/3D-PBG) for PEMFC, in which highly graphitized 3D-PBG not only provides a robust framework to support Pt but also B dopants further enhances the deposition of Pt and their electronic interaction, resulting in high-performance PEMFC at ultra-low Pt loading. The cell with Pt/3D-PBG at 80.0 μgPt cm-2 as cathode delivers a maximum power density of 0.90 W cm-2 (H2/Air, 150.0 kPa) and exhibits high durability meeting the Department of Energy (DOE) 2025 technical targets, which has been rarely achieved in the previous reports. Additionally, theoretical calculations reveal that the BC2O and BCO2 dopants facilitate the adsorption of Pt precursors, generating more nucleation sites for Pt and the BC2O, B4C, and BC3 dopants enhance the interfacial interaction between graphene and Pt and induce a downward shift in the d-band center of Pt, leading to the high activity and durability of Pt/3D-PBG as cathode. This work provides new highlights for developing an efficient catalyst layer with enhanced interaction between Pt and heteroatom-doped graphene with highly graphitic degree for ultra-low Pt loading PEMFC.

Melatonin mitigates nickel oxide nanoparticles induced phytotoxicity in soybean by reducing metal accumulation, enhancing antioxidant defense and promoting nitrogen assimilation

Heavy metals like nickel (Ni) from anthropogenic activities damage plant growth, posing challenges to agriculture. Melatonin (ME), a potent bio-regulator, has shown promise in alleviating stress induced by heavy metals. However, the mechanisms through which ME alleviates NiO-NPs phytotoxicity remain unclear. Our results showed that NiO-NPs reduced root and shoot length as well as biomass by 14 %, 12 %, 21 %, and 14 %, respectively, compared to control. However, the combined effect of ME (75 µM) and NiO-NPs (100 mg kg-1) significantly increased these parameters by 12-28 % compared to NiO-NPs. Moreover, co-exposure of ME (75 µM) and NiO-NPs notably decreased the Ni contents in root and shoot compared to NiO-NPs treatment. This reduction was associated with enhanced levels of phytohormones (ABA, JA, SA, and GA4) and secondary metabolite production, showing a 12-32 % improvement compared to NiO-NPs alone. ME further enhanced SOD, POD, CAT, and APX activities by 14-21 % while reducing oxidative enzymes (MDA, H2O2) by 17-21 %. Similarly, ME (75 µM) upregulated POD, CAT, and APX gene expression by 1.33-1.6-fold, while SOD was downregulated. Additionally, ME improved nodule formation (14 %), N2 content (19-21 %), N2-assimilation enzymes (UE, NR, GS, GOGAT, GDH) by 19-29 %, and nutrient balance in roots (16-24 %) and shoots (19-25 %). These findings provide insights into ME's role in mitigating NiO-NPs toxicity and enhancing N2-acquisition in soybeans, offering strategies for sustainable agriculture.

Charge Transfer Modulation in g-C3N4/CeO2 Composites: Electrocatalytic Oxygen Reduction for H2O2 Production

The electrocatalytic two-electron oxygen reduction reaction (2e-ORR) represents one of the most prospective avenues for the in situ synthesis of hydrogen peroxide (H2O2). However, the four-electron competition reaction constrains the efficiency of H2O2 synthesis. Therefore, there is an urgent need to develop superior catalysts to facilitate the H2O2 synthesis. In this study, graphite-phase carbon nitride and cerium dioxide composites (g-C3N4/CeO2) with varying CeO2 loadings were prepared with favorable 2e-ORR electrocatalysts. The optimized composite, containing 20 wt % CeO2 (g-C3N4/CeO2-20%) exhibited the highest Faradaic efficiency (FE) of 97% and notable H2O2 yielding of 9.84 mol gcat.-1 h-1 at the potential of 0.3 V (vs RHE) in a 0.1 M KOH electrolyte. Density functional theory calculations revealed that the improvement of the selectivity and yield of H2O2 for the composites were attributed to the charge transfer between g-C3N4 and CeO2, which causes the active site C atom donating electrons to form C+, thereby enhancing the adsorption and desorption of *OOH intermediates. Additionally, the g-C3N4/CeO2-20% composite exhibits excellent 2e-ORR performance in neutral and acidic electrolytes and demonstrates superior capability in electro-Fenton degradation of organic pollutants. This study not only provides new insights into the electrocatalytic mechanism of g-C3N4/CeO2 composites but also demonstrates an effective method for designing 2e-ORR catalysts.

Molecular Understanding of the Role of Catalyst Particle Arrangement in Local Mass Transport Resistance for Fuel Cells

Platinum (Pt) catalyst performance loss caused by a high local oxygen transport resistance is an urgent problem to be solved for proton exchange membrane fuel cells (PEMFCs). Rationally arranging Pt particles on carbon support is the primary approach for reducing mass transport resistance. Herein, using a unique method coupling Hybrid Reverse Monte Carlo, molecular dynamics simulations, and experimental measurements, a Pt particle arrangement strategy is proposed to reduce local oxygen transport resistance, based on a molecular-level understanding of its impact. The densely arranged Pt particles with a small interparticle distance lead to the denser ionomer layer due to the co-attraction effect, leading to a high local oxygen transport resistance. The nonuniformly arranged Pt particles with various interparticle distances cause the heterogeneous ionomer density, inducing the heterogeneous oxygen transport. Increasing the Pt-Pt interparticle distance from 2 to 5 nm substantially reduces the local oxygen transport resistance by over 50%. The uniform arrangement of Pt particles makes the ionomer layer density more homogeneous, resulting in more uniform oxygen transport. Therefore, uniformly arranging Pt particles with an interparticle distance of >5 nm on carbon support is preferred for reducing local oxygen transport resistance and improving the homogeneity of oxygen transport.

Metallic PtC monolayer as a promising hydrogen evolution electrocatalyst

Reasonable design of hydrogen evolution reaction (HER) electrocatalysts with low Pt loading and excellent catalytic performance is a key challenge in finding efficient and cost attractive catalysts. Pt with its unique d-electrons provides new opportunities for the development of HER catalysts when it forms compounds with highly earth-abundant C. Herein, we focused on designing highly efficient catalysts composed of Pt and C elements using first-principles structure search simulations, identifying four stability PtCx monolayers. The novel PtC monolayer with a zigzag C chain not only possesses lower Pt loading but also shows inherent metallicity. Meanwhile, its H2O adsorption and dissociation abilities are efficient and facile. The HER activity of the PtC monolayer is comparable to that of commercial Pt, with desirable ΔGH* values and larger exchange current density, which are mainly attributed to lower charge donation of Pt, larger occupation of Pt PDOS at the Fermi level, and paired electrons of the zigzag C chain. Moreover, its excellent HER activity can be maintained even at high H coverage under strain and solvent effect. All these attractive properties render the PtC monolayer an appropriate HER catalyst.

Asymmetric Atomic Coordination of Platinum Skin Layer on Intermetallic Platinum-Cobalt Particles

Pt-based intermetallic alloy particles with a Pt skin layer have higher catalytic activity than solid-solution alloy particles and have attracted considerable attention for practical applications in polymer electrolyte fuel cells. However, the reason for the superior performance of intermetallic alloys is not yet fully understood. Because the catalytic reaction proceeds on the topmost surface of the particle, it is necessary to clarify the relationship between the periodic structure of the intermetallic alloy and the Pt atomic coordination on the surface. This study investigated the Pt-Pt interatomic distance of a Pt skin layer formed on intermetallic Pt3Co particles at atomic resolution through precise measurements using scanning transmission electron microscopy and theoretical calculations. The Pt atomic coordination on the surface shows good agreement between experimental observations and theoretical models, although the experimental image is a projection and thus provides indirect results. The theoretical calculation model revealed that structural relaxation at the Pt and Pt3Co interfaces led to two distinct Pt bonding states at the surface, including asymmetric atomic coordination. The asymmetric coordination of the Pt site deepens the d-band center, diversifies the oxygen adsorption energies, and enhances catalytic activity. Further exploration and control of the unique surface Pt coordination environments formed on the periodic structures of intermetallic alloys should reveal promising routes for the development of catalytic particles.

D-band state control engineering over ZnIn2S4 for enhanced photoreduction of CO2 to CH4

Metal-based photocatalysts with d10 electronic configurations exhibit good photocatalytic performance due to strong band edge dispersion, however, the weak bonding between d10 metal sites and CO2 through 2p-3d orbital hybridization limits their activity and selectivity for CO2 to CH4 conversion. Herein, a strategy for modulating the d-band center is proposed to promote the formation of CH4 in the photocatalytic CO2 reduction process. In a model system taking ZnIn2S4 (ZIS) as photocatalysts, highly thermodynamically electronegative elements (such as Bi, Cu, and Co) are doped to upshift the d-band center of ZIS, enhance the selectivity and yield of CH4. In the absence of cocatalysts or photosensitizers, the CO2 photoreduction products of all doped ZIS samples shifts from pure CO to a mixture of CO and CH4, with CH4 being the predominant product. Among all samples, Bi-doped ZnIn2S4 (Bi-ZIS) demonstrates the highest performance, achieving a CH4 selectivity of 63.68 % and a high evolution rate of 21.07 µmol·g-1·h-1 during visible-light-driven CO2 reduction. Density functional theory (DFT) calculations indicate that doping highly electronegative elements can modulate the electron cloud distribution of ZIS, thereby raising its d-band center. This shift reduces the energy barrier for CO2 photoreduction to CH4, enhancing the binding energy between active sites and intermediates (such as *OCH2 and *OCH3), facilitating the formation of CH4. Consequently, this study not only validates the effectiveness of the d-band center modulation strategy but also offers a novel perspective for optimizing the activity and product selectivity of d10 metal-based photocatalysts in CO2RR.

Identification of catechin species using a colorimetric and fluorescence dual-mode sensor array based on peroxidase-like PtNi bunched nanoparticles

Catechins in tea, as promoters of human health, have attracted widespread attention. Herein, a dual-signal mode (colorimetric and fluorescence) sensor array for catechin species fingerprinting was built based on PtNi bunched nanoparticle (PtNi-BNP)-o-phenylenediamine (OPD)-H2O2 system. PtNi-BNPs catalyze the reaction between OPD and H2O2 to produce oxidized OPD (oxOPD) with both colorimetric (yellow) and fluorescent properties. As an antioxidant, catechins can inhibit the above reaction, resulting in a lighter color and reduced fluorescence intensity in the reaction solution. Owing to the varying inhibitory effects of different catechins on the reaction, they produce unique colorimetric-fluorescence response patterns. These diverse responses were recorded and processed using linear discriminant analysis (LDA), and six catechin species were identified using the sensor array. Furthermore, our work provides a convenient method for simultaneous differentiation of catechins in mixtures and real samples. Such a sensor array with minimal sensor element and abundant signal outputs considerably saves cost and time, thus providing a powerful tool for the discrimination and assessment of catechins.

Platinum-Nickel@High-Entropy Alloy Core@Satellite Nanowires as Efficient Bifunctional Electrocatalysts for PEMFC

The optimized composition and precisely tailored structure configuration play critical roles in enhancing the catalytic reaction kinetics. Here we report a distinctive core@satellite strategy for designing the advanced platinum-nickel@platinum-nickel-copper-cobalt-indium high-entropy alloy nanowires (Pt3Ni@HEA NWs) as efficient bifunctional catalysts in the proton exchange membrane fuel cell. Impressively, the Pt3Ni@HEA NWs/C shows 19.4/15.3 times higher mass/specific activity than that of commercial Pt/C for the oxygen reduction reaction. More importantly, synchronously as the cathodic and anodic catalysts, it can achieve a high membrane electrode assembly power density of 1653.5 mW cm-2 and long-term stability (only 3.9% voltage loss) for 280 h, largely outperforming those of commercial Pt/C. The weakened Pt-CO binding strength, quick removal of CO with linear adsorption, and favorable CO adsorption form contribute to the high performance of Pt3Ni@HEA NWs/C. This core@satellite strategy provides a new paradigm to develop the comprehensively efficient Pt-based functional catalysts for fuel cells and beyond.

Controlling the growth mode of Au depositing on Au nanobipyramids via ligand coverage for SERS enhancement

Gold deposition on Au nanoparticles is a common method to control the shape and further modify the properties of nanoparticles as their properties have a strong correlation with their nanostructures. For Au nanobipyramid (Au NBP), it has advantages such as the enhancement of electric field and a higher tunability in plasmon wavelength than the Au nanorod and thus owns a greater potential in shape control. In this paper, we demonstrate a scheme of depositing Au on the surface of Au NBP with the presence of a type of ligand 2-mercaptobenzoimidazole-5-carboxylic acid (MBIA) to synthesize Au NBP@Au dimers. The growth mode of Au depositing on Au NBP can be controlled by the coverage of MBIA. As the coverage is low, with a concentration of MBIA below 0.4 mM, the rough core-shell nanostructure is synthesized; However, as the coverage is high, with a concentration of MBIA over 0.8 mM, gold deposition may form islands on the surface of Au NBP. The SERS performance of Au depositing on Au NBP can also be enhanced by growth mode. For the rough-surface core-shell growth mode, the enhancement is more significant as the EF is improved from 3.5 × 105 to 1.06 × 106 than the islands-growing growth mode due to the coupling between core and shell. And our results show that with multiple types of nanosturctures easy to obtained by changing modified ligand coverage, the controlled growth has a great potential in the dimer design and SERS enhancement using Au NBP.

Synergistic effect of Fe-Ru alloy and Fe-N-C sites on oxygen reduction reaction

In the pursuit of optimizing Fe-N-C catalysts for the oxygen reduction reaction (ORR), the incorporation of alloy nanoparticles has emerged as a prominent strategy. In this work, we effectively synthesized the FeRu-NC catalyst by anchoring Fe-Ru alloy nanoparticles and FeN4 single atom sites onto carbon nanotubes. The FeRu-NC catalyst exhibits significantly enhanced ORR activity and long-term stability, with a high half-wave potential of 0.89 V (vs. RHE) in alkaline conditions, and the half-wave potential remains nearly unchanged after 5000 cycles. The zinc-air battery (ZAB) assembled with FeRu-NC demonstrates a power density of 169.1 mW cm-2, surpassing that of commercial Pt/C. Density functional theory (DFT) calculations reveal that the synergistic interaction between the Fe-Ru alloy and FeN4 single atoms alters the electronic structure and facilitates charge transfer at the FeN4 sites, thereby modulating the adsorption and desorption of ORR intermediates. This enhancement in catalytic activity for the ORR process underscores the potential of this approach for refining M-N-C catalysts, providing novel insights into their optimization strategies.

d-Electrons of Platinum Alloy Steering CO Pathway for Low-Charge Potential Li-CO2 Batteries

Aprotic Li-CO2 batteries suffer from sluggish solid-solid co-oxidation kinetics of C and Li2CO3, requiring extremely high charging potentials and leading to serious side reactions and poor energy efficiency. Herein, we introduce a novel approach to address these challenges by modulating the reaction pathway with tailored Pt d-electrons and develop an aprotic Li-CO2 battery with CO and Li2CO3 as the main discharge products. Note that the gas-solid co-oxidation reaction between CO and Li2CO3 is both kinetically and thermodynamically more favorable. Consequently, the Li-CO2 batteries with CoPt alloy-supported on nitrogen-doped carbon nanofiber (CoPt@NCNF) cathode exhibit a charging potential of 2.89 V at 50 μA cm-2, which is the lowest charging potential to date. Moreover, the CoPt@NCNF cathode also shows exceptional cycling stability (218 cycles at 50 μA cm-2) and high energy efficiency up to 74.6 %. Comprehensive experiments and theoretical calculations reveal that the lowered d-band center of CoPt alloy effectively promotes CO desorption and inhibits further CO reduction to C. This work provides promising insights into developing efficient and CO-selective Li-CO2 batteries.

Precise Synthesis of Dual-Single-Atom Electrocatalysts through Pre-Coordination-Directed in Situ Confinement for CO2 Reduction

Dual-single-atom catalysts (DSACs) are the next paradigm shift in single-atom catalysts because of the enhanced performance brought about by the synergistic effects between adjacent bimetallic pairs. However, there are few methods for synthesizing DSACs with precise bimetallic structures. Herein, a pre-coordination strategy is proposed to precisely synthesize a library of DSACs. This strategy ensures the selective and effective coordination of two metals via phthalocyanines with specific coordination sites, such as -F- and -OH-. Subsequently, in situ confinement inhibits the migration of metal pairs during high-temperature pyrolysis, and obtains the DSACs with precisely constructed metal pairs. Despite changing synthetic parameters, including transition metal centers, metal pairs, and spatial geometry, the products exhibit similar atomic metal pairs dispersion properties, demonstrating the universality of the strategy. The pre-coordination strategy synthesized DSACs shows significant CO2 reduction reaction performance in both flow-cell and practical rechargeable Zn-CO2 batteries. This work not only provides new insights into the precise synthesis of DSACs, but also offers guidelines for the accelerated discovery of efficient catalysts.

Strain engineering of CoSANC catalyst toward enhancing the oxygen reduction reaction activity

Developing efficient and cost-effective platinum-group metal-free (PGMF) catalysts for the oxygen reduction reaction (ORR) is crucial for energy conversion and storage devices. Among these catalysts, metal-nitrogen-carbon (MNC) materials, particularly cobalt single-atom catalysts (CoSANC), show promise as ORR electrocatalysts. However, their ORR activity is often hindered by strong hydroxyl (OH) adsorption on the Co sites. While the impact of strain engineering on MNC electrocatalysts has been minimally explored, recent studies suggest its potential to enhance catalytic performance and optimize intrinsic activity in traditional bulk catalysts. In this context, we investigate the effect of surface strain on CoSANC for ORR activity and correlate substrate-strain-induced geometric distortions with catalytic activity using experimental and theoretical methods. The findings suggest that the d-band center gap of spin states (Δεd) may be a preferred descriptor for predicting strain-dependent ORR performance in MNC catalysts. Leveraging CoSANC moiety placed on a substrate with an average size of 1.0 μm, we achieve performance comparable to that of commercial Pt/C catalysts when used as a cathode catalyst in zinc-air batteries. This investigation unveils the structure-function relationship of MNC electrocatalysts regarding strain engineering and provides valuable insights for future ORR activity design and enhancement.

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.

Fe Single Atoms Anchored on N-doped Mesoporous Carbon Microspheres for Promoted Oxygen Reduction Reaction

Fe single atoms (Fe SAs) based catalysts have received much attention in electrocatalytic oxygen reduction reaction (ORR) due to its low-cost and high activity. Yet, the facile synthesis of efficient and stable Fe SAs catalysts is still challenging. Here, we reported a Fe SAs anchored on N-doped mesoporous carbon microspheres (NC) catalyst via spraying drying and pyrolysis processes. The highly active Fe SAs are uniformly distributed on the NC matrix, which prevented the aggregation benefiting from the enhanced Fe-N bonds. Also, the mesoporous carbon structure is favorable for fast electron and mass transfer. The optimized Fe@NC-2-900 catalyst shows positive half wave potential (E1/2=0.86 V vs reversible hydrogen electrodes (RHE)) and starting potential (Eonset=0.98 V vs RHE) in ORR, which is comparable to the commercial Pt/C catalyst (E1/2=0.87 V, Eonset=1.08 V vs RHE). Outstanding stability with a current retention rate of 92.5 % for 9 hours and good methanol tolerance are achieved. The assembled zinc-air batteries showed good stability up to 500 hours at a current density of 5 mA cm-2. This work shows potentials of Fe SAs based catalysts for the practical application in ORR and pave a new avenue for promoting their catalytic performances.

Weakening Pd─O Bonds by an Amorphous Pd Layer to Promote Electrocatalysis

Construction of core-shell structured electrocatalysts with a thin noble metal shell is an effective strategy for lowering the usage of the noble metal and improving electrocatalytic properties because of the structure-induced geometric and electronic effects. Here, the synthesis of a novel core-shell structured nanocatalyst consisting of a thin amorphous Pd shell and a crystalline PdCu core and its significantly improved electrocatalytic properties for both formic acid oxidation and oxygen reduction reactions are shown. The electrocatalyst exhibits 4.1 times higher catalytic peak current density and better stability in the formic acid oxidation compared to both a PdCu nanoalloy catalyst and a Commercial Pd-C catalyst. An excellent electrocatalytic performance of the core-shell nanocatalyst is also observed in the oxygen reduction reaction. Computational calculation results reveal that tuning of the electronic state of Pd by the amorphous shell and the Cu in the PdCu core weaken the binding strength of surface Pd─O bonds, leading to a bond elongation to facilitate bond breaking. As a result, the electrocatalytic activity in both formic acid oxidation and oxygen reduction reactions is enhanced.

Harnessing the Synergistic Interplay between Atomic-Scale Vacancies and Ligand Effect to Optimize the Oxygen Reduction Activity and Tolerance Performance

Defect engineering is an effective strategy for regulating the electrocatalysis of nanomaterials, yet it is seldom considered for modulating Pt-based electrocatalysts for the oxygen reduction reaction (ORR). In this study, we designed Ni-doped vacancy-rich Pt nanoparticles anchored on nitrogen-doped graphene (Vac-NiPt NPs/NG) with a low Pt loading of 3.5 wt . % and a Ni/Pt ratio of 0.038 : 1. Physical characterizations confirmed the presence of abundant atomic-scale vacancies in the Pt NPs induces long-range lattice distortions, and the Ni dopant generates a ligand effect resulting in electronic transfer from Ni to Pt. Experimental results and theoretical calculations indicated that atomic-scale vacancies mainly contributed the tolerance performances towards CO and CH3OH, the ligand effect derived from a tiny of Ni dopant accelerated the transformation from *O to *OH species, thereby improved the ORR activity without compromising the tolerance capabilities. Benefiting from the synergistic interplay between atomic-scale vacancies and ligand effect, as-prepared Vac-NiPt NPs/NG exhibited improved ORR activity, sufficient tolerance capabilities, and excellent durability. This study offers a new avenue for modulating the electrocatalytic activity of metal-based nanomaterials.

Rigid Ligand Confined Synthesis of Carbon Supported Dimeric Fe Sites with High-Performance Oxygen Reduction Reaction Activity for Quasi-Solid-State Rechargeable Zn-Air Batteries

Dimeric metal sites (DiMSs) in carbon-based single atom catalysts (SACs) offer distinct advantages in optimizing the adsorption energies of the catalytic intermediates and reaction pathways over single atom sites, which inspires the investigations on the rational design of DiMSs-based SACs and the accurate discernment of catalytic mechanisms. Here, dimeric Fe sites on carbon blacks (DiFe-N/CBs) are prepared using the precursor of metal-organic complex with a controlled structure, and the rigid ligand confinement secures the preservation of dimeric Fe sites during the thermal treatment. DiFe-N/CBs shows excellent electrocatalytic performance for oxygen reduction reaction (ORR) with a high half-wave potential of 0.917 V, and excellent durability with negligible activity decay. Theoretical studies reveal that the dimeric Fe sites have an optimal adsorption of OOH* with the Yeager-type binding, illustrating the advantages of DiMSs over SAs in catalyzing ORR. The rechargeable aqueous and quasi-solid-state Zn-air batteries assembled using DiFe-N/CBs-based air cathodes achieve small voltage gaps after long term charge/discharge test, showing great promises for practical applications. This synthetic strategy serves a novel platform to produce a scope of catalysts incorporating multimeric metal sites, and studies on the catalytic mechanism lay the foundation for establishing cooperative effect for multidentate adsorption reactions.

High Oxygen Reduction Efficiency and Durability of Nano-Honeycomb Pt3(NiFeCo) Replenished by High-Entropy Metallic Glass Support

Developing low-Pt oxygen reduction reaction (ORR) catalysts with high efficiency and robustness is critical for practical fuel cells. The most advanced ORR catalysts either feature high percentages of Pt (>70 at.%) or exhibit poor durability when reducing Pt loading. Herein, a multicomponent solid-solution Pt3(FeCoNi) honeycomb nano-framework supported by the specially designed high-entropy metallic glass (MG) is reported for efficient ORR. This hybrid catalyst with a low surface Pt loading of 5.79 µg cm-2 displays exceptional mass and specific activities of 7.02 A mgpt -1 and 8.15 mA cmPt -2 at 0.9 V, respectively, which are ≈15 and 22 times higher compared with commercial Pt/C. The analyses reveal the weakened chemisorption of oxygenated species, which is induced by the strong strain and ligand effects originating from the synergistic multicomponent alloying. This in turn enhances the intrinsic ORR activity. Moreover, benefiting from a unique replenishment behavior, the hybrid catalyst delivers ultra-high durability with negligible activity decay even after 50 000 potential cycles. This mechanism is achieved by sacrificing the interior MG supplementary support to dynamically compensate for the loss of catalytically active surface. The work provides an alternative way to design more efficient and durable low-Pt electrocatalysts for electrochemical devices.

Assessing the Effect of a Schwarz P Surface on the Oxygen Electroreduction Performance of Porous Single-Atom Catalysts

The surface curvature of catalysts has a decisive impact on their catalytic performance. However, the influence of a negative-Gaussian-curvature surface on the catalytic performance of porous catalysts has remained unexplored due to the lack of suitable samples. Bicontinuous-structured porous structures can serve as ideal models, but they are known as "Plumber's nightmare" due to their highly difficult preparation. Here, using metal-organic frameworks as the precursor and polymer cubosomes as the template, a bicontinuous mesoporous Fe single-atom catalyst (named bmFeSAC) with a Schwarz P surface is synthesized. The bmFeSAC catalyst has a large specific surface area of 916 m2 g-1 and uniformly distributed Fe-N4 active sites with a 1.80 wt.% Fe content. The continuous channels enabled high utilization efficiency of the Fe-N4 catalytic sites, while the negative-Gaussian-curvature surface enabled low reaction energy barrier. As an electrocatalyst of the oxygen reduction reaction, bmFeSAC delivered a high half-wave potential of 0.931 V versus. RHE in alkaline electrolyte, reaching the leading level among those of the reported state-of-the-art electrocatalysts. Furthermore, the bmFeSAC-based Zn-air batteries exhibited excellent performance, demonstrating the potential application of bmFeSAC. This study revealed that a bicontinuous-structured porous structure can improve catalytic activity by increasing the utilization ratio of catalytic sites and, more importantly, by regulating the electronic structure of catalyst surfaces through the negative-Gaussian-curvature.

Lattice Strain Regulated by Hetero/Homo Atom Interface Merging on NiMo Nanocluster for High-Performance Hydrogen Production

Lattice strain engineering represents a cutting-edge approach capable of delivering enhanced performance across various applications. The lattice strain can affect the performance of electrochemical catalysts by changing the binding energy between the surface-active sites and intermediates. In this work, lattice strain is regulated through a homo/heterogeneous atomic interface merging. The strong lattice strain and electronic interactions between Ni and Mo facilitated the reaction kinetic of HER. The prepared NiMo@SSM exhibits excellent HER catalytic performance with 70 mV overpotential at the current density of 10 mA cm-2 and long-term stability. The method of controlling lattice strain through hetero/homo atom interface merging provides a new strategy for designing high-performance alkaline HER electrocatalysts.

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.

Understanding the Curvature Effect of FeCo Nanoalloy Encapsulated by Nitrogen-Doped Carbon Nanotubes for High-Performance Lithium-Sulfur Batteries

Well-designed structures of the electrocatalyst provide excellent catalytic activity and high structural stability during the sulfur reduction reaction of Lithium-sulfur batteries (LSBs). In this study, a novel and efficient structure is developed to encapsulate bimetallic FeCo nanoalloy catalysts within N-doped carbon nanotube (NCNT) on carbon nanofibers (FeCo@NCNT/CNFs) using a combination of electrospinning and rapid-cooling techniques. The NCNT matrix with abundant sites not only serves as a high pathway for electron transport during the reaction, but its encapsulation structure also acts as armor to protect the FeCo nanoalloy. Further, the curvature effect of the FeCo@NCNT structure facilitates greater electron transfer from the FeCo nanoalloy to the NCNT, and lowering the reaction barrier for the liquid-solid conversion process. As a result, the S/FeCo@NCNT/CNFs cathode can achieve exceptional cycle performance of 500 cycles at 5 C, with an ultra-low capacity fade rate of 0.031% per cycle. Moreover, even under extreme temperature conditions of -20 and 80 °C, the battery still delivers a specific capacity of 827.16 and 697.46 mAh g-1 at 1 C. This work shows an effective insight into enhancing the LiPS conversion kinetics over a wide temperature range in Li-S batteries.

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.

NiS2 nanoboxes wrapped in carbon with a core-shell structure for high-performance sodium storage

One-dimensional nitrogen-doped carbon nanotube wrapped NiS2 core-shell nanoboxes have been developed. The hollow interior and protective carbon layer significantly enhance sodium storage properties, showing high reversible capacities and superior cycling stability at high current densities. Density functional theory calculations indicated that the heterostructure remarkably enhances the charge transfer process.

Second-Shell Coordination Environment Modulation for MnN4 Active Sites by Oxygen Doping to Boost Oxygen Reduction Performance

As a category of transition metal-nitrogen-carbon (M-N-C) catalysts, Mn-based single-atom catalysts (SACs) are considered as promising non-precious metal catalysts for stable oxygen reduction reaction (ORR) due to their Fenton-inactive character (versus Fe) and more abundant earth reserves (versus Ni, Co). However, their ORR activity is unsatisfactory. Besides, the structure-activity relationship via tuning the coordination environment of the second coordination shell for transition metal single sites is still elusive. Here, a Mn SAC with O doping in the second-shell of atomically dispersed Mn centers (MnSAC-O/C) as highly efficient and stable ORR catalyst is developed. X-ray absorption spectroscopy combined with theoretical calculations verifies the O doping in the second-shell of Mn center, and reveals the distortion of local environment of Mn center in the MnSAC-O/C. The MnSAC-O/C exhibits high ORR performance with a half-wave potential of 0.898 V, superior to MnSAC-C, commercial Pt/C and most reported non-noble metal-based SACs. More importantly, MnSAC-O/C based zinc-air batteries (ZABs) deliver outstanding durability with stable operation exceeding 930 h. Theoretical calculations confirm that O doping breaks the symmetry of charge distribution of MnN4 active center and facilitates OH* desorption, thus attributing to the promoted ORR activity.

Sub-Nanometer Pt Nanowires with Disordered Shells for Highly Active Elelctrocatalytic Oxidation of Formic Acid

Controlled synthesis of one-dimensional materials at atomic-scale dimensions represents a milestone in nanotechnology, offering the potential to maximize atom utilization while enhancing catalytic performance. However, achieving structural stability and durability at such fine scales requires precise control over material structure and local chemical environment. Here, we introduce dimethylamine (DMA) as a small-molecule modifier, in contrast to conventional long-chain surfactants, to interact with surface Pt atoms. This approach facilitates the removal of surface Pt atoms bonded to nitrogen atoms in DMA during solubilization in water, effectively stripping the size of Pt nanowires down to sub-nanometer. The resulting Pt subnanometer nanowires (subNWs) feature a monoatomic-layer surface composed of disordered, bonding-unsaturated Pt atoms, and an interior crystalline core as narrow as 0.58 nm in diameter. These unique structural characteristics confer the Pt subNWs with an electrochemically active surface-area of 189 m2 ⋅ g-1 during formic acid oxidation. Furthermore, the amorphous-like surface structure lowers the free energy of *OCOH intermediates and inhibits the formation of toxic byproducts CO, demonstrating exceptional electrocatalytic activity of 18.1 A ⋅ mg-1, surpassing most reported Pt-based electrocatalysts. Our work introduces a novel strategy for the controlled construction of nanowire-structures at sub-nanometer scale, effectively bridging the gap between ultrafine structural design and performance stability.

Polyoxotungstate Featuring Zinc-Ion-Triggered Structural Transformation as An Efficient Electrolyte Additive for Aqueous Zinc-Ion Batteries

It is promising but still challenging for the widespread application of aqueous zinc batteries due to the poor reversibility of the zinc anode caused by prevalent dendrite growth and pronounced interfacial side reactions. Herein, we report a rare soluble and water-stable high-nuclearity {Nd9Si4W39} polyoxotungstate. Interestingly, upon encountering Zn2+ ions, the discrete {Nd9Si4W39} nanocluster undergoes a structural transformation to form an infinitely extended cluster-based {[Zn(H2O)4]3[Nd9Si4W39]2} two-dimensional honeycomb layer, with which atomic-level Zn2+ ion effects in reconstructing the layer are determined. More interestingly, we demonstrate that the structural transformation property renders the {Nd9Si4W39} cluster an efficient electrolyte additive for aqueous zinc batteries, enabling the formation of the 2D layer as a protective layer on the zinc anode, significantly enhancing the reversibility of the zinc anode. Compared to the pristine Zn//Zn symmetric battery, the Zn//Zn symmetric battery with the {Nd9Si4W39} additive exhibits an extended lifespan of over 2000 hours at a current density of 1 mA cm-2. In situ optical microscopy, Raman spectroscopy, and molecular dynamics simulations reveal that the formation of the protective layer effectively promotes uniform zinc deposition, and inhibits zinc agglomeration, dendrite growth, and side reactions, thereby enabling the zinc anode to exhibit high reversibility and long-term service life.

Operando elucidation of hydrogen production mechanisms on sub-nanometric high-entropy metallenes

Precise morphological control and identification of structure-property relationships pose formidable challenges for high-entropy alloys, severely limiting their rational design and application in multistep and tandem reactions. Herein, we report the synthesis of sub-nanometric high-entropy metallenes with up to eight metallic elements via a one-pot wet-chemical approach. The PdRhMoFeMn high-entropy metallenes exhibit high electrocatalytic hydrogen evolution performances with 6, 23, and 26 mV overpotentials at -10 mA cm-2 in acidic, neutral, and alkaline media, respectively, and high stability. The electrochemical measurements, theoretical simulations, and operando X-ray absorption spectroscopy reveal the actual active sites along with their dynamics and synergistic mechanisms in various electrolytes. Specially, Mn sites have strong binding affinity to hydroxyl groups, which enhances the water dissociation process at Pd sites with low energy barrier while Rh sites with optimal hydrogen adsorption free energy accelerate hydride coupling, thereby markedly boosting its intrinsic ability for hydrogen production.

Collectively optimized Pt-O bond and morphology engineering of structurally ordered Pt3Zn intermetallic for high-efficiency zinc-air devices

We report an ordered Pt3Zn intermetallic with an optimized Pt-O bond, featuring a unique nanocube (NC) morphology for high-efficiency zinc-air devices. Rechargeable zinc-air batteries based on the Pt3Zn NC catalyst exhibit a superior electrochemical performance. Theoretical calculations demonstrate that alloying with Zn atoms modifies the electronic structure of the Pt surface, optimizing Pt binding energy with OHabs/COabs intermediates and thus enhancing electrocatalytic activity.

Template-directed synthesis of one-dimensional hexagonal PdTe nanowires for efficient ethanol electrooxidation

A template-directed synthesis of one-dimensional hexagonal PdTe nanowires using Te nanowires as a template through a two-step hydrothermal process is developed, which exhibit excellent mass activity of 4.4 A mgPd-1 for ethanol electrooxidation in an alkaline medium. This work enriches the controlled synthesis of one-dimensional noble metal chalcogenide nanomaterials.

An Effective Route to Enhance Pt/C Electrocatalyst Durability through Addition of Ceramic Nanoparticles to Facilitate Pt Redeposition

Platinum particle growth during long-term operations is one of the well-known bottlenecks offsetting the performance and stability of Pt-based electrocatalysts in polymer electrolyte membrane (PEM) fuel cells and PEM water electrolyzers. In this research, the addition of certain ceramic nanoparticulate additives to the catalyst ink was evaluated as a means of improving the electrochemical stability of a carbon-supported platinum (Pt/C) electrocatalyst in gas diffusion electrodes (GDEs) during an accelerated stress test (AST). GDEs prepared using three nanoparticulate ceramic additives (TiN, ATO, and TiO2) with three loadings (replacing 5, 10, and 15 wt % of the catalyst) were studied for their electrochemical performance, i.e., the initial electrochemical surface area (ECSA) and stability during AST in a liquid cell. TiN appeared to be an optimal additive among the three to (i) improve the stability by ∼40% during 1600 cycles, (ii) prohibit Pt nanoparticle agglomeration due to coalescence and Ostwald ripening, and (iii) reduce Pt dissolution during the AST, without compromising a high initial ECSA. The fundamental mechanism lies in the fact that the ceramic nanoparticles can act as additional nucleation sites for redeposition of the dissolved Pt during AST; X-ray photoelectron spectroscopy (XPS) indicates strong interactions between platinum and ceramic nanoparticles. Eventually, the superior sample was used as the cathode catalyst in an electrolyzer to compare the electrochemical performance with that of a commercial Pt/C sample. As confirmed by single-cell tests in this research, the method studied and the associated concept here to enhance the durability of Pt-based electrocatalysts are facile and scalable and hence may be readily adopted by relevant stakeholders.

A self-reactivated PdCu catalyst for aldehyde electro-oxidation with anodic hydrogen production

The low-potential aldehyde oxidation reaction can occur at low potential (~0 VRHE) and release H2 at the anode, enabling hydrogen production with less than one-tenth of the energy consumption required for water splitting. Nevertheless, the activity and stability of Cu catalysts remain inadequate due to the oxidative deactivation of Cu-based materials. Herein, we elucidate the deactivation and reactivation cycle of Cu electrocatalyst and develop a self-reactivating PdCu catalyst that exhibits significantly enhanced stability. Initially, in-situ Raman spectroscopy confirm the cycle involved in electrochemical oxidation and non-electrochemical reduction. Subsequently, in-situ Raman spectroscopy and X-ray absorption fine structure reveal that the Pd component accelerates the rate of the non-electrochemical reduction, thereby enhancing the stability of the Cu-based electrocatalyst. Finally, a bipolar hydrogen production device is assembled utilizing the PdCu electrocatalyst, which can deliver a current of 400 mA cm-2 at 0.42 V and operate continuously for 120 h. This work offers guidance to enhance the stability of the Cu-based electrocatalyst in a bipolar hydrogen production system.

Cobalt Nitride-Implanted PtCo Intermetallic Nanocatalysts for Ultrahigh Fuel Cell Cathode Performance

Stable and active oxygen reduction electrocatalysts are essential for practical fuel cells. Herein, we report a novel class of highly ordered platinum-cobalt (Pt-Co) alloys embedded with cobalt nitride. The intermetallic core-shell catalyst demonstrates an initial mass activity of 0.88 A mgPt-1 at 0.9 V with 71% retention after 30,000 potential cycles of an aggressive square-wave accelerated durability test and loses only 9% of its electrochemical surface area, far exceeding the US Department of Energy 2025 targets, with unprecedented stability and only a minimal voltage loss under practical fuel cell operating conditions. We discover that regulating the atomic ordering in the core results in an optimal lattice configuration that accelerates the oxygen reduction kinetics. The presence of cobalt nitride decorated within PtCo superlattices guarantees a larger barrier to Co dissolution, leading to the excellent endurance of the electrocatalysts. This work brings up a transformative structural engineering strategy for rationally designing high-performing Pt-based catalysts with a unique atomic configuration for broad practical uses in energy conversion technology.

Overcoming the Limitation of Ionomers on Mass Transport and Pt Activity to Achieve High-Performing Membrane Electrode Assembly

The membrane electrode assembly (MEA) is one of the critical components in proton exchange membrane fuel cells (PEMFCs). However, the conventional MEA cathode with a covered-type catalyst/ionomer interfacial structure severely limits oxygen transport efficiency and Pt activity, hardly achieving the theoretical performance upper bound of PEMFCs. Here, we design a noncovered catalyst/ionomer interfacial structure with low proton transport resistance and high oxygen transport efficiency in the cathode catalyst layer (CL). This noncovered interfacial structure employs the ionomer cross-linked carbon particles as long-range and fast proton transport channels and prevents the ionomer from directly covering the Pt/C catalyst surface in the CL, freeing the oxygen diffusion process from passing through the dense ionomer covering layer to the Pt surface. Moreover, the structure improves oxygen transport within the pores of the CL and achieves more than 20% lower pressure-independent oxygen transport resistance compared to the covered-type structure. Fuel-cell diagnostics demonstrate that the noncovered catalyst/ionomer interfacial structure provides exceptional fuel-cell performance across the kinetic and mass transport-limited regions, with 77% and 67% higher peak power density than the covered-type interfacial structure under 0 kPagauge of oxygen and air conditions, respectively. This alternative interfacial structure provides a new direction for optimizing the electrode structure and improving mass-transport paths of MEA.

Influence of the Pt/ionomer/water interface on the oxygen reduction reaction: insights into the micro-three-phase interface

Understanding the Pt/ionomer/water interface structure and its impact on the oxygen reduction reaction (ORR) activity is essential for enhancing catalyst utilization and performance of fuel cells. This study aimed to investigate the influence of sulfonic acid groups on the Pt/ionomer/water interface and the ORR mechanism. By using a combination of DFT, AIMD, and microkinetic simulations, the results showed that when the sulfonic acid group is located at the edge of the Helmholtz plane, it creates an optimal three-phase interface, providing more available active sites, a stronger interfacial electric field, and a more continuous H-bond network. This configuration results in the *OOH dissociation becoming the rate-determining step, demonstrating significantly higher intrinsic ORR activity with a much lower theoretical overpotential of 0.11 V. Conversely, when the sulfonic acid group is in contact with the Pt surface, it causes the Pt surface's d-band center to shift down, weakens the interfacial electric field, and disrupts the H-bond network, resulting in a blocking effect on the ORR with an overpotential of 0.23 V. These insights shed light on the role of solid-solid-liquid interfaces in the ORR performance and provide valuable information for the rational design of catalyst interfaces.

2D MXene/MBene Superlattice with Narrow Bandgap as Superior Electrocatalyst for High-Performance Lithium-Oxygen Battery

Lithium-oxygen (Li-O2) battery with large theoretical energy density (≈3500 Wh kg-1) is one of the most promising energy storage and conversion systems. However, the slow kinetics of oxygen electrode reactions inhibit the practical application of Li-O2 battery. Thus, designing efficient electrocatalysts is crucial to improve battery performance. Here, Ti3C2 MXene/Mo4/3B2-x MBene superlattice is fabricated its electrocatalytic activity toward oxygen redox reactions in Li-O2 battery is studied. It is found that the built-in electric field formed by a large work function difference between Ti3C2 and Mo4/3B2-x will power the charge transfer at the interface from titanium (Ti) site in Ti3C2 to molybdenum (Mo) site in Mo4/3B2-x. This charge transfer increases the electron density in 4d orbital of Mo site and decreases the d-band center of Mo site, thus optimizing the adsorption of intermediate product LiO2 at Mo site and accelerating the kinetics of oxygen electrode reactions. Meanwhile, the formed film-like discharge products (Li2O2) improve the contact with electrode and facilitate the decomposition of Li2O2. Based on the above advantages, the Ti3C2 MXene/Mo4/3B2-x MBene superlattice-based Li-O2 battery exhibits large discharge specific capacity (17 167 mAh g-1), low overpotential (1.16 V), and superior cycling performance (475 cycles).

Concave Grain Boundaries Stabilized by Boron Segregation for Efficient and Durable Oxygen Reduction

The oxygen reduction reaction (ORR) is a critical process that limits the efficiency of fuel cells and metal-air batteries due to its slow kinetics, even when catalyzed by platinum (Pt). To reduce Pt usage, enhancing both the specific activity and electrochemically active surface area (ECSA) of Pt catalysts is essential. Here, ultrafine, grain boundary (GB)-rich Pt nanoparticle assemblies are proposed as efficient ORR catalysts. These nanowires offer a large ECSA and a high density of concave GB sites, which improve specific activity. Atoms at these GB sites exhibit increased coordination and lattice distortion, leading to a favorable reduction in oxygen binding energy and enhanced ORR performance. Furthermore, boron segregation stabilizes these GBs, preserving active sites during catalysis. The resulting boron-stabilized Pt nanoassemblies demonstrate ORR specific and mass activities of 9.18 mA cm-2 and 6.40 A mg-1 Pt (at 0.9 V vs. RHE), surpassing commercial Pt/C catalysts by over 35-fold, with minimal degradation after 60 000 potential cycles. This approach offers a versatile platform for optimizing the catalytic performance of a wide range of nanoparticle systems.

Formation Characteristics of Pt-Ni Alloy Nanoparticles Fabricated by Nanolamination of Atomic Layer Deposition in Hydrogen

Forced-flow atomic layer deposition nanolamination is employed to fabricate Pt-Ni nanoparticles on XC-72, with the compositions ranging from Pt94Ni6 to Pt67Ni33. Hydrogen is used as a co-reactant for depositing Pt and Ni. The growth rate of Pt is slower than that using oxygen reactant, and the growth exhibits preferred orientation along the (111) plane. Ni shows much slower growth rate than Pt, and it is only selectively deposited on Pt, not on the substrate. Higher ratios of Ni would hinder subsequent stacking of Pt atoms, resulting in lower overall growth rate and smaller particles (1.3-2.1 nm). Alloying of Pt with Ni causes shifted lattice that leads to larger lattice parameter and d-spacing as Ni fraction increases. From the electronic state analysis, Pt 4f peaks are shifted to lower binding energies with increasing the Ni content, suggesting charge transfer from Ni to Pt. Schematic of the growth behavior is proposed. Most of the alloy nanoparticles exhibit higher electrochemical surface area and oxygen reduction reaction activity than those of commercial Pt. Especially, Pt83Ni17 and Pt87Ni13 show excellent mass activities of 0.76 and 0.59 A mgPt -1, respectively, higher than the DOE target of 2025, 0.44 A mgPt -1.

Carbon-anchoring synthesis of Pt1Ni1@Pt/C core-shell catalysts for stable oxygen reduction reaction

Proton-exchange-membrane fuel cells demand highly efficient catalysts for the oxygen reduction reaction, and core-shell structures are known for maximizing precious metal utilization. Here, we reported a controllable "carbon defect anchoring" strategy to prepare Pt1Ni1@Pt/C core-shell nanoparticles with an average size of ~2.6 nm on an in-situ transformed defective carbon support. The strong Pt-C interaction effectively inhibits nanoparticle migration or aggregation, even after undergoing stability tests over 70,000 potential cycles, resulting in only 1.6% degradation. The stable Pt1Ni1@Pt/C catalysts have high oxygen reduction reaction mass activity and specific activity that reach 1.424 ± 0.019 A/mgPt and 1.554 ± 0.027 mA/cmPt2 at 0.9 V, respectively, attributed to the optimal compressive strain. The experimental results are generally consistent with the theoretical predictions made by our comprehensive microkinetic model which incorporates essential kinetics and thermodynamics of oxygen reduction reaction. The consistent results obtained in our study provide compelling evidence for the high accuracy and reliability of our model. This work highlights the synergy between theory-guided catalyst design and appropriate synthetic methodologies to translate the theory into practice, offering valuable insights for future catalyst development.

Ultra-Thin RuIr Alloy as Durable Electrocatalyst for Seawater Hydrogen Evolution Reaction

The development of efficient, high-performance catalysts for hydrogen evolution reaction (HER) remains a significant challenge, especially in seawater media. Here, RuIr alloy catalysts are prepared by the polyol reduction method. Compared with single-metal catalysts, the RuIr alloy catalysts exhibited higher activity and stability in seawater electrolysis due to their greater number of reactive sites and solubility resistance. The RuIr alloy has an overpotential of 75 mV@10 mA cm-2, which is similar to that of Pt/C (73 mV), and can operate stably for 100 hours in alkaline seawater. Density functional theory (DFT) calculations indicate that hydrogen atoms adsorbed at the top sites of Ru and Ir atoms are more favorable for HER and are most likely to be the reactive sites. This work provides a reference for developing highly efficient and stable catalysts for seawater electrolysis.

Crystal-Phase-Selective Etching of Heterophase Au Nanostructures

Selective oxidative etching is one of the most effective ways to prepare hollow nanostructures and nanocrystals with specific exposed facets. The mechanism of selective etching in noble metal nanostructures mainly relies on the different reactivity of metal components and the distinct surface energy of multimetallic nanostructures. Recently, phase engineering of nanomaterials (PEN) offers new opportunities for the preparation of unique heterostructures, including heterophase nanostructures. However, the synthesis of hollow multimetallic nanostructures based on crystal-phase-selective etching has been rarely studied. Here, a crystal-phase-selective etching method is reported to selectively etch the unconventional 4H and 2H phases in the heterophase Au nanostructures. Due to the coating of Pt-based alloy and the crystal-phase-selective etching of 4H-Au in 4H/face-centered cubic (fcc) Au nanowires, the well-defined ladder-like Au@PtAg nanoframes are prepared. In addition, the 2H-Au in the fcc-2H-fcc Au nanorods and 2H/fcc Au nanosheets can also be selectively etched using the same method. As a proof-of-concept application, the ladder-like Au@PtAg nanoframes are used for the electrocatalytic hydrogen evolution reaction (HER) in acidic media, showing excellent performance that is comparable to the commercial Pt/C catalyst.

Rapid Preparation of Platinum Catalyst in Low-Temperature Molten Salt Using Microwave Method for Formic Acid Catalytic Oxidation Reaction

In this paper, platinum nanoparticles with a size of less than 50 nm were rapidly and successfully synthesized in low-temperature molten salt using a microwave method. The morphology and structure of the product were characterized by SEM, TEM, EDX, XRD, etc. The TEM and SEM results showed that the prepared product was a nanostructure with concave and uniform size. The EDX result indicated that the product was pure Pt, and the XRD pattern showed that the diffraction peaks of the product were consistent with the standard spectrum of platinum. The obtained Pt/C nanoparticles exhibited remarkable electrochemical performance in a formic acid catalytic oxidation reaction (FAOR), with a peak mass current density of 502.00 mA·mg-1Pt and primarily following the direct catalytic oxidation pathway. In addition, in the chronoamperometry test, after 24 h, the mass-specific activity value of the Pt concave NPs/C catalyst (10.91 mA·mg-1Pt) was approximately 4.5 times that of Pt/C (JM) (2.35 mA·mg-1Pt). The Pt/C NPs exhibited much higher formic acid catalytic activity and stability than commercial Pt/C. The microwave method can be extended to the preparation of platinum-based alloys as well as other catalysts.

Resolving optimal ionomer interaction in fuel cell electrodes via operando X-ray absorption spectroscopy

To bridge the gap between oxygen reduction electrocatalysts development and their implementation in real proton exchange membrane fuel cell electrodes, an important aspect to be understood is the interaction between the carbon support, the active sites, and the proton conductive ionomer as it greatly affects the local transportations to the catalyst surface. Here we show that three Pt/C catalysts, synthesized using the polyol method with different carbon supports (low surface area Vulcan, high surface area Ketjenblack, and biomass-derived highly ordered mesoporous carbon), revealed significant variations in ionomer-catalyst interactions. The Pt/C catalysts supported on ordered mesoporous carbon derived from biomass showed the best performance under the gas diffusion electrode configuration. Through a unique approach of operando X-ray Absorption Spectroscopy combined with gas sorption analysis, we were able to demonstrate the beneficial effect of mesopore presence for optimal ionomer-catalyst interaction at both molecular and structural level.

0D/2D heterojunction constructed by Ag2S quantum dots anchored on graphdiyne (g-CnH2n-2) nanosheets for wide spectrum photocatalytic H2 evolution

Precisely crafting heterojunctions for efficient charge separation is a major obstacle in the realm of photocatalytic hydrogen evolution. A 0D/2D heterojunction was successfully fabricated by anchoring Ag2S quantum dots (Ag2S QDs) onto graphdiyne (GDY) nanosheets (Ag2S QDs/GDY) using a straightforward physical mixing technique. This unique structure allows for excellent contact between GDY and Ag2S QDs, thereby enhancing the rate of charge transfer. The light absorption capabilities of Ag2S QDs/GDY extend up to 1200 nm, enabling strong absorption of light, including infrared. Through DFT calculations and in-situ XPS analysis, it was demonstrated that incorporating Ag2S QDs onto GDY effectively modulates the electronic structure, promotes an internal electric field, and facilitates directional electron transfer. This directed electron transfer enhances the utilization of electrons by GDY and Ag2S QDs, with the added benefit of Ag2S QDs serving as electron reservoirs for efficient photocatalytic hydrogen evolution. A 7 %Ag2S QDs/GDY composite exhibited impressive efficiency and stable performance in photocatalytic hydrogen evolution (2418 μmol g-1 h-1), which is much higher than that of GDY and Ag2S QDs. This study conclusively demonstrates that the 0D/2D heterojunction formed by GDY and Ag2S QDs can establish high-quality contact and efficient charge transfer, ultimately enhancing photocatalytic performance.

Atom-glue stabilized Pt-based intermetallic nanoparticles

Pt-based nanoparticles (NPs) have been widely used in catalysis. However, this suffers from aggregation and/or sintering at working conditions. We demonstrate a robust strategy for stabilizing PtCo NPs under high temperature with strong interaction between M-N-C and PtCo NPs with Pt-M-N coordination, namely, "atom glue." Such atom glue for stabilizing Pt-based NPs can be extended to Zn, Mn, Fe, Ni, Co, and Cu, being a versatile strategy for stabilizing PtCo NPs, which substantially promotes the performance toward oxygen reduction reaction (ORR) and fuel cell. Impressively, the mass activity (MA) reaches 2.99 A mgPt-1 for ORR over g-Zn-N-C/PtCo, and 79.3% of the initial MA is maintained after 90K cycles in fuel cell. This work provides a versatile strategy for stabilizing Pt-based NPs via atom glue, which is likely to spark widespread interest across various fields.

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.

Direct Identification of O─O Bond Formation Through Three-Step Oxidation During Water Splitting by Operando Soft X-ray Absorption Spectroscopy

Anionic redox allows the direct formation of O─O bonds from lattice oxygens and provides higher catalytic in the oxygen evolution reaction (OER) than does the conventional metal ion mechanism. While previous theories have predicted and experiments have suggested the possible O─O bond, it has not yet been directly observed in the OER process. In this study, operando soft X-ray absorption spectroscopy (sXAS) at the O K-edge and the operando Raman spectra is performed on layered double CoFe hydroxides (LDHs) after intercalation with [Cr(C2O4)3]3-, and revealed a three-step oxidation process, staring from Co2+ to Co3+, further to Co4+ (3d6L), and ultimately leading to the formation of O─O bonds and O2 evolution above a threshold voltage (1.4 V). In contrast, a gradual oxidation of Fe is observed in CoFe LDHs. The OER activity exhibits a significant enhancement, with the overpotential decreasing from 300 to 248 mV at 10 mA cm-2, following the intercalation of [Cr(C2O4)3]3- into CoFe LDHs, underscoring a crucial role of anionic redox in facilitating water splitting.

Entropy-Driven Ostwald Ripening Reversal Promotes the Formation of Low-Platinum Intermetallic Fuel Cell Catalysts

Strain engineering has been widely used to optimize platinum-based oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs). PtM3 (M is base metals), a well-known high-compressive-strain intermetallic alloy, shows promise as a low platinum ORR catalyst due to high intrinsic activity. However, during the alloying of Pt with a threefold amount of M, a notable phase separation between Pt and M may occur, with M particles rapidly sintering while Pt particles grow slowly, posing a challenge in achieving a well-defined PtM3 intermetallic alloy. Here, an entropy-driven Ostwald ripening reversal phenomenon is discovered that enables the synthesis of small-sized Pt(FeCoNiCu)3 intermetallic ORR catalysts. High entropy promotes the thermodynamic driving force for the alloying Pt with M, which triggers the Ostwald ripening reversal of sintered FeCoNiCu particles and facilitates the formation of uniform Pt(FeCoNiCu)3 intermetallic catalysts. The prepared Pt(FeCoNiCu)3 catalysts exhibit a high specific activity of 3.82 mA cm-2, along with a power density of ≈1.3 W cm-2 at 0.67 V and 94 °C with a cathode Pt loading of 0.1 mg cm-2 in H2-air fuel cell.