Controllable synthesis of M (M = Cr, Mo and W) and Fe co-doped Co2P catalysts for efficient urea electrolysis

Abstract

Hydrogen production by urea electrolysis is a green, energy conservation and environment protection method. Compared with traditional water electrolysis for hydrogen production, it not only saves costs and energy consumption, but also can treat urea wastewater to purify the environment. In this paper, the sea urchin-like nanoneedles (M (M = Cr, Mo and W)–FeCo2P/NF) arrays with different doping elements M (M = Cr, Mo and W) were prepared by hydrothermal method and moderate temperature phosphating method. It is proved that the doping of different elements in the same group cooperates to adjust the electronic structure of Co2P, thereby increasing the electrochemical active area and improving the active site. What is noteworthy is that Mo–FeCo2P/NF material only needs potential of 1.305 V and overpotential of 232 mV to drive 50 mA cm−2 for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). The Mo–FeCo2P/NF (±) electrolyser can drive a current density of 10 mA cm−2 at a potential of 1.471 V, and is stable for at least 12 h in urea electrolysis. The density functional theory (DFT) demonstrates that Mo–FeCo2P/NF electrode has a moderate Gibbs free energy (GH∗) of H adsorption. This work put forward a new strategy for improving the activity and stability of transition metal phosphides by doping strategy for urea electrolysis.