Cr-doped NiO nanocrystals anchored on wood-based carbon for enhanced electrocatalytic oxidation of urea

The urea oxidation reaction (UOR) has potential application in water electrolysis-assisted hydrogen generation, fuel cells, and the treatment of urea-containing wastewater. In this work, the composite (Cr-NiO/CWF) was synthesized by anchoring Cr and NiO onto carbonized wood fiber (CWF) by hydrothermal method combined with pyrolysis, utilizing biomass wood fiber (WF) as the precursor for the carbon substrate. The optimal Cr-NiO/CWF has significant UOR activity, and the current density (j) can reach 310.40 mA cm⁻² at 1.67 V, while the required potential for UOR is 1.36 V at the j value of 10 mA cm⁻². After 12 h of long-term chronoamperometry (CA) testing, the j retention rate of Cr-NiO/CWF is 90 %. The excellent properties of Cr-NiO/CWF composites are mainly ascribed to the effective modulation of the electronic structure by Cr doping, which optimizes the adsorption behavior of the reactants and products. Cr-NiO nanoparticles enhance the carrier mobility and accelerate the electron transfer rate between Cr-NiO and carbon substrate. Moreover, Cr-NiO nanoparticles are tightly anchored onto the nitrogen-doped carbon substrate to enhance the stability of the composite.