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- oxygen reduction reaction (ORR) due to their cost-effectiveness. Defect engineering have been used on developing high active catalyst, which can effectively modify active sites and promote electron transfer. Here, we prepared carbon-coated Ni3S2 (Ni3S2@C), where the additional sulfur vacancies (VS) induced by the carbon layer are coupled with active nickel sites. It is demonstrated that the carbon layer can regulate the quantity of VS in Ni3S2. Materials with higher concentration of VS exhibit enhanced 2e- ORR activity. DFT calculations indicate that the *OOH binding energy (ΔG) decreases with an increase of VS, favoring the protonation of *OOH to generate H2O2. Upon performance testing, the average H2O2 selectivity was 92.3%, with the highest yield reaching up to 3860 mmol·gcat-1·h-1. It is noteworthy that Ni3S2@C exhibits high stability, with only a slight decrease in 2e- pathway selectivity after 5000 cycles.