Silver-doped molybdenum carbide catalyst with high activity for electrochemical water splitting

Abstract

A hybrid catalyst composed of silver (Ag) doped wire-like molybdenum carbide (Mo_xC_y) with pure β-phase and carbon nanotubes (CNTs) was coated well on a carbon rod electrode for the hydrogen evolution reaction (HER). The effects of Ag loading amount and carbonization temperature on the crystal form of Mo_xC_y were investigated in detail. It is found that the Mo_xC_y crystal form can be tuned by adjusting the preparation conditions, and nanostructured wire-like Mo₂C with pure β-phase was obtained at a temperature over 750 °C. Ag/Mo_xC_y composite nanomaterials were investigated by X-ray diffraction, UV/vis spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy and Brunauer–Emmett–Teller surface area analysis. The hybrid catalyst was further deposited on the carbon nanotube (CNT) modified carbon rod substrate. Due to the high surface area and 3D porous network-like microstructure, the Ag/Mo₂C/CNTs hybrid electrode showed enhanced catalytic performance when comparing with the corresponding pure one. Particularly, for the Ag-doped Mo₂C/CNTs hybrid electrode with an optimum 1 Ag : 5 Mo molar ratio of the precursors, a current density of 10 mA cm⁻² was obtained by applying an overpotential of 142 mV in 0.5 mol L⁻¹ H₂SO₄ solution. It is expected that such a hybrid electrode can be widely applied for effective electrolysis of water to produce hydrogen.