Modulating Electronic Structure of PtCo-Ptrich Nanowires with Ru atoms for Boosted Hydrogen Evolution Catalysis

Rational design and development of highly efficient hydrogen evolution reaction (HER) electrocatalysts is of great significance for the development of green water electrolysis hydrogen production technology. Ru-engineered 1D PtCo-Pt_rich nanowires (Ru-Pt_richCo NWs) are fabricated by a facile electrodeposition method. The rich Pt surface on 1D Pt₃Co contributes to the fully exposed active sites and enhanced intrinsic catalytic activity (co-engineered by Ru and Co atoms) for HER. The incorporation of Ru atoms can not only accelerate the water dissociation in alkaline condition to provide sufficient H^* but also modulate the electronic structure of Pt to achieve optimized H^* adsorption energy. As a result, Ru-Pt_richCo NWs have exhibited ultralow HER overpotentials (η) of 8 and 112 mV to achieve current densities of 10 and 100 mA cm⁻² in 1 m KOH, respectively, which far exceed those of commercial Pt/C catalyst (η₁₀ = 29 mV, η₁₀₀ = 206 mV). Density functional theory (DFT) calculations further demonstrate that the incorporated Ru atoms possess strong water adsorption capacity (−0.52 vs −0.12 eV for Pt), facilitating water dissociation. The Pt atoms in the outermost Pt-rich skin of Ru-Pt_richCo NWs achieve optimized H^* adsorption free energy (ΔG_H*) of −0.08 eV, boosting hydrogen generation.     

Significantly Stabilizing Hydrogen Evolution Reaction Induced by Nb-Doping Pt/Co(OH)2 Nanosheets

High stability and efficiency of electrocatalysts are crucial for hydrogen evolution reaction (HER) toward water splitting in an alkaline media. Herein, a novel nano-Pt/Nb-doped Co(OH)₂ (Pt/Nb Co(OH)₂) nanosheet is designed and synthesized using water-bath treatment and solvothermal reduction approaches. With nano-Pt uniformly anchored onto Nb Co(OH)₂ nanosheet, the synthesized Pt/Nb Co(OH)₂ shows outstanding electrocatalytic performances for alkaline HER, achieving a high stability for at least 33 h, a high mass activity of 0.65 mA µg⁻¹ Pt, and a good catalytic activity with a low overpotential of 112 mV at 10 mA cm⁻². Both experimental and theoretical results prove that Nb-doping significantly optimizes the hydrogen adsorption free energy to accelerate the Heyrovsky step for HER, and boosts the adsorption of H₂O, which further enhances the water activation. This study provides a new design methodology for the Nb-doped electrocatalysts in an alkaline HER field by facile and green way.     

Ultrahigh Mass Activity Pt Entities Consisting of Pt Single atoms,Clusters, and Nanoparticles for Improved Hydrogen Evolution Reaction

Platinum is one of the best-performing catalysts for the hydrogen evolution reaction (HER). However, high cost and scarcity severely hinder the large-scale application of Pt electrocatalysts. Constructing highly dispersed ultrasmall Platinum entities is thereby a very effective strategy to increase Pt utilization and mass activities, and reduce costs. Herein, highly dispersed Pt entities composed of a mixture of Pt single atoms, clusters, and nanoparticles are synthesized on mesoporous N-doped carbon nanospheres. The presence of Pt single atoms, clusters, and nanoparticles is demonstrated by combining among others aberration-corrected annular dark-field scanning transmission electron microscopy, X-ray absorption spectroscopy, and electrochemical CO stripping. The best catalyst exhibits excellent geometric and Pt HER mass activity, respectively ≈4 and 26 times higher than that of a commercial Pt/C reference and a Pt catalyst supported on nonporous N-doped carbon nanofibers with similar Pt loadings. Noteworthily, after optimization of the geometrical Pt electrode loading, the best catalyst exhibits ultrahigh Pt and catalyst mass activities (56 ± 3 A mg⁻¹_Pt and 11.7 ± 0.6 A mg⁻¹_Cat at −50 mV vs. reversible hydrogen electrode), which are respectively ≈1.5 and 58 times higher than the highest Pt and catalyst mass activities for Pt single-atom and cluster-based catalysts reported so far.     

Enhanced the Efficiency of Electrocatalytic CO2-to-CO Conversion by Cd Species Anchored into Metal-Organic Framework

Metal-organic frameworks (MOFs) as a promising platform for electrocatalytic CO₂ conversion are still restricted by the low efficiency or unsatisfied selectivity for desired products. Herein, zirconium-based porphyrinic MOF hollow nanotubes with Cd sites (Cd-PCN-222HTs) are reported for electrocatalytic CO₂-to-CO conversion. The dispersed Cd species are anchored in PCN-222HTs and coordinated by N atoms of porphyrin structures. It is discovered that Cd-PCN-222HTs have glorious electrocatalytic activity for selective CO production in ionic liquid-water (H₂O)-acetonitrile (MeCN) electrolyte. The CO Faradaic efficiency (FE_CO) of >80% could be maintained in a wide potential range from −2.0 to −2.4 V versus Ag/Ag⁺, and the maximum current density could reach 68.0 mA cm⁻² at −2.4 V versus Ag/Ag⁺ with a satisfied turnover frequency of 26 220 h⁻¹. The enhanced efficiency of electrocatalytic CO₂ conversion of Cd-PCN-222HTs is closely related to its hollow structure, anchored Cd species, and good synergistic effect with electrolyte. The density functional theory calculations indicate that the dispersed Cd sites anchored in PCN-222HTs not only favor the formation of *COOH intermediate but also hinder the hydrogen evolution reaction, resulting in high activity of electrocatalytic CO₂-to-CO conversion.     

High-Performance Bifunctional Porous Iron-Rich Phosphide/Nickel Nitride Heterostructures for Alkaline Seawater Splitting

Seawater is the most abundant natural water resource in the world, which is an inexhaustible and low-cost feedstock for hydrogen production by alkaline water electrolysis. It is appearling to develop robust and stable electrocatalysts for alkaline seawater electrolysis. However, the development of seawater electrolysis is seriously impeded by anodic chloride corrosion and chlorine evolution reaction, and few non-noble electrocatalysts show prominent catalytic performance and excellent durability. Here, a heterogeneous electrocatalyst constructed by in situ growing highly dispersed iron-rich bimetallic phosphide nanoparticles on metallic Ni₃N (Fe_2−2xCo_2xP/Ni₃N), which exhibits outstanding bifunctional catalytic activities for alkaline seawater splitting, is reported. The optimal (Fe_0.74Co_0.26)₂P/Ni₃N and Fe₂P/Ni₃N electrocatalysts demand only 113 and 212 mV to afford 100 mA cm⁻² for hydrogen and oxygen evolution reactions (HER and OER) in 1 m KOH, respectively, thus substantially expediting overall water/seawater electrolysis at 100 mA cm⁻² with 1.592/1.645 V. Particularly, Fe₂P/Ni₃N displays an unprecedented overpotential of 302 mV at 500 mA cm⁻², which represents the best alkaline seawater oxygen evolution activity among the ever-reported non-noble electrocatalysts; and thus substantially expedites overall water/seawater splitting at 500 mA cm⁻² with 1.701/1.768 V, surpassing most of the reported non-noble lectrocatalysts. This work provides a new approach for developing high-performance electrocatalysts for seawater splitting.     

Sn-Ag Synergistic Effect Enhances High-Rate Electrocatalytic CO2-to-Formate Conversion on Porous Poly(Ionic Liquid) Support

The electrocatalytic transformation of carbon dioxide (CO₂) to formate is a promising route for highly efficient conversion and utilization of CO₂ gas, due to the low production cost and the ease of storage of formate. In this work, porous poly(ionic liquid) (PPIL)-based tin-silver (Sn-Ag) bimetallic hybrids (PPIL^m-Sn_xAg_10-x) are prepared for high-performance formate electrolytic generation. Under optimal conditions, an excellent formate Faradaic efficiency of 95.5% with a high partial current density of 214.9 mA cm⁻² is obtained at −1.03 V (vs reversible hydrogen electrode). Meanwhile, the high selectivity of formate (>≈83%) is maintained in a wide potential range (>630 mV). Mechanistic studies demonstrate that the presence of Ag-species is vital for the formation, maintenance, and high dispersion of tetravalent Sn(IV)-species, which accounts for the active sites for CO₂-to-formate conversion. Further, the introduction of Ag-species significantly enhances the activity by increasing the electron density near the Fermi energy level.     

Electronic Modulation of Metal-Organic Frameworks Caused by Atomically Dispersed Ru for Efficient Hydrogen Evolution

Designing excellent electrocatalysts for the hydrogen evolution reaction (HER) is extremely significant in producing clean and sustainable hydrogen fuel. Herein, a rational strategy is developed to fabricate a promising electrocatalyst by introducing atomically dispersed Ru into a cobalt-based metal-organic framework (MOF), Co-BPDC (Co(bpdc)(H₂O)₂, BPDC: 4,4'-Biphenyldicarboxylic acid). The obtained CoRu-BPDC nanosheet arrays exhibit remarkable HER performance with an overpotential of 37 mV at a current density of 10 mA cm⁻² in alkaline media, which is superior to most of the MOF-based electrocatalysts and comparable to the commercial Pt/C. Synchrotron radiation-based X-ray absorption fine structure (XAFS) spectroscopy studies verify that the isolated Ru atoms are dispersed in Co-BPDC nanosheets with the formation of five-coordinated Ru-O₅ species. XAFS spectroscopy combined with density functional theory (DFT) calculations unravels that atomically dispersed Ru can modulate the electronic structure of the as-obtained Co-BPDC, contributing to the optimization of binding strength for H* and the enhancement of HER performance. This work opens a new avenue to rationally design highly-active single-atom modified MOF-based HER electrocatalysts via modulating electronic structures of MOF.     

Light Field-Enhanced Single-Site Cu Electrocatalyst for Nitrogen Fixation

Direct electrocatalytic reduction of N₂ to NH₃ under mild conditions is attracting considerable interests but still remains enormous challenges in terms of respect of intrinsic catalytic activity and limited electrocatalytic efficiency. Herein, a photo-enhanced strategy is developed to improve the NRR activity on Cu single atoms catalysts. The atomically dispersed Cu single atoms supported TiO₂ nanosheets (Cu SAs/TiO₂) achieve a Faradaic Efficiency (12.88%) and NH₃ yield rate (6.26 µg h⁻¹ mg_cat⁻¹) at −0.05 V versus RHE under the light irradiation field, in which NH₃ yield rate is fivefold higher than that under pure electrocatalytic nitrogen reduction reaction (NRR) process and is remarkably superior in comparison to most of the similar type electrocatalysts. The existence of external light field improves electron transfer ability between Cu O and Ti O, and thus optimizes the accumulation of surface charges on Cu sites, endowing more electrons involved in nitrogen fixation. This work reveals an atomic-scale mechanistic understanding of field effect-enhanced electrochemical performance of catalysts and it provides predictive guidelines for the rational design of photo-enhanced electrochemical N₂ reduction catalysts.     

Ultrafine NiFe-Based (Oxy)Hydroxide Nanosheet Arrays with Rich Edge Planes and Superhydrophilic-Superaerophobic Characteristics for Oxygen Evolution Reaction

NiFe-based (oxy)hydroxides are the benchmark catalysts for the oxygen evolution reaction (OER) in alkaline medium, however, it is still challenging to control their structures and compositions. Herein, molybdates (NiFe(MoO₄)_x) are applied as unique precursors to synthesize ultrafine Mo modified NiFeO_xH_y (oxy)hydroxide nanosheet arrays. The electrochemical activation process enables the molybdate ions (MoO₄²⁻) in the precursors gradually dissolve, and at the same time, hydroxide ions (OH⁻) in the electrolyte diffuse into the precursor and react with Ni²⁺ and Fe³⁺ ions in confined space to produce ultrafine NiFeO_xH_y (oxy)hydroxides nanosheets (<10 nm), which are densely arranged into microporous arrays and maintain the rod-like morphology of the precursor. Such dense ultrafine nanosheet arrays produce rich edge planes on the surface of NiFeO_xH_y (oxy)hydroxides to expose more active sites. More importantly, the capillary phenomenon of microporous structures and hydrophilic hydroxyl groups induce the superhydrophilicity and the rough surface produces the superaerophobic characteristic for bubbles. With these advantages, the optimized catalyst exhibits excellent performance for OER, with a small overpotential of 182 mV at 10 mA cm⁻² and long-term stability (200 h) at 200 mA cm⁻². Theoretical calculations show that the modification of Mo enhances the electron delocalization and optimizes the adsorption of intermediates.     

Defective TiO2−x for High-Performance Electrocatalytic NO Reduction toward Ambient NH3 Production

Synthesis of green ammonia (NH₃) via electrolysis of nitric oxide (NO) is extraordinarily sustainable, but multielectron/proton-involved hydrogenation steps as well as low concentrations of NO can lead to poor activities and selectivities of electrocatalysts. Herein, it is reported that oxygen-defective TiO₂ nanoarray supported on Ti plate (TiO_2−x/TP) behaves as an efficient catalyst for NO reduction to NH₃. In 0.2 m phosphate-buffered electrolyte, such TiO_2−x/TP shows competitive electrocatalytic NH₃ synthesis activity with a maximum NH₃ yield of 1233.2 µg h⁻¹ cm⁻² and Faradaic efficiency of 92.5%. Density functional theory calculations further thermodynamically faster NO deoxygenation and protonation processes on TiO_2−x (101) compared to perfect TiO₂ (101). And the low energy barrier of 0.7 eV on TiO_2−x (101) for the potential-determining step further highlights the greatly improved intrinsic activity. In addition, a Zn-NO battery is fabricated with TiO_2−x/TP and Zn plate to obtain an NH₃ yield of 241.7 µg h⁻¹ cm⁻² while providing a peak power density of 0.84 mW cm⁻².     

Ultra-Low Pt Doping and Pt–Ni Pair Sites in Amorphous/Crystalline Interfacial Electrocatalyst Enable Efficient Alkaline Hydrogen Evolution

Noble metal doping can achieve an increase in mass activity (MA) without sacrificing catalysis efficiency and stability, so that alkaline hydrogen evolution reaction (HER) performance of the catalyst can be optimized to the maximum degree. However, its excessively large ionic radius makes it difficult to achieve either interstitial doping or substitutional doping under mild conditions. Herein, a hierarchical nanostructured electrocatalyst with enriched amorphous/crystalline interfaces for high-efficiency alkaline HER is reported, which is composed of amorphous/crystalline (Co, Ni)₁₁(HPO₃)₈(OH)₆ homogeneous hierarchical structure with an ultra-low doped Pt (Pt-a/c-NiHPi). Benefiting from the structural flexibility of the amorphous component, extremely low Pt (0.21 wt.%, totally 3.31 µg Pt on 1 cm⁻² NF) are stably doped on it via a simple two-phase hydrothermal method. The DFT calculations show that due to the strongly electron transfer between the crystalline/amorphous components at the interfaces, electrons finally concentrate toward Pt and Ni in the amorphous components, thus the electrocatalyst has near-optimal energy barriers and adsorption energy for H₂O^* and H^*. With the above benefits, the obtained catalyst exhibits an exceptionally high MA (39.1 mA µg⁻¹_Pt) at 70 mV, which is almost the highest level among the reported Pt-based electrocatalysts for alkaline HER.     

High Density Single Fe Atoms on Mesoporous N-Doped Carbons: Noble Metal-Free Electrocatalysts for Oxygen Reduction Reaction in Acidic and Alkaline Media

It remains a challenge to develop efficient noble metal-free electrocatalysts for the oxygen reduction reaction (ORR) in various renewable energy systems. Single atom catalysts have recently drawn great attention as promising candidates both due to their high activity and their utmost atom utilization for electrocatalytic ORR. Herein, the synthesis of an efficient ORR electrocatalyst that is composed of N-doped mesoporous carbon and a high density (4.05 wt%) of single Fe atoms via pyrolysis Fe-conjugated polymer is reported. Benefiting from the abundant atomic Fe–N₄ sites on its conductive, mesoporous carbon structures, this material exhibits an excellent electrocatalytic activity for ORR, with positive onset potentials of 0.93 and 0.98 V in acidic and alkaline media, respectively. Its electrocatalytic performance for ORR is also comparable to that of Pt/C (20 wt%) in both media. Furthermore, it electrocatalyzes the reaction almost fully to H₂O (or barely to H₂O₂). Additionally, it is durable and tolerates the methanol crossover reaction well. Furthermore, a proton exchange membrane fuel cell and a zinc–air battery assembled using it on their cathode deliver high maximum power densities (320 and 91 mW cm⁻², respectively). Density functional theory calculation reveals that the material's decent electrocatalytic performance for ORR is due to its atomically dispersed Fe–N₄ sites.     

Atomically Dispersed Ni–N4 Sites Assist Pt3Ni Nanocages with Pt Skin to Synergistically Enhance Oxygen Reduction Activity and Stability

Currently, the rarity and high cost of platinum (Pt)-based electrocatalysts seriously limit their commercial application in fuel cells cathode. Decorating Pt with atomically dispersed metal–nitrogen sites possibly offers an effective pathway to synergy tailor their catalytic activity and stability. Here active and stable oxygen reduction reaction (ORR) electrocatalysts (Pt₃Ni@Ni–N₄–C) by in situ loading Pt₃Ni nanocages with Pt skin on single-atom nickel–nitrogen (Ni–N₄) embedded carbon supports are designed and constructed. The Pt₃Ni@Ni–N₄–C exhibits excellent mass activity (MA) of 1.92 A mg_Pt⁻¹ and specific activity of 2.65 mA cm_Pt⁻², together with superior durability of 10 mV decay in half-wave potential and only 2.1% loss in MA after 30 000 cycles. Theoretical calculations demonstrate that Ni–N₄ sites significant redistribute of electrons and make them transfer from both the adjacent carbon and Pt atoms to the Ni–N₄. The resultant electron accumulation region successfully anchored Pt₃Ni, that not only improves structural stability of the Pt₃Ni, but importantly makes the surface Pt more positive to weaken the adsorption of *OH to enhance ORR activity. This strategy lays the groundwork for the development of super effective and durable Pt-based ORR catalysts.     

Phase Segregation in Cu0.5Ni0.5 Alloy Boosting Urea-Assisted Hydrogen Production in Alkaline Media

Coupling urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) is promising for energy-efficient hydrogen production. However, developing cheap and highly active bifunctional electrocatalysts for overall urea electrolysis remains challenging. In this work, a metastable Cu_0.5Ni_0.5 alloy is synthesized by a one-step electrodeposition method. It only requires the potentials of 1.33 and −28 mV to obtain the current density of ±10 mA cm⁻² for UOR and HER, respectively. The metastable alloy is considered to be the main reason causing the above excellent performances. In the alkaline medium, the as-prepared Cu_0.5Ni_0.5 alloy exhibits good stability for HER; and conversely, NiOOH species can be rapidly formed during the UOR due to the phase segregation of Cu_0.5Ni_0.5 alloy. In particular, for the energy-saving hydrogen generation system coupled with HER and UOR, only 1.38 V of voltage is needed at 10 mA cm⁻²; and at 100 mA cm⁻², the voltage decreases by ≈305 mV compared with that of the routine water electrolysis system (HER || OER). Compared with some catalysts reported recently, the Cu_0.5Ni_0.5 catalyst owns superior electrocatalytic activity and durability. Furthermore, this work provides a simple, mild, and rapid method for designing highly active bifunctional electrocatalysts toward urea-supporting overall water splitting.     

Preparation of Pt/multiwalled carbon nanotubes modified Au electrodes via Pt–Cu co-electrodeposition/Cu stripping protocol for high-performance electrocatalytic oxidation of methanol

Pt nanoparticles well dispersed on multiwalled carbon nanotubes (MWCNTs) were prepared for high-performance electrocatalytic oxidation of methanol in both acidic and alkaline media via the co-electrodeposition/stripping (CS) protocol, namely, co-electrodeposition of Pt and Cu followed by electrochemical stripping of Cu, as examined by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The Pt catalyst prepared by the CS protocol on MWCNTs (Pt_cs/MWCNTs/Au) exhibited a specific electrocatalytic activity of 519 and 2210 A g⁻¹ toward cyclic voltammetric electrooxidation (50 mV s⁻¹) of methanol in 0.5 M CH₃OH + 0.5 M H₂SO₄ and 0.5 M CH₃OH + 1.0 M NaOH media, respectively, which are larger than those prepared by conventional electrodeposition from chloroplatinic acid on Au and MWCNTs/Au, as well as that by a CS protocol on Au. The Pt_cs/MWCNTs/Au electrode also possessed the highest stability, which maintained 91% and 90% of its initial catalytic activity after 120-cycle CV in 0.5 M CH₃OH + 0.5 M H₂SO₄ and 0.5 M CH₃OH + 1.0 M NaOH, respectively. The electrode kinetics of methanol oxidation is also briefly discussed. The nanosubstrate-based CS protocol is simple, convenient and efficient, which is expected to find wide applications in film electrochemistry and electrocatalysis.     

N-Doping Coupled with Co-Vacancies Activating Sulfur Atoms and Narrowing Bandgap for CoS Toward Synergistically Accelerating Hydrogen Evolution

The combination of hetero-elemental doping and vacancy engineering will be developed as one of the most efficient strategies to design excellent electrocatalysts for hydrogen evolution reaction (HER). Herein, a novel strategy for N-doping coupled with Co-vacancies is demonstrated to precisely activate inert S atoms adjacent to Co-vacancies and significantly improve charge transfer for CoS toward accelerating HER. In this strategy, N-doping favors the presence of Co-vacancies, due to greatly decreasing their formation energy. The as-developed strategy realizes the upshift of S 3p orbitals followed by more overlapping between S 3p_y and H 1s orbitals, which results in the favorable hydrogen atom adsorption free energy change (ΔG_H) to activate inert S atoms as newborn catalytical sites. Besides, this strategy synergistically decreases the bandgap of CoS, thereby achieving satisfactory electrical conductivity and low charge-transfer resistance for the as-obtained electrocatalysts. With an excellent HER activity of −89.0 mV at 10.0 mA cm⁻² in alkaline environments, this work provides a new approach to unlocking inert sites and significantly improving charge transfer toward cobalt-based materials for highly efficient HER.     

Synergistic Modulation of Electronic Interaction to Enhance Intrinsic Activity and Conductivity of Fe–Co–Ni Hydroxide Nanotube for Highly Efficient Oxygen Evolution Electrocatalyst

The large-scale hydrogen production and application through electrocatalytic water splitting depends crucially on the development of highly efficient, cost-effective electrocatalysts for oxygen evolution reaction (OER), which, however, remains challenging. Here, a new electrocatalyst of trimetallic Fe–Co–Ni hydroxide (denoted as FeCoNiO_xH_y) with a nanotubular structure is developed through an enhanced Kirkendall process under applied potential. The FeCoNiO_xH_y features synergistic electronic interaction between Fe, Co, and Ni, which not only notably increases the intrinsic OER activity of FeCoNiO_xH_y by facilitating the formation of *OOH intermediate, but also substantially improves the intrinsic conductivity of FeCoNiO_xH_y to facilitate charge transfer and activate catalytic sites through electrocatalyst by promoting the formation of abundant Co³⁺. Therefore, FeCoNiO_xH_y delivers remarkably accelerated OER kinetics and superior apparent activity, indicated by an ultra-low overpotential potential of 257 mV at a high current density of 200 mA cm⁻². This work is of fundamental and practical significance for synergistic catalysis related to advanced energy conversion materials and technologies.     

Flexible Co–Mo–N/Au Electrodes with a Hierarchical Nanoporous Architecture as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

Designing highly active and robust electrocatalysts for oxygen evolution reaction (OER) is crucial for many renewable energy storage and conversion devices. Here, self-supported monolithic hybrid electrodes that are composed of bimetallic cobalt–molybdenum nitride nanosheets vertically aligned on 3D and bicontinuous nanoporous gold (NP Au/CoMoN_x) are reported as highly efficient electrocatalysts to boost the sluggish reaction kinetics of water oxidation in alkaline media. By virtue of the constituent CoMoN_x nanosheets having large accessible CoMoO_x surface with remarkably enhanced electrocatalytic activity and the nanoporous Au skeleton facilitating electron transfer and mass transport, the NP Au/CoMoN_x electrode exhibits superior OER electrocatalysis in 1 m KOH, with low onset overpotential (166 mV) and Tafel slope (46 mV dec⁻¹). It only takes a low overpotential of 370 mV to reach ultrahigh current density of 1156 mA cm⁻², ≈140-fold higher than free CoMoN_x nanosheets. The electrocatalytic performance makes it an attractive candidate as the OER catalyst in the water electrolysis.     

Cactus‐Like Hollow Cu2‐xS@Ru Nanoplates as Excellent and Robust Electrocatalysts for the Alkaline Hydrogen Evolution Reaction

The development of Pt‐free electrocatalysts for the hydrogen evolution reaction (HER) recently is a focus of great interest. While several strategies are developed to control the structural properties of non‐Pt catalysts and boost their electrocatalytic activities for the HER, the generation of highly reactive defects or interfaces by combining a metal with other metals, or with metal oxides/sulfides, can lead to notably enhanced catalytic performance. Herein, the preparation of cactus‐like hollow Cu_2‐x S@Ru nanoplates (NPs) that contain metal/metal sulfide heterojunctions and show excellent catalytic activity and durability for the HER in alkaline media is reported. The initial formation of Ru islands on presynthesized Cu_1.94S NPs, via cation exchange between three Cu⁺ ions and one Ru³⁺, induces the growth of the Ru phase, which is concomitant with the dissolution of the Cu_1.94S nanotemplate, culminating in the formation of a hollow nanostructure with numerous thin Ru pillars. Hollow Cu_2‐x S@Ru NPs exhibit a small overpotential of 82 mV at a current density of ?10 mA cm^?2 and a low Tafel slope of 48 mV dec^?1 under alkaline conditions; this catalyst is among state‐of‐the‐art HER electrocatalysts in alkaline media. The excellent performance of hollow Cu_2‐x S@Ru NPs originates from the facile dissociation of water in the Volmer step.