Coordination Optimization of Co Active Sites by Sb-Induced Phase Transition for Enhanced Electrochemical Propylene Epoxidation at Low Cl⁻ Concentration Conditions

Electrochemical propylene epoxidation mediated by Cl⁻ presents a sustainable pathway for propylene oxide (PO) production. Its practical viability hinges on achieving high efficiency at low Cl⁻ concentrations using cost-effective non-noble metal catalysts. However, low Cl⁻ concentrations lead to sluggish oxidation kinetics, and non-noble metal catalysts face corrosion issues. This paper describes the strategy to address these challenges by introducing a rutile-phase CoSb₂O₆ electrocatalyst with coordination-optimized Co active sites. The obtained electrocatalyst achieves a high PO Faradaic efficiency of 83.7% at 1.55 V versus Ag/AgCl. The optimized Co sites enhance the adsorption of the *Cl intermediate, thereby promoting the initial electron transfer step and accelerating the subsequent epoxidation process. Furthermore, Sb incorporation stabilizes the electrocatalyst by mitigating the penetration of corrosive halide species. The good performance of the CoSb₂O₆ electrocatalyst at low Cl⁻ concentration enables the use of natural seawater as the electrolyte for the electrochemical epoxidation reaction. This work provides a new framework for producing epoxides through a sustainable approach.