Controllable Synthesis of In-Plane Mo/Mo2c Heterojunction Nanosheets for Enhanced Hydrogen Evolution Reaction

Abstract

Two-dimensional (2D) molybdenum carbide (Mo2C) is a potential electrocatalyst for the hydrogen evolution reaction (HER) due to its Pt-like electronic structure, high electrical conductivity, and abundant active sites. However, its practical application as an HER catalyst is hindered by the sluggish kinetics due to the strong hydrogen absorption. Herein, 2D in-plane Mo/Mo2C heterojunction nanosheets are prepared from bulk MoS2 by a molten salt-assisted technique. The ultraviolet photoelectron spectra and density-functional theory calculations reveal that electrons are transferred from Mo to Mo2C and fill Mo2C antibonding orbitals, which weakens Mo-H bonding, enhances H2O adsorption and dissociation, optimizes H adsorption/desorption of in-plane Mo/Mo2C heterojunction nanosheets, and thus promotes the HER kinetics. The Mo/Mo2C heterojunction nanosheets electrocatalyst exhibits low overpotentials of 90 and 96 mV at 10 mA cm-2 and small Tafel slopes (54.9 and 64.2 mV dec-1) in alkaline and acidic electrolytes, respectively. Moreover, Mo/Mo2C shows a small overpotential of 280 mV at 500 mA cm-2 in the alkaline conditions, surpassing that of the commercial Pt/C electrode. The stability is excellent as confirmed by an increase of potential of only about 10 mV after operation for 100 h at a high current density of 300 mA cm-2. The results reveal a simple and effective strategy to boost the catalytic HER activity boding well for high-efficiency commercial water splitting.

Keywords: hydrogen evolution reaction, in-plane heterostructure, molybdenum carbide, 2D nanosheets, Mo-H bonding