Revealing the reactant adsorption role of high-valence WO3 for boosting urea-assisted water splitting

Ni-based electrocatalysts are considered a promising choice for urea-assisted hydrogen production. However, its application remains challenging owing to the high occupancy of d orbital at the Ni site, which suppresses the reactant adsorption to achieve satisfactory urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) activity. Herein, the WO₃ site with empty d orbital is introduced into Ni₃S₂ to construct dual active sites for regulating the adsorption of reactive molecules. Experimental and theoretical calculations indicate that the electron transfer from Ni₃S₂ to WO₃ forms electron-deficient Ni with sufficient empty d orbitals for optimizing urea/H₂O adsorption and tuning the adsorption behavior of the amino and carbonyl groups in urea. Consequently, the Ni₃S₂-WO₃/NF presents a remarkably low potential of 1.38 V to reach 10 mA cm⁻² for UOR-assisted HER. This work highlights the significance of constructing synergistic dual active sites toward developing advanced catalysts for urea-assisted hydrogen production.