Controllable synthesis of molybdenum-based electrocatalysts for a hydrogen evolution reaction

Abstract

In order to explore low-cost, high efficiency, precious metal-free materials for electrochemical water splitting, three types of molybdenum-based compounds (MoO₂, MoC and Mo₂C) were synthesized by tuning the ratio of glucose and ammonium molybdate via a two-step procedure. TEM images reveal a uniform dispersion of the three molybdenum-based nanoparticles on the carbon support, and in particular, MoC and Mo₂C exhibit ultra-small particle sizes which are lower than 3 nm. When used as catalysts for the HER in both acid and basic media, Mo₂C exhibits the best catalytic activity with a small overpotential of 135 mV in acid media and 96 mV in alkaline media at a current density of 10 mA cm⁻², which is about 105 mV and 30 mV higher than that with Pt/C, respectively. The enhanced catalytic activity of Mo₂C could originate from the excellent crystal structure, the high electronic conductivity of the carbon support with a high degree of graphitization and the ultra-small particle size, which provides a large surface area and active sites.