Controlled synthesis of Fe doped NiCoM (M=O, P, S and Se) as robust electrocatalyst for urea electrolysis

Abstract

Electrochemistry urea electrolysis method is more significant in practical application and cost saving than water splitting technology for production of hydrogen. In this work, a series of Fe doped NiCoM (M=O, P, S and Se) materials with unique structure of nanosheet and nanoneedle were successfully synthesized on Ni foam by typical hydrothermal and annealing processes. What is noteworthy is that Fe-NiCoP, as an efficient bifunctional electrode, presents superior electrochemistry activity for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) with requiring a potential of 1.369 V at 100 mA cm−2 and overpotential of 150 mV at 10 mA cm−2. In the process of electrolysis of urea, the Fe-NiCoP//Fe-NiCoP electrode couple display superior electrochemical performance (cell voltage of 1.50 V @ 10 mA cm−2). The enhanced electrocatalytic activity of Fe-NiCoP electrodes was attributed to improved reaction kinetics by Ni12P5 and increased conductivity by Fe-Co2P, resulting in rapid electron transfer, increased active site exposure and good conductivity. Density functional theory calculations show that the Ni12P5 material exhibits a small Gibbs free energy for hydrogen adsorption and plays a major role in hydrogen production. This work provides a novel idea for the research and exploitation of low cost and robust UOR and HER electrocatalysts.