Engineering of novel vanadium-doped Ni₄N@CuCoN_0.6 heterostructure for enhancing urea oxidation reaction at high...

Exploring highly effective nickel-based catalytic materials for urea oxidation reaction (UOR) at high current density remains a challenging task for urea electrolysis. Herein, the vanadium-doped Ni₄N@CuCoN_0.6 heterostructure with brush shape structure supported on copper foam (denoted as V-doped-Ni₄N@CuCoN_0.6/CF) is prepared to serve as a highly-performing UOR electrocatalyst at high current density (E_10/500/1000 = 1.26/1.40/1.45 V). Thanks to the construction of heterojunction, the local charge density undergoes redistribution at the V-doped-Ni₄N@CuCoN_0.6/CF interface between Ni₄N and CuCoN_0.6, thereby significantly enriching the active site and facilitating the adsorption process of urea molecules in a 1.0 M KOH + 0.5 M urea solution. Notably, V-doping exerts an additional influence by modulating the electronic structure of the catalyst, potentially optimizing the urea adsorption/CO₂ desorption process and reducing the energy barrier for the rate-determining step. Operando electrochemical impedance spectroscopy results show direct oxidation for urea molecules on the surface of V-doped-Ni₄N@CuCoN_0.6/CF, indicating that V-doping and heterostructure can effectively improve electron transfer. Furthermore, because the brush shape structure can be beneficial for bubble release and liquid transport on the catalyst's surface, for UOR stability, V-doped-Ni₄N@CuCoN_0.6/CF  can maintain at 500 mA cm^-2 for 80 h. Overall, this work suggests a highly-performing UOR electrocatalyst and provides a promising strategy for developing highly-efficient catalysts for UOR applications.