Adsorption Energy Optimization of Co3O4 through Rapid Surface Sulfurization for Efficient Counter Electrode in Dye-Sensitized Solar Cells

High-efficiency electrocatalysts have been widely applied in various fields, especially in the counter electrode (CE) of dye-sensitized solar cells (DSSCs). Different from the usual methods for developing high-performance CE materials through searching new materials and designing new nanostructure, we utilized a rapid surface sulfurization treatment to activate the well-known Co3O4 material by increasing the adsorption energy of iodine (I) atom in the electrolyte of DSSCs. The density functional theory (DFT) calculation indicated the adsorption energy of Co3O4 (E-ad(I) 0.347 eV) toward I atom was dramatically increased to 0.835 eV through just transforming Co3O4 at surface into Co3S4. After a short activation time of 30 s, Co3O4 CEs showed a superior catalytic performance toward iodide electrolyte comparable with traditional Pt CE, generating a power conversion efficiency of 8.6% in DSSCs. This method of adjusting adsorption energy via surface sulfurization is applicable in the activation of other metal oxides, and provides a convenient but efficient way to modify the simple abundant materials for their different electrocatalytic applications.