Phase‐Transition of Mo2C Induced by Tungsten Doping as Heterointerface‐Rich Electrocatalyst for Optimizing Hydrogen Evolution Activity

Abstract

AbstractElectrochemical hydrogen evolution reaction (HER) from water splitting driven by renewable energy is considered a promising method for large‐scale hydrogen production, and as an alternative to noble‐metal electrocatalysts, molybdenum carbide (Mo2C) has exhibited effective HER performance. However, the strong bonding strength of intermediate adsorbed H (Hads) with Mo active site slows down the HER kinetics of Mo2C. Herein, using phase‐transition strategy, hexagonal β‐Mo2C could be easily transferred to cubic δ‐Mo2C through electron injection triggered by tungsten (W) doping, and heterointerface‐rich Mo2C‐based composites, including β‐Mo2C, δ‐Mo2C, and MoO2, are presented. Experimental results and density functional theory calculations reveal that W doping mainly contributes to the phase‐transition process, and the generated heterointerfaces are the dominant factor in inducing remarkable electron accumulation around Mo active sites, thus weakening the Mo─H coupling. Wherein, the β‐Mo2C/MoO2 interface plays an important role in optimizing the electronic structure of Mo 3d orbital and hydrogen adsorption Gibbs free energy (ΔGH*), enabling these Mo2C‐based composites to have excellent intrinsic catalytic activity like low overpotential (η10 = 99.8 mV), small Tafel slope (60.16 dec−1), and good stability in 1 m KOH. This work sheds light on phase‐transition engineering and offers a convenient route to construct heterointerfaces for large‐scale HER production.