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

Abstract 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 Fe 2 N and reduced graphene oxide (P‐Fe 2 N/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 Fe 2 N 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‐Fe 2 N/rGO. Density functional theory calculations reveal that both the P‐connected N atoms and the Fe atoms in P‐Fe 2 N/rGO catalyst are the main active sites for H* adsorption. The hydrogen‐binding free energy |Δ G H* | value is close to zero for P‐Fe 2 N/rGO, suggesting a good balance between the Volmer and Heyrovsky/Tafel steps in HER kinetics. As expected, P‐Fe 2 N/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.