In Situ Carbon Thermal Reduction to Enrich Sulfur-Vacancy in Nickel Disulfide Cathode for Efficient Synthesizing Hydrogen Peroxide.

Transition metal catalysts are widely used in the 2e ORR due to their cost-effectiveness. However, they often encounter issues related to low activity. Defect engineering are used on developing highly active catalysts, which can effectively modify active sites and promote electron transfer. Here, carbon-coated NiS (NiS@C), where the additional sulfur vacancies (V) is prepared induced by the carbon layer is coupled with active nickel sites. Through in situ and ex situ experiments combined with DFT calculations, it is demonstrated that the carbon layer can regulate the quantity of V in NiS. Materials with a higher concentration of V exhibit enhanced 2e ORR activity and higher HO selectivity. In situ Raman spectroscopy confirms that Ni serves as the key active site in this catalyst. DFT calculations indicate that the OOH binding energy (ΔG) decreases with an increase in the number of V, favoring the protonation of *OOH to generate HO. Upon performance testing, the average HO selectivity is 92.3%, with the highest yield reaching up to 3860 mmol gcat h. It is noteworthy that NiS@C exhibits high stability, with only a slight decrease in 2e pathway selectivity after 5000 cycles of ADT.