Construction of ZIF-67-Derived Cobalt Sulfide@Carbon Aerogel toward Interface-Enhanced Electrochemical Activities for the Oxygen Evolution Reaction

Developing low-cost and high-efficiency OER electrocatalysts holds the key to hydrogen production from electrochemical water splitting. In this study, cobalt sulfide hollow nanospheres derived from ZIF-67 were immobilized on a potato starch-derived carbon aerogel (Co-S@CA) using a solvothermal method followed by annealing. The synergistic effects of Co-S and three-dimensional carbon aerogel (CA) facilitate rapid charge transfer, high electrochemical surface area, and better electronic structure, enhancing the electrochemical activity of the composite. The synthesized Co-S@CA catalyst exhibited remarkable catalytic performance with an overpotential of 291 mV at 10 mA cm^-2 and a Tafel slope of 61.8 mV dec^-1, outperforming the commercial RuO₂ catalyst. The Co-S@CA catalyst demonstrates excellent stability with negligible increase in overpotential after 60 h of a stability test. Density functional theory (DFT) calculations further supported the experimental results, showing that the interfacial charge transfer between Co-S and carbon generates a built-in electric field and upshifts the d-band center, enhancing charge-transfer capability and lowering the theoretical overpotential for the OER. These improvements significantly boost the catalytic activity. This study highlights the potential of Co-S@CA composites as highly efficient electrocatalysts for renewable energy applications.