Sn-Ag Synergistic Effect Enhances High-Rate Electrocatalytic CO2-to-Formate Conversion on Porous Poly(Ionic Liquid) Support

The electrocatalytic transformation of carbon dioxide (CO2) to formate is a promising route for highly efficient conversion and utilization of CO2 gas, due to the low production cost and the ease of storage of formate. In this work, porous poly(ionic liquid) (PPIL)-based tin-silver (Sn-Ag) bimetallic hybrids (PPILm-SnxAg10-x) are prepared for high-performance formate electrolytic generation. Under optimal conditions, an excellent formate Faradaic efficiency of 95.5% with a high partial current density of 214.9 mA cm(-2) is obtained at -1.03 V (vs reversible hydrogen electrode). Meanwhile, the high selectivity of formate (>approximate to 83%) is maintained in a wide potential range (>630 mV). Mechanistic studies demonstrate that the presence of Ag-species is vital for the formation, maintenance, and high dispersion of tetravalent Sn(IV)-species, which accounts for the active sites for CO2-to-formate conversion. Further, the introduction of Ag-species significantly enhances the activity by increasing the electron density near the Fermi energy level.