Intermediate-Temperature Electrocatalytic CO₂ Reduction with a Coordination Polymer Glass Electrolyte

Electrocatalytic CO₂ reduction at intermediate temperatures (100–150 °C) has been expected to have many advantages from reaction kinetics and product selectivity viewpoints, but the reaction attempt has been strictly hindered because of the difficulties of membrane-electrode assembly (MEA) fabrication and the limited selection of electrolyte consisting of proton (H⁺)-conductive materials. In this study, we fabricated an MEA for the electrocatalytic reduction of gaseous CO₂ at the intermediate temperatures. Cyclic voltammetry of ferrocene in a H-cell separated by a membrane of [Zn(HPO₄)(H₂PO₄)₂](ImH₂)₂ glass (1g, Im = imidazolate) confirmed their H⁺-exchange ability and stability in N-methyl-2-pyrrolidone at 120 °C. We prepared an MEA with 1g and confirmed higher catalytic activity and reactant selectivity at 120 °C than at 30 and 80 °C and observed over 99% product selectivity to carbon monoxide (CO) at 80 and 120 °C.