Integration of Anodic and Cathodic Catalysts of Earth-Abundant Materials for Efficient, Scalable CO2 Reduction

A fully integrated electrochemical cell for co-production of formate (HCOO-) and oxygen (O-2) from carbon dioxide (CO2) and water using only earth-abundant elements has been developed. The process converts CO2 to formate using electrons derived from anodic water oxidation. A novel cathodic catalyst system, consisting of a tin (Sn) cathode in combination with the soluble heterocycle 2-picoline, was identified for CO2 reduction. Water oxidation takes place at a fluorine-doped tin oxide electrode coated with an electrodeposited cobalt oxide (CoOx) electrocatalyst. Use of 2-picoline as a soluble cathodic co-catalyst lowered the overpotential and enhanced the stability of the Sn-mediated CO2 reduction process. Fluorophosphate served as a redox-stable electrolyte to buffer the anode compartment at mildly acidic pH (similar to 5 to 5.5), thereby stabilizing the CoOx electrocatalyst and supporting efficient water oxidation. The complete electrochemical cell maintained a stable cell voltage of less than 3 V over 5 days, with an average formate faradaic yield of 34 %. These results are presented together with an economical analysis of large-scale solar-driven production of formate/formic acid from CO2 and water.