Flexible Honeycombed Nanoporous/Glassy Hybrid for Efficient Electrocatalytic Hydrogen Generation

Nanoporous cobalt-doped AlNi3/NiO architecture for high performing hydrogen evolution at high current densities

Engineering platinum-free catalysts for hydrogen evolution reaction (HER) with high activity and stability is essential for electrochemical hydrogen production. In this paper, we report the synthesis of cobalt-doped AlNi3/NiO (Co-AlNi3/NiO) electrode with three-dimensional nanoporous structure via chemical dealloying method. Density functional theory (DFT) calculations reveal that Co-AlNi3/NiO can accelerate water adsorption / dissociation and optimize adsorption-desorption energies of H* intermediates, thus improving the intrinsic HER activity. Both the introduction of Co and Al can efficiently ameliorate the electronic density around Ni sites of NiO and AlNi3, which can effectively reduce the energy barrier towards Volmer-Heyrovsky reaction and thus synergistically promote the hydrogen evolution. Benefiting from the large electrochemical active surface area, high electrical conductivity and electronic effect, the nanoporous Co-AlNi3/NiO catalyst exhibits remarkable HER activity with an overpotential of 73 mV at a current density of 10 mA cm-2 in alkaline condition, outperforming most of the reported non-precious metal catalysts. The nanoporous Co-AlNi3/NiO catalyst can operate continuously over 1000 h at high current densities with a robust stability. This work provides a new vision for the development of low-cost and efficient electrocatalysts for energy conversion applications.

Constructing Nanoporous Ir/Ta2 O5 Interfaces on Metallic Glass for Durable Acidic Water Oxidation

Although proton exchange membrane water electrolyzers (PEMWE) are considered as a promising technique for green hydrogen production, it remains crucial to develop intrinsically effective oxygen evolution reaction (OER) electrocatalysts with high activity and durability. Here, a flexible self-supporting electrode with nanoporous Ir/Ta2O5 electroactive surface is reported for acidic OER via dealloying IrTaCoB metallic glass ribbons. The catalyst exhibits excellent electrocatalytic OER performance with an overpotential of 218 mV for a current density of 10 mA cm-2 and a small Tafel slope of 46.1 mV dec-1 in acidic media, superior to most electrocatalysts. More impressively, the assembled PEMWE with nanoporous Ir/Ta2 O5 as an anode shows exceptional performance of electrocatalytic hydrogen production and can operate steadily for 260 h at 100 mA cm-2 . In situ spectroscopy characterizations and density functional theory calculations reveal that the modest adsorption of OOH* intermediates to active Ir sites lower the OER energy barrier, while the electron donation behavior of Ta2 O5 to stabilize the high-valence states of Ir during the OER process extended catalyst's durability.

Nanoscale Oxygenous Heterogeneity in FePC Glass for Highly Efficient and Reusable Catalytic Performance

Metallic glass, with its unique disordered atomic structure and high density of low-coordination sites, is regarded as the most competitive new catalyst for environmental catalysis. However, the efficiency and stability of metallic glass catalysts are often affected by their atomic configuration. Thus, the design and regulation of the nanoscale structure of metallic glasses to improve their catalytic efficiency and stability remains a challenge. Herein, a non-noble component, Fe75 P15 C10 amorphous ribbon, is used as a precursor to fabricate a hierarchical gradient catalyst with nanoscale heterogeneous and oxygenous amorphous structure by simple annealing and acid-immersing. The resulting catalyst offers an ultrahigh catalytic ability of kSA• C0 = 3101 mg m-2  min-1 and excellent reusability of 39 times without efficiency decay in dye wastewater degradation. Theoretical calculations indicate that the excellent catalytic performance of the catalyst can be attributed to its unique heterogeneous nanoglass structure, which induces oxygen atoms. Compared to the FePC structure, the FeP/FePCO structure exhibits strong charge transferability, and the energy barrier of the rate-determining steps of the conversion of S2 O8 2- to SO4 -• is reduced from 2.52 to 0.97 eV. This study reveals that a heterogeneous nanoglass structure is a new strategy for obtaining high catalytic performance.

Defect Engineering of a High-Entropy Metallic Glass Surface for High-Performance Overall Water Splitting at Ampere-Level Current Densities

Platinum-based electrocatalysts possess high water electrolysis activity and are essential components for hydrogen evolution reaction (HER). A major challenge, however, is how to break the cost-efficiency trade-off. Here, a novel defect engineering strategy is presented to construct a nanoporous (FeCoNiB0.75 )97 Pt3 (atomic %) high-entropy metallic glass (HEMG) with a nanocrystalline surface structure that contains large amounts of lattice distortion and stacking faults to achieve excellent electrocatalytic performance using only 3 at% of Pt. The defect-rich HEMG achieves ultralow overpotentials at ampere-level current density of 1000 mA cm-2 for HER (104 mV) and oxygen evolution reaction (301 mV) under alkaline conditions, while retains a long-term durability exceeding 200 h at 100 mA cm-2 . Moreover, it only requires 81 and 122 mV to drive the current densities of 1000 and 100 mA cm-2 for HER under acidic and neutral conditions, respectively. Modelling results reveal that lattice distortion and stacking fault defects help to optimize atomic configuration and modulate electronic interaction, while the surface nanoporous architecture provides abundant active sites, thus synergistically contributing to the reduced energy barrier for water electrolysis. This defect engineering approach combined with a HEMG design strategy is expected to be widely applicable for development of high-performance alloy catalysts.

Design and Synthesis of Noble Metal-Based Alloy Electrocatalysts and Their Application in Hydrogen Evolution Reaction

Hydrogen energy is regarded as the ultimate energy source for future human society, and the preparation of hydrogen from water electrolysis is recognized as the most ideal way. One of the key factors to achieve large-scale hydrogen production by water splitting is the availability of highly active and stable electrocatalysts. Although non-precious metal electrocatalysts have made great strides in recent years, the best hydrogen evolution reaction (HER) electrocatalysts are still based on noble metals. Therefore, it is particularly important to improve the overall activity of the electrocatalysts while reducing the noble metals load. Alloying strategies can shoulder the burden of optimizing electrocatalysts cost and improving electrocatalysts performance. With this in mind, recent work on the application of noble metal-based alloy electrocatalysts in the field of hydrogen production from water electrolysis is summarized. In this review, first, the mechanism of HER is described; then, the current development of synthesis methods for alloy electrocatalysts is presented; finally, an example analysis of practical application studies on alloy electrocatalysts in hydrogen production is presented. In addition, at the end of this review, the prospects, opportunities, and challenges facing noble metal-based alloy electrocatalysts are tried to discuss.

Dynamic Electrodeposition on Bubbles: An Effective Strategy toward Porous Electrocatalysts for Green Hydrogen Cycling

ConspectusClosed-loop cycling of green hydrogen is a promising alternative to the current hydrocarbon economy for mitigating the energy crisis and environmental pollution. It stores energy from renewable energy sources like solar, wind, and hydropower into the chemical bond of dihydrogen (H₂) via (photo)electrochemical water splitting, and then the stored energy can be released on demand through the reverse reactions in H₂-O₂ fuel cells. The sluggish kinetics of the involved half-reactions like hydrogen evolution reaction (HER), oxygen evolution reaction (OER), hydrogen oxidation reaction (HOR), and oxygen reduction reaction (ORR) limit its realization. Moreover, considering the local gas-liquid-solid triphase microenvironments during H₂ generation and utilization, rapid mass transport and gas diffusion are critical as well. Accordingly, developing cost-effective and active electrocatalysts featuring three-dimensional hierarchically porous structures are highly desirable to promote the energy conversion efficiency. Traditionally, the synthetic approaches of porous materials include soft/hard templating, sol-gel, 3D printing, dealloying, and freeze-drying, which often need tedious procedures, high temperature, expensive equipment, and/or harsh physiochemical conditions. In contrast, dynamic electrodeposition on bubbles using the in situ formed bubbles as templates can be conducted at ambient conditions with an electrochemical workstation. Moreover, the whole preparation process can be finished within minutes/hours, and the resulting porous materials can be employed as catalytic electrodes directly, avoiding the use of polymeric binders like Nafion and the consequent issues like limited catalyst loading, reduced conductivity, and inhibited mass transport.In this Account, we summarize our contributions to the dynamic electrodeposition on bubbles toward advanced porous electrocatalysts for green hydrogen cycling. These dynamic electrosynthesis strategies include potentiodynamic electrodeposition that linearly scans the applied potentials, galvanostatic electrodeposition that fixes the applied currents, and electroshock which quickly switches the applied potentials. The resulting porous electrocatalysts range from transition metals to alloys, nitrides, sulfides, phosphides, and their hybrids. We mainly focus on the 3D porosity design of the electrocatalysts by tuning the electrosynthesis parameters to tailor the behaviors of bubble co-generation and thus the reaction interface. Then, their electrocatalytic applications for HER, OER, overall water splitting (OWS), biomass oxidation (to replace OER), and HOR are introduced, with a special emphasis on the porosity-promoted activity. Finally, the remaining challenges and future perspective are also discussed. We hope this Account will encourage more efforts into this attractive research field of dynamic electrodeposition on bubbles for various energy catalytic reactions like carbon dioxide/monoxide reduction, nitrate reduction, methane oxidation, chlorine evolution, and others.

Direct Urea/H2O2 Fuel Cell with a Hierarchical Porous Nanoglass Anode for High-Efficiency Energy Conversion

Direct urea/H₂O₂ fuel cells (DUFCs) constitute a sustainable bifunctional energy conversion technique devoted to simultaneously eliminating environmental wastewater with urea and generating clean energy. However, exploring an efficient anode material for DUFCs still remains a huge challenge. In this work, a Ni-P hierarchical porous nanoglass (HPNG) catalytic electrode was developed via a low-cost, industrially available electrodeposition technique, which exhibits one of the best performances reported so far in the urea oxidation reaction (UOR), with a potential of 1.330 V at a current density of 10 mA cm^-2 and a Tafel slope of 9.77 mV dec^-1. The superior UOR performance of the HPNG electrode is attributed to the excellent intrinsic catalytic activity of NG with a high-energy state and an extremely enlarged surface area from the unique 3D hierarchical porous structure. Furthermore, a DUFC system with the HPNG anode shows a performance breakthrough as indicated by the maximum power density of 38.15 mW cm^-2 for 0.5 M urea, representing one of the best yet reported DUFCs. Our work demonstrates the feasibility of the scalable production of HPNG electrodes and is expected to be a great contribution to the development of the practical use of DUFCs in the near future for bifunctional energy conversion.

Annealing and electrochemically activated amorphous ribbons: Surface nanocrystallization and oxidation effects enhanced for oxygen evolution performance

Annealing and cyclic voltammetry (CV) are essential for the activation of amorphous alloy ribbons. Various amorphous alloy ribbons have been activated in the fields of environmental catalysts using either annealing or CV. However, the combination of the two methods for improving the oxygen evolution reaction (OER) performance has rarely been reported. This combination is expected to significantly improve the OER performance of amorphous ribbons. Here, we developed an "annealing +CV-activation" integrated strategy to treat a free-standing NiFeBSiP ribbon, which as an efficient and stable oxygen-evolving electrode. The "annealing +CV-activation" strategy induces the nanocrystallization and oxidation effects on the surface of the NiFeBSiP ribbon. The effects significantly increase the electron transfer ability, the Ni/Fe/P oxidation state and the surface area of the NiFeBSiP ribbon, which consequently leads to enhancing the OER performance. As a result, the treated ribbon exhibits a low overpotential of 269 mV at 10 mA cm^-2 and a small Tafel slope of 40.5 mV dec^-1, which are much better than the OER performance of the as-spun ribbon. The enhanced OER performance of the NiFeBSiP ribbon demonstrates the significant and promising effect of the "annealing +CV-activation" integrated strategy for designing high-efficiency amorphous alloy ribbons electrocatalysts.

Attractive Electron Delocalization Behavior of FeCoMoPB Amorphous Nanoplates for Highly Efficient Alkaline Water Oxidation

The rational design of high-performance and cost-effective electrocatalysts to overcome the kinetically sluggish water oxidation reaction is a grand challenge in water electrolysis. Transitional metals with incompletely filled d orbitals are expected to have intrinsic electronic interaction to promote the reaction kinetics, however, the construction of multiple active sites is still a bottleneck problem. Here, inspired by an amorphous alloy design strategy with chemical tunability, a noble-metal-free FeCoMoPB amorphous nanoplate for superior alkaline water oxidation is developed. The achieved overpotentials at current densities of 10, 100, and 500 mA cm^-2 are 239, 281, and 331 mV, respectively, while retaining a reliable stability of 48 h, outperforming most currently available electrocatalysts. Experimental and theoretical results reveal that the chemical complexity of the amorphous nanoplate leads to the formation of multiple active sites that is able to greatly lower the free energy of the rate-determining step during the water oxidation reaction. Moreover, the Mo element would result in an electron delocalization behavior to promote electron redistribution at its surrounding regions for readily donating and taking electrons. This amorphous alloy design strategy is expected to stimulate the development of more efficient electrocatalysts that is applicable in energy devices, such as metal-air batteries, fuel cells, and water electrolysis.

Boosting Oxygen-Evolving Activity via Atom-Stepped Interfaces Architected with Kinetic Frustration

A highly active interface is extremely critical for the catalytic efficiency of an electrocatalyst; however, facilely tailoring its atomic packing characteristics remains challenging. Herein, a simple yet effective strategy is reported to obtain copious high-energy atomic steps at the interface via controlling the solidification behavior of glass-forming metallic liquids. By adjusting the chemical composition and cooling rate, highly faceted FeNi₃ nanocrystals are in situ formed in an FeNiB metallic glass (MG) matrix, leading to the creation of order/disorder interfaces. Benefiting from the catalytically active and stable atomic steps at the jagged interfaces, the resultant free-standing FeNi₃ nanocrystal/MG composite exhibits a low oxygen-evolving overpotential of 214 mV at 10 mA cm^-2 , a small Tafel slope of 32.4 mV dec^-1 , and good stability in alkaline media, outperforming most state-of-the-art catalysts. This approach is based on the manipulation of nucleation and crystal growth of the solid-solution nanophases (e.g., FeNi₃ ) in glass-forming liquids, so that the highly stepped interface architecture can be obtained due to the kinetic frustration effect in MGs upon undercooling. It is envisaged that the atomic-level stepped interface engineering via the physical metallurgy method can be easily extended to other MG systems, providing a new and generic paradigm for designing efficient yet cost-effective electrocatalysts.

Co3O4 Nanopetals Grown on the Porous CuO Network for the Photocatalytic Degradation

Designing a novel photocatalytic composite for the efficient degradation of organic dyes remains a serious challenge. Herein, the multi-layered Co₃O₄@NP-CuO photocatalyst with unique features, i.e., the self-supporting, hierarchical porous network as well as the construction of heterojunction between Co₃O₄ and CuO, are synthesized by dealloying-electrodeposition and subsequent thermal treatment techniques. It is found that the interwoven ultrathin Co₃O₄ nanopetals evenly grow on the nanoporous CuO network (Co₃O₄@NP-CuO). The three-dimensional (3D) hierarchical porous structure for the catalyst provides more surface area to act as active sites and facilitates the absorption of visible light in the photodegradation reaction. Compared with the commercial CuO and Co₃O₄ powders, the newly designed Co₃O₄@NP-CuO composite exhibits superior photodegradation performance for RhB. The enhanced performance is mainly due to the construction of heterojunction of Co₃O₄/CuO, greatly promoting the efficient carrier separation for photocatalysis. Furthermore, the possible photocatalytic mechanism is analyzed in detail. This work provides a promising strategy for the fabrication of a new controllable heterojunction to improve photocatalytic activity.

Nanostructured Metallic Glass in a Highly Upgraded Energy State Contributing to Efficient Catalytic Performance

Metallic glasses (MGs), with high density of low coordination sites and high Gibbs free energy state, are novel promising and competitive candidates in the family of electrochemical catalysts. However, it remains a grand challenge to modify the properties of MGs by control of the disordered atomic structure. Recently, nanostructured metallic glasses (NGs), consisting of amorphous nanometer-sized grains connected by amorphous interfaces, have been reported to exhibit tunable properties compared to the MGs with identical chemical composition. Here, it is demonstrated that electrodeposited Ni-P NG is characterized by an extremely high energy state due to its heterogeneous structure, which significantly promotes the catalytic performance. Moreover, the Ni-P NG with a heterogeneous structure is a perfect precursor for the fabrication of unique honey-like nanoporous structure, which displays superior catalytic performance in the urea oxidation reaction (UOR). Specifically, modified Ni-P NG requires a potential of mere 1.36 V at 10 mA cm^-2 , with a Tafel slope of 13 mV dec^-1 , which is the best UOR performance in Ni-based alloys. The present work demonstrates that the nanostructurization of MGs provides a universal and effective pathway to upgrade the energy state of MGs for the design of high-performance catalysts in energy conversion.

Design of Hierarchical Porosity Via Manipulating Chemical and Microstructural Complexities in High-Entropy Alloys for Efficient Water Electrolysis

Achieving a porous architecture with multiple-length scales and utilizing the synergetic effects of multicomponent chemicals bring up new opportunities for further improving the electrocatalytic performance of nanocatalysts. Herein, the synthesis of a self-supported hierarchical porous electrocatalyst based on a high-entropy alloy (HEA) containing multiple transitional metals via physical metallurgy and dealloying strategies is reported. Microscale phase separation and nanoscale spinodal decomposition are modulated in a highly concentrated FeCoNiCu HEA, which makes it possible to obtain a porous structure with different length scales, i.e., relatively large porous channels formed by removing one separated phase and ultrafine mesopores obtained from leaching out one decomposition phase. The resultant hierarchical porous HEA exhibits superior water splitting performance, which takes full advantage of the enlarged surface area offered by the bi-continuous mesoporous structure with the exceptional intrinsic reactivity originating from the synergetic electronic effects of the different components in alloying. Moreover, the microscale porous structure plays an important role in the significantly improved mass transportation, as well as the durability during electrocatalysis. This effective strategy that simultaneously utilizes the chemical and microstructural advantages of HEAs opens up a new avenue for developing HEA-based, high-performance porous electrocatalysts for various energy conversion/store applications.

Hydrogen Spillover-Bridged Volmer/Tafel Processes Enabling Ampere-Level Current Density Alkaline Hydrogen Evolution Reaction under Low Overpotential

Water-alkaline electrolysis holds a great promise for industry-scale hydrogen production but is hindered by the lack of enabling hydrogen evolution reaction electrocatalysts to operate at ampere-level current densities under low overpotentials. Here, we report the use of hydrogen spillover-bridged water dissociation/hydrogen formation processes occurring at the synergistically hybridized Ni₃S₂/Cr₂S₃ sites to incapacitate the inhibition effect of high-current-density-induced high hydrogen coverage at the water dissociation site and concurrently promote Volmer/Tafel processes. The mechanistic insights critically important to enable ampere-level current density operation are depicted from the experimental and theoretical studies. The Volmer process is drastically boosted by the strong H₂O adsorption at Cr_5c sites of Cr₂S₃, the efficient H₂O* dissociation via a heterolytic cleavage process (Cr_5c-H₂O* + S_3c(#) → Cr_5c-OH* + S_3c-H^#) on the Cr_5c/S_3c sites in Cr₂S₃, and the rapid desorption of OH* from Cr_5c sites of Cr₂S₃ via a new water-assisted desorption mechanism (Cr_5c-OH* + H₂O(aq) → Cr_5c-H₂O* + OH^-(aq)), while the efficient Tafel process is achieved through hydrogen spillover to rapidly transfer H^# from the synergistically located H-rich site (Cr₂S₃) to the H-deficient site (Ni₃S₂) with excellent hydrogen formation activity. As a result, the hybridized Ni₃S₂/Cr₂S₃ electrocatalyst can readily achieve a current density of 3.5 A cm^-2 under an overpotential of 251 ± 3 mV in 1.0 M KOH electrolyte. The concept exemplified in this work provides a useful means to address the shortfalls of ampere-level current-density-tolerant Hydrogen evolution reaction (HER) electrocatalysts.

Nanoscale Heterogeneities of Non-Noble Iron-Based Metallic Glasses toward Efficient Water Oxidation at Industrial-Level Current Densities

Scaling up the production of cost-effective electrocatalysts for efficient water splitting at the industrial level is critically important to achieve carbon neutrality in our society. While noble-metal-based materials represent a high-performance benchmark with superb activities for hydrogen and oxygen evolution reactions, their high cost, poor scalability, and scarcity are major impediments to achieve widespread commercialization. Herein, a flexible freestanding Fe-based metallic glass (MG) with an atomic composition of Fe₅₀Ni₃₀P₁₃C₇ was prepared by a large-scale metallurgical technique that can be employed directly as a bifunctional electrode for water splitting. The surface hydroxylation process created unique structural and chemical heterogeneities in the presence of amorphous FeOOH and Ni₂P as well as nanocrystalline Ni₂P that offered various active sites to optimize each rate-determining step for water oxidation. The achieved overpotentials for the oxygen evolution reaction were 327 and 382 mV at high current densities of 100 and 500 mA cm^-2 in alkaline media, respectively, and a cell voltage of 1.59 V was obtained when using the MG as both the anode and the cathode for overall water splitting at a current density of 10 mA cm^-2. Theoretical calculations unveiled that amorphous FeOOH makes a significant contribution to water molecule adsorption and oxygen evolution processes, while the amorphous and nanocrystalline Ni₂P stabilize the free energy of hydrogen protons (ΔG_H*) in the hydrogen evolution process. This MG alloy design concept is expected to stimulate the discovery of many more high-performance catalytic materials that can be produced at an industrial scale with customized properties in the near future.

High-Entropy Alloys for Electrocatalysis: Design, Characterization, and Applications

High-entropy alloys (HEAs) are expected to function well as electrocatalytic materials, owing to their widely adjustable composition and unique physical and chemical properties. Recently, HEA catalysts are extensively studied in the field of electrocatalysis; this motivated the authors to investigate the relationship between the structure and composition of HEAs and their electrocatalytic performance. In this review, the latest advances in HEA electrocatalysts are systematically summarized, with special focus on nitrogen fixation, the carbon cycle, water splitting, and fuel cells; in addition, by combining this with the characterization and analysis of HEA microstructures, rational design strategies for optimizing HEA electrocatalysts, including controllable preparation, component regulation, strain engineering, defect engineering, and theoretical prediction are proposed. Moreover, the existing issues and future trends of HEAs are predicted, which will help further develop these high-entropy materials.

Mesoporous NiCo alloy/reduced graphene oxide nanocomposites as efficient hydrogen evolution catalysts

Water electrolysis is a clean and efficient route for producing high-purity hydrogen. Developing highly efficient, stable and inexpensive electrocatalysts to replace Pt is currently a major challenge for the widespread application of water splitting. Herein, we report a facile and novel strategy for the synthesis of mesoporous NiCo alloy nanoparticle/reduced graphene oxide (MNiCo/rGO) composites via electroless deposition technique. Owing to the synergistic interaction of Ni and Co, the mesoporous structure of NiCo alloy, and the optimized combination of the mesoporous NiCo with rGO, the obtained optimal MNi₆₃Co₃₇/rGO₅ catalyst exhibits outstanding electrocatalytic performance for hydrogen evolution reaction (HER) with a low overpotential of 115 mV to reach the current density of 10 mA cm^-2, and a small Tafel slope of 45 mV dec^-1, as well as a high durability in alkaline solution. These remarkable merits make it a favorable alternative to noble metal Pt-based catalysts for HER, thereby further promoting the development of non-noble metal electrocatalysts.

An Efficient RuTe2 /Graphene Catalyst for Electrochemical Hydrogen Evolution Reaction in Acid Electrolyte

Developing efficient powder catalysts for hydrogen evolution reaction (HER) in the acidic electrolyte is significant for hydrogen generation in the proton exchange membrane (PEM) water electrolysis technique. Herein, we demonstrated an efficient catalyst for HER in the acid media based on the graphene supported ruthenium telluride nanoparticles (RuTe₂ /Gr). The catalysts were easily fabricated by a facile microwave irradiation/thermal annealing approach, and orthorhombic RuTe₂ crystals were found anchored over the graphene surface. The defective structure was demonstrated in the aberration-corrected transmission electron microscopy images for RuTe₂ crystals and graphene support. This catalyst required an overpotential of 72 mV to drive 10 mA cm^-2 for HER when loading on the inert glass carbon electrode; Excellent catalytic stability in acidic media was also observed to offer 10 mA cm^-2 for 10 hours. The Volmer-Tafel mechanism was indicated on RuTe₂ /Gr catalyst by Tafel slope of 33 mV dec^-1 , similar to that of Pt/C catalysts. The high catalytic performance of RuTe₂ /Gr could be attributed to its high dispersion on the graphene surface, high electrical conductivity and low charge transfer resistance. This powder catalyst has potential application in the PEM water electrolysis technique because of its low cost and high stability.

A Novel Multinary Intermetallic as an Active Electrocatalyst for Hydrogen Evolution

Electrochemical water splitting offers an attractive approach for hydrogen production. However, the lack of high-performance cost-effective electrocatalyst severely hinders its applications. Here, a multinary high-entropy intermetallic (HEI) that possesses an unusual periodically ordered structure containing multiple non-noble elements is reported, which can serve as a highly efficient electrocatalyst for hydrogen evolution. This HEI exhibits excellent activities in alkalinity with an overpotential of 88.2 mV at a current density of 10 mA cm^-2 and a Tafel slope of 40.1 mV dec^-1 , which are comparable to those of noble catalysts. Theoretical calculations reveal that the chemical complexity and surprising atomic configurations provide a strong synergistic function to alter the electronic structure. Furthermore, the unique L1₂ -type ordered structure enables a specific site-isolation effect to further stabilize the H₂ O/H* adsorption/desorption, which dramatically optimizes the energy barrier of hydrogen evolution. Such an HEI strategy uncovers a new paradigm to develop novel electrocatalyst with superior reaction activities.

Enhanced electro-catalytic performance of Pd-based hierarchical nanoporous structures fabricated by micropatterning and dealloying of Pd-Ni-P metallic glass

Pd-based catalysts are of significance for their application in direct alcohol fuel cells, due to the superior electro-catalytic performance and CO poisoning resistance. In this work, using Pd₃₂Ni₄₈P₂₀ metallic glassy ribbon as precursor, micro/nano hierarchical nanoporous structure was constructed by the hybrid approach of thermal plastic micropatterning and subsequently electrochemical dealloying at 0.88 V for 120 min in 0.5 M H₂SO₄ and 0.5 M H₃PO₄. This hierarchical structure was composed of the periodical micro-rods and nanoporous structure, where the chemical constituent was 80.33 at% Pd, 4.87 at% Ni, 4.96 at% P, and 9.84 at% O. The nanoporous structures showed an enhanced methanol electro-oxidation performance in alkaline medium, owing to their enlarged specific surface area. Compared to single nanoporous structure, the hierarchical nanoporous structure exhibited much better electro-catalysis, mainly attributed to the large surface area and high mass transfer efficiency, indicating a promising perspective for the application in alkaline direct alcohol fuel cells.