Sea Urchin–Like CoS2@WS2/NF Bifunctional Catalyst for Efficient Overall Water Splitting

Metal sulfides have been shown to exhibit better electrical conductivity, mechanical and thermal stability, and higher electrochemical activity than their corresponding metal oxide counterparts. The one-dimensional nanoclusters and three-dimensional microspheres were assembled together by a well-designed synthetic strategy to finally form a sea urchin-like CoS₂@WS₂/NF composite electrode material. The stable chemical properties and firm physical structure remain stable before and after the catalytic reaction, and the unique structure, sea urchin-like morphology, is conducive to mass transfer and gas release during the reaction. In this nanocomposite, one-dimensional nanoclusters provide efficient electron transfer, while three-dimensional nanospheres provide strong and reliable mechanical support. When CoS₂@WS₂/NF was used as a bifunctional electrocatalyst at a current density of 10 mA cm⁻² in 1.0 M KOH aqueous solution, it exhibited overpotentials as low as 127 mV and 415 mV to drive hydrogen evolution reaction (HER) and HER, respectively. Oxygen evolution reaction (OER) is responsive while having high durability. When evaluated as a two-electrode system, it delivers a small value of 1.66 V up to 10 mA cm⁻², further demonstrating the superiority of the bifunctional water release function.