Crafting amorphous VO2–crystalline NiS2 heterostructures as bifunctional electrocatalysts for efficient water splitting: The different cocatalytic function of VO2

The rational design of bifunctional electrocatalysts is essential to achieve efficient hydrogen production from water splitting. Here, inspired by cocatalysts widely utilized in photocatalysis , we designed a heterostructure comprising amorphous VO 2 and crystalline NiS 2 , aiming at using VO 2 cocatalyst to boost activity of NiS 2 for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Intriguingly, we found that VO 2 displayed different co-catalytic function in boosting the OER and HER. Specifically, the VO 2 optimized the binding energy of hydrogen intermediate on NiS 2 and thus improved the HER activity. As for the OER, the amorphous VO 2 was easily dissolved in the KOH electrolyte, resulting in the generation of abundant oxygen vacancies in the in-situ generated active phase of NiOOH from NiS 2 , thereby drastically enhancing the OER activity. Consequently, the obtained VO 2 –NiS 2 @CC displayed excellent performance for overall water splitting, with a low voltage of 1.53 V at 10 mA cm −2 .