Accelerating the reaction kinetics of Ni _{1− <i>x</i>} O/Ni(OH) ₂ /NF by defect engineering for urea-assisted water splitting

Developing electrocatalysts with fast reaction kinetics for the urea oxidation reaction (UOR) in the field of sustainable hydrogen production through urea-assisted water splitting remains challenging. Here, Ni_1-<i>x</i>O/Ni(OH)₂ supported on nickel foam (Ni_1-<i>x</i>O/Ni(OH)₂/NF) is prepared <i>via</i> a defect engineering strategy by combining Zn doping and acid etching. The doped Zn species are partially removed, facilitating the formation of NiOOH during acid etching. Residual Zn species modulate the electronic structure of nickel sites, which intrinsically accelerate the reaction kinetics of Ni_1-<i>x</i>O/Ni(OH)₂/NF. Ni_1-<i>x</i>O/Ni(OH)₂/NF exhibits excellent performance for the UOR with a low potential of 1.346 V <i>versus</i> the reversible hydrogen electrode to attain 100 mA cm^-2, fast reaction kinetics (18.7 mV dec^-1), and excellent stability in an alkaline electrolyte. The enhanced reaction kinetics of Ni_1-<i>x</i>O/Ni(OH)₂/NF are clearly elucidated by <i>operando</i> electrochemical impedance spectroscopy and <i>in situ</i> Raman spectroscopy. Our study offers an effective approach for designing promising Ni-based UOR catalysts for the practical application of urea-assisted water splitting.