Concentrated formate produced through co‐electrolysis of CO2 and methanol in a zero‐gap electrolyzer

Abstract Recent progresses have highlighted the enormous potentials of renewable electricities driven carbon dioxide (CO 2 ) electrolysis in achieving carbon neutrality. However, its further industrial application is limited by low liquid product concentrations, which requires energy‐intensive downstream separation processing. Herein we report a CO 2 and methanol co‐electrolysis strategy to produce formate at both electrodes and collect highly concentrated formate in zero‐gap CO 2 electrolyzers. An anion exchange membrane was employed to enable formate product crossover from cathode to anode. A bismuth silicate derived nanofiber electrocatalyst with rich grain boundaries was synthesized and exhibited excellent formate selectivity (Faradaic efficiency >95%), high activity (partial current density >500 mA cm −2 ), as well as good stability (>120 h). Coupled with NiOX anode catalyst for methanol selective oxidation to formate in a zero‐gap electrolyzer, we demonstrate a ~180% of formate Faradaic efficiency and a full‐cell voltage of 2.43 V at an industrially relevant current density of 0.2 A cm −2 . By decoupling product generation and collection, our electrolyzer produced a highly concentrated formate of 3.24 M, which could be directly used as anode fuel for fuel cells.