Modulation of the electronic structure of Co2P by Mo, Fe co-doping for efficient urea electrolysis

Abstract

Hydrogen production by urea splitting not only plays an energy-saving role in the production of hydrogen energy, but also can purify wastewater containing urea, which has great advantages compared with hydrogen production by water splitting. In this study, Mo, Fe co-doped bifunctional Co2P electrodes were prepared through hydrothermal and moderate-temperature phosphating methods. Under the synergistic effect of bimetallic cations, the electronic structure of Co2P is effectively modulated, thus showing excellent electrochemistry performance in urea splitting. In the electrolyte solution of 1 M KOH and 0.5 M urea, the potential of urea oxidation reaction (UOR) is 1.26V, 1.316 V and 1.336V for driving current density of 10, 50 and 100 mA cm−2, and the overpotential of hydrogen evolution reaction (HER) is 194 mV, 244 mV and 268 mV for driving current density of 10, 50 and 100 mA cm−2. The overall urea electrolysis only requires a voltage of 1.415 V and 1.686 V to drive a current density of 10 and 50 mA cm−2, which is one of the best catalytic activities reported to date. The experimental results show that the increased activity is assigned to the rapid charge transfer, the exposure of more active sites and the improved conductivity due to the doping of bimetallic ions. Density functional theory (DFT) demonstrates that the prepared Mo, Fe co-doped Co2P electrodes has the smallest Gibbs free energy for hydrogen adsorption compared with Fe co-doped Co2P electrodes. This work laid a new foundation for the synthesis of bimetallic cation-doped transition metal phosphide (TMP) for urea-assisted water splitting.