Phase‐Transition of Mo<sub>2</sub>C Induced by Tungsten Doping as Heterointerface‐Rich Electrocatalyst for Optimizing Hydrogen Evolution Activity
Wansong Chen, Mang Niu, Zhaozuo Zhang, Lin Chen, Xing Li, Jinming Zhang, Ruoxin Sun, Haijie Cao, Xiaoxia Wang
Abstract
Abstract Electrochemical 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 (Mo 2 C) has exhibited effective HER performance. However, the strong bonding strength of intermediate adsorbed H ( H ads ) with Mo active site slows down the HER kinetics of Mo 2 C. Herein, using phase‐transition strategy, hexagonal β‐Mo 2 C could be easily transferred to cubic δ‐Mo 2 C through electron injection triggered by tungsten (W) doping, and heterointerface‐rich Mo 2 C‐based composites, including β‐Mo 2 C, δ‐Mo 2 C, and MoO 2 , 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‐Mo 2 C/MoO 2 interface plays an important role in optimizing the electronic structure of Mo 3d orbital and hydrogen adsorption Gibbs free energy (Δ G H* ), enabling these Mo 2 C‐based composites to have excellent intrinsic catalytic activity like low overpotential ( η 10 = 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.