Embedding RhPx in N,P Co‐Doped Carbon Nanoshells Through Synergetic Phosphorization and Pyrolysis for Efficient Hydrogen Evolution

Rational design and controllable synthesis of well‐defined nanostructures with high stability and Pt‐like activity for hydrogen evolution reaction (HER) are critical for renewable energy conversion. Herein, a unique pyrolysis strategy is demonstrated for the synthesis of RhP_x nanoparticles (NPs) in N, P co‐doped thin carbon nanoshells (RhP_x@NPC nanoshells) that display high electrocatalytic activity and stability over a wide pH range. This strategy involves simultaneous phosphorization and pyrolysis processes that can produce highly‐dispersed RhP_x NPs within N, P co‐doped carbon nanoshells and at the same time induce thinning of carbon nanoshells from inside out. The resulting RhP_x@NPC nanoshells not only possess Pt‐like activity for HER with low overpotentials to achieve 10 mA cm^?2 (22 mV in 0.5 m H₂SO₄, 69 mV in 1.0 m KOH, and 38 mV in 1.0 m phosphate buffered saline (PBS)) but also provide long‐term durability in a wide pH range. The remarkable HER performance of RhP_x@NPC nanoshells is ascribed to the high surface area, abundant mesoporosity, strong catalyst–support interaction, ultrathin carbon encapsulation, and N, P co‐doping. This work provides an effective strategy for designing heterostructured electrocatalysts with high catalytic activity and stability desired for reactions that may occur under harsh conditions.     

Hybridization of Bimetallic Molybdenum‐Tungsten Carbide with Nitrogen‐Doped Carbon: A Rational Design of Super Active Porous Composite Nanowires with Tailored Electronic Structure for Boosting Hydrogen Evolution Catalysis

An ecofriendly and robust strategy is developed to construct a self‐supported monolithic electrode composed of N‐doped carbon hybridized with bimetallic molybdenum‐tungsten carbide (Mo_xW_2?xC) to form composite nanowires for hydrogen evolution reaction (HER). The hybridization of Mo_xW_2?xC with N‐doped carbon enables effective regulation of the electrocatalytic performance of the composite nanowires, endowing abundant accessible active sites derived from N‐doping and Mo_xW_2?xC incorporation, outstanding conductivity resulting from the N‐doped carbon matrix, and appropriate positioning of the d‐band center with a thermodynamically favorable hydrogen adsorption free energy (ΔG_H*) for efficient hydrogen evolution catalysis, which forms a binder‐free 3D self‐supported monolithic electrode with accessible nanopores, desirable chemical compositions and stable composite structure. By modulating the Mo/W ratio, the optimal Mo_1.33W_0.67C @ NC nanowires on carbon cloth achieve a low overpotential (at a geometric current density of 10 mA cm^?2) of 115 and 108 mV and a small Tafel slope of 58.5 and 55.4 mV dec^?1 in acidic and alkaline environments, respectively, which can maintain 40 h of stable performance, outperforming most of the reported metal‐carbide‐based HER electrocatalysts.     

Synergistically Tuning Electronic Structure of Porous β‐Mo2C Spheres by Co Doping and Mo‐Vacancies Defect Engineering for Optimizing Hydrogen Evolution Reaction Activity

The development of novel non‐noble electrocatalysts with controlled structure and surface composition is critical for efficient electrochemical hydrogen evolution reaction (HER). Herein, the rational design of porous molybdenum carbide (β‐Mo₂C) spheres with different surface engineered structures (Co doping, Mo vacancies generation, and coexistence of Co doping and Mo vacancies) is performed to enhance the HER performance over the β‐Mo₂C‐based catalyst surface. Density functional theory calculations and experimental results reveal that the synergistic effect of Co doping with Mo vacancies increases the electron density around the Fermi‐level and modulates the d band center of β‐Mo₂C so that the strength of the Mo? H bond is reasonably optimized, thus leading to an enhanced HER kinetics. As expected, the optimized Co₅₀‐Mo₂C‐12 with porous structure displays a low overpotential (η₁₀ = 125 mV), low‐onset overpotential (η_onset = 27 mV), and high exchange current density (j₀ = 0.178 mA cm^?2). Furthermore, this strategy is also successfully extended to develop other effective metal (e.g., Fe and Ni) doped β‐Mo₂C electrocatalyst, indicating that it is a universal strategy for the rational design of highly efficient metal carbide‐based HER catalysts and beyond.     

Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen‐Doped Carbon Nanotubes for Hydrogen Evolution Reaction

Finding an abundant and cost‐effective electrocatalyst for the hydrogen evolution reaction (HER) is crucial for a global production of hydrogen from water electrolysis. This work reports an exceptionally large surface area hybrid catalyst electrode comprising semicrystalline molybdenum sulfide (MoS_2+x) catalyst attached on a substrate based on nitrogen‐doped carbon nanotubes (N‐CNTs), which are directly grown on carbon fiber paper (CP). It is shown here that nitrogen‐doping of the carbon nanotubes improves the anchoring of MoS_2+x catalyst compared to undoped carbon nanotubes and concurrently stabilizes a semicrystalline structure of MoS_2+x with a high exposure of active sites for HER. The well‐connected constituents of the hybrid catalyst are shown to facilitate electron transport and as a result of the good attributes, the MoS_2+x/N‐CNT/CP electrode exhibits an onset potential of ?135 mV for HER in 0.5 m H₂SO₄, a Tafel slope of 36 mV dec^?1, and high stability at a current density of ?10 mA cm^?2.     

Controllable Synthesis of Nanosized Amorphous MoSx Using Temporally Shaped Femtosecond Laser for Highly Efficient Electrochemical Hydrogen Production

Amorphous molybdenum sulfide (a‐MoS_x) is regarded as a promising electrocatalyst for hydrogen evolution reaction (HER) due to its disorder structures with a significant number of defect‐rich active sites. Here, a green, one‐step, and controllable method is developed to photoregulate the chemical reactions and synthesize nanosized a‐MoS_x by temporally shaped femtosecond laser ablation of ammonium tetrathiomolybdate aqueous solution. By adjusting the laser energy and pulse delay to control photoinduced and/or photothermal‐induced reduction/oxidation, the S to Mo ratio x can be modulated from 1.53 to 3.07 and the ratio of the Mo^V defect species, bridging S₂^2?, and terminal S₂^2? ligands can be controlled. The optimized a‐MoS_x catalysts (x = 2.73) exhibit high catalytic activity with a low Tafel slope of 40 mV dec^?1, high double‐layer capacitance of 74.47 mF cm^?2, and large current density of 516 mA cm^?2 at an overpotential of 250 mV. The high catalytic activity can be mainly attributed to Mo^V defect species and bridging S₂^2? ligands, or most likely dominated by the Mo^V defect species. This study not only provides an alternatively controllable method to prepare a‐MoS_x as efficient HER catalysts but also contributes to the understanding of the origin of its catalytic activity.     

Refining Energy Levels in ReS2 Nanosheets by Low‐Valent Transition‐Metal Doping for Dual‐Boosted Electrochemical Ammonia/Hydrogen Production

Electrocatalytic nitrogen reduction reaction (NRR) and hydrogen evolution reaction (HER) are intriguing approaches to nitrogen fixation and hydrogen production under ambient conditions, given the need to discover efficient and stable catalysts to light up the “green chemistry” future. However, bottlenecks are often found during N₂/H₂O activation, the very first step of NRR/HER, due to energetic electron injection from the surface of electrocatalysts. It is reported that the bottlenecks for both NRR and HER can be tackled by engineering the energy level via low‐valent transition‐metal doping, simultaneously, where rhenium disulfide (ReS₂) is employed as a model platform to prove the concept. The doped low‐valent transition‐metal domains (e.g., Fe, Co, Ni, Cu, Zn) in ReS₂ provide more active sites for N₂/H₂O chemisorption and electron transfer, not only weakening the N?N/O? H bonds for easier dissociation through proton coupling, but also elevating d‐band center toward the Fermi level with more electron energy for N₂/H₂O reduction. As a result, it is found that iron‐doped ReS₂ nanosheets wrapped nitrogen‐doped carbon nanofiber (Fe‐ReS₂@N‐CNF) catalyst exhibits superior electrochemical activity with eightfold higher ammonia production yield of 80.4 µg h^?1 mg^?1_cat., and lower onset overpotential of 146 mV and Tafel slope of 63 mV dec^?1, when comparing with the pristine ReS₂.     

Activating Basal Planes and S‐Terminated Edges of MoS2 toward More Efficient Hydrogen Evolution

Molybdenum disulfide (MoS₂) has been considered as a promising alternative to platinum (Pt)‐based catalyst for hydrogen evolution reaction (HER) due to its low cost and high catalytic activity. However, stable 2H phase of MoS₂ (2H‐MoS₂) exhibits low catalytic activity in HER due to the inert basal plane and S‐edge. Thus, to exploit the basal plane and S‐edge for additional electrocatalytic activity, a facile strategy is developed to prepare P‐doped 2H‐MoS₂ film on conductive substrate via low‐temperature heat treatment. Due to the inherent difficulty of P‐doping into MoS₂ crystal structure, oxygen (O)‐doping is utilized to aid the P‐doping process, as supported by the first‐principles calculations. Interestingly, P‐doping could dramatically reduce Mo valence charge, which results in the functionalization of the inert MoS₂ basal plane and S‐edge. In agreement with simulation results, P‐doped 2H‐MoS₂ electrode exhibits enhanced catalytic performance in H₂ generation with low onset potential (130 mV) and small Tafel slope of 49 mV dec^?1. The enhanced catalytic performance arises from the synergistic effect of the activated basal plane, S‐edge, and Mo‐edge sites, leading to favorable hydrogen adsorption energies. Most importantly, improved cyclic stability is achieved, which reveals chemically inert properties of P‐doped 2H‐MoS₂ in acidic electrolyte.     

Metal (Ni,Co)‐Metal Oxides/Graphene Nanocomposites as Multifunctional Electrocatalysts

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) along with hydrogen evolution reaction (HER) have been considered critical processes for electrochemical energy conversion and storage through metal‐air battery, fuel cell, and water electrolyzer technologies. Here, a new class of multifunctional electrocatalysts consisting of dominant metallic Ni or Co with small fraction of their oxides anchored onto nitrogen‐doped reduced graphene oxide (rGO) including Co‐CoO/N‐rGO and Ni‐NiO/N‐rGO are prepared via a pyrolysis of graphene oxide and cobalt or nickel salts. Ni‐NiO/N‐rGO shows the higher electrocatalytic activity for the OER in 0.1 m KOH with a low overpotential of 0.24 V at a current density of 10 mA cm^?2, which is superior to that of the commercial IrO₂. In addition, it exhibits remarkable activity for the HER, demonstrating a low overpotential of 0.16 V at a current density of 20 mA cm^?2 in 1.0 m KOH. Apart from similar HER activity to the Ni‐based catalyst, Co‐CoO/N‐rGO displays the higher activity for the ORR, comparable to Pt/C in zinc‐air batteries. This work provides a new avenue for the development of multifunctional electrocatalysts with optimal catalytic activity by varying transition metals (Ni or Co) for these highly demanded electrochemical energy technologies.     

A Composite of Carbon‐Wrapped Mo2C Nanoparticle and Carbon Nanotube Formed Directly on Ni Foam as a High‐Performance Binder‐Free Cathode for Li‐O2 Batteries

Cathode design is indispensable for building Li‐O₂ batteries with long cycle life. A composite of carbon‐wrapped Mo₂C nanoparticles and carbon nanotubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin. The Mo₂C nanoparticles with well‐controlled particle size act as a highly active oxygen reduction reactions/oxygen evolution reactions (ORR/OER) catalyst. The carbon coating can prevent the aggregation of the Mo₂C nanoparticles. The even distribution of Mo₂C nanoparticles results in the homogenous formation of discharge products. The skeleton of porous carbon with carbon nanotubes protrudes from the composite, resulting in extra voids when applied as a cathode for Li‐O₂ batteries. The batteries deliver a high discharge capacity of ≈10 400 mAh g^?1 and a low average charge voltage of ≈4.0 V at 200 mA g^?1. With a cutoff capacity of 1000 mAh g^?1, the Li‐O₂ batteries exhibit excellent charge–discharge cycling stability for over 300 cycles. The average potential polarization of discharge/charge gaps is only ≈0.9 V, demonstrating the high ORR and OER activities of these Mo₂C nanoparticles. The excellent cycling stability and low potential polarization provide new insights into the design of highly reversible and efficient cathode materials for Li‐O₂ batteries.     

Engineering Fe–Fe3C@Fe–N–C Active Sites and Hybrid Structures from Dual Metal–Organic Frameworks for Oxygen Reduction Reaction in H2–O2 Fuel Cell and Li–O2 Battery

Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe₃C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction reaction (ORR) electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe₃C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm^?2 in peak power density) and an aprotic Li–O₂ battery (8749 mAh g^?1 in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe₃C contribution to the catalyst performance, suggesting Fe₃C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications.     

Cobalt‐Doping in Molybdenum‐Carbide Nanowires Toward Efficient Electrocatalytic Hydrogen Evolution

Efficient hydrogen evolution reaction (HER) over noble‐metal‐free electrocatalysts provides one of the most promising pathways to face the energy crisis. Herein, facile cobalt‐doping based on Co‐modified MoO_x–amine precursors is developed to optimize the electrochemical HER over Mo₂C nanowires. The effective Co‐doping into Mo₂C crystal structure increases the electron density around Fermi level, resulting in the reduced strength of Mo–H for facilitated HER kinetics. As expected, the Co‐Mo₂C nanowires with an optimal Co/Mo ratio of 0.020 display a low overpotential (η₁₀ = 140 and 118 mV for reaching a current density of –10 mA cm^?2; η₁₀₀ = 200 and 195 mV for reaching a current density of –100 mA cm^?2), a small Tafel slope (39 and 44 mV dec^?1), and a low onset overpotential (40 and 25 mV) in 0.5 m H₂SO₄ and 1.0 m KOH, respectively. This work highlights a feasible strategy to explore efficient electrocatalysts via engineering on composition and nanostructure.     

Development and Simulation of Sulfur‐doped Graphene Supported Platinum with Exemplary Stability and Activity Towards Oxygen Reduction

Sulfur‐doped graphene (SG) is prepared by a thermal shock/quench anneal process and investigated as a unique Pt nanoparticle support (Pt/SG) for the oxygen reduction reaction (ORR). Particularly, SG is found to induce highly favorable catalyst‐support interactions, resulting in excellent half‐cell based ORR activity of 139 mA mg_Pt ^?1 at 0.9 V vs RHE, significant improvements over commercial Pt/C (121 mA mg_Pt ^?1) and Pt‐graphene (Pt/G, 101 mA mg_Pt ^?1). Pt/SG also demonstrates unprecedented stability, maintaining 87% of its electrochemically active surface area following accelerated degradation testing. Furthermore, a majority of ORR activity is maintained, providing 108 mA mg_Pt ^?1, a remarkable 171% improvement over Pt/C (39.8 mA mg_Pt ^?1) and an 89% improvement over Pt/G (57.0 mA mg_Pt ^?1). Computational simulations highlight that the interactions between Pt and graphene are enhanced significantly by sulfur doping, leading to a tethering effect that can explain the outstanding electrochemical stability. Furthermore, sulfur dopants result in a downshift of the platinum d‐band center, explaining the excellent ORR activity and rendering SG as a new and highly promising class of catalyst supports for electrochemical energy technologies such as fuel cells.     

Activating Basal Planes of NiPS3 for Hydrogen Evolution by Nonmetal Heteroatom Doping

NiPS₃, one of the most promising catalysts among transition metal trichalcogenidophosphates (MTPs) in hydrogen evolution reaction (HER) electrocatalysis, is still inhibited by its unsatisfactory activity originating from its semiconducting nature and inert basal plane. Here, it is proposed, for the first time, to engineer the basal surface activity of NiPS₃ by nonmetal heteroatom doping, and predict that the degree to which the valance band of NiPS₃ is filled dominates not only the electrical conductivity of the catalyst, but also the strength of hydrogen adsorption at its surface. Direct experimental evidence is offered that in all the single nonmetal doping samples, C‐doped NiPS₃ exhibits the optimum activity owing to its moderate filled state of valance band and that C, N codoping even shows Pt‐like activity with an ultralow overpotential of 53.2 mV to afford 10 mA cm^?2 current density and a high exchange current density of 0.7 mA cm^?2 in 1 m KOH. The findings that less valance electrons of dopants than substitutional atoms are of pivotal importance for improving HER activity of NiPS₃ catalyst pave the way for readily designing novel MTPs of ever high performance to replace the incumbent Pt‐based catalysts.     

MO‐Co@N‐Doped Carbon (M = Zn or Co): Vital Roles of Inactive Zn and Highly Efficient Activity toward Oxygen Reduction/Evolution Reactions for Rechargeable Zn–Air Battery

A highly efficient bifunctional oxygen catalyst is required for practical applications of fuel cells and metal–air batteries, as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are their core electrode reactions. Here, the MO‐Co@N‐doped carbon (NC, M = Zn or Co) is developed as a highly active ORR/OER bifunctional catalyst via pyrolysis of a bimetal metal–organic framework containing Zn and Co, i.e., precursor (CoZn). The vital roles of inactive Zn in developing highly active bifunctional oxygen catalysts are unraveled. When the precursors include Zn, the surface contents of pyridinic N for ORR and the surface contents of Co–N_x and Co³⁺/Co²⁺ ratios for OER are enhanced, while the high specific surface areas, high porosity, and high electrochemical active surface areas are also achieved. Furthermore, the synergistic effects between Zn‐based and Co‐based species can promote the well growth of multiwalled carbon nanotubes (MWCNTs) at high pyrolysis temperatures (≥700 °C), which is favorable for charge transfer. The optimized CoZn‐NC‐700 shows the highly bifunctional ORR/OER activity and the excellent durability during the ORR/OER processes, even better than 20 wt% Pt/C (for ORR) and IrO₂ (for OER). CoZn‐NC‐700 also exhibits the prominent Zn–air battery performance and even outperforms the mixture of 20 wt% Pt/C and IrO₂.     

Ru–Ru2PΦNPC and NPC@RuO2 Synthesized via Environment‐Friendly and Solid‐Phase Phosphating Process by Saccharomycetes as N/P Sources and Carbon Template for Overall Water Splitting in Acid Electrolyte

Although numerous ruthenium‐based phosphates possess high catalytic activities for hydrogen evolution reaction (HER), most of them rely on dangerous and toxic synthesis routes. Biological slices confirm that Ru ions can penetrate the cell walls of saccharomycete, which facilitates the adsorption of Ru ions. Herein, based on a green synthesis process by saccharomycete cells as the carbon template and nitrogen/phosphorus (N/P) sources, novel Janus‐like ruthenium–ruthenium phosphide nanoparticles embedded into a N/P dual‐doped carbon matrix (Ru–Ru₂PΦNPC) electrocatalyst for HER are synthesized. Electrochemical tests reveal that Ru–Ru₂PΦNPC displays remarkable performance with a low overpotential of 42 mV at 10 mA cm^?2 and demonstrates superior stability at a high current density in 0.5 m H₂SO₄. Furthermore, ruthenium oxide nanoparticles coated N/P dual‐doped carbon (NPC@RuO₂) are also synthesized with a yolk–shell structure using saccharomycete cells as the core template and RuO₂ as a shell to isolate saccharomycete cells from the oxidation reaction during calcination in air. The NPC@RuO₂ as oxygen evolution reaction electrocatalyst possesses a low overpotential of 220 mV at 10 mA cm^?2. Finally, the Ru–Ru₂PΦNPC is integrated as a cathode and NPC@RuO₂ is integrated as an anode to construct a two‐electrode electrolyzer to enable an excellent performance for overall water splitting with a cell voltage of 1.50 V at 10 mA cm^?2 in 0.5 m H₂SO₄.     

Promoting Active Sites in Core–Shell Nanowire Array as Mott–Schottky Electrocatalysts for Efficient and Stable Overall Water Splitting

Developing earth‐abundant, active, and robust electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a vital challenge for efficient conversion of sustainable energy sources. Herein, metal–semiconductor hybrids are reported with metallic nanoalloys on various defective oxide nanowire arrays (Cu/CuO_x, Co/CoO_x, and CuCo/CuCoO_x) as typical Mott–Schottky electrocatalysts. To build the highway of continuous electron transport between metals and semiconductors, nitrogen‐doped carbon (NC) has been implanted on metal–semiconductor nanowire array as core–shell conductive architecture. As expected, NC/CuCo/CuCoO_x nanowires arrays, as integrated Mott–Schottky electrocatalysts, present an overpotential of 112 mV at 10 mA cm^?2 and a low Tafel slope of 55 mV dec^?1 for HER, simultaneously delivering an overpotential of 190 mV at 10 mA cm^?2 for OER. Most importantly, NC/CuCo/CuCoO_x architectures, as both the anode and the cathode for overall water splitting, exhibit a current density of 10 mA cm^?2 at a cell voltage of 1.53 V with excellent stability due to high conductivity, large active surface area, abundant active sites, and the continuous electron transport from prominent synergetic effect among metal, semiconductor, and nitrogen‐doped carbon. This work represents an avenue to design and develop efficient and stable Mott–Schottky bifunctional electrocatalysts for promising energy conversion.     

Toward Full Exposure of “Active Sites”: Nanocarbon Electrocatalyst with Surface Enriched Nitrogen for Superior Oxygen Reduction and Evolution Reactivity

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play a decisive role for the efficiency of fuel cells and metal‐air batteries. The nitrogen doped carbon materials with low cost and long durability are potential catalysts to replace precious metal catalyst for oxygen electrochemistry; however, the unexposed active sites induced by the bulk dopant atoms are hardly accessible and consequently scarcely contribute to the catalytic property. In this study, carbon nanotubes (CNTs) are selected as the platform to demonstrate the potential of full exposure of ‘active sites’ at the surface. Novel N‐doped carbon coaxial nanocables with the pristine CNTs as the core and the N‐doped carbon layers as the shell are proposed. The accessible and efficient utilization of the integrated nitrogen atoms enriched on the surface, together with the undestroyed intact inner walls, render the electrocatalyst much enhanced electrocatalytic activity and high electrical conductivity of 3.3 S cm^?1, therefore, N‐doped nanocables afford higher oxygen reduction current, ～51 mV positively shift onset potential, low peroxide generation, as well as lower overpotential and higher current for oxygen evoluation reaction.     

Iron–Nitrogen‐Doped Vertically Aligned Carbon Nanotube Electrocatalyst for the Oxygen Reduction Reaction

A highly active iron–nitrogen‐doped carbon nanotube catalyst for the oxygen reduction reaction (ORR) is produced by employing vertically aligned carbon nanotubes (VA‐CNT) with a high specific surface area and iron(II) phthalocyanine (FePc) molecules. Pyrolyzing the composite easily transforms the adsorbed FePc molecules into a large number of iron coordinated nitrogen functionalized nanographene (Fe–N–C) structures, which serve as ORR active sites on the individual VA‐CNT surfaces. The catalyst exhibits a high ORR activity, with onset and half‐wave potentials of 0.97 and 0.79 V, respectively, versus reversible hydrogen electrode, a high selectivity of above 3.92 electron transfer number, and a high electrochemical durability, with a 17 mV negative shift of E _1/2 after 10 000 cycles in an oxygen‐saturated 0.5 m H₂SO₄ solution. The catalyst demonstrates one of the highest ORR performances in previously reported any‐nanotube‐based catalysts in acid media. The excellent ORR performance can be attributed to the formation of a greater number of catalytically active Fe–N–C centers and their dense immobilization on individual tubes, in addition to more efficient mass transport due to the mesoporous nature of the VA‐CNTs.     

Facile Synthesis of Manganese‐Oxide‐Containing Mesoporous Nitrogen‐Doped Carbon for Efficient Oxygen Reduction

Developing low‐cost non‐precious metal catalysts for high‐performance oxygen reduction reaction (ORR) is highly desirable. Here a facile, in situ template synthesis of a MnO‐containing mesoporous nitrogen‐doped carbon (m‐N‐C) nanocomposite and its high electrocatalytic activity for a four‐electron ORR in alkaline solution are reported. The synthesis of the MnO‐m‐N‐C nanocomposite involves one‐pot hydrothermal synthesis of Mn₃O₄@polyaniline core/shell nanoparticles from a mixture containing aniline, Mn(NO₃)₂, and KMnO₄, followed by heat treatment to produce N‐doped ultrathin graphitic carbon coated MnO hybrids and partial acid leaching of MnO. The as‐prepared MnO‐m‐N‐C composite catalyst exhibits high electrocatalytic activity and dominant four‐electron oxygen reduction pathway in 0.1 M KOH aqueous solution due to the synergetic effect between MnO and m‐N‐C. The pristine MnO shows little electrocatalytic activity and m‐N‐C alone exhibits a dominant two‐electron process for ORR. The MnO‐m‐N‐C composite catalyst also exhibits superior stability and methanol tolerance to a commercial Pt/C catalyst, making the composite a promising cathode catalyst for alkaline methanol fuel cell applications. The synergetic effect between MnO and N‐doped carbon described provides a new route to design advanced catalysts for energy conversion.     

Novel Molybdenum Carbide–Tungsten Carbide Composite Nanowires and Their Electrochemical Activation for Efficient and Stable Hydrogen Evolution

Development of nonnoble metal catalysts for hydrogen evolution reaction (HER) is critical to enable an efficient production of hydrogen at low cost and large scale. In this work, a novel bimetallic carbide nanostructure consisting of Mo₂C and WC is synthesized. Based on a highly conductive WC backbone, nanosized Mo₂C particles are integrated onto WC, forming a well‐defined and highly robust nanowire structure. More importantly, it is found that electrochemical activation can partially remove surface carbon and activate the catalyst by changing its surface hydrophilicity. As a result, the residual carbon contributes positively to the activity, besides its role of protecting carbide from oxidation. Benefiting from the structure, the catalyst achieves high activity, stable electrolysis towards HER.