Boosting alkaline urea oxidation with a nickel sulfide/cobalt oxide heterojunction catalyst via interface engineering

Urea electrooxidation holds significant promise for addressing the slow anodic oxygen evolution reaction (OER) in water splitting due to its favorable thermodynamic potential. However, the development of highly active catalysts for urea oxidation reaction (UOR) remains challenging. To address this, a p-n heterostructure nickel sulfide/cobalt oxide catalyst grown on nickel foam, referred to Ni 3 S 2 /Co 3 O 4 -NF, composed of Ni 3 S 2 nanosheets and Co 3 O 4 nanoneedles supported on foam nickel, is proposed. The p-n heterojunction plays a crucial role in altering the electronic structure of catalysts, facilitating efficient charge transfer from n-type Ni 3 S 2 to p-type Co 3 O 4 . Density functional theory calculations reveal that the built-in electric field at the Ni 3 S 2 /Co 3 O 4 p-n heterojunction interface induces the formation of local electrophilic/nucleophilic regions, promoting the adsorption and decomposition process of urea molecules. The testing results demonstrate that the Ni 3 S 2 /Co 3 O 4 -NF p-n heterojunction catalyst exhibits excellent urea catalytic activity, requiring only a potential of 1.288 V to drive a current density of 10 mA cm −2 , and displays remarkable durability over a 100-h operation period. This study presents significant insights for the design of p-n heterojunction catalysts and enhances our understanding of optimizing electrocatalyst activity through interface engineering. Graphical abstract