Metal-Doped CoS Nanosheets: Breaking Scaling Limitations for Enhanced Urea Electrooxidation and Hydrogen Evolution

The electrocatalytic urea oxidation reaction (UOR) is a promising approach to lowering the energy barrier of the anode half-reaction in water splitting for energy-efficient hydrogen production and to remove excess urea from blood or dialysis fluid. However, the sluggish kinetics and large overpotential caused by scaling relationships significantly limit the development of the UOR technology. Herein, bifunctional amorphous M-CoS (M = Zr, Cu, Mn, Fe) nanosheets were synthesized via a one-step electrodeposition process. Among them, Zr-CoS exhibited exceptional electrocatalytic performance, achieving 10 mA cm^-2 in UOR at an overpotential of 1.26 V, outperforming recently reported catalysts, while CoS demonstrated 10 mA cm^-2 in the hydrogen evolution reaction at an impressively low overpotential of -175 mV. Density functional theory calculations revealed that doped Cu and Zr ions migrated to the adsorption sites of N atoms before and after C-N cleavage, breaking the limitation of scaling relationships. Meanwhile, the energy barrier of the C-N cleavage step showed a good linear relationship with the variation of integrated crystal orbital Hamilton population (ΔICOHP), indicating that ΔICOHP was a good descriptor to evaluate UOR performances. This work not only emphasized the outstanding performances of Zr-CoS but also offered innovative insights into the role of metal sulfides in UOR.