Surface-Engineered PtNi-O Nanostructure with Record-High Performance for Electrocatalytic Hydrogen Evolution Reaction

Composition-controlled synthesis of Pt-Pd-Cu ternary metal nanoparticles for an enhanced electrocatalytic hydrogen evolution reaction

Developing efficient and cost-effective electrocatalysts for the hydrogen evolution reaction (HER) is critical for advancing green hydrogen production. In this study, we synthesized Pt-Pd-Cu ternary nanoparticles (NPs) with tunable compositions via a one-pot solvothermal method, highlighting the pivotal role of Pd as an "electron bridge" to optimize electronic interactions and HER performance. By precisely tuning the precursor ratios of Pd and Cu, we achieved PtPdxCu1-x NPs with uniform size and tailored compositions, demonstrating exceptional control over alloy formation through a scalable synthesis approach. Regarding the HER, as the Cu content increases, an inverse-volcano-shaped overpotential at 10 mA cm-2 becomes evident. Specifically, PtPd0.8Cu0.2 exhibits optimal performance, with an overpotential of merely 31.0 mV. In addition, the decrease in Tafel slope from 169.6 mV dec-1 to 58.7 mV dec-1 indicates that the rate-determining step shifts from mass diffusion to electron transfer. Moreover, the impacts of composition and reaction time on the preparation were thoroughly investigated, and the unconventional process of reduction was put forward. Additionally, the method was extended to synthesize other ternary PtCu0.5M0.5 NPs. Among various elements, only tin, lead, and gold could completely replicate the synthesis process, and high-entropy alloys are successfully prepared based on these selected metals. This research provides valuable insights into the synthesis and properties of Pt-based NPs and their potential applications in the HER.

Coupling Amorphization and Compositional Optimization of Ternary Metal Phosphides toward High-Performance Electrocatalytic Hydrogen Production

Amorphous materials, with abundant active sites and unique electronic configurations, have the potential to outperform their crystalline counterparts in high-performance catalysis for clean energy. However, their synthesis and compositional optimization remain underexplored due to the strict conditions required for their formation. Here, we report the synthesis of ternary platinum-nickel-phosphorus (PtNiP) amorphous nanoparticles (ANPs) within milliseconds by flash Joule heating, which features ultrafast cooling that enables the vitrification of metal precursors. Through compositional optimization, the Gibbs free energy of hydrogen adsorption for Pt4Ni4P1 ANPs is optimized at 0.02 eV, an almost ideal value, even surpassing that of the benchmark metallic platinum catalyst. As a result, the PtNiP ANPs exhibited superior activity in electrocatalytic hydrogen evolution in acid electrolyte (η10 ∼ 14 mV, Tafel slope ∼ 18 mV dec-1, and mass activity 5× higher than state-of-the-art Pt/C). Life-cycle assessment and technoeconomic analysis suggest that, compared to existing processes, our approach enables notable reductions in greenhouse gas emission, energy consumption, and production cost for practical electrolyzer catalyst manufacturing.

Pt-Skin Coated PtNi Alloy in Carbon Nanoshells for Enhanced Hydrogen Evolution Activity and Durability

Hydrogen, as an environmentally sustainable energy carrier, offers substantial potential for addressing the global energy crisis. The development of highly efficient catalysts to accelerate the hydrogen evolution reaction (HER) is critical for the realization of electrochemical hydrogen production via water splitting. Herein, a novel heterogeneous catalyst consisting of PtNi nanoalloys with Pt-enriched surfaces is obtained, which are uniformly distributed within nitrogen-doped hollow carbon nanoshells derived from a complex of Ni-EDTA (ethylene diamine tetraacetate). Remarkably, the fabricated NE-PtNiNC catalyst demonstrates exceptional HER performance, exhibiting an ultra-low overpotential of 3 mV at 10 mA cm-2 and 6.8-fold higher mass activity compared to the commercial Pt/C catalyst, positioning it as one of the most advanced catalysts to date. Additionally, it shows outstanding stability over 200 h and exhibits promising potential for practical deployment in two-electrode water electrolysis systems. Theoretical analyses further reveal that the Pt-skin@PtNi structure, with its lowest d-band center, fosters a more pronounced overlap of the 5d electron cloud at the surface Pt sites. This interaction results in increased electron density on the Pt skin, facilitating water dissociation and significantly enhancing the intrinsic HER activity and durability.

Manipulating Interfacial Water Via Metallic Pt1Co6 Sites on Self-Adaptive Metal Phosphides to Enhance Water Electrolysis

Metallizing active sites to control the structural and kinetic dissociation of water at the catalyst-electrolyte interface, along with elucidating its mechanism under operating conditions, is a pivotal innovation for the hydrogen evolution reaction (HER). Here, a design of singly dispersed Pt-Co sites in a fully metallic state on nanoporous Co2P, tailored for HER, is introduced. An anion-exchange-membrane water electrolyzer equipped with this catalyst can achieve the industrial current densities of 1.0 and 2.0 A cm-2 at 1.71 and 1.85 V, respectively. It is revealed that the singly dispersed Pt-Co sites undergo self-adaptive distortion under operating conditions, which form a Pt1Co6 configuration with a strongly negative charge that optimizes reactant binding and reorganizes the interfacial water structure, resulting in an improved concentration of potassium (K+) ions in the closest ion plane. The K+ ions interact cooperatively with H2O (K·H2O), which strengthens the Pt-H binding interaction and facilitates the polarization of the H─OH bond, leading to improved HER activity. This study not only propels the advancement of cathodic catalysts for water electrolysis but also delineates a metallization strategy and an interface design principle, thereby enhancing electrocatalytic reaction rates.

Electron rearrangement at the crystalline-amorphous heterogeneous interface boosts alkaline hydrogen production

Modifying the platinum (Pt) local reaction microenvironment is a critical and complex challenge in enhancing electrochemical performance. Herein, amorphous Co(OH)2 and crystalline Pt (labeled as ac-Pt@Co(OH)2) featuring abundant crystalline-amorphous (c-a) interfaces are designed to boost the hydrogen evolution reaction (HER). The engineered structure creates an advantageous chemical environment at the local level, enhancing hydrogen adsorption efficiency and resulting in exceptional HER performance. The ac-Pt@Co(OH)2 achieves a low Tafel slope of 28.5 mV dec-1 and requires merely 95 mV overpotential to reach 200 mA cm-2 in alkaline electrolyte (1 M KOH), surpassing those of conventional Pt/C catalysts (39.4 mV dec-1, 256 mV). In situ advanced characterization investigations reveal dynamic electron rearrangement at the c-a interface, where Co species initially accept electrons from Pt to optimize the adsorption of *H species and then donate electrons to Pt for accelerating reduction kinetics. Theoretical calculations reveal that amorphous Co(OH)2 promotes the dissociation of water molecules to produce active *H, and electron rearrangement at the c-a interface downshifts the d-band center, thereby optimizing the *H adsorption strength and enhancing HER activity. The ac-Pt@Co(OH)2-based alkaline anion-exchange membrane water electrolyzer (AEMWE) maintains a current density of 500 mA cm-2 over 500 h.

Pt/α-MoC Catalyst Boosting pH-Universal Hydrogen Evolution Reaction at High Current Densities

Constructing subnanometric electrocatalysts is an efficient method to synergistically accelerate H2O dissociation and H+ reduction for pH-universal hydrogen evolution reaction (HER) for industrial water electrolysis to produce green hydrogen. Here, we construct a subnanometric Pt/α-MoC catalyst, where the α-MoC component can dissociate water effectively, with the rapid proton release kinetics of Pt species on Pt/α-MoC to obtain a good HER performance at high current densities in all-pH electrolytes. Quasi-in situ X-ray photoelectron spectroscopy analyses and density functional theory calculations confirm the highly efficient water dissociation capability of α-MoC and the thermodynamically favorable desorption process of hydrolytically dissociated protons on Pt sites at the high current density. Consequently, Pt/α-MoC requires only a low overpotential of 125 mV to achieve a current density of 1000 mA cm-2. Moreover, a Pt/α-MoC-based proton exchange membrane water electrolysis device exhibits a low cell voltage (1.65 V) and promising stability over 300 h with no performance degradation at an industrial-level current density of 1 A cm-2. Notably, even at a current of 100 A, the cell voltage remains low at 2.15 V, demonstrating Pt/α-MoC's promising potential as a scalable alternative for industrial hydrogen production. These findings elucidate the synergistic mechanism of α-MoC and atomically dispersed Pt in promoting efficient HER, offering valuable guidance for the design of electrocatalysts in high current density hydrogen.

Facilitating alkaline hydrogen evolution kinetics via interfacial modulation of hydrogen-bond networks by porous amine cages

The electrode-electrolyte interface is pivotal in the electrochemical kinetics. However, modulating the electrochemical interface at the atomic or molecular level is challenging due to the lack of efficient interfacial regulators. Here, we employ a porous amine cage as an interfacial modifier to Pt cluster in a confining configuration, largely enhancing alkaline HER kinetics by facilitating charge transfer. In situ electrochemical surface-enhanced Raman spectra, in combination with the ab initio molecular dynamics simulation, elucidates that the interaction between water and the -NH- moiety of cage frame softens the H-bonds net of interfacial water, making it more flexible for charge transfer. Moreover, our investigation pinpointed that the -NH- moiety acted as a pump for charge transfer by Grotthuss mechanism, lowering the kinetic barrier for hydrogen adsorption. Our findings highlight the strategy of establishing a soft-confining interfacial modifier by porous cage, offering opportunities to optimize electrochemical interfaces and promote reaction kinetics in a targeted way.

Ohmic Contact Heterostructures Immobilized Pt Single Atoms for Boosting Alkaline Hydrogen Evolution Reaction

Pt single-atoms catalysts have been widely confirmed as ideal electrocatalysts for high-efficiency hydrogen evolution reaction (HER), but their activity and durability at high current density remain great challenges, especially in alkaline media. Herein, a unique Ohmic contact heterostructure is fabricated by integrating Ni and NiO to immobilize Pt single-atoms (Ni-NiO-Pt) via Pt-O4 coordination for boosting the alkaline HER. Owing to transient high temperature and pressure in the laser ablation process, Ohmic contact heterojunctions are constructed at the interfaces between metal Ni core and nanoporous semiconducting NiO shell with adequate oxygen vacancies. The large work function difference triggers the electron transfer from Ni to Pt-decorated NiO, which dramatically eliminates the electron conduction impedance and regulates the charge redistribution. Density functional theory calculation unveils that the multiple regulations of energy barrier and charge redistribution on Ohmic contact endow Ni-NiO-Pt with outstanding electrical conductivity and favorable hydrogen binding energy. Consequently, Ni-NiO-Pt displays superior alkaline HER performances with an overpotential of 23.54 mV at 10 mA cm-2 and protruding durability for 75 h at 500 mA cm-2, drastically outperforming commercial Pt/C and most reported HER electrocatalysts. The immobilization of Pt single-atoms on Ohmic contact opens up an avenue toward the rational design of high-efficiency electrocatalysts.

Methanol-Enhanced Low-Cell-Voltage Hydrogen Generation at Industrial-Grade Current Density by Triadic Active Sites of Pt1-Pdn-(Ni,Co)(OH)x

Methanol (ME) is a liquid hydrogen carrier, ideal for on-site-on-demand H2 generation, avoiding its costly and risky distribution issues, but this "ME-to-H2" electric conversion suffers from high voltage (energy consumption) and competitive oxygen evolution reaction. Herein, we demonstrate that a synergistic cofunctional Pt1Pdn/(Ni,Co)(OH)x catalyst with Pt single atoms (Pt1) and Pd nanoclusters (Pdn) anchored on OH-vacancy(VOH)-rich (Ni,Co)(OH)x nanoparticles create synergistic triadic active sites, allowing for methanol-enhanced low-voltage H2 generation. For MOR, OH* is preferentially adsorbed on Pdn and then interacts with the intermediates (such as *CHO or *CHOOH) adsorbed favorably on neighboring Pt1 with the assistance of hydrogen bonding from the surface hydrogen of (Ni,Co)(OH)x. The enhanced selectivity of the *CHOOH pathway, instead of *CO, sustains the MOR activity to a practically high current density. For HER, triadic Pt1, Pdn, and OH-vacancy sites on (Ni,Co)(OH)x create an "acid-base" microenvironment to facilitate water adsorption and splitting, forming H* species on Pt1 and Pdn, and *OH at the vacancy, to promote efficient H2 evolution from the asymmetric Pt1 and Pdn sites via the Tafel mechanism. The triadic-site synergy opens new avenues for the design and synthesis of highly efficient and stable cofunctional catalysts for "on-site-on-demand" H2 production, here facilitated by liquid methanol.

Photoelectrochemical Ethylene Glycol Oxidization Coupled with Hydrogen Generation Using Metal Oxide Photoelectrodes

Photoelectrochemical (PEC) water splitting represents a promising approach for harnessing solar energy and transforming it into storable hydrogen. However, the complicated 4-electron transfer process of water oxidation reaction imposes kinetic limitations on the overall efficiency. Herein, we proposed a strategy by substituting water oxidation with the oxidation of ethylene glycol (EG), which is a hydrolysis byproduct of polyethylene terephthalate (PET) plastic waste. To achieve this, we developed and synthesized BiVO4/NiCo-LDH photoanodes capable of achieving a high Faradaic efficiency (FE) exceeding 85 % for the oxidation of EG to formate in a strongly alkaline environment. The reaction mechanism was further elucidated using in situ FTIR spectroscopy. Additionally, we successfully constructed an unassisted PEC device for EG oxidation and hydrogen generation by pairing the translucent Mo : BiVO4/NiCo-LDH photoanode with a state-of-the-art Cu2O photocathode, resulting in an approximate photocurrent density of 2.3 mA/cm2. Our research not only offers a PEC pathway for converting PET plastics into valuable chemicals but also enables simultaneous hydrogen production.

Facile Aqueous Route to Large-Scale Superhydrophilic TiO2-Incorporated Graphitic Carbon Nitride-Coated Ni(OH)2 and Ni2P Nano-Architecture Arrays as Efficient Electrocatalysts for Enhanced Hydrogen Production

Water splitting by an electrochemical method to generate hydrogen gas is an economic and green approach to resolve the looming energy and environmental crisis. Designing a composite electrocatalyst having integrated multichannel charge separation, robust stability, and low-cost facile scalability could be considered to address the issue of electrochemical hydrogen evolution. Herein, we report a superhydrophilic, noble-metal-free bimetallic nanostructure TiO2/Ni2P coated on graphitic polyacrylonitrile carbon fibers (g-C/TiO2/Ni2P) using a facile hydrothermal method followed by phosphorylation. In an aqueous-based route, PAN is dissolved in water in the presence of ZnCl2, followed by wet-spinning to prepare scalable PAN/ZnCl2 fibers. The nitrogen-contained porous graphitic carbon fibers are prepared via the pyrolysis of PAN/ZnCl2 fibers; now ZnCl2 acts as a volatile porogen to form porous matrix structures. Finally, the as-prepared graphitic carbon fibers are electrochemically activated by incorporating TiO2/Ni2P active sites. The materials formed in this work show excellent electrocatalytic activity for the hydrogen evolution reaction. The as-synthesized g-C/TiO2/Ni2P catalyst shows a low overpotential, its electrocatalytic activity is improved, and its efficiency is better than that of the commercial Pt/C catalyst. At a current density of -10 mA/cm2, the g-C/TiO2/Ni2P catalyst shows an overpotential of 55 mV, while the commercial Pt/C catalyst shows an overpotential of 77 mV. Our work provides a facile aqueous scalable route with no need for noble metals that can be considered as a potential alternative for the commercial Pt/C catalyst.

Soft nanoforest of metal single atoms for free diffusion catalysis

Metal single atoms are of increasing importance in catalytic reactions. However, the mass diffusion is yet substantially limited by the confined surface of the support in comparison to homogeneous catalysis. Here, we demonstrate that cylindrical micellar brushes with highly solvated poly(2-vinylpyridine) coronas can immobilize 33 types of metal single atoms with 8.3 to 40.9 weight % contents on conventional electrodes under ambient conditions. This is favored by the forest-like hierarchically open soft structure of the micellar brushes and the dynamic coordination between the metals and the pyridine groups. It was found that the nanoforests of individual noble metal single atoms can be well solvated in an aqueous electrolyte to comprehensively expose the atomic active sites and the nanoforest of Pt single atoms on nickel foam reveals high electrochemical performance for hydrogen evolution. The micellar brush support also enables the simultaneous anchoring of multiple single atoms on the cathode of an anion-exchange membrane electrolyzer for long-term stable water electrolysis.

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

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

In Situ Transformed CoOOH@Co3S4 Heterostructured Catalyst for Highly Efficient Catalytic OER Application

The deprived electrochemical kinetics of the oxygen evolution reaction (OER) catalyst is the prime bottleneck and remains the major obstacle in the water electrolysis processes. Herein, a facile hydrothermal technique was implemented to form a freestanding polyhedron-like Co3O4 on the microporous architecture of Ni foam, its reaction kinetics enhanced through sulfide counterpart transformation in the presence of Na2S, and their catalytic OER performances comparatively investigated in 1 M KOH medium. The formed Co3S4 catalyst shows outstanding catalytic OER activity at a current density of 100 mA cm-2 by achieving a relatively low overpotential of 292 mV compared to the pure Co3O4 catalyst and the commercial IrO2 catalyst. This enhancement results from the improved active centers and conductivity, which boost the intrinsic reaction kinetics. Further, the optimized Co3S4 catalyst exhibits admirable prolonged durability up to 72 h at varied current rates with insignificant selectivity decay. The energy dispersive X-ray spectroscopy (EDX) and Raman spectra measured after the prolonged OER stability test reveal a partial transformation of the active catalyst into an oxyhydroxide phase (i.e., CoOOH@Co3S4), which acts as an active catalyst phase during the electrolysis process.

Insights into the pH effect on hydrogen electrocatalysis

Hydrogen electrocatalytic reactions, including the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR), play a crucial role in a wide range of energy conversion and storage technologies. However, the HER and HOR display anomalous non-Nernstian pH dependent kinetics, showing two to three orders of magnitude sluggish kinetics in alkaline media compared to that in acidic media. Fundamental understanding of the origins of the intrinsic pH effect has attracted substantial interest from the electrocatalysis community. More critically, a fundamental molecular level understanding of this effect is still debatable, but is essential for developing active, stable, and affordable fuel cells and water electrolysis technologies. Against this backdrop, in this review, we provide a comprehensive overview of the intrinsic pH effect on hydrogen electrocatalysis, covering the experimental observations, underlying principles, and strategies for catalyst design. We discuss the strengths and shortcomings of various activity descriptors, including hydrogen binding energy (HBE) theory, bifunctional theory, potential of zero free charge (pzfc) theory, 2B theory and other theories, across different electrolytes and catalyst surfaces, and outline their interrelations where possible. Additionally, we highlight the design principles and research progress in improving the alkaline HER/HOR kinetics by catalyst design and electrolyte optimization employing the aforementioned theories. Finally, the remaining controversies about the pH effects on HER/HOR kinetics as well as the challenges and possible research directions in this field are also put forward. This review aims to provide researchers with a comprehensive understanding of the intrinsic pH effect and inspire the development of more cost-effective and durable alkaline water electrolyzers (AWEs) and anion exchange membrane fuel cells (AMFCs) for a sustainable energy future.

Hydrogen spillover inspired bifunctional Platinum/Rhodium Oxide-Nitrogen-Doped carbon composite for enhanced hydrogen evolution and oxidation reactions in base

The poor activity of Pt-based-catalysts for alkaline hydrogen oxidation/evolution reaction (HOR/HER) encourages scientific society to design an effective electrocatalyst to develop alkaline fuel cells/electrolyzers. Herein, platinum/rhodium oxide-nitrogen-doped carbon (Pt/Rh2O3-CNx) composite is prepared for alkaline HER and HOR inspired by hydrogen spillover. The HER performance of Pt/Rh2O3-CNx is ∼ 6 times higher than Pt/C. In HOR, Pt/Rh2O3-CNx possesses an exchange current density of 657.60 mA/mgmetal, which is ∼ 3.4 times higher than Pt/C. Hydrogen and hydroxyl binding energy (HBE and OHBE) contribute equally to alkaline HOR/HER. The experimental and theoretical evidence suggests that the enhanced HER and HOR activity of Pt/Rh2O3-CNx may be due to hydrogen spillover from Pt to Rh2O3. Small work function difference [0.08 eV] of the system suggested hydrogen-spillover is feasible, which has been justified by reaction-free energy calculations. We proposed that the dissociation of hydrogen (H2) and water (H2O) occurs at Pt to form Pt-adsorbed hydrogen species (Pt-Had). Then, some Had moves to Rh2O3 through hydrogen spillover and reacts with neighboring Had or adsorbed hydroxyl species (OHad) to form H2 or H2O, which enhances the HER and HOR activity, respectively. The role of water-metal-hydroxyl species in the electrical double layer was also demonstrated on alkaline HOR/HER. This work may help to design the hydrogen-spillover-based catalysts for several renewable energy technologies.

In Situ Engineering Multifunctional Active Sites of Ruthenium-Nickel Alloys for pH-Universal Ampere-Level Current-Density Hydrogen Evolution

Developing robust non-platinum electrocatalysts with multifunctional active sites for pH-universal hydrogen evolution reaction (HER) is crucial for scalable hydrogen production through electrochemical water splitting. Here ultra-small ruthenium-nickel alloy nanoparticles steadily anchored on reduced graphene oxide papers (Ru-Ni/rGOPs) as versatile electrocatalytic materials for acidic and alkaline HER are reported. These Ru-Ni alloy nanoparticles serve as pH self-adaptive electroactive species by making use of in situ surface reconstruction, where surface Ni atoms are hydroxylated to produce bifunctional active sites of Ru-Ni(OH)2 for alkaline HER, and selectively etched to form monometallic Ru active sites for acidic HER, respectively. Owing to the presence of Ru-Ni(OH)2 multi-site surface, which not only accelerates water dissociation to generate reactive hydrogen intermediates but also facilitates their recombination into hydrogen molecules, the self-supported Ru90Ni10/rGOP hybrid electrode only takes overpotential of as low as ≈106 mV to deliver current density of 1000 mA cm-2, and maintains exceptional stability for over 1000 h in 1 m KOH. While in 0.5 m H2SO4, the Ru90Ni10/rGOP hybrid electrode exhibits acidic HER catalytic behavior comparable to commercially available Pt/C catalyst due to the formation of monometallic Ru shell. These electrochemical behaviors outperform some of the best Ru-based catalysts and make it attractive alternative to Pt-based catalysts toward highly efficient HER.

Emerging Doped Metal-Organic Frameworks: Recent Progress in Synthesis, Applications, and First-Principles Calculations

Metal-organic frameworks (MOFs) are crystalline porous materials with a long-range ordered structure and excellent specific surface area and have found a wide range of applications in diverse fields, such as catalysis, energy storage, sensing, and biomedicine. However, their poor electrical conductivity and chemical stability, low capacity, and weak adhesion to substrates have greatly limited their performance. Doping has emerged as a unique strategy to mitigate the issues. In this review, the concept, classification, and characterization methods of doped MOFs are first introduced, and recent progress in the synthesis and applications of doped MOFs, as well as the rapid advancements and applications of first-principles calculations based on the density functional theory (DFT) in unraveling the mechanistic origin of the enhanced performance are summarized. Finally, a perspective is included to highlight the key challenges in doping MOF materials and an outlook is provided on future research directions.

Directional surface reconstruction of C and S Co-Doped Co2VO4/CoP for the cooperative enhancement of hydrogen production via seawater electrolysis

The endeavor to architect bifunctional electrocatalysts that exhibit both exceptional activity and durability heralds an era of boundless potential for the comprehensive electrolysis of seawater, an aspiration that, nevertheless, poses a substantial challenge. Within this work, we describe the precise engineering of a three-dimensional interconnected nanoparticle system named SCdoped Co2VO4/CoP (SCCo2VO4), achieved through a meticulously arranged hydrothermal treatment sequence followed by gas-phase carbonization and phosphorization. The resulting SCCo2VO4 electrode exhibits outstanding bifunctional electrocatalytic stability, attributed to the strategic anionic doping and abundant heterogeneous interfaces. Doping not only adjusts the electronic structure, enhancing electron transfer efficiency but also optimizes the surface-active sites. This electrode prodigiously necessitated an extraordinarily minimal overpotential of merely 92 and 350 mV to attain current densities of 10 and 50 mA cm-2 for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, in 1 M KOH solution. Noteworthily, when integrated into an electrolyzer for the exhaustive splitting of seawater, the SCP-Co2VO4 manifested an exceptionally low cell voltage of 2.08 V@50 mA cm-2 and showcased a durability that eclipses that of most hitherto documented nickel-based bifunctional materials. Further elucidation through Density Functional Theory (DFT) analyses underscored that anion doping and the inherent heterostructure adeptly optimize the Gibbs free energy of intermediates comprising hydrogen, chlorine, and oxygen (manifested as OH, O, OOH) within the HER and OER paradigms, thus propelling the electrochemical kinetics of seawater splitting to unprecedented velocities. These revelations unfurl a pioneering design philosophy for the creation of cost-effective yet superior catalysts aimed at the holistic division of water molecules, charting a course towards the realization of efficient and sustainable hydrogen production methodologies.

Interfacial Electronic Modulation of Mo5N6/Ni3S2 Heterojunction Array Boosts Electrocatalytic Alkaline Overall Water Splitting

Bifunctional electrocatalysts with excellent activity and durability are highly desirable for alkaline overall water splitting, yet remain a significant challenge. In this contribution, palm-like Mo5N6/Ni3S2 heterojunction arrays anchored in conductive Ni foam (denoted as Mo5N6-Ni3S2 HNPs/NF) are developed. Benefiting from the optimized electronic structure configuration, hierarchical branched structure and abundant heterogeneous interfaces, the as-synthesized Mo5N6-Ni3S2 HNPs/NF electrode exhibits remarkably stable bifunctional electrocatalytic activity in 1 m KOH solution. It only requires ultralow overpotentials of 59 and 190 mV to deliver a current density of 10 mA cm-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 m KOH solution, respectively. Importantly, the overall water splitting electrolyzer assembled by Mo5N6-Ni3S2 HNPs/NF exhibits an exceptionally low cell voltage (1.48 V@10 mA cm-2) and outstanding durability, surpassing most of the reported Ni-based bifunctional materials. Density functional theory (DFT) further confirms the heterostructure can optimize the Gibbs free energies of H and O-containing intermediates (OH, O, OOH) during HER and OER processes, thereby accelerating the catalytic kinetics of electrochemical water splitting. The findings provide a new design strategy toward low-cost and excellent catalysts for overall water splitting.

Ultrafine CoRu alloy nanoclusters densely anchored on Nitrogen-Doped graphene nanotubes for a highly efficient hydrogen evolution reaction

Designing highly efficient and stable electrocatalysts for hydrogen evolution reactions (HER) is essential to the production of green and renewable hydrogen. Metal-organic framework (MOF) precursor strategies are promising for the design of excellent electrocatalysts because of their porous architectures and adjustable compositions. In this study, a hydrogen-bonded organic framework (HOF) nanowire was developed as a precursor and template for the controllable and scalable synthesis of CoRu-MOF nanotubes. After calcination in Ar, the CoRu-MOF nanotubes were converted into N-doped graphene (NG) nanotubes with ultrafine CoRu nanoclusters (hereon called Co-xRu@NG-T; x  = 0, 5, 10, 15, 25 representing the Ru content of 0-0.25 mmol; T = 400 °C to 700 °C) that were densely encapsulated and isolated on the shell. Taking advantage of the synergistic effects of the porous, one-dimensional hollow structure and ultrafine CoRu nanoclusters, the optimized Co-15Ru@NG-500 catalyst demonstrated superior catalytic performance for HERs in alkaline electrolytes with an overpotential of only 30 mV at 10 mA cm-2 and robust durability for 2000 cycles, which outperforms many typical catalytic materials, such as commercial Pt/C. This work introduces a novel high-efficiency and cost-effective HER catalyst for application in commercial water-splitting electrolysis.

Unraveling and Resolving the Inconsistencies in Tafel Analysis for Hydrogen Evolution Reactions

The Tafel slope represents a critical kinetic parameter for mechanistic studies of electrochemical reactions, including the hydrogen evolution reaction (HER). Linear fitting of the polarization curve in a N2-saturated electrolyte is commonly used to determine Tafel slopes, which is, however, frequently plagued with inconsistencies. Our systematic studies reveal that the Tafel slopes derived from this approach are loading- and potential-dependent, and could substantially exceed the theoretical limits. Our analyses indicate that this discrepancy is largely attributed to the locally trapped HER-generated H2 in the catalyst layer. A non-negligible hydrogen oxidation reaction (HOR) current more prominently offsets the HER current at the smaller HER overpotential regime, resulting in an artificially smaller Tafel slope. On the other hand, at the higher overpotential where the HOR current becomes negligible, the locally trapped H2 substantially suppresses further HER current growth, leading to an artificially larger Tafel slope. The Butler-Volmer method accounts for both the HER and HOR currents in the fitting, which offers a more reliable method for pure Pt catalysts but is less applicable to transition-metal decorated Pt surfaces with distinct HER/HOR kinetics. Our studies underscore the challenges in Tafel slope analysis and the need for strict controls for reliable comparisons among different catalyst systems.

Hybrid Acid/Base Electrolytic Cell for Hydrogen Generation and Methanol Conversion Implemented by Bifunctional Ni/MoN Nanorod Electrocatalyst

Combining the methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER) within an integrated electrolytic system may offer the advantages of enhanced kinetics of the anode, reduced energy consumption, and the production of high-purity hydrogen. Herein, it is reported the construction of Ni─MoN nanorod arrays supported on a nickel foam substrate (Ni─MoN/NF) as a bifunctional electrocatalyst for electrocatalytic hydrogen production and selective methanol oxidation to formate. Remarkably, The optimal Ni─MoN/NF catalyst displays exceptional HER performance with an overpotential of only 49 mV to attain 10 mA cm-2 in acid, and exhibits a high activity for MOR to achieve 100 mA cm-2 at 1.48 V in alkali. A hybrid acid/base electrolytic cell with Ni─MoN/NF electrode as anode and cathode is further developed for an integrated HER-MOR cell, which only requires a voltage of 0.56 V at 10 mA cm-2 , significantly lower than that of the HER-OER system (0.70 V). The density functional theory studies reveal that the incorporation of Ni effectively modulates the electronic structure of MoN, thereby resulting in enhanced catalytic activity. The unique combination of high electrocatalytic activity and excellent stability make the Ni─MoN/NF catalyst a promising candidate for practical applications in electrocatalytic hydrogen production and methanol oxidation.

Strategically Designed Pd-Induced Changes in Alkaline Hydrogen Evolution Reaction and Oxygen Evolution Reaction Performances of Electrochemical Water Oxidation by the Galvanically Synthesized MoO2/MoO3 Composite Thin Film

Electrochemical water oxidation is believed to be an effective pathway to produce clean, carbon-free, and environmentally sustainable green energy. In this work, we report a simple, easy-to-construct, facile, low-cost, and single-step galvanic technique to synthesize a Pd-supported temperature-assisted MoOx thin film nanocomposite for effective water oxidation. The most suitable nanocomposite exhibits very low overpotential at 10 mA/cm2 with smaller Tafel slope values for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) processes in an alkaline medium. The formation of a metal oxide-metal junction accelerates the growth of more active sites, promoting induced electronic synergism at the MoOx-Pd interface. This endows higher electrical conductivity and faster electron transfer kinetics, thus accelerating the faster water dissociation reaction following the Tafel-Volmer mechanism to boost the HER process in an alkaline medium. The excellent electrochemical HER and OER performances of our electrocatalyst even supersede the accomplishments of the benchmark catalysts Pt/C and RuO2. Moreover, neither of these two catalysts demonstrates both catalytic reactions, i.e., HER and OER at the same time, which have been observed for our synthesized catalyst. Our findings illustrate the potential of a thin-film MoOx-Pd nanocomposite to be an exceedingly effective electrocatalyst developed by interface engineering strategies. This also provides insight into designing several other semiconductor composite catalysts using simple synthesis techniques for highly efficient HER/OER processes that could be alternatives to benchmark electrocatalysts for water electrolysis.

Metal Alloys-Structured Electrocatalysts: Metal-Metal Interactions, Coordination Microenvironments, and Structural Property-Reactivity Relationships

Metal alloys-structured electrocatalysts (MAECs) have made essential contributions to accelerating the practical applications of electrocatalytic devices in renewable energy systems. However, due to the complex atomic structures, varied electronic states, and abundant supports, precisely decoding the metal-metal interactions and structure-activity relationships of MAECs still confronts great challenges, which is critical to direct the future engineering and optimization of MAECs. Here, this timely review comprehensively summarizes the latest advances in creating the MAECs, including the metal-metal interactions, coordination microenvironments, and structure-activity relationships. First, the fundamental classification, design, characterization, and structural reconstruction of MAECs are outlined. Then, the electrocatalytic merits and modulation strategies of recent breakthroughs for noble and non-noble metal-structured MAECs are thoroughly discussed, such as solid solution alloys, intermetallic alloys, and single-atom alloys. Particularly, unique insights into the bond interactions, theoretical understanding, and operando techniques for mechanism disclosure are given. Thereafter, the current states of diverse MAECs with a unique focus on structural property-reactivity relationships, reaction pathways, and performance comparisons are discussed. Finally, the future challenges and perspectives for MAECs are systematically discussed. It is believed that this comprehensive review can offer a substantial impact on stimulating the widespread utilization of metal alloys-structured materials in electrocatalysis.

Hydrogen-bonded linear chain assemblies of palladium(II)-selenoether complexes: solid state aggregates as templates for nano-structural Pd17Se15 leading to efficient electrocatalytic activity

A analogous series of 2-(3,5-dimethylpyrazol-1-yl)phenyl substituted selenoether complexes of palladium [PdCl2(RSeC6H4dmpz)]; (R = CH2COOH (1), CH2CH2COOH (2), and CH2CH2OH (3); dmpz = dimethylpyrazole) were ably synthesized in a facile manner and exhaustively characterized. Insight into molecular structures of these complexes was keenly probed through single crystal X-ray diffraction (XRD) analysis, unfolding the structural scaffolds and laying into molecular aggregation, availed through hydrogen bonding interactions borne out of tethered protic groups. The complexes were converted to capping free palladium selenide (Pd17Se15) nanoparticles through pyrolysis and evaluated for their electrocatalytic efficacy towards the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in alkaline medium. In an alkaline medium, PSNP1 (Pd17Se15) obtained from the hydrogen bonded aggregate of complex PdCl2L1 (1) produced good HER activity. PSNP1 had a little decrease in current density after 300 continuous cycles, which proves that the catalyst presents high stability in the recycling process. For the electrocatalytic oxidation of CH3OH, the electrocatalytic rate constant (k) obtained was 0.3 × 103 cm3 mol-1 s-1.

Intermetallic Nanocrystals for Fuel-Cells-Based Electrocatalysis

Electrocatalysis underpins the renewable electrochemical conversions for sustainability, which further replies on metallic nanocrystals as vital electrocatalysts. Intermetallic nanocrystals have been known to show distinct properties compared to their disordered counterparts, and been long explored for functional improvements. Tremendous progresses have been made in the past few years, with notable trend of more precise engineering down to an atomic level and the investigation transferring into more practical membrane electrode assembly (MEA), which motivates this timely review. After addressing the basic thermodynamic and kinetic fundamentals, we discuss classic and latest synthetic strategies that enable not only the formation of intermetallic phase but also the rational control of other catalysis-determinant structural parameters, such as size and morphology. We also demonstrate the emerging intermetallic nanomaterials for potentially further advancement in energy electrocatalysis. Then, we discuss the state-of-the-art characterizations and representative intermetallic electrocatalysts with emphasis on oxygen reduction reaction evaluated in a MEA setup. We summarize this review by laying out existing challenges and offering perspective on future research directions toward practicing intermetallic electrocatalysts for energy conversions.

CO2 reduction reaction on Sc-doped nanocages as catalysts

CONTEXT

The catalytic ability of Sc-doped C46 and Sc-doped Al23P23 as catalysts of CO2-RR to create the CH4 and CH3OH is investigated. The mechanisms of CO2-RR are examined by theoretical methods and ΔGreaction of reaction steps of CO2-RR mechanisms are calculated. The overpotential of CH4 and CH3OH production on Sc-doped C46 and Sc-doped Al23P23 is calculated. The Sc atoms of Sc-doped C46 and Sc-doped Al23P23 can adsorb the CO2 molecule as the first step of CO2-RR. The CH4 is produced from hydrogenation of *CH3O and the *CO → *CHO reaction step is the rate limiting step for CH4 production. The CH3OH can be formed on Sc-doped C46 and Sc-doped Al23P23 by *CO → *CHO → *CH2O → *CH3O → CH3OH mechanism and HCOOH → *CHO → *CH2O → *CH3O → CH3OH mechanism. The Sc-C46 and Sc-Al23P23 can catalyze the CO2-RR to produce the CH4 and CH3OH by acceptable mechanisms.

METHODS

Here, the structures are optimized by PW91PW91/6-311+G (2d, 2p) and M06-2X/cc-pVQZ methods in GAMESS software. The frequencies of nanocages and their complexes with species of CO2-RR are investigated by mentioned methods. The transition state of each reaction step of CO2-RR is searched by Berny method to find the CO2-RR intermediates. The ∆Eadsorption of intermediates of CO2-RR on surfaces of nanocages is calculated and the ∆Greaction of reaction steps of CO2-RR is calculated.

Optimizing Pt-Based Alloy Electrocatalysts for Improved Hydrogen Evolution Performance in Alkaline Electrolytes: A Comprehensive Review

The splitting of water through electrocatalysis offers a sustainable method for the production of hydrogen. In alkaline electrolytes, the lack of protons forces water dissociation to occur before the hydrogen evolution reaction (HER). While pure Pt is the gold standard electrocatalyst in acidic electrolytes, since the 5d orbital in Pt is nearly fully occupied, when it overlaps with the molecular orbital of water, it generates a Pauli repulsion. As a result, the formation of a Pt-H* bond in an alkaline environment is difficult, which slows the HER and negates the benefits of using a pure Pt catalyst. To overcome this limitation, Pt can be alloyed with transition metals, such as Fe, Co, and Ni. This approach has the potential not only to enhance the performance but also to increase the Pt dispersion and decrease its usage, thus overall improving the catalyst's cost-effectiveness. The excellent water adsorption and dissociation ability of transition metals contributes to the generation of a proton-rich local environment near the Pt-based alloy that promotes HER. Significant progress has been achieved in comprehending the alkaline HER mechanism through the manipulation of the structure and composition of electrocatalysts based on the Pt alloy. The objective of this review is to analyze and condense the latest developments in the production of Pt-based alloy electrocatalysts for alkaline HER. It focuses on the modified performance of Pt-based alloys and clarifies the design principles and catalytic mechanism of the catalysts from both an experimental and theoretical perspective. This review also highlights some of the difficulties encountered during the HER and the opportunities for increasing the HER performance. Finally, guidance for the development of more efficient Pt-based alloy electrocatalysts is provided.

Synergetic Effect and Phase Engineering by Formation of Ti3C2Tx Modified 2H/1T-MoSe2 Composites for Enhanced HER

The typical semi conductivity and few active sites of hydrogen evolution of 2H MoSe2 severely restrict its electrocatalytic hydrogen evolution performance. At the same time, the 1T MoSe2 has metal conductivity and plentiful hydrogen evolution sites, making it feasible to optimize the electrocatalytic hydrogen evolution behavior of MoSe2 using phase engineering. In this study, we, through a simple one-step hydrothermal method, composed 1T/2H MoSe2, and then used newly emerging transition metal carbides with several atomic-layer thicknesses Ti3C2Tx to improve the conductivity of a MoSe2-based electrocatalyst. Finally, MoSe2@Ti3C2Tx was successfully synthesized, according to the control of the additional amount of Ti3C2Tx, to form a proper MoSe2/ Ti3C2Tx heterostructure with a better electrochemical HER performance. As obtained MoSe2@4 mg-Ti3C2Tx achieved a low overpotential, a small Tafel slope and this work offers additional insight into broadened MoSe2 and MXenes-based catalyst's electrochemical application.

Bimetallic RuNi Electrocatalyst Coated MWCNTs Cathode for an Efficient and Stable Li-CO2 and Li-CO2 Mars Batteries Performance with Low Overpotential

Rechargeable lithium-CO2 (Li-CO2 ) batteries are an attractive energy storage technology that can reduce fossil fuel usage and limit the adverse environmental impact of CO2 emissions. However, the high charge overpotential, unstable cycling, and incomplete understanding of the electrochemical process limit its advancement for practical applications. Herein, we develop a Li-CO2 battery by designing a bimetallic ruthenium-nickel catalyst onto multi-walled carbon nanotubes (RuNi/MWCNTs) catalyst as cathode by solvothermal method, which exhibits a lower overpotential of 1.15 V and a discharge capacity of 15,165 mAh g-1 with outstanding coulombic efficiency of 97.4 %. The battery can also operate at high rates and have a stable cycle of more than 80 cycles at a current density of 200 mA g-1 with a fixed 500 mAh g-1 capacity. Furthermore, Mars exploration is made feasible with the Li-CO2 Mars battery composed of the RuNi/MWCNTs as cathode catalyst, which performs very similarly to that of pure CO2 atmosphere. This approach may simplify the process of developing high-performance Li-CO2 batteries to achieve carbon negativity on Earth and for future interplanetary Mars missions.

Hydrogen Evolution Reaction on Single-Atom Pt Doped in Ni Matrix under Strong Alkaline Condition

Pt catalyst has been considered as the state-of-the-art catalyst for hydrogen evolution reaction (HER) under acid condition. However, its catalytic kinetics under alkaline conditions is not well-understood. Herein, we report a Ni-Pt(SAs) (SAs = single atoms) catalyst with Pt atomically dispersed in a Ni matrix, and it possesses an impressive HER performance with an overpotential as low as 210 mV at 500 mA cm-2 in strong alkaline electrolyte (7 M KOH), which is much higher than Pt nanoparticle-modified Ni catalyst (Ni-Pt(NPs)). Kinetics analysis reveals that Pt doping in the Ni matrix can accelerate the Volmer step on the Ni-Pt surface. Moreover, Ni-Pt(SAs) displays a more favorable kinetics for H2 formation reaction at high current density than Ni-Pt(NPs). Theoretical calculations reveal that atomically dispersed Pt weakens the adsorption of both H and OH on the surface of Ni-Pt electrode and promotes H2 formation from surface H on Ni-Pt(SAs).

Highly Dispersed Ni-Pt Bimetallic Cocatalyst: The Synergetic Effect Yields Pt-Like Activity in Photocatalytic Hydrogen Evolution

Achieving high photocatalytic activity with the lowest possible platinum (Pt) consumption is crucial for reducing the cost of Pt-based cocatalysts and enabling large-scale applications. Bimetallic Ni-Pt cocatalysts exhibit excellent photocatalytic performance and are considered one of the most promising photocatalysts capable of replacing pure Pt for hydrogen evolution reaction (HER). However, the synergistic photocatalytic mechanism between bimetallic Ni-Pt cocatalysts needs to be further investigated. Herein, we deposit highly dispersed Ni-Pt bimetallic cocatalysts on the surface of TiO2 by radiolytic reduction. We study the dynamics of photogenerated charge carriers of the Ni-Pt-comodified TiO2 and propose their underlying electron transfer mechanisms, in which Pt acts as an electron trap, whereas Ni serves as an electron supplier. The synergistic effect is Ni/Pt ratio-dependent and can confer bimetallic Ni-Pt to pure Pt-like photocatalytic activity in HER. The Ni2-Pt1-comodified TiO2 is optimized to be the most cost-effective photocatalyst with robust stability, which exhibits about 40-fold higher performance than bare TiO2.

Strain and Surface Engineering of Multicomponent Metallic Nanomaterials with Unconventional Phases

Multicomponent metallic nanomaterials with unconventional phases show great prospects in electrochemical energy storage and conversion, owing to unique crystal structures and abundant structural effects. In this review, we emphasize the progress in the strain and surface engineering of these novel nanomaterials. We start with a brief introduction of the structural configurations of these materials, based on the interaction types between the components. Next, the fundamentals of strain, strain effect in relevant metallic nanomaterials with unconventional phases, and their formation mechanisms are discussed. Then the progress in surface engineering of these multicomponent metallic nanomaterials is demonstrated from the aspects of morphology control, crystallinity control, surface modification, and surface reconstruction. Moreover, the applications of the strain- and surface-engineered unconventional nanomaterials mainly in electrocatalysis are also introduced, where in addition to the catalytic performance, the structure-performance correlations are highlighted. Finally, the challenges and opportunities in this promising field are prospected.

Amorphous nickel hydroxide shell tailors local chemical environment on platinum surface for alkaline hydrogen evolution reaction

In analogy to natural enzymes, an elaborated design of catalytic systems with a specifically tailored local chemical environment could substantially improve reaction kinetics, effectively combat catalyst poisoning effect and boost catalyst lifetime under unfavourable reaction conditions. Here we report a unique design of 'Ni(OH)2-clothed Pt-tetrapods' with an amorphous Ni(OH)2 shell as a water dissociation catalyst and a proton conductive encapsulation layer to isolate the Pt core from bulk alkaline electrolyte while ensuring efficient proton supply to the active Pt sites. This design creates a favourable local chemical environment to result in acidic-like hydrogen evolution reaction kinetics with a lowest Tafel slope of 27 mV per decade and a record-high specific activity and mass activity in alkaline electrolyte. The proton conductive Ni(OH)2 shell can also effectively reject impurity ions and retard the Oswald ripening, endowing a high tolerance to solution impurities and exceptional long-term durability that is difficult to achieve in the naked Pt catalysts. The markedly improved hydrogen evolution reaction activity and durability in an alkaline medium promise an attractive catalyst material for alkaline water electrolysers and renewable chemical fuel generation.

Electronic Structure Engineering of Pt Species over Pt/WO3 toward Highly Efficient Electrocatalytic Hydrogen Evolution

Pt-based supported materials, a widely used electrocatalyst for hydrogen evolution reaction (HER), often experience unavoidable electron loss, resulting in a mismatching of electronic structure and HER behavior. Here, a Pt/WO3 catalyst consisting of Pt species strongly coupled with defective WO3 polycrystalline nanorods is rationally designed. The electronic structure engineering of Pt sites on WO3 can be systematically regulated, and so that the optimal electron-rich Pt sites on Pt/WO3 -600 present an excellent HER activity with only 8 mV overpotential at 10 mA cm-2 . Particularly, the mass activity reaches 7015 mA mg-1 at the overpotential of 50 mV, up to 26-fold higher than that of the commercial Pt/C. The combination of experimental and theoretical results demonstrates that the O vacancies of WO3 effectively mitigate the tendency of electron transfer from Pt sites to WO3 , so that the d-band center could reach an appropriate level relative to Fermi level, endowing it with a suitableΔ G H ∗ $\Delta {G_{{{\rm{H}}^ * }}}$ . This work identifies the influence of the electronic structure on catalytic activity.

Harmonious Heterointerfaces Formed on 2D-Pt Nanodendrites by Facet-Respective Stepwise Metal Deposition for Enhanced Hydrogen Evolution Reaction

The performance of nanocrystal (NC) catalysts could be maximized by introducing rationally designed heterointerfaces formed by the facet- and spatio-specific modification with other materials of desired size and thickness. However, such heterointerfaces are limited in scope and synthetically challenging. Herein, we applied a wet chemistry method to tunably deposit Pd and Ni on the available surfaces of porous 2D-Pt nanodendrites (NDs). Using 2D silica nanoreactors to house the 2D-PtND, an 0.5-nm-thick epitaxial Pd or Ni layer (e-Pd or e-Ni) was exclusively formed on the flat {110} surface of 2D-Pt, while a non-epitaxial Pd or Ni layer (n-Pd or n-Ni) was typically deposited at the {111/100} edge in absence of nanoreactor. Notably, these differently located Pd/Pt and Ni/Pt heterointerfaces experienced distinct electronic effect to influence unequally in electrocatalytic synergy for hydrogen evolution reaction (HER). For instance, an enhanced H2 generation on the Pt{110} facet with 2D-2D interfaced e-Pd deposition and faster water dissociation on the edge-located n-Ni overpowered their facet-located counterparts in respective HER catalysis. Therefore, a feasible assembling of the valuable heterointerfaces in the optimal 2D n-Ni/e-Pd/Pt catalyst overcame the sluggish alkaline HER kinetics, with a catalytic activity 7.9 times higher than that of commercial Pt/C.

Artificial Photosynthesis: Current Advancements and Future Prospects

Artificial photosynthesis is a technology with immense potential that aims to emulate the natural photosynthetic process. The process of natural photosynthesis involves the conversion of solar energy into chemical energy, which is stored in organic compounds. Catalysis is an essential aspect of artificial photosynthesis, as it facilitates the reactions that convert solar energy into chemical energy. In this review, we aim to provide an extensive overview of recent developments in the field of artificial photosynthesis by catalysis. We will discuss the various catalyst types used in artificial photosynthesis, including homogeneous catalysts, heterogeneous catalysts, and biocatalysts. Additionally, we will explore the different strategies employed to enhance the efficiency and selectivity of catalytic reactions, such as the utilization of nanomaterials, photoelectrochemical cells, and molecular engineering. Lastly, we will examine the challenges and opportunities of this technology as well as its potential applications in areas such as renewable energy, carbon capture and utilization, and sustainable agriculture. This review aims to provide a comprehensive and critical analysis of state-of-the-art methods in artificial photosynthesis by catalysis, as well as to identify key research directions for future advancements in this field.

Modulate the metallic Sb state on ultrathin PdSb-based nanosheets for efficient formic acid electrooxidation

Incorporation of oxophilic metals into Pd-based nanostructures has shown great potential in small molecule electrooxidation owing to their superior anti-poisoning capability. However, engineering the electronic structure of oxophilic dopants in Pd-based catalysts remains challenging and their impact on electrooxidation reactions is rarely demonstrated. Herein, we have developed a method for synthesizing PdSb-based nanosheets, enabling the incorporation of the Sb element in a predominantly metallic state despite its high oxophilic nature. Moreover, the Pd₉₀Sb₇W₃ nanosheet serves as an efficient electrocatalyst for the formic acid oxidation reaction (FAOR), and the underlying promotion mechanism is investigated. Among the as-prepared PdSb-based nanosheets, the Pd₉₀Sb₇W₃ nanosheet exhibits a remarkable 69.03% metallic state of Sb, surpassing the values observed for the Pd₈₆Sb₁₂W₂ (33.01%) and Pd₈₃Sb₁₄W₃ (25.41%) nanosheets. X-ray photoelectron spectroscopy (XPS) and CO stripping experiments confirm that the Sb metallic state contributes the synergistic effect of their electronic and oxophilic effect, thus leading to an effective electrooxidation removal of CO and significantly enhanced FAOR electrocatalytic activity (1.47 A mg^-1; 2.32 mA cm^-1) compared with the oxidated state of Sb. This work highlights the importance of modulating the chemical valence state of oxophilic metals to enhance electrocatalytic performance, offering valuable insights for the design of high-performance electrocatalysts for electrooxidation of small molecules.

Nanocomposite Electrocatalysts for Hydrogen Evolution Reactions (HERs) for Sustainable and Efficient Hydrogen Energy-Future Prospects

Hydrogen is considered a good clean and renewable energy substitute for fossil fuels. The major obstacle facing hydrogen energy is its efficacy in meeting its commercial-scale demand. One of the most promising pathways for efficient hydrogen production is through water-splitting electrolysis. This requires the development of active, stable, and low-cost catalysts or electrocatalysts to achieve optimized electrocatalytic hydrogen production from water splitting. The objective of this review is to survey the activity, stability, and efficiency of various electrocatalysts involved in water splitting. The status quo of noble-metal- and non-noble-metal-based nano-electrocatalysts has been specifically discussed. Various composites and nanocomposite electrocatalysts that have significantly impacted electrocatalytic HERs have been discussed. New strategies and insights in exploring nanocomposite-based electrocatalysts and utilizing other new age nanomaterial options that will profoundly enhance the electrocatalytic activity and stability of HERs have been highlighted. Recommendations on future directions and deliberations for extrapolating information have been projected.

Size-Dependent Geometrical Structures of Platinum Oxide Cluster Cations Studied by Ion Mobility-Mass Spectrometry

Structures of platinum oxide cluster cations (Pt_nO_m⁺) were studied by ion mobility-mass spectrometry in combination with theoretical calculations. Structures of oxygen-equivalent Pt_nO_n⁺ (n = 3-7) clusters were discussed from the comparison between their collision cross sections (CCSs) obtained by mobility measurement and simulated CCSs of their structural candidates from structural optimization calculations. Assigned structures of Pt_nO_n⁺ were found to be composed of Pt frameworks and bridging O atoms, which follows the previous theoretical prediction on the neutral clusters. The structures change from planar (n = 3 and 4) to three-dimensional (n = 5-7) with increasing cluster size by deforming platinum frameworks. Comparison with other group-10 metal oxide cluster cations (M_nO_n⁺; M = Ni and Pd) showed that the Pt_nO_n⁺ structures have a similar tendency to Pd_nO_n⁺ rather than Ni_nO_n⁺.

Coherent hexagonal platinum skin on nickel nanocrystals for enhanced hydrogen evolution activity

Metastable noble metal nanocrystals may exhibit distinctive catalytic properties to address the sluggish kinetics of many important processes, including the hydrogen evolution reaction under alkaline conditions for water-electrolysis hydrogen production. However, the exploration of metastable noble metal nanocrystals is still in its infancy and suffers from a lack of sufficient synthesis and electronic engineering strategies to fully stimulate their potential in catalysis. In this paper, we report a synthesis of metastable hexagonal Pt nanostructures by coherent growth on 3d transition metal nanocrystals such as Ni without involving galvanic replacement reaction, which expands the frontier of the phase-replication synthesis. Unlike noble metal substrates, the 3d transition metal substrate owns more crystal phases and lower cost and endows the hexagonal Pt skin with substantial compressive strains and programmable charge density, making the electronic properties particularly preferred for the alkaline hydrogen evolution reaction. The energy barriers are greatly reduced, pushing the activity to 133 mA cmgeo-2 and 17.4 mA μgPt-1 at -70 mV with 1.5 µg of Pt in 1 M KOH. Our strategy paves the way for metastable noble metal catalysts with tailored electronic properties for highly efficient and cost-effective energy conversion.

Strain engineering of high-entropy alloy catalysts for electrocatalytic water splitting

Developing active and cost-effective bifunctional electrocatalysts for overall water splitting is challenging but mandatory for renewable energy technologies. We report a high-entropy alloy (HEA) of PtIrCuNiCr as a bifunctional electrocatalyst for overall water splitting, which shows a low overpotential of ca. 190 mV at the current density of 10 mA cm^-2. Compared with pure metals, HEAs exhibit remarkable surface strain due to severe lattice distortion in their crystal structures. Theoretical calculations reveal that the strain can regulate the binding energy of intermediates on catalysts by adjusting the metal-metal bonding energy. It pushes the HEA toward the top of volcano plots to achieve superior electrocatalytic activity for both hydrogen and oxygen evolution reactions. The strain effect of HEAs on electrocatalysis can be well engineered by tuning the catalyst radius or configurational entropy. This work renders a systematic strain regulation strategy for designing a high-performance HEA catalyst for overall water splitting.

Alloying Pt into Ni partially amorphous for promoted alkaline hydrogen production

Aiming at the sluggish water dissociation step in alkaline hydrogen evolution reaction (HER), the platinum-nickel alloy material (PtNi₁₀/C) featuring unique crystalline/amorphous structure supported on carbon black is deliberately designed and fabricated via a reversely rapid co-precipitation and mild thermal reduction strategy. Electrochemical results show that only 66 mV of overpotential is needed for PtNi₁₀/C to drive a current density of 10 mA cm^-2 at a lower platinum loading (8.3 μg_Pt cm-2 geo), which is much lower than that of other catalysts with a single metal source(S-Ni/C and S-Pt/C) and even the commercial Pt/C catalyst (20 wt%). The target catalyst also exhibits smaller tafel slope value (16.73 mV dec^-1) and electrochemical impedance value, enabling a fast kinetics rate for water dissociation. Partial crystallization facilitates moderate adsorption of intermediates, while the high-valence Ni(II) and Pt(II) species serve as pivotal driving force for the kinetic dissociation of water. The unique microstructure of PtNi₁₀/C shows a remarkable advantage toward HER in alkaline but acidic medium. In addition, other transition metal-based catalysts following the similar protocol are also fabricated and present varying degrees of HER performance. Hence, the facile and rapid co-precipitation/thermal reduction strategy proposed in this study provides some guidelines for designing high-efficiency alkaline HER catalysts.

Interfacial Engineering of Polycrystalline Pt5 P2 Nanocrystals and Amorphous Nickel Phosphate Nanorods for Electrocatalytic Alkaline Hydrogen Evolution

Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is important for hydrogen economy but suffers from sluggish reaction kinetics due to a large water dissociation energy barrier. Herein, Pt₅ P₂ nanocrystals anchoring on amorphous nickel phosphate nanorods as a high-performance interfacial electrocatalyst system (Pt₅ P₂ NCs/a-NiPi) for the alkaline HER are demonstrated. At the unique polycrystalline/amorphous interface with abundant defects, strong electronic interaction, and optimized intermediate adsorption strength, water dissociation is accelerated over abundant oxophilic Ni sites of amorphous NiPi, while hydride coupling is promoted on the adjacent electron-rich Pt sites of Pt₅ P₂ . Meanwhile, the ultra-small-sized Pt₅ P₂ nanocrystals and amorphous NiPi nanorods maximize the density of interfacial active sites for the Volmer-Tafel reaction. Pt₅ P₂ NCs/a-NiPi exhibits small overpotentials of merely 9 and 41 mV at -10 and -100 mA cm^-2 in 1 M KOH, respectively. Notably, Pt₅ P₂ NCs/a-NiPi exhibits an unprecedentedly high mass activity (MA) of 14.9 mA µg_Pt ^-1 at an overpotential of 70 mV, which is 80 times higher than that of Pt/C and represents the highest MA of reported Pt-based electrocatalysts for the alkaline HER. This work demonstrates a phosphorization and interfacing strategy for promoting Pt utilization and in-depth mechanistic insights for the alkaline HER.

P-induced bottom-up growth of Fe-doped Ni12P5 nanorod arrays for urea oxidation reaction

Synthesis of regular morphology catalysts with self-growing substrates is one of the effective methods to solve the problem of easy shedding of heterogeneous catalysts. In this study, Fe-doped Ni₁₂P₅ nanorods were prepared by depositing 1,1' -bis (diphenylphosphine) ferrocene (DPPF) on N-doped C/NF. The bottom-up growth of the nanorod is ascribed to the preferential adsorption of DPPF with a P site to NF that is surface-doped with the solid-solving C, and the length of nanorods can reach tens of microns and has good robustness. The N-doped carbon-constrained rod-shaped Fe-doped Ni₁₂P₅ catalyst (Fe-Ni₁₂P₅/N_dC/NF-800) that grows on NF has excellent catalytic performance for the urea oxidation reaction. In addition, the current density can be maintained as high as 100 mA cm^-2 and the current attenuation is weak for 12 h, and the rod shape remains good. This work provides a new idea for synthesizing self-growing catalysts with regular morphology to improve the performance of heterogeneous catalysts.

Facile synthesis of defect-rich RuCu nanoflowers for efficient hydrogen evolution reaction in alkaline media

Developing high-performance electrocatalysts toward hydrogen evolution reaction (HER) in alkaline media is highly desirable for industrial applications in the field of water splitting but is still challenging. Herein, we successfully synthesized RuCu nanoflowers (NFs) with tunable atomic ratios using a facile wet chemistry method. The Ru₃Cu NFs need only 55 mV to achieve a current density of 10 mA cm^-2, which shows ideal durability with only 4 mV decay after 2000 cycles, largely outperforming the catalytic properties of commercial Pt/C. The Ru₃Cu NFs comprise many nanosheets that can provide more active sites for HER. In addition, the introduction of Cu can modulate the electronic structure of Ru, facilitate water dissociation, and optimize H adsorption/desorption ability. Thus, the flower-like structure together with the proper incorporation of Cu boosts HER performance.

Enhancing Resistance to Chloride Corrosion by Controlling the Morphologies of PtNi Electrocatalysts for Alkaline Seawater Hydrogen Evolution

A solvothermal method to prepare PtNi alloys that have differing morphologies is described. By adjusting the feed ratio of Pt and Ni precursors in this process, PtNi alloys with different compositions (Pt : Ni atomic ratio from 1 : 3 to 3 : 1) and morphologies (evolution from nanobranches to nanoparticles) are generated. The prepared Pt₄₈ Ni₅₂ alloy, which has a composite morphology comprised of nanobranches and nanoparticles, exhibits superior activity and durability towards the hydrogen evolution reaction (HER) in seawater compared to those of commercial Pt/C catalyst and other PtNi alloys that have different compositions and morphologies. The excellent seawater HER performance of Pt₄₈ Ni₅₂ is ascribed to its nanobranch/nanoparticle morphology that optimally facilitates electron accumulation on Pt, which enhances resistance to chloride corrosion in seawater.

Mixed-Dimensional Pt-Ni Alloy Polyhedral Nanochains as Bifunctional Electrocatalysts for Direct Methanol Fuel Cells

Pt nanocatalysts play a critical role in direct methanol fuel cells (DMFCs) due to their appropriate adsorption/desorption energy, yet suffer from an unbalanced relationship between size-dependent activity and stability. Herein, mixed-dimensional Pt-Ni alloy polyhedral nanochains (Pt-Ni PNCs) with an ordered assembly of a nanopolyhedra-nanowire-nanopolyhedra architecture are fabricated as bifunctional electrocatalysts for DMFCs, effectively alleviating the size effect. The Pt-Ni PNCs exhibit 7.23 times higher mass activity for the anodic methanol oxidation reaction (MOR) than that of commercial Pt/C. In situ Fourier transform infrared spectroscopy and CO stripping measurements demonstrate the prominent stability of the Pt-Ni PNCs to resist CO poisoning. For the cathodic oxygen reduction reaction (ORR), a positive half-wave potential exceeding Pt/C is achieved by the Pt-Ni PNCs, and it can be well maintained for 10 000 cycles with negligible activity decay. The designed nanostructure can alleviate the agglomeration and dissolution problems of 0D small-sized Pt-Ni alloy nanocrystals and enrich surface atom steps and active facets of 1D chain-like nanostructures. This work provides a proposed strategy to improve the catalytic performance of Pt-based nanocatalysts by constructing novel interfacial relationships in mixed dimensions to alleviate the imbalance between catalytic activity and catalytic stability caused by size effects.