Hierarchical Superhydrophilic/Superaerophobic NiS/VS Nanorod-Based Bifunctional Electrocatalyst Supported on Nickel Foam for Overall Urea Electrolysis.

The design and preparation of effective nonprecious metal-based catalysts for the urea oxidation reaction (UOR) coupled with the hydrogen evolution reaction (HER) are of great significance to solve both energy shortage and environmental pollution problems. In this study, a novel hierarchical superhydrophilic and superaerophobicity three-dimensional nanorod-like bifunctional catalyst with a heterostructure (NiS/VS) was prepared on nickel foam via a simple one-step hydrothermal method, serving as an excellent electrocatalyst for both UOR and HER. The formed heterostructure significantly alters the electronic structure, optimizing charge transfer and increasing the number of active sites, which enhances the electrocatalytic performance of NiS/VS. As a result, this catalyst requires an extremely low potential of 1.396 V at the current density of 100 mA cm for UOR and only 164 mV overpotential at -10 mA cm for HER. Notably, a constructed two-electrode electrolyzer system (NiS/VS∥NiS/VS) demonstrates extraordinary activity and long-term stability, achieving a current density of 10 mA cm at a low cell voltage of 1.48 V, which is superior to majority of the reported catalysts. This work demonstrates that the formation of heterostructures can effectively enhance the catalytic activity of nanomaterials toward UOR and HER and provides a feasible strategy for fabricating highly efficient nonprecious metal overall urea electrocatalysts.