Collaborative optimization of thermodynamic and kinetic for Ni-based hydroxides in electrocatalytic urea oxidation reaction

Abstract

Ni-based hydroxides are brilliant electrocatalysts for alkaline urea oxidation reaction (UOR). Herein, multiple Ni-based hydroxides were investigated by electrocatalytic test for UOR performance. Electrocatalytic performance of different ratios of NiCo LDHs was further determined to exploring electrochemical reaction pathway and thermodynamic mechanism. Results indicate appropriate Co element doping content in Ni hydroxide could greatly improve UOR performance. Results of XPS and in situ Raman indicate only part of NiCo hydroxides were converted to NiCo oxyhydroxides which drive the subsequent UOR. Moreover, electrocatalytic UOR on NiCo oxyhydroxides is found in competition with redox of NiCo hydroxides. Density function theory (DFT) calculation manifests that the energy barrier of UOR on NiCo oxyhydroxides is lower than redox of NiCo hydroxides which become the limitation reaction. Energy barrier gap between UOR and redox which provide driving force for UOR which is the primary cause of fast kinetic.