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

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 Ni₃S₂ (Ni₃S₂@C), where the additional sulfur vacancies (V_S) 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_S in Ni₃S₂. Materials with a higher concentration of V_S exhibit enhanced 2e^- ORR activity and higher H₂O₂ 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_S, favoring the protonation of *OOH to generate H₂O₂. Upon performance testing, the average H₂O₂ selectivity is 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 of ADT.