Bimetallic Sulfides with Vacancy Modulation Exhibit Enhanced Electrochemical Performance

Transition bimetallic sulfides show significant promise for energy-related applications because of their plentiful active sites and synergistic redox activity. However, limited pore size and low-conductivity issues hinder their application. The structure of NiCo-S with rich sulfur vacancies is first predicted by density functional theory (DFT) calculations. Different sulfur vacancy concentrations are modeled by DFT calculations, and the results confirm that sulfur vacancies enhance the conductivity of the electrode material and are more beneficial for the adsorption of OH* species. It is verified by the differential charge density that the electric field formed on the surface of the electrode can lead to strong interfacial interactions by electron aggregation, which promotes electron/ion transfer kinetics. Furthermore, NiCo-S nanosheets are prepared on carbon cloth enriched with different concentrations of sulfur vacancies (denoted as NiCo-Sv-x, with x representing the concentration of sulfur vacancies) by sulfide etching NiCo-MOF and annealing under H2/Ar atmosphere. The NiCo-Sv-x electrodes obtained are applied to the cathode of supercapacitors and the anode of the oxygen evolution reaction. Through combining experimental and theoretical analysis, the effect of vacancy defect engineering on the electrochemical performance of the electrode materials is further confirmed. This work constructs transition metal sulfides with different sulfur vacancy concentrations through DFT model prediction and experimental validation, further confirming the effect of vacancy defect engineering on the electrochemical performance of electrode materials. Therefore, this modulation of sulfur vacancy concentration by vacancy defects contributes to the construction of electrode materials with excellent performance for energy applications. image