Hierarchical\nSuperhydrophilic/Superaerophobic Ni<sub>3</sub>S<sub>2</sub>/VS<sub>2</sub> Nanorod-Based Bifunctional Electrocatalyst\nSupported on Nickel Foam for Overall Urea Electrolysis

The\ndesign and preparation of effective nonprecious metal-based\ncatalysts for the urea oxidation reaction (UOR) coupled with the hydrogen\nevolution reaction (HER) are of great significance to solve both energy\nshortage and environmental pollution problems. In this study, a novel\nhierarchical superhydrophilic and superaerophobicity three-dimensional\nnanorod-like bifunctional catalyst with a heterostructure (Ni<sub>3</sub>S<sub>2</sub>/VS<sub>2</sub>) was prepared on nickel foam\nvia a simple one-step hydrothermal method, serving as an excellent\nelectrocatalyst for both UOR and HER. The formed heterostructure significantly\nalters the electronic structure, optimizing charge transfer and increasing\nthe number of active sites, which enhances the electrocatalytic performance\nof Ni<sub>3</sub>S<sub>2</sub>/VS<sub>2</sub>. As a result, this catalyst\nrequires an extremely low potential of 1.396 V at the current density\nof 100 mA cm<sup>–2</sup> for UOR and only 164 mV overpotential\nat −10 mA cm<sup>–2</sup> for HER. Notably, a constructed\ntwo-electrode electrolyzer system (Ni<sub>3</sub>S<sub>2</sub>/VS<sub>2</sub>∥Ni<sub>3</sub>S<sub>2</sub>/VS<sub>2</sub>) demonstrates\nextraordinary activity and long-term stability, achieving a current\ndensity of 10 mA cm<sup>–2</sup> at a low cell voltage of 1.48\nV, which is superior to majority of the reported catalysts. This work\ndemonstrates that the formation of heterostructures can effectively\nenhance the catalytic activity of nanomaterials toward UOR and HER\nand provides a feasible strategy for fabricating highly efficient\nnonprecious metal overall urea electrocatalysts.