Ultrafine Co Nanoparticles Encapsulated in Carbon‐Nanotubes‐Grafted Graphene Sheets as Advanced Electrocatalysts for the Hydrogen Evolution Reaction

The rational design of an efficient and inexpensive electrocatalyst based on earth‐abundant 3d transition metals (TMs) for the hydrogen evolution reaction still remains a significant challenge in the renewable energy area. Herein, a novel and effective approach is developed for synthesizing ultrafine Co nanoparticles encapsulated in nitrogen‐doped carbon nanotubes (N‐CNTs) grafted onto both sides of reduced graphene oxide (rGO) (Co@N‐CNTs@rGO) by direct annealing of GO‐wrapped core–shell bimetallic zeolite imidazolate frameworks. Benefiting from the uniform distribution of Co nanoparticles, the in‐situ‐formed highly graphitic N‐CNTs@rGO, the large surface area, and the abundant porosity, the as‐fabricated Co@N‐CNTs@rGO composites exhibit excellent electrocatalytic hydrogen evolution reaction (HER) activity. As demonstrated in electrochemical measurements, the composites can achieve 10 mA cm^?2 at low overpotential with only 108 and 87 mV in 1 m KOH and 0.5 m H₂SO₄, respectively, much better than most of the reported Co‐based electrocatalysts over a wide pH range. More importantly, the synthetic strategy is versatile and can be extended to prepare other binary or even ternary TMs@N‐CNTs@rGO (e.g., Co–Fe@N‐CNTs@rGO and Co–Ni–Cu@N‐CNTs@rGO). The strategy developed here may open a new avenue toward the development of nonprecious high‐performance HER catalysts.     

Ruthenium Nanoparticles on Cobalt‐Doped 1T′ Phase MoS2 Nanosheets for Overall Water Splitting

2D MoS₂ nanostructures have recently attracted considerable attention because of their outstanding electrocatalytic properties. The synthesis of unique Co–Ru–MoS₂ hybrid nanosheets with excellent catalytic activity toward overall water splitting in alkaline solution is reported. 1T′ phase MoS₂ nanosheets are doped homogeneously with Co atoms and decorated with Ru nanoparticles. The catalytic performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is characterized by low overpotentials of 52 and 308 mV at 10 mA cm^?2 and Tafel slopes of 55 and 50 mV decade^?1 in 1.0 m KOH, respectively. Analysis of X‐ray photoelectron and absorption spectra of the catalysts show that the MoS₂ well retained its metallic 1T′ phase, which guarantees good electrical conductivity during the reaction. The Gibbs free energy calculation for the reaction pathway in alkaline electrolyte confirms that the Ru nanoparticles on the Co‐doped MoS₂ greatly enhance the HER activity. Water adsorption and dissociation take place favorably on the Ru, and the doped Co further catalyzes HER by making the reaction intermediates more favorable. The high OER performance is attributed to the catalytically active RuO₂ nanoparticles that are produced via oxidation of Ru nanoparticles.     

Cr‐Doped FeNi–P Nanoparticles Encapsulated into N‐Doped Carbon Nanotube as a Robust Bifunctional Catalyst for Efficient Overall Water Splitting

Exploring high‐efficiency, stable, and cost‐effective bifunctional electrocatalysts for overall water splitting is greatly desirable and challenging. Herein, a newly designed hybrid catalyst with Cr‐doped FeNi–P nanoparticles encapsulated into N‐doped carbon nanotubes (Cr‐doped FeNi–P/NCN) with unprecedented electrocatalytic activity is developed by a simple one‐step heating treatment. The as‐synthesized Cr‐doped FeNi–P/NCN with moderate Cr doping exhibits admirable oxygen evolution reaction and hydrogen evolution reaction activities with overpotentials of 240 and 190 mV to reach a current density of 10 mA cm^?2 in 1 m KOH solution. When used in overall water splitting as a bifunctional catalyst, it needs only 1.50 V to give a current density of 10 mA cm^?2, which is superior to its typically integrated Pt/C and RuO₂ counterparts (1.54 V @ 10 mA cm^?2). Density functional theory calculation confirms that Cr doping into a FeNi‐host can effectively alter the relative Gibbs adsorption energy and reduces the theoretical overpotential. Additionally, the synergetic effects between Cr‐doped FeNi–P nanoparticles and NCNs are regarded as significant contributors to accelerate charge transfer and promote electrocatalytic activity in hybrid catalysts.     

Atomic Layer Deposition‐Assisted Fabrication of Co‐Nanoparticle/N‐Doped Carbon Nanotube Hybrids as Efficient Electrocatalysts for the Oxygen Evolution Reaction

Transition metal (TM)‐based carbon hybrids have numerous applications in the field of regenerative electrochemical energy. The synergetic effects of high conductivity of carbon supports and abundant catalytic active sites in TMs make these hybrids promising oxygen evolution reaction (OER) electrocatalysts. However, strategies for modulating the catalytic active species in the above hybrids are limited despite being highly sought after. Furthermore, the exact roles of chemical species in the hybrids (e.g., N, C, or TM) mainly responsible for this high OER performance remain unknown. Herein, an innovative approach based on atomic layer deposition is developed to tune the true active species in Co nanoparticle/N‐doped carbon nanotube (Co/N‐CNT) hybrids. Specifically, the configuration predominantly promoting water oxidation in an alkaline medium is identified as pyridinic N–Co–C. Furthermore, a physicochemical intact interface between metallic Co nanoparticles and conductive N‐CNTs is demonstrated to induce synergetic effects for accelerating charge transfer and enhancing electrocatalytic activity as well as stability in the hybrid catalysts. The optimized hybrid catalyst is revealed to exhibit outstanding alkaline OER activity and stability, outperforming RuO₂, a benchmark novel OER electrocatalyst.     

Ultrafine Dual‐Phased Carbide Nanocrystals Confined in Porous Nitrogen‐Doped Carbon Dodecahedrons for Efficient Hydrogen Evolution Reaction

Designing novel non‐noble electrocatalysts with controlled structures and composition remains a great challenge for efficient hydrogen evolution reaction (HER). Herein, a rational synthesis of ultrafine carbide nanocrystals confined in porous nitrogen‐doped carbon dodecahedrons (PNCDs) by annealing functional zeolitic imidazolate framework (ZIF‐8) with molybdate or tungstate is reported. By controlling the substitution amount of MO₄ units (M = Mo or W) in the ZIF‐8 framework, dual‐phase carbide nanocrystals confined in PNCDs (denoted as MC‐M₂C/PNCDs) can be obtained, which exhibit superior activity toward the HER to the single‐phased MC/PNCDs and M₂C/PNCDs. The evenly distributed ultrafine nanocrystals favor the exposure of active sites. PNCDs as the support facilitate charge transfer and protect the nanocrystals from aggregation during the HER process. Moreover, the strong coupling interactions between MC and M₂C provide beneficial sites for both water dissociation and hydrogen desorption. This work highlights a new feasible strategy to explore efficient electrocatalysts via engineering on nanostructure and composition.     

Metal–Carbon Hybrid Electrocatalysts Derived from Ion‐Exchange Resin Containing Heavy Metals for Efficient Hydrogen Evolution Reaction

Transition metal–carbon hybrids have been proposed as efficient electrocatalysts for hydrogen evolution reaction (HER) in acidic media. Herein, effective HER electrocatalysts based on metal–carbon composites are prepared by controlled pyrolysis of resin containing a variety of heavy metals. For the first time, Cr₂O₃ nanoparticles of 3–6 nm in diameter homogeneously dispersed in the resulting porous carbon framework (Cr–C hybrid) is synthesized as efficient HER electrocatalyst. Electrochemical measurements show that Cr–C hybrids display a high HER activity with an onset potential of ?49 mV (vs reversible hydrogen electrode), a Tafel slope of 90 mV dec^?1, a large catalytic current density of 10 mA cm^?2 at ?123 mV, and the prominent electrochemical durability. X‐ray photoelectron spectroscopic measurements confirm that electron transfer occurs from Cr₂O₃ into carbon, which is consistent with the reported metal@carbon systems. The obtained correlation between metals and HER activities may be exploited as a rational guideline in the design and engineering of HER electrocatalysts.     

Polyaniline Derived N‐Doped Carbon‐Coated Cobalt Phosphide Nanoparticles Deposited on N‐Doped Graphene as an Efficient Electrocatalyst for Hydrogen Evolution Reaction

The development of highly efficient and durable non‐noble metal electrocatalysts for the hydrogen evolution reaction (HER) is significant for clean and renewable energy research. This work reports the synthesis of N‐doped graphene nanosheets supported N‐doped carbon coated cobalt phosphide (CoP) nanoparticles via a pyrolysis and a subsequent phosphating process by using polyaniline. The obtained electrocatalyst exhibits excellent electrochemical activity for HER with a small overpotential of ?135 mV at 10 mA cm^?2 and a low Tafel slope of 59.3 mV dec^?1 in 0.5 m H₂SO₄. Additionally, the encapsulation of N‐doped carbon shell prevents CoP nanoparticles from corrosion, exhibiting good stability after 14 h operation. Moreover, the as‐prepared electrocatalyst also shows outstanding activity and stability in basic and neutral electrolytes.     

Novel MOF‐Derived Co@N‐C Bifunctional Catalysts for Highly Efficient Zn–Air Batteries and Water Splitting

Metal–organic frameworks (MOFs) and MOF‐derived materials have recently attracted considerable interest as alternatives to noble‐metal electrocatalysts. Herein, the rational design and synthesis of a new class of Co@N‐C materials (C‐MOF‐C2‐T) from a pair of enantiotopic chiral 3D MOFs by pyrolysis at temperature T is reported. The newly developed C‐MOF‐C2‐900 with a unique 3D hierarchical rodlike structure, consisting of homogeneously distributed cobalt nanoparticles encapsulated by partially graphitized N‐doped carbon rings along the rod length, exhibits higher electrocatalytic activities for oxygen reduction and oxygen evolution reactions (ORR and OER) than that of commercial Pt/C and RuO₂, respectively. Primary Zn–air batteries based on C‐MOF‐900 for the oxygen reduction reaction (ORR) operated at a discharge potential of 1.30 V with a specific capacity of 741 mA h g_Zn^–1 under 10 mA cm^–2. Rechargeable Zn–air batteries based on C‐MOF‐C2‐900 as an ORR and OER bifunctional catalyst exhibit initial charge and discharge potentials at 1.81 and 1.28 V (2 mA cm^–2), along with an excellent cycling stability with no increase in polarization even after 120 h – outperform their counterparts based on noble‐metal‐based air electrodes. The resultant rechargeable Zn–air batteries are used to efficiently power electrochemical water‐splitting systems, demonstrating promising potential as integrated green energy systems for practical applications.     

Hierarchically Porous W‐Doped CoP Nanoflake Arrays as Highly Efficient and Stable Electrocatalyst for pH‐Universal Hydrogen Evolution

It is still challenging to develop high‐efficiency and low‐cost non‐noble metal‐based electrocatalysts for hydrogen evolution reaction (HER) in pH‐universal electrolytes. Herein, hierarchically porous W‐doped CoP nanoflake arrays on carbon cloth (W‐CoP NAs/CC) are synthesized via facile liquid‐phase reactions and a subsequent phosphorization process. The W‐CoP NAs/CC hybrid can be directly employed as a binder‐free electrocatalyst and delivers superior HER performance in pH‐universal electrolytes. Especially, it delivers very low overpotentials of 89, 94, and 102 mV to reach a current density of 10 mA cm^–2 in acidic, alkaline, and neutral electrolytes, respectively. Furthermore, it shows a nearly 100% Faradaic efficiency as well as superior long‐term stability with no decreasing up to 36 h in pH‐universal electrolytes. The outstanding electrocatalytic performance of W‐CoP NAs/CC can be mainly attributed to the porous W‐doped nanoflake arrays, which not only afford rich exposed active sites, but also accelerate the access of electrolytes and the diffusion of H₂ bubbles, thus efficiently promoting the HER performance. This work provides a new horizon to rationally design and synthesize highly effective and stable non‐noble metal phosphide‐based pH‐universal electrocatalysts for HER.     

Metal–Organic‐Framework‐Derived Hybrid Carbon Nanocages as a Bifunctional Electrocatalyst for Oxygen Reduction and Evolution

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are cornerstone reactions for many renewable energy technologies. Developing cheap yet durable substitutes of precious‐metal catalysts, especially the bifunctional electrocatalysts with high activity for both ORR and OER reactions and their streamlined coupling process, are highly desirable to reduce the processing cost and complexity of renewable energy systems. Here, a facile strategy is reported for synthesizing double‐shelled hybrid nanocages with outer shells of Co‐N‐doped graphitic carbon (Co‐NGC) and inner shells of N‐doped microporous carbon (NC) by templating against core–shell metal–organic frameworks. The double‐shelled NC@Co‐NGC nanocages well integrate the high activity of Co‐NGC shells into the robust NC hollow framework with enhanced diffusion kinetics, exhibiting superior electrocatalytic properties to Pt and RuO₂ as a bifunctional electrocatalyst for ORR and OER, and hold a promise as efficient air electrode catalysts in Zn–air batteries. First‐principles calculations reveal that the high catalytic activities of Co‐NGC shells are due to the synergistic electron transfer and redistribution between the Co nanoparticles, the graphitic carbon, and the doped N species. Strong yet favorable adsorption of an OOH* intermediate on the high density of uncoordinated hollow‐site C atoms with respect to the Co lattice in the Co‐NGC structure is a vital rate‐determining step to achieve excellent bifunctional electrocatalytic activity.     

Synergistic Coupling of Ni Nanoparticles with Ni3C Nanosheets for Highly Efficient Overall Water Splitting

Exploring earth‐abundant bifunctional electrocatalysts with high efficiency for water electrolysis is extremely demanding and challenging. Herein, density functional theory (DFT) predictions reveal that coupling Ni with Ni₃C can not only facilitate the oxygen evolution reaction (OER) kinetics, but also optimize the hydrogen adsorption and water adsorption energies. Experimentally, a facile strategy is designed to in situ fabricate Ni₃C nanosheets on carbon cloth (CC), and simultaneously couple with Ni nanoparticles, resulting in the formation of an integrated heterostructure catalyst (Ni–Ni₃C/CC). Benefiting from the superior intrinsic activity as well as the abundant active sites, the Ni–Ni₃C/CC electrode demonstrates excellent bifunctional electrocatalytic activities toward the OER and hydrogen evolution reaction (HER), which are superior to all the documented Ni₃C‐based electrocatalysts in alkaline electrolytes. Specifically, the Ni–Ni₃C/CC catalyst exhibits the low overpotentials of only 299 mV at the current density of 20 mA cm^?2 for the OER and 98 mV at 10 mA cm^?2 for the HER in 1 m KOH. Furthermore, the bifunctional Ni–Ni₃C/CC catalyst can propel water electrolysis with excellent activity and nearly 100% faradic efficiency. This work highlights an easy approach for designing and constructing advanced nickel carbide‐based catalysts with high activity based on the theoretical predictions.     

Significant Enhancement of Water Splitting Activity of N‐Carbon Electrocatalyst by Trace Level Co Doping

Replacement of precious metal electrocatalysts with highly active and cost efficient alternatives for complete water splitting at low voltage has attracted a growing attention in recent years. Here, this study reports a carbon‐based composite co‐doped with nitrogen and trace amount of metallic cobalt (1 at%) as a bifunctional electrocatalyst for water splitting at low overpotential and high current density. An excellent electrochemical activity of the newly developed electrocatalyst originates from its graphitic nanostructure and highly active Co‐N_x sites. In the case of carefully optimized sample of this electrocatalyst, 10 mA cm^?2 current density can be achieved for two half reactions in alkaline solutions—hydrogen evolution reaction and oxygen evolution reaction—at low overpotentials of 220 and 350 mV, respectively, which are smaller than those previously reported for nonprecious metal and metal‐free counterparts. Based on the spectroscopic and electrochemical investigations, the newly identified Co‐N_x sites in the carbon framework are responsible for high electrocatalytic activity of the Co,N‐doped carbon. This study indicates that a trace level of the introduced Co into N‐doped carbon can significantly enhance its electrocatalytic activity toward water splitting.     

Dual‐Native Vacancy Activated Basal Plane and Conductivity of MoSe2 with High‐Efficiency Hydrogen Evolution Reaction

Although transition metal dichalcogenide MoSe₂ is recognized as one of the low‐cost and efficient electrocatalysts for the hydrogen evolution reaction (HER), its thermodynamically stable basal plane and semiconducting property still hamper the electrocatalytic activity. Here, it is demonstrated that the basal plane and edges of 2H‐MoSe₂ toward HER can be activated by introducing dual‐native vacancy. The first‐principle calculations indicate that both the Se and Mo vacancies together activate the electrocatalytic sites in the basal plane and edges of MoSe₂ with the optimal hydrogen adsorption free energy (ΔG_H*) of 0 eV. Experimentally, 2D MoSe₂ nanosheet arrays with a large amount of dual‐native vacancies are fabricated as a catalytic working electrode, which possesses an overpotential of 126 mV at a current density of 100 mV cm^?2, a Tafel slope of 38 mV dec^?1, and an excellent long‐term durability. The findings pave a rational pathway to trigger the activity of inert MoSe₂ toward HER and also can be extended to other layered dichalcogenide.     

Nitrogen‐Doped Graphene‐Encapsulated Nickel–Copper Alloy Nanoflower for Highly Efficient Electrochemical Hydrogen Evolution Reaction

Development of high‐performance and low‐cost nonprecious metal electrocatalysts is critical for eco‐friendly hydrogen production through electrolysis. Herein, a novel nanoflower‐like electrocatalyst comprising few‐layer nitrogen‐doped graphene‐encapsulated nickel–copper alloy directly on a porous nitrogen‐doped graphic carbon framework (denoted as Ni_x Cu_y @ NG‐NC) is successfully synthesized using a facile and scalable method through calcinating the carbon, copper, and nickel hydroxy carbonate composite under inert atmosphere. The introduction of Cu can effectively modulate the morphologies and hydrogen evolution reaction (HER) performance. Moreover, the calcination temperature is an important factor to tune the thickness of graphene layers of the Ni_x Cu_y @ NG‐NC composites and the associated electrocatalytic performance. Due to the collective effects including unique porous flowered architecture and the synergetic effect between the bimetallic alloy core and graphene shell, the Ni₃Cu₁@ NG‐NC electrocatalyst obtained under optimized conditions exhibits highly efficient and ultrastable activity toward HER in harsh environments, i.e., a low overpotential of 122 mV to achieve a current density of 10 mA cm^?2 with a low Tafel slope of 84.2 mV dec^?1 in alkaline media, and a low overpotential of 95 mV to achieve a current density of 10 mA cm^?2 with a low Tafel slope of 77.1 mV dec^?1 in acidic electrolyte.     

Nickel@Nitrogen‐Doped Carbon@MoS2 Nanosheets: An Efficient Electrocatalyst for Hydrogen Evolution Reaction

Developing cheap, abundant, and easily available electrocatalysts to drive the hydrogen evolution reaction (HER) at small overpotentials is an urgent demand of hydrogen production from water splitting. Molybdenum disulfide (MoS₂) based composites have emerged as competitive electrocatalysts for HER in recent years. Herein, nickel@nitrogen‐doped carbon@MoS₂ nanosheets (Ni@NC@MoS₂) hybrid sub‐microspheres are presented as HER catalyst. MoS₂ nanosheets with expanded interlayer spacings are vertically grown on nickel@nitrogen‐doped carbon (Ni@NC) substrate to form Ni@NC@MoS₂ hierarchical sub‐microspheres by a simple hydrothermal process. The formed Ni@NC@MoS₂ composites display excellent electrocatalytic activity for HER with an onset overpotential of 18 mV, a low overpotential of 82 mV at 10 mA cm^?2, a small Tafel slope of 47.5 mV dec^?1, and high durability in 0.5 H₂SO₄ solution. The outstanding HER performance of the Ni@NC@MoS₂ catalyst can be ascribed to the synergistic effect of dense catalytic sites on MoS₂ nanosheets with exposed edges and expanded interlayer spacings, and the rapid electron transfer from Ni@NC substrate to MoS₂ nanosheets. The excellent Ni@NC@MoS₂ electrocatalyst promises potential application in practical hydrogen production, and the strategy reported here can also be extended to grow MoS₂ on other nitrogen‐doped carbon encapsulated metal species for various applications.     

Structural Design and Electronic Modulation of Transition‐Metal‐Carbide Electrocatalysts toward Efficient Hydrogen Evolution

As the key of hydrogen economy, electrocatalytic hydrogen evolution reactions (HERs) depend on the availability of cost‐efficient electrocatalysts. Over the past years, there is a rapid rise in noble‐metal‐free electrocatalysts. Among them, transition metal carbides (TMCs) are highlighted due to their structural and electronic merits, e.g., high conductivity, metallic band states, tunable surface/bulk architectures, etc. Herein, representative efforts and progress made on TMCs are comprehensively reviewed, focusing on the noble‐metal‐like electronic configuration and the relevant structural/electronic modulation. Briefly, specific nanostructures and carbon‐based hybrids are introduced to increase active‐site abundance and to promote mass transportation, and heteroatom doping and heterointerface engineering are encouraged to optimize the chemical configurations of active sites toward intrinsically boosted HER kinetics. Finally, a perspective on the future development of TMC electrocatalysts is offered. The overall aim is to shed some light on the exploration of emerging materials in energy chemistry.     

Single Tungsten Atoms Supported on MOF‐Derived N‐Doped Carbon for Robust Electrochemical Hydrogen Evolution

Tungsten‐based catalysts are promising candidates to generate hydrogen effectively. In this work, a single‐W‐atom catalyst supported on metal–organic framework (MOF)‐derived N‐doped carbon (W‐SAC) for efficient electrochemical hydrogen evolution reaction (HER), with high activity and excellent stability is reported. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) and X‐ray absorption fine structure (XAFS) spectroscopy analysis indicate the atomic dispersion of the W species, and reveal that the W₁N₁C₃ moiety may be the favored local structure for the W species. The W‐SAC exhibits a low overpotential of 85 mV at a current density of 10 mA cm^?2 and a small Tafel slope of 53 mV dec^?1, in 0.1 m KOH solution. The HER activity of the W‐SAC is almost equal to that of commercial Pt/C. Density functional theory (DFT) calculation suggests that the unique structure of the W₁N₁C₃ moiety plays an important role in enhancing the HER performance. This work gives new insights into the investigation of efficient and practical W‐based HER catalysts.     

Amorphous Ruthenium‐Sulfide with Isolated Catalytic Sites for Pt‐Like Electrocatalytic Hydrogen Production Over Whole pH Range

Electrocatalytic hydrogen evolution reaction (HER) is an efficient way to generate hydrogen fuel for the storage of renewable energy. Currently, the widely used Pt‐based catalysts suffer from high costs and limited electrochemical stability; therefore, developing an efficient alternative catalyst is very urgent. Herein, one pot hydrothermal synthesis is reported of amorphous ruthenium‐sulfide (RuS_x) nanoparticles (NPs) supported on sulfur‐doped graphene oxide (GO). The as‐obtained composite serves as a Pt‐like HER electrocatalyst. Achieving a current density of ?10 mA cm^?2 only requires a small overpotential (?31, ?46, and ?58 mV in acidic, neutral, and alkaline electrolyte, respectively) with high durability. The isolated Ru active site inducing Volmer–Heyrovsky mechanism in the RuS_x NPs is demonstrated by the Tafel analysis and X‐ray absorption spectroscopy characterization. Theoretical simulation indicates the isolated Ru site exhibits Pt‐like Gibbs free energy of hydrogen adsorption (?0.21 eV) therefore generating high intrinsic HER activity. Moreover, the strong bonding between the RuS_x and S–GO, as well as pH tolerance of RuS_x are believed to contribute to the high stability. This work shows a new insight for amorphous materials and provides alternative opportunities in designing advanced electrocatalysts with low‐cost for HER in the hydrogen economy.     

Room‐Temperature Sustainable Synthesis of Selected Platinum Group Metal (PGM = Ir,Rh, and Ru) Nanocatalysts Well‐Dispersed on Porous Carbon for Efficient Hydrogen Evolution and Oxidation

Electroless deposition via a spontaneous redox reaction between the metal precursor and support is believed to be a promising approach for the syntheses of supported metal nanoparticles (SMNPs). However, its widespread applications are significantly prohibited by the low reductivity and high cost of support. To overcome these shortcomings, a porous carbon (PC) is herein developed as a promising matrix for the electroless deposition of metal NPs. Benefiting from abundant oxygen‐based surface functional groups, the PC shows stronger reducibility (low redox potential) than conventional carbon substrate such as carbon nanotubes or graphene oxide, enabling a facile electroless deposition of Ir, Rh, and Ru NPs on its surface. These SMNPs exhibit an impressive electrocatalytic activity for the hydrogen evolution reaction (HER) or hydrogen oxidation reaction (HOR). For example, the Rh NP/PC can deliver an HER current density of 10 mA cm^?2 with a small overpotential of 21 mV in 0.5 m H₂SO₄, while the Ru NP/PC exhibits excellent HOR activity in 0.1 m KOH in terms of high mass and surface specific exchange current density of 263 A g^?1_Ru and 0.227 mA cm^?2_Ru. The present strategy may open up opportunities for mass production of efficient supported NPs for diverse applications.     

Hydrogen‐Etched Bifunctional Sulfur‐Defect‐Rich ReS2/CC Electrocatalyst for Highly Efficient HER and OER

The design on synthesizing a sturdy, low‐cost, clean, and sustainable electrocatalyst, as well as achieving high performance with low overpotential and good durability toward water splitting, is fairly vital in environmental and energy‐related subject. Herein, for the first time the growth of sulfur (S) defect engineered self‐supporting array electrode composed of metallic Re and ReS₂ nanosheets on carbon cloth (referred as Re/ReS₂/CC) via a facile hydrothermal method and the following thermal treatment with H₂/N₂ flow is reported. It is expected that, for example, the as‐prepared Re/ReS₂‐7H/CC for the electrocatalytic hydrogen evolution reaction (HER) under acidic medium affords a quite low overpotential of 42 mV to achieve a current density of 10 mA cm^?2 and a very small Tafel slope of 36 mV decade^?1, which are comparable to some of the promising HER catalysts. Furthermore, in the two‐electrode system, a small cell voltage of 1.30 V is recorded under alkaline condition. Characterizations and density functional theory results expound that the introduced S defects in Re/ReS₂‐7H/CC can offer abundant active sites to advantageously capture electron, enhance the electron transport capacity, and weaken the adsorption free energy of H* at the active sites, being responsible for its superior electrocatalytic performance.