Superlattice in a Ru Superstructure for Enhancing Hydrogen Evolution

Deep Reconstruction of Ruthenate Perovskite Oxide Enables Efficient pH-Universal Hydrogen Evolution Reaction

Designing highly efficient, stable, and pH-universal perovskites for hydrogen evolution reaction (HER) is urgently needed yet remains a grand challenge. Herein, a titanium-containing strontium ruthenate (SrTi0.5Ru0.5O3, STRO) is developed as an excellent HER electrocatalyst in a wide pH range. The introduction of Ti into SrRuO3 significantly reduces the size of STRO, endowing with a high reactivity that facilitates a deep surface-reconstruction during HER. Furthermore, Sr2+ leaching triggered reconstruction leads to STRO breaking into tiny nanoparticles accompanied by high-valence ruthenium (Ru) species reducing to metallic Ru. The generated active species, increased accessible sites, and improved electrical conductivity greatly boost HER. The reconstructed STRO displays remarkable HER activities with exceptional low overpotentials of 18, 24, and 55 mV at 10 mA cm-2 in 1 m KOH, 0.5 m H2SO4, and 1 m PBS, respectively, surpassing most perovskites reported previously and comparable to or even outperforming that of commercial Pt/C. Moreover, the STRO exhibits excellent stabilities over 200 h in alkaline and acidic media, superior to that of Pt/C. This work not only provides insights into structure reconstruction of perovskites during HER, but also opens new perspectives for developing high-efficiency and pH-universal electrocatalysts for future energy applications.

Ruthenium Nanoclusters and Single Atoms on α-MoC/N-Doped Carbon Achieves Low-Input/Input-Free Hydrogen Evolution via Decoupled/Coupled Hydrazine Oxidation

The hydrazine oxidation-assisted H2 evolution method promises low-input and input-free hydrogen production. However, developing high-performance catalysts for hydrazine oxidation (HzOR) and hydrogen evolution (HER) is challenging. Here, we introduce a bifunctional electrocatalyst α-MoC/N-C/RuNSA, merging ruthenium (Ru) nanoclusters (NCs) and single atoms (SA) into cubic α-MoC nanoparticles-decorated N-doped carbon (α-MoC/N-C) nanowires, through electrodeposition. The composite showcases exceptional activity for both HzOR and HER, requiring -80 mV and -9 mV respectively to reach 10 mA cm-2. Theoretical and experimental insights confirm the importance of two Ru species for bifunctionality: NCs enhance the conductivity, and its coexistence with SA balances the H ad/desorption for HER and facilitates the initial dehydrogenation during the HzOR. In the overall hydrazine splitting (OHzS) system, α-MoC/N-C/RuNSA excels as both anode and cathode materials, achieving 10 mA cm-2 at just 64 mV. The zinc hydrazine (Zn-Hz) battery assembled with α-MoC/N-C/RuNSA cathode and Zn foil anode can exhibit 97.3 % energy efficiency, as well as temporary separation of hydrogen gas during the discharge process. Therefore, integrating Zn-Hz with OHzS system enables self-powered H2 evolution, even in hydrazine sewage. Overall, the amalgamation of NCs with SA achieves diverse catalytic activities for yielding multifold hydrogen gas through advanced cell-integrated-electrolyzer system.

Constructing Built-in-Electric Field for Boosting Electrocatalytic Water Splitting

Electrocatalytic water splitting shows great potential for producing clean and green hydrogen, but it is hindered by slow reaction kinetics. Advanced electrocatalysts are needed to lower the energy barriers. The establishment of built-in electric fields (BIEF) in heterointerfaces has been found to be beneficial for speeding up electron transfer, increasing electrical conductivity, adjusting the local reaction environment, and optimizing the chemisorption energy with intermediates. Engineering and modifying the BIEF in heterojunctions offer significant opportunities to enhance the electronic properties of catalysts, thus improving the reaction kinetics. This comprehensive review focuses on the latest advances in BIEF engineering in heterojunction catalysts for efficient water electrolysis. It highlights the fundamentals, engineering, modification, characterization, and application of BIEF in electrocatalytic water splitting. The review also discusses the challenges and future prospects of BIEF engineering. Overall, this review provides a thorough examination of BIEF engineering for the next generation of water electrolysis devices.

Synergistic Effects of PtRhNiFeCu High Entropy Alloy Nanocatalyst for Hydrogen Evolution and Oxygen Reduction Reactions

The unique properties of high entropy alloy (HEA) catalysts, particularly their severe lattice distortion and the synergistic effect of multiple components, endow them with exceptional multifunctional catalytic performance. Herein, it is revealed for the first time, that the ultrasmall PtRhNiFeCu HEA nanoparticles catalyst shows outstanding catalytic activity for both hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The catalyst exhibits an impressively low overpotential of 13 mV at 10 mA cm-2, a Tafel slope of 29.6 mV dec-1, and high mass activity of 7.6 A mgPt -1 at -50 mV in alkaline media, and long-term stability of at least 20 h. Moreover, the catalyst also demonstrates effective catalytic activity for acidic ORR with a commendable performance of 1.23 A mgPt -1, much exceeding the commercial Pt/C catalyst. Density functional theory (DFT) calculations unveil that the efficient electrocatalytic performance for HER and ORR can be primarily attributed to the synergistic effect between components tailors and optimizes the electronic structure of PtRhNiFeCu/C HEA, which not only enhances the HER activity through increasing water capture capability, decreasing energetic barrier for water dissociation, and optimizing hydrogen absorption but also initiates non-platinum active sites with high ORR activity, achieving the improved ORR performance.

Ammonia-Induced FCC Ru Nanocrystals for Efficient Alkaline Hydrogen Electrocatalysis

The urgent development of effective electrocatalysts for hydrogen evolution and hydrogen oxidation reaction (HER/HOR) is needed due to the sluggish alkaline hydrogen electrocatalysis. Here, an unusual face-centered cubic (fcc) Ru nanocrystal with favorable HER/HOR performance is offered. Guided by the lower calculated surface energy of fcc Ru than that of hcp Ru in NH3, the carbon-supported fcc Ru electrocatalyst is facilely synthesized in the NH3 reducing atmosphere. The specific HOR kinetic current density of fcc Ru can reach 23.4 mA cmPGM -2, which is around 20 and 21 times greater than that of hexagonal close-packed (hcp) Ru and Pt/C, respectively. Additionally, the HER specific activity is enhanced more than six times in fcc Ru electrocatalyst when compared to Pt/C. Experimental and theoretical analysis indicate that the phase transition from hcp Ru to fcc Ru can negatively shift the d band center, weaken the interaction between catalysts and key intermediates and therefore enhances the HER/HOR kinetics.

Evolution of Grain Boundaries Promoted Hydrogen Production for Industrial-Grade Current Density

The development of efficient and durable high-current-density hydrogen production electrocatalysts is crucial for the large-scale production of green hydrogen and the early realization of hydrogen economic blueprint. Herein, the evolution of grain boundaries through Cu-mediated NiMo bimetallic oxides (MCu-BNiMo), which leading to the high efficiency of electrocatalyst for hydrogen evolution process (HER) in industrial-grade current density, is successfully driven. The optimal MCu0.10-BNiMo demonstrates ultrahigh current density (>2 A cm-2) at a smaller overpotential in 1 m KOH (572 mV), than that of BNiMo, which does not have lattice strain. Experimental and theoretical calculations reveal that MCu0.10-BNiMo with optimal lattice strain generated more electrophilic Mo sites with partial oxidation owing to accelerated charge transfer from Cu to Mo, which lowers the energy barriers for H* adsorption. These synergistic effects lead to the enhanced HER performance of MCu0.10-BNiMo. More importantly, industrial application of MCu0.10-BNiMo operated in alkaline electrolytic cell is also determined, with its current density reached 0.5 A cm-2 at 2.12 V and 0.1 A cm-2 at 1.79 V, which is nearly five-fold that of the state-of-the-art HER electrocatalyst Pt/C. The strategy provides valuable insights for achieving industrial-scale hydrogen production through a highly efficient HER electrocatalyst.

Hollow Ru/RuO2 nanospheres with nanoparticulate shells for high performance electrocatalytic oxygen evolution reactions

This work shows that hollow Ru/RuO2 nanoparticles having nanoparticulate shells (HN-Ru/RuO2) can be prepared using hollow microporous organic polymers with Ru species (H-MOP-Ru) as precursors. Using silica spheres as templates, H-MOPs were prepared through the Sonogashira-Hagihara coupling of 1,3,5-triethynylbenzene with 2,3-ethoxymethylenedioxy-1,4-diiodobenzene. Acid hydrolysis of cyclic ethyl orthoformate protecting groups generated catechol moieties to form H-MOP-Cat. Then, H-MOP-Ru was obtained by incorporating Ru species into H-MOP-Cat. Heat-treatment of H-MOP-Ru under air induced the formation of HN-Ru/RuO2 with a diameter of 61 nm and shells consisting of 6-7 nm nanoparticles. Due to the hollow structure and nanoparticulate shells, HN-Ru/RuO2 showed a high surface area of 80 m2 g-1 and a pore volume of 0.18 cm3 g-1. The HN-Ru/RuO2 showed enhanced electrocatalytic performance for the oxygen evolution reaction (OER) with an overpotential of 295 mV @ 10 mA cm-2 and a Tafel slope of 46 mV dec-1 in alkaline electrolyte, compared with control RuO2 such as commercial Ru/RuO2 nanoparticles (A-Ru/RuO2) and home-made Ru/RuO2 nanoparticles (N-Ru/RuO2) prepared via the same synthetic procedure as HN-Ru/RuO2. While HN-Ru/RuO2 inevitably contained Pd originated from coupling catalysts, it showed superior performance to Ru/RuO2 nanoparticles with the same Pd content (N1-Ru/RuO2), indicating that the efficient electrocatalytic performance of HN-Ru/RuO2 is attributable to its hollow structure and nanoparticulate shells.

Rapid High-Temperature Liquid Shock Synthesis of High-Entropy Alloys for Hydrogen Evolution Reaction

High-entropy-alloy nanoparticles (HEA-NPs) show great potential as electrocatalysts for water splitting, fuel cells, CO2 conversion, etc. However, fine-tuning the surface, morphology, structure, and crystal phase of HEA remains a great challenge. Here, the high-temperature liquid shock (HTLS) technique is applied to produce HEA-NPs, e.g., PtCoNiRuIr HEA-NPs, with tunable elemental components, ultrafine particle size, controlled crystal phases, and lattice strains. HTLS directly applied Joule heating on the liquid mixture of metal precursors, capping agents, and reducing agents, which is feasible for controlling the morphology and structure such as the atomic arrangement of the resulting products, thereby facilitating the rationally designed nanocatalysts. Impressively, the as-obtained PtCoNiRuIr HEA-NPs delivered superior activity and long-term stability for the hydrogen evolution reaction (HER), with low overpotentials at 10 mA cm-2 and 1 A cm-2 of only 18 and 408 mV, respectively, and 10000 CV stable cycles in 0.5 M H2SO4. Furthermore, in the near future, by combining the HTLS method with artificial intelligence (AI) and theoretical calculations, it is promising to provide an advanced platform for the high-throughput synthesis of HEA nanocatalysts with optimized performance for various energy applications, which is of great significance for achieving a carbon-neutral society with an effective and environmentally friendly energy system.

Nanotip-Induced Electric Field for Hydrogen Catalysis

Local electric field induced by the lightning-rod effect attracts great attention for regulating the local microenvironment and electronic properties of active sites. Nevertheless, local electric-field-assisted applications are mainly limited to metals with strong surface plasmonic resonance properties (e.g., Au, Ag, and Cu). Herein, we fabricate RuCu snow-like nanosheets (SNSs) with high-curvature nanotips for enhancing the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER). Theoretical simulations show that RuCu SNSs can induce a strong local electric field around the sharp nanotips, which favors the accumulation of OH- for HOR and H+ for HER. Cu incorporation can modulate the binding strength of OH* and H*, leading to significantly enhanced HOR and HER performance. Impressively, the mass activity of RuCu SNSs for alkaline HOR is 31.3 times higher than that of RuCu nanocrystals without sharp tips. Besides, the required overpotential for reaching 10 mA cm-2 during HER over RuCu SNSs is 14.0 mV.

Constructing built-in electric field via ruthenium/cerium dioxide Mott-Schottky heterojunction for highly efficient electrocatalytic hydrogen production

Ensuring the consumption rate of noble metals while guaranteeing satisfactory hydrogen evolution reaction (HER) performance at different pH values is imperative to the development of Ru-based catalysts. Herein, we design a Mott-Schottky electrocatalyst (Ru/CeO2) with a built-in electric field (BEF) based on density functional theory (DFT). The Ru/CeO2 achieves the criterion current density of 10 mA cm-2 at overpotentials of 55 mV, 80 mV, and 120 mV in alkaline, acidic and neutral media, respectively. Both theoretical calculations and experimental analysis confirm that the improved HER activity in the Ru/CeO2 catalyst could be due to the successful construction of BEF at the interface between the prepared Ru clusters and CeO2. Under the action of BEF, the electron-deficient Ru atoms can optimize the adsorption energy of H* and H2O and thus promote HER kinetics. Furthermore, the Ru/CeO2 catalyst delivers a power density of approximately 94.5 mW cm-2 in alkaline-acidic Zn-H2O cell applications while maintaining good H2 production stability. In this work, we optimize the electrocatalytic performance of the Ru/CeO2 catalyst through examination of the interfacial BEF electrical charge, which combines hydrogen production with power generation and provides a promising method for sustainable energy conversion.

Confinement Engineering of Zinc Single-Atom Triggered Charge Redistribution on Ruthenium Site for Alkaline Hydrogen Production

Optimizing the interaction between metal and support in the supported metal catalysts effectively refines the electronic structure and boosts the catalytic properties of loaded active components. Herein a method is introduced to confine ultrafine ruthenium (Ru) nanoparticles within atomically dispersed Zn-N4 sites on a N-doped carbon network (Ru/Zn-N-C) through the strong electronic metal-support interaction, achieving superior catalytic activity and stability for alkaline hydrogen evolution. Spectroscopic data and theoretical modeling elucidate that the remarkable catalytic performance of Ru sites stems from their strong electronic coupling with neighboring Zn-N4 moiety and pyridinic N/pyrrolic N. This interaction induces an electron-deficient state of Ru, thereby accelerating the dissociation of H2 O and lowering the energy barriers for the desorption of OH* and H*. This insight provides a deeper understanding of the catalytic mechanisms at play. Furthermore, alkaline water electrolyzer using this catalyst as cathode delivers a mass activity of 3 A mgcat -1 at 2.0 V, much surpassing Ru-C. This research opens a novel pathway for the development of advanced materials , tailored for energy storage and conversion applications.

Ru nanoclusters anchored on boron- and nitrogen-doped carbon for a highly efficient hydrogen evolution reaction in alkaline seawater

Electrochemical seawater splitting is an intriguing strategy for green hydrogen production. Constructing advanced electrocatalysts for the hydrogen evolution reaction (HER) in seawater is extremely demanded for accelerating the sluggish kinetic process. Herein, a Ru nanocluster anchored on boron- and nitrogen-doped carbon (Ru/NBC) catalyst was successfully synthesized for the HER in alkaline/seawater electrolytes. Remarkably, Ru/NBC exhibits outstanding activity and durability, delivering low overpotentials@10 mA cm-2 in 1.0 M KOH (30 mV) and 1.0 M KOH + seawater electrolyte (35 mV), outperforming Pt/C, Ru/NC, Ru/BC and Ru/C. Additionally, Ru/NBC also provides a high specific activity of 0.093 mA cm-2ECSA at an overpotential of 150 mV, which is higher than those of Ru/NC, Ru/BC and Ru/C, respectively. Density functional theory calculation results demonstrate that the Ru-B formed interfacial chemical bond can regulate the electronic structure of Ru active sites of Ru/NBC, which can facilitate the adsorption of water and hydrogen in alkaline media. This work provides a feasible strategy to fabricate outstanding electrocatalysts for the HER in alkaline/alkaline seawater electrolytes.

D-Band Center Optimization of Edge-Rich Ultrathin RuZn Nanosheets With Moiré Superlattices for pH-Universal Hydrogen Evolution Reaction

Electrocatalytic hydrogen evolution reaction (HER) is a promising way to produce pure and clean hydrogen. However, the preparation of efficient and economical catalysts for pH-universal HER remains a challenging but rewarding task. Herein, ultrathin RuZn nanosheets (NSs) with moiré superlattices and abundant edges are synthesized. The RuZn NSs with unique structure exhibit superb HER performance with overpotentials of 11, 13, and 29 mV to achieve 10 mA cm-2 in 1 M KOH, 1 M PBS, and 0.5 M H2 SO4 , respectively, which is substantially lower than those of Ru NSs and RuZn NSs without moiré superlattices. Density functional theory investigations reveal that the charge transfer from Zn to Ru will lead the appropriate downshift of the d-band center of surface Ru atoms, thus accelerating hydrogen desorption from the Ru sites, lowering the dissociation energy barrier of water and greatly improving the HER performance. This work provides an effective design scheme for high-performance HER electrocatalysts over a wide pH range, and propose a general route to prepare Ru-based bimetallic nanosheets with moiré superlattices.

Lattice-Strain Engineering for Heterogenous Electrocatalytic Oxygen Evolution Reaction

The energy efficiency of metal-air batteries and water-splitting techniques is severely constrained by multiple electronic transfers in the heterogenous oxygen evolution reaction (OER), and the high overpotential induced by the sluggish kinetics has become an uppermost scientific challenge. Numerous attempts are devoted to enabling high activity, selectivity, and stability via tailoring the surface physicochemical properties of nanocatalysts. Lattice-strain engineering as a cutting-edge method for tuning the electronic and geometric configuration of metal sites plays a pivotal role in regulating the interaction of catalytic surfaces with adsorbate molecules. By defining the d-band center as a descriptor of the structure-activity relationship, the individual contribution of strain effects within state-of-the-art electrocatalysts can be systematically elucidated in the OER optimization mechanism. In this review, the fundamentals of the OER and the advancements of strain-catalysts are showcased and the innovative trigger strategies are enumerated, with particular emphasis on the feedback mechanism between the precise regulation of lattice-strain and optimal activity. Subsequently, the modulation of electrocatalysts with various attributes is categorized and the impediments encountered in the practicalization of strained effect are discussed, ending with an outlook on future research directions for this burgeoning field.

Nanoarchitectonics of Metallene Materials for Electrocatalysis

Controlling the synthesis of metal nanostructures is one approach for catalyst engineering and performance optimization in electrocatalysis. As an emerging class of unconventional electrocatalysts, two-dimensional (2D) metallene electrocatalysts with ultrathin sheet-like morphology have gained ever-growing attention and exhibited superior performance in electrocatalysis owing to their distinctive properties originating from structural anisotropy, rich surface chemistry, and efficient mass diffusion capability. Many significant advances in synthetic methods and electrocatalytic applications for 2D metallenes have been obtained in recent years. Therefore, an in-depth review summarizing the progress in developing 2D metallenes for electrochemical applications is highly needed. Unlike most reported reviews on the 2D metallenes, this review starts by introducing the preparation of 2D metallenes based on the classification of the metals (e.g., noble metals, and non-noble metals) instead of synthetic methods. Some typical strategies for preparing each kind of metal are enumerated in detail. Then, the utilization of 2D metallenes in electrocatalytic applications, especially in the electrocatalytic conversion reactions, including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, fuel oxidation reaction, CO₂ reduction reaction, and N₂ reduction reaction, are comprehensively discussed. Finally, current challenges and opportunities for future research on metallenes in electrochemical energy conversion are proposed.

Monolayer supertubes of Carbon-Armored platinum nanocrystals enabling robust oxygen reduction electrocatalysis

Self-assembled superstructures composed of nanocrystals (NCs) have shown immense potential for enhancing the performance in electrocatalytic applications. However, there has been limited research on the self-assembly of platinum (Pt) into low-dimensional superstructures as efficient electrocatalysts for oxygen reduction reaction (ORR). In this study, we designed a unique tubular superstructure composed of monolayer or sub-monolayer carbon-armored platinum nanocrystals (Pt NCs) using a template-assisted epitaxial assembly approach. The organic ligands on the surface of Pt NCs were in situ carbonized, resulting in few-layer graphitic carbon shells that encapsulate Pt NCs. Due to their monolayer assembly and tubular geometry, the Pt utilization of the supertubes was 1.5 times higher than that of conventional carbon-supported Pt NCs. As a result, such Pt supertubes exhibit remarkable electrocatalytic performance for the ORR in acidic media, with a high half-wave potential of 0.918 V and a high mass activity of 181 A g^-1_Pt at 0.9 V, which are comparable to commercial carbon-supported Pt (Pt/C) catalysts. Furthermore, the Pt supertubes demonstrate robust catalytic stability, as confirmed by long-term accelerated durability tests and identical-location transmission electron microscopy. This study presents a new approach to designing Pt superstructures for highly efficient and stable electrocatalysis.

Kinetic-Modulated Crystal Phase of Ru for Hydrogen Oxidation

Crystal-phase-engineering provides a powerful strategy for regulating the catalytic performance yet remains great challenge. Herein, the kinetic-modulated crystal-phase-control of Ru nanosheet assemblies (Ru NAs) is demonstrated by simply altering the concentration of citric acid (CA). Detailed experimental results reveal that high concentration of CA retards the growth kinetics and thus leads to the formation of metastable face-centered cubic (fcc) Ru NAs, while low concentration of CA results in the fast growth kinetics and the preferential formation of Ru NAs with stable hexagonal close packed (hcp) phase. Moreover, Ru NAs with different phases are used as catalyst for hydrogen oxidation reaction (HOR) to evaluate the effects of crystal phase on catalytic performance. Impressively, Ru NAs with fcc phase display a mass activity of 2.75 A mg_Ru ^-1 at 50 mV, which is much higher than those of Ru NAs with fcc/hcp (1.02 A mg_Ru ^-1 ) and hcp (0.74 A mg_Ru ^-1 ) phases. Theoretical calculations show that fcc Ru NAs display weaker adsorption toward ^* H and lower energy barrier toward the rate-determining step (RDS) during HOR. This work provides a facile strategy for regulating the crystal phase of Ru nanocrystals, which may attract rapid interests of researchers in materials, chemistry, and catalysis.

Ligand Hybridization for Electro-reforming Waste Glycerol into Isolable Oxalate and Hydrogen

The electro-reforming of glycerol is an emerging technology of simultaneous hydrogen production and biomass valorization. However, its complex reaction network and limited catalyst tunability restrict the precise steering toward high selectivity. Herein, we incorporated the chelating phenanthrolines into the bulk nickel hydroxide and tuned the electronic properties by installing functional groups, yielding tunable selectivity toward formate (max 92.7 %) and oxalate (max 45.3 %) with almost linear correlation with the Hammett parameters. Further combinatory study of intermediate analysis and various spectroscopic techniques revealed the electronic effect of tailoring the valence band that balances between C-C cleavage and oxidation through the key glycolaldehyde intermediate. A two-electrode electro-reforming setup using the 5-nitro-1,10-phenanthroline-nickel hydroxide catalyst was further established to convert crude glycerol into pure H₂ and isolable sodium oxalate with high efficiency.

Hollow Heterostructured Nanocatalysts for Boosting Electrocatalytic Water Splitting

The implementation of electrochemical water splitting demands the development and application of electrocatalysts to overcome sluggish reaction kinetics of hydrogen/oxygen evolution reaction (HER/OER). Hollow nanostructures, particularly for hollow heterostructured nanomaterials can provide multiple solutions to accelerate the HER/OER kinetics owing to their advantageous merit. Herein, the recent advances of hollow heterostructured nanocatalysts and their excellent performance for water splitting are systematically summarized. Starting by illustrating the intrinsically advantageous features of hollow heterostructures, achievements in engineering hollow heterostructured electrocatalysts are also highlighted with the focus on structural design, interfacial engineering, composition regulation, and catalytic evaluation. Finally, some perspective insights and future challenges of hollow heterostructured nanocatalysts for electrocatalytic water splitting are also discussed.

Heterostructure Engineering of 2D Superlattice Materials for Electrocatalysis

Exploring low-cost and high-efficient electrocatalyst is an exigent task in developing novel sustainable energy conversion systems, such as fuel cells and electrocatalytic fuel generations. 2D materials, specifically 2D superlattice materials focused here, featured highly accessible active areas, high density of active sites, and high compatibility with property-complementary materials to form heterostructures with desired synergetic effects, have demonstrated to be promising electrocatalysts for boosting the performance of sustainable energy conversion and storage devices. Nevertheless, the reaction kinetics, and in particular, the functional mechanisms of the 2D superlattice-based catalysts yet remain ambiguous. In this review, based on the recent progress of 2D superlattice materials in electrocatalysis applications, the rational design and fabrication of 2D superlattices are first summarized and the application of 2D superlattices in electrocatalysis is then specifically discussed. Finally, perspectives on the current challenges and the strategies for the future design of 2D superlattice materials are outlined. This review attempts to establish an intrinsic correlation between the 2D superlattice heterostructures and the catalytic properties, so as to provide some insights into developing high-performance electrocatalysts for next-generation sustainable energy conversion and storage.

Perovskite-Socketed Sub-3 nm Copper for Enhanced CO2 Electroreduction to C2

In situ socketing metal nanoparticles onto perovskite oxides has shown great potential in heterogeneous catalysis, but its employment in boosting ambient CO₂ electroreduction (CER) is unexplored. Here, a CER catalyst of perovskite-socketed sub-3 nm Cu equipped with strong metal-support interactions (SMSIs) is constructed to promote efficient and stable CO₂ -to-C₂₊ conversion. For such a catalyst, plentiful sub-3 nm ellipsoid Cu particles are homogeneously and epitaxially anchored on the perovskite backbones, with concomitant creation of significant SMSIs. These SMSIs are able to not only modulate electronic structure of active Cu and facilitate adsorption/activation of key intermediates, but also to strengthen perovskite-Cu adhesion and intensify resistance to structural degradation. Beneficial from these advantageous merits, when evaluated in CER, it performs comparably to or better than most reported Cu-based heteronanostructures. Relative to a physical-mixture counterpart, it features marked improvements (up to 6.2 folds) in activity and selectivity for C₂₊ , together with greatly boosted stability (>80 h). This work gives a new avenue to rationally design more advanced Cu-based heteronanostructures for CER.

Lattice Strain and Schottky Junction Dual Regulation Boosts Ultrafine Ruthenium Nanoparticles Anchored on a N-Modified Carbon Catalyst for H2 Production

Ruthenium-based materials are considered great promising candidates to replace Pt-based catalysts for hydrogen production in alkaline conditions. Herein, we adopt a facile method to rationally design a neoteric Schottky catalyst in which uniform ultrafine ruthenium nanoparticles featuring lattice compressive stress are supported on nitrogen-modified carbon nanosheets (Ru NPs/NC) for efficient hydrogen evolution reaction (HER). Lattice strain and Schottky junction dual regulation ensures that the Ru NPs/NC catalyst with an appropriate nitrogen content displays superb H₂ evolution in alkaline media. Particularly, Ru NPs/NC-900 with 1.3% lattice compressive strain displays attractive activity and durability for the HER with a low overpotential of 19 mV at 10 mA cm^-2 in 1.0 M KOH electrolyte. The in situ X-ray absorption fine structure measurements indicate that the low-valence Ru nanoparticle with shrinking Ru-Ru bond acts as catalytic active site during the HER process. Furthermore, multiple spectroscopy analysis and density functional theory calculations demonstrate that the lattice strain and Schottky junction dual regulation tunes the electron density and hydrogen adsorption of the active center, thus enhancing the HER activity. This strategy provides a novel concept for the design of advanced electrocatalysts for H₂ production.