Oxygen-tolerant electroproduction of C2 products from simulated flue gas

Abstract

The electroreduction of carbon dioxide (CO₂) to C₂ products is a promising approach to divert and utilize CO₂ emissions. However, the requirement of a purified CO₂ feedstock decreases the economic feasibility of CO₂ electrolysis. Direct utilization of industrial flue gas streams is encumbered by low CO₂ concentrations and reactive oxygen (O₂) impurities. We demonstrate that pressurization enables efficient CO₂ electroreduction of dilute CO₂ streams (15% v/v); however, with the inclusion of O₂ (4% v/v), the oxygen reduction reaction (ORR) displaces CO₂ reduction and consumes up to 99% of the applied current in systems based on previously-reported catalysts. We develop a hydrated ionomer catalyst coating strategy that selectively slows O₂ transport and stabilizes the copper catalyst. Applying this strategy, we convert an O₂-containing flue gas to C₂ products at a faradaic efficiency (FE) of 68% and a non-iR-corrected full cell energetic efficiency (EE) of 26%.