Nanoengineered NiO/ZnO Heterostructure-Integrated WS ₂ Nanostructures as a Bifunctional Catalyst for Water/Seawater Splitting Applications

Transition-metal oxides and sulfides are compelling materials for electrochemical energy conversion due to their cost-effectiveness, corrosion resistance, and environmental innocuous nature. Integration of multiple transition-metal heteroatoms to engineer surface architectures and nanoscale morphologies represents a robust strategy for the development and synthesis of electrocatalysts with enhanced catalytic efficiency and superior activity. Synthesis of nanomaterials that can act as a bifunctional catalyst for water/seawater splitting is still a considerable challenge. In this regard, we report the NiO/ZnO heterostructures integrated within WS 2 nanostructures as a bifunctional catalyst for water-splitting applications. The optimized catalyst WS 2 @NiO/ZnO showed remarkable electrocatalytic properties for hydrogen and oxygen evolution reactions. It showed overpotential values of 131 and 320 mV for the HER and OER, respectively, at 10 mA/cm 2 in acidic and alkaline media, along with excellent response across a wide range of pH and in seawater-based electrolytes. Adequate amount of sulfur and oxygen content provides additional exposed active sites for a faster kinetic process. Moreover, high electrochemical surface area, mass activity, and low Tafel slope demonstrate remarkable ability of fabricated nanostructures. Also, radically decreased charge-transfer resistance facilitates an accelerated rate of the water-splitting reaction.