UIO‐66‐NH2‐Derived Mesoporous Carbon Catalyst Co‐Doped with Fe/N/S as Highly Efficient Cathode Catalyst for PEMFCs

Efficient, low‐cost catalysts are desirable for the sluggish oxygen reduction reaction (ORR). Herein, UIO‐66‐NH₂‐derived multi‐element (Fe, S, N) co‐doped porous carbon catalyst is reported, Fe/N/S‐PC, with an octahedral morphology, a well‐defined mesoporous structure, and highly dispersed doping elements, synthesized by a double‐solvent diffusion‐pyrolysis method (DSDPM). The morphology of the UIO‐66‐NH₂ precursor is perfectly inherited by the derived carbon material, resulting in a high surface area, a well‐defined mesoporous structure, and atomic‐level dispersion of the doping elements. Fe/N/S‐PC demonstrates outstanding catalytic activity and durability for the ORR in both alkaline and acidic solutions. In 0.1 m KOH, its half‐potential reaches 0.87 V (vs reversible hydrogen electrode (RHE)), 30 mV more positive than that of a 20 wt% Pt/C catalyst. In 0.1 m HClO₄, it reaches 0.785 V (vs RHE), only 65 mV less than that of Pt/C. The catalyst also exhibits excellent performance in acidic hydrogen/oxygen proton exchange membrane fuel cells. A membrane electrode assembly (MEA) with the catalyst as the cathode reaches 700 mA·cm^‐2 at 0.6 V and a maximum power density of 553 mW·cm^‐2, ranking it among the best MEAs with a nonprecious metal catalyst as the cathode.     

Holey Reduced Graphene Oxide Coupled with an Mo2N–Mo2C Heterojunction for Efficient Hydrogen Evolution

An in situ catalytic etching strategy is developed to fabricate holey reduced graphene oxide along with simultaneous coupling with a small‐sized Mo₂N–Mo₂C heterojunction (Mo₂N–Mo₂C/HGr). The method includes the first immobilization of H₃PMo₁₂O₄₀ (PMo₁₂) clusters on graphite oxide (GO), followed by calcination in air and NH₃ to form Mo₂N–Mo₂C/HGr. PMo₁₂ not only acts as the Mo heterojunction source, but also provides the Mo species that can in situ catalyze the decomposition of adjacent reduced GO to form HGr, while the released gas (CO) and introduced NH₃ simultaneously react with the Mo species to form an Mo₂N–Mo₂C heterojunction on HGr. The hybrid exhibits superior activity towards the hydrogen evolution reaction with low onset potentials of 11 mV (0.5 m H₂SO₄) and 18 mV (1 m KOH) as well as remarkable stability. The activity in alkaline media is also superior to Pt/C at large current densities (>88 mA cm^?2). The good activity of Mo₂N–Mo₂C/HGr is ascribed to its small size, the heterojunction of Mo₂N–Mo₂C, and the good charge/mass‐transfer ability of HGr, as supported by a series of experiments and theoretical calculations.     

Robust Fe3Mo3C Supported IrMn Clusters as Highly Efficient Bifunctional Air Electrode for Metal–Air Battery

Catalysts at the air cathode for oxygen reduction and evolution reactions are central to the stability of rechargeable metal–air batteries, an issue that is gaining increasing interest in recent years. Herein, a highly durable and efficient carbide‐based bifunctional catalyst consisting of iron–molybdenum carbide (Fe₃Mo₃C) and IrMn nanoalloys is demonstratred. This carbide is chemically stable in alkaline media and over the potential range of an air cathode. More importantly, Fe₃Mo₃C is very active for oxygen reduction reaction (ORR) in alkaline media. Fe₃Mo₃C supported IrMn as a bifunictional catalysts exhibits superior catalytic performance than the state of the art ORR catalyst (Pt/C) and the oxygen evolution reaction catalyst (Ir/C). IrMn/Fe₃Mo₃C enables Zn–air batteries to achieve long‐term cycling performance over 200 h with high efficiency. The extraordinarily high performance of IrMn/Fe₃Mo₃C bifunictional catalyst provides a very promising alternative to the conventional Pt/C and Ir/C catalyst for an air cathode in alkaline electrolyte.     

2D Nanoporous Fe−N/C Nanosheets as Highly Efficient Non‐Platinum Electrocatalysts for Oxygen Reduction Reaction in Zn‐Air Battery

It is an ongoing challenge to fabricate nonprecious oxygen reduction reaction (ORR) catalysts that can be comparable to or exceed the efficiency of platinum. A highly active non‐platinum self‐supporting Fe?N/C catalyst has been developed through the pyrolysis of a new type of precursor of iron coordination complex, in which 1,4‐bis(1H‐1,3,7,8–tetraazacyclopenta(1)phenanthren‐2‐yl)benzene (btcpb) functions as a ligand complexing Fe(II) ions. The optimal catalyst pyrolyzed at 700 °C (Fe?N/C?700) shows the best ORR activity with a half‐wave potential (E_1/2) of 840 mV versus reversible hydrogen electrode (RHE) in 0.1 m KOH, which is more positive than that of commercial Pt/C (E_1/2: 835 mV vs RHE). Additionally, the Fe?N/C?700 catalyst also exhibits high ORR activity in 0.1 m HClO₄ with the onset potential and E_1/2 comparable to those of the Pt/C catalyst. Notably, the Fe?N/C?700 catalyst displays superior durability (9.8 mV loss in 0.1 m KOH and 23.6 mV loss in 0.1 m HClO₄ for E_1/2 after 8000 cycles) and better tolerance to methanol than Pt/C. Furthermore, the Fe?N/C?700 catalyst can be used for fabricating the air electrode in Zn–air battery with a specific capacity of 727 mA hg^?1 at 5 mA cm^?2 and a negligible voltage loss after continuous operation for 110 h.     

Tuning the Activity of Carbon for Electrocatalytic Hydrogen Evolution via an Iridium‐Cobalt Alloy Core Encapsulated in Nitrogen‐Doped Carbon Cages

Graphene, a 2D material consisting of a single layer of sp²‐hybridized carbon, exhibits inert activity as an electrocatalyst, while the incorporation of heteroatoms (such as N) into the framework can tune its electronic properties. Because of the different electronegativity between N and C atoms, electrons will transfer from C to N in N‐doped graphene nanosheets, changing inert C atoms adjacent to the N‐dopants into active sites. Notwithstanding the achieved progress, its intrinsic activity in acidic media is still far from Pt/C. Here, a facile annealing strategy is adopted for Ir‐doped metal‐organic frameworks to synthesize IrCo nanoalloys encapsulated in N‐doped graphene layers. The highly active electrocatalyst, with remarkably reduced Ir loading (1.56 wt%), achieves an ultralow Tafel slope of 23 mV dec^?1 and an overpotential of only 24 mV at a current density of 10 mA cm^?2 in 0.5 m sulfuric acid solution. Such superior performance is even superior to the noble‐metal catalyst Pt. Surface structural and computational studies reveal that the superior behavior originates from the decreased ΔG_H* for HER induced by the electrons transferred from the alloy core to the graphene layers, which is beneficial for enhancing C? H binding.     

Ganoderma‐Like MoS2/NiS2 with Single Platinum Atoms Doping as an Efficient and Stable Hydrogen Evolution Reaction Catalyst

Herein, a unique ganoderma‐like MoS₂/NiS₂ hetero‐nanostructure with isolated Pt atoms anchored is reported. This novel ganoderma‐like heterostructure can not only efficiently disperse and confine the few‐layer MoS₂ nanosheets to fully expose the edge sites of MoS₂, and provide more opportunity to capture the Pt atoms, but also tune the electronic structure to modify the catalytic activity. Because of the favorable dispersibility and exposed large specific surface area, single Pt atoms can be easily anchored on MoS₂ nanosheets with ultrahigh loading of 1.8 at% (the highest is 1.3 at% to date). Owing to the ganoderma‐like structure and platinum atoms doping, this catalyst shows Pt‐like catalytic activity for the hydrogen evolution reaction with an ultralow overpotential of 34 mV and excellent durability of only 2% increase in overpotential for 72 h under the constant current density of 10 mA cm⁻².     

Big to Small: Ultrafine Mo2C Particles Derived from Giant Polyoxomolybdate Clusters for Hydrogen Evolution Reaction

Due to its electronic structure, similar to platinum, molybdenum carbides (Mo₂C) hold great promise as a cost‐effective catalyst platform. However, the realization of high‐performance Mo₂C catalysts is still limited because controlling their particle size and catalytic activity is challenging with current synthesis methods. Here, the synthesis of ultrafine β‐Mo₂C nanoparticles with narrow size distribution (2.5 ± 0.7 nm) and high mass loading (up to 27.5 wt%) on graphene substrate using a giant Mo‐based polyoxomolybdate cluster, Mo₁₃₂ ((NH₄)₄₂[Mo₁₃₂O₃₇₂(CH₃COO)₃₀(H₂O)₇₂]·10CH₃COONH₄·300H₂O) is demonstrated. Moreover, a nitrogen‐containing polymeric binder (polyethyleneimine) is used to create Mo? N bonds between Mo₂C nanoparticles and nitrogen‐doped graphene layers, which significantly enhance the catalytic activity of Mo₂C for the hydrogen evolution reaction, as is revealed by X‐ray photoelectron spectroscopy and density functional theory calculations. The optimal Mo₂C catalyst shows a large exchange current density of 1.19 mA cm^?2, a high turnover frequency of 0.70 s^?1 as well as excellent durability. The demonstrated new strategy opens up the possibility of developing practical platinum substitutes based on Mo₂C for various catalytic applications.     

Confining Sub-Nanometer Pt Clusters in Hollow Mesoporous Carbon Spheres for Boosting Hydrogen Evolution Activity

Electrochemical water splitting is considered as a promising approach to produce clean and sustainable hydrogen fuel. As a new class of nanomaterials with high ratio of surface atoms and tunable composition and electronic structure, metal clusters are promising candidates as catalysts. Here, a new strategy is demonstrated to synthesize active and stable Pt-based electrocatalysts for hydrogen evolution by confining Pt clusters in hollow mesoporous carbon spheres (Pt₅/HMCS). Such a structure would effectively stabilize the Pt clusters during the ligand removal process, leading to remarkable electrocatalytic performance for hydrogen production in both acidic and alkaline solutions. Particularly, the optimal Pt₅/HMCS electrocatalyst exhibits 12 times the mass activity of Pt in commercial Pt/C catalyst with similar Pt loading. This study exemplifies a simple yet effective approach to improve the cost effectiveness of precious-metal-based catalysts with stabilized metal clusters.     

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.     

Carbon‐Encapsulated WOx Hybrids as Efficient Catalysts for Hydrogen Evolution

Developing non‐noble metal catalysts as Pt substitutes, with good activity and stability, remains a great challenge for cost‐effective electrochemical evolution of hydrogen. Herein, carbon‐encapsulated WO_x anchored on a carbon support (WO_x@C/C) that has remarkable Pt‐like catalytic behavior for the hydrogen evolution reaction (HER) is reported. Theoretical calculations reveal that carbon encapsulation improves the conductivity, acting as an electron acceptor/donor, and also modifies the Gibbs free energy of H* values for different adsorption sites (carbon atoms over the W atom, O atom, W? O bond, and hollow sites). Experimental results confirm that WO_x@C/C obtained at 900 °C with 40 wt% metal loading has excellent HER activity regarding its Tafel slope and overpotential at 10 and 60 mA cm^?2, and also has outstanding stability at ?50 mV for 18 h. Overall, the results and facile synthesis method offer an exciting avenue for the design of cost‐effective catalysts for scalable hydrogen generation.     

Metal‐Tuned Acetylene Linkages in Hydrogen Substituted Graphdiyne Boosting the Electrochemical Oxygen Reduction

Different from graphene with the highly stable sp²‐hybridized carbon atoms, which shows poor controllability for constructing strong interactions between graphene and guest metal, graphdiyne has a great potential to be engineered because its high‐reactive acetylene linkages can effectively chelate metal atoms. Herein, a hydrogen‐substituted graphdiyne (HsGDY) supported metal catalyst system through in situ growth of Cu₃Pd nanoalloys on HsGDY surface is developed. Benefiting from the strong metal‐chelating ability of acetylenic linkages, Cu₃Pd nanoalloys are intimately anchored on HsGDY surface that accordingly creates a strong interaction. The optimal HsGDY‐supported Cu₃Pd catalyst (HsGDY/Cu₃Pd‐750) exhibits outstanding electrocatalytic activity for the oxygen reduction reaction (ORR) with an admirable half‐wave potential (0.870 V), an impressive kinetic current density at 0.75 V (57.7 mA cm^?2) and long‐term stability, far outperforming those of the state‐of‐the‐art Pt/C catalyst (0.859 V and 15.8 mA cm^?2). This excellent performance is further highlighted by the Zn–air battery using HsGDY/Cu₃Pd‐750 as cathode. Density function theory calculations show that such electrocatalytic performance is attributed to the strong interaction between Cu₃Pd and C?C bonds of HsGDY, which causes the asymmetric electron distribution on two carbon atoms of C?C bond and the strong charge transfer to weaken the shoulder‐to‐shoulder π conjugation, eventually facilitating the ORR process.     

Sustainable Hydrothermal Carbonization Synthesis of Iron/Nitrogen‐Doped Carbon Nanofiber Aerogels as Electrocatalysts for Oxygen Reduction

It is urgent to develop new kinds of low‐cost and high‐performance nonprecious metal (NPM) catalysts as alternatives to Pt‐based catalysts for oxygen reduction reaction (ORR) in fuel cells and metal–air batteries, which have been proved to be efficient to meet the challenge of increase of global energy demand and CO₂ emissions. Here, an economical and sustainable method is developed for the synthesis of Fe, N codoped carbon nanofibers (Fe–N/CNFs) aerogels as efficient NPM catalysts for ORR via a mild template‐directed hydrothermal carbonization (HTC) process, where cost‐effective biomass‐derived d (+)‐glucosamine hydrochloride and ferrous gluconate are used as precursors and recyclable ultrathin tellurium nanowires are used as templates. The prepared Fe/N‐CNFs catalysts display outstanding ORR activity, i.e., onset potential of 0.88 V and half‐wave potential of 0.78 V versus reversible hydrogen electrode in an alkaline medium, which is highly comparable to that of commercial Pt/C (20 wt% Pt) catalyst. Furthermore, the Fe/N‐CNFs catalysts exhibit superior long‐term stability and better tolerance to the methanol crossover effect than the Pt/C catalyst in both alkaline and acidic electrolytes. This work suggests the great promise of developing new families of NPM ORR catalysts by the economical and sustainable HTC process.     

Biomass Derived N‐Doped Porous Carbon Supported Single Fe Atoms as Superior Electrocatalysts for Oxygen Reduction

Exploring sustainable and high‐performance electrocatalysts for the oxygen reduction reaction (ORR) is the crucial issue for the large‐scale application of fuel cell technology. A new strategy is demonstrated to utilize the biomass resource for the synthesis of N‐doped hierarchically porous carbon supported single‐atomic Fe (SA‐Fe/NHPC) electrocatalyst toward the ORR. Based on the confinement effect of porous carbon and high‐coordination natural iron source, SA‐Fe/NHPC, derived from the hemin‐adsorbed bio‐porphyra‐carbon by rapid heat‐treatment up to 800 °C, presents the atomic dispersion of Fe atoms in the N‐doped porous carbon. Compared with the molecular hemin and nanoparticle Fe samples, the as‐prepared SA‐Fe/NHPC exhibits a superior catalytic activity (E _1/2 = 0.87 V and J _k = 4.1 mA cm^?2, at 0.88 V), remarkable catalytic stability (≈1 mV negative shift of E _1/2, after 3000 potential cycles), and outstanding methanol‐tolerance, even much better than the state‐of‐the‐art Pt/C catalyst. The sustainable and effective strategy for utilizing biomass to achieve high‐performance single‐atom catalysts can also provide an opportunity for other catalytic applications in the atomic scale.     

Edge Segregated Polymorphism in 2D Molybdenum Carbide

Molybdenum carbide (Mo₂C), a class of unterminated MXene, is endowed with rich polymorph chemistry, but the growth conditions of the various polymorphs are not understood. Other than the most commonly observed T‐phase Mo₂C, little is known about other phases. Here, Mo₂C crystals are successfully grown consisting of mixed polymorphs and polytypes via a diffusion‐mediated mechanism, using liquid copper as the diffusion barrier between the elemental precursors of Mo and C. By controlling the thickness of the copper diffusion barrier layer, the crystal growth can be controlled between a highly uniform AA‐stacked T‐phase Mo₂C and a “wedding cake” like Mo₂C crystal with spatially delineated zone in which the Bernal‐stacked Mo₂C predominate. The atomic structures, as well as the transformations between distinct stackings, are simulated and analyzed using density functional theory (DFT)‐based calculations. Bernal‐stacked Mo₂C has a d band closer to the Fermi energy, leading to a promising performance in catalysis as verified in hydrogen evolution reaction (HER).     

Synthesis of Few‐Layer MoS2 Nanosheet‐Coated TiO2 Nanobelt Heterostructures for Enhanced Photocatalytic Activities

MoS₂ nanosheet‐coated TiO₂ nanobelt heterostructures—referred to as TiO₂@MoS₂—with a 3D hierarchical configuration are prepared via a hydrothermal reaction. The TiO₂ nanobelts used as a synthetic template inhibit the growth of MoS₂ crystals along the c‐axis, resulting in a few‐layer MoS₂ nanosheet coating on the TiO₂ nanobelts. The as‐prepared TiO₂@MoS₂ heterostructure shows a high photocatalytic hydrogen production even without the Pt co‐catalyst. Importantly, the TiO₂@MoS₂ heterostructure with 50 wt% of MoS₂ exhibits the highest hydrogen production rate of 1.6 mmol h^?1g^?1. Moreover, such a heterostructure possesses a strong adsorption ability towards organic dyes and shows high performance in photocatalytic degradation of the dye molecules.     

Formation of Mo–Polydopamine Hollow Spheres and Their Conversions to MoO2/C and Mo2C/C for Efficient Electrochemical Energy Storage and Catalyst

Highly uniform hierarchical Mo–polydopamine hollow spheres are synthesized for the first time through a liquid‐phase reaction under ambient temperature. A self‐assembly mechanism of the hollow structure of Mo–polydopamine precursor is discussed in detail, and a determined theory is proposed in a water‐in‐oil system. Via different annealing process, these precursors can be converted into hierarchical hollow MoO₂/C and Mo₂C/C composites without any distortion in shape. Owing to the well‐organized structure and nanosize particle embedding, the as‐prepared hollow spheres exhibit appealing performance both as the anode material for lithium‐ion batteries and as the catalyst for hydrogen evolution reaction (HER). Accordingly, MoO₂/C delivers a high reversible capacity of 940 mAh g^?1 at 0.1 A g^?1 and 775 mAh g^?1 at 1 A g^?1 with good rate capability and long cycle performance. Moreover, Mo₂C/C also exhibits an enhanced electrocatalytic performance with a low overpotential for HER in both acidic and alkaline conditions, as well as remarkable stability.     

Fabrication of Supported AuPt Alloy Nanocrystals with Enhanced Electrocatalytic Activity for Formic Acid Oxidation through Conversion Chemistry of Layer‐Deposited Pt2+ on Au Nanocrystals

The exploitation of nanoconfined conversion of Au‐ and Pt‐containing binary nanocrystals for developing a controllable synthesis of surfactant‐free AuPt nanocrystals with enhanced formic acid oxidation (FAO) activity is reported, which can be stably and evenly immobilized on various support materials to diversify and optimize their electrocatalytic performance. In this study, an atomic layer of Pt²⁺ species is discovered to be spontaneously deposited in situ on the Au nanocrystal generated from a reverse‐microemulsion solution. The resulting Au/Pt²⁺ nanocrystal thermally transforms into a reduced AuPt alloy nanocrystal during the subsequent solid‐state conversion process within the SiO₂ nanosphere. The alloy nanocrystals can be isolated from SiO₂ in a surfactant‐free form and then dispersedly loaded on the carbon sphere surface, allowing for the production of a supported electrocatalyst that exhibits much higher FAO activity than commercial Pt/C catalysts. Furthermore, by involving Fe₃O₄ nanocrystals in the conversion process, the AuPt alloy nanocrystals can be grown on the oxide surface, improving the durability of supported metal catalysts, and then uniformly loaded on a reduced graphene oxide (RGO) layer with high electroconductivity. This produces electrocatalytic AuPt/Fe₃O₄/RGO nanocomposites whose catalyst‐oxide‐graphene triple‐junction structure provides improved electrocatalytic properties in terms of both activity and durability in catalyzing FAO.     

Direct Synthesis of Large‐Area 2D Mo2C on In Situ Grown Graphene

As a new member of the MXene group, 2D Mo₂C has attracted considerable interest due to its potential application as electrodes for energy storage and catalysis. The large‐area synthesis of Mo₂C film is needed for such applications. Here, the one‐step direct synthesis of 2D Mo₂C‐on‐graphene film by molten copper‐catalyzed chemical vapor deposition (CVD) is reported. High‐quality and uniform Mo₂C film in the centimeter range can be grown on graphene using a Mo–Cu alloy catalyst. Within the vertical heterostructure, graphene acts as a diffusion barrier to the phase‐segregated Mo and allows nanometer‐thin Mo₂C to be grown. Graphene‐templated growth of Mo₂C produces well‐faceted, large‐sized single crystals with low defect density, as confirmed by scanning transmission electron microscopy (STEM) measurements. Due to its more efficient graphene‐mediated charge‐transfer kinetics, the as‐grown Mo₂C‐on‐graphene heterostructure shows a much lower onset voltage for hydrogen evolution reactions as compared to Mo₂C‐only electrodes.     

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.     

High‐Efficient,Stable Electrocatalytic Hydrogen Evolution in Acid Media by Amorphous FexP Coating Fe2N Supported on Reduced Graphene Oxide

Development of efficient and durable non‐Pt catalysts for hydrogen evolution reaction (HER) in acid media is highly desirable. Iron nitride has emerged as a promising catalyst for its cost‐effective nature, but the corresponding acidic stability must be promoted. Herein, phosphorus‐decorated Fe₂N and reduced graphene oxide (P‐Fe₂N/rGO) composite are designed and synthesized. X‐ray photoelectron spectroscopy and X‐ray absorption fine structure (XAFS) show that a thin layer amorphous iron phosphide is coated on the surface of Fe₂N nanoparticles, which could be responsible for the well resistance of chemical corrosion in acidic media. Meanwhile, the P‐decoration could tune the electronic state and coordination environment of iron atom as evidenced by XAFS, resulting in dramatically enhanced electrocatalytic activity of P‐Fe₂N/rGO. Density functional theory calculations reveal that both the P‐connected N atoms and the Fe atoms in P‐Fe₂N/rGO catalyst are the main active sites for H* adsorption. The hydrogen‐binding free energy |ΔG_H*| value is close to zero for P‐Fe₂N/rGO, suggesting a good balance between the Volmer and Heyrovsky/Tafel steps in HER kinetics. As expected, P‐Fe₂N/rGO catalyst could achieve a low η_onset of 22.4 mV, a small Tafel plot of 48.7 mV dec^?1, and remarkable stability for HER in acid electrolyte.