The carbon dioxide redox flow battery: Bifunctional CO2 reduction/formate oxidation electrocatalysis on binary and ternary catalysts

Abstract For over two hundred years, starting with Volta's pile, most battery innovations focused on diverse metals or metallic species at one or both electrodes. Due to unprecedented growth in battery demand, there are challenges regarding the supply of diverse minerals coupled with the high energy intensity and carbon footprint of metal production. Herein, we introduce a novel class of non-metal flow batteries, the CO2 redox flow battery (CRB). In the present variant, the CRB utilizes the CO2/HCOO− redox couple at the negative electrode and Br−/Br2 at the positive electrode with a battery open-circuit cell potential of 1.5 V. The bifunctional electrocatalyst enabling the interconversion of CO2 and formate with low activation overpotentials is critical for the CRB. We study bimetallic (PdSn) and ternary (PdSnPb, PdSnIn) electrocatalysts demonstrating the beneficial role of perovskite catalyst support and electrochemical activation. A preliminary CRB with batch electrolytes and gas diffusion negative electrode containing activated PdSn/LaCoO3 catalyst, produced a peak power density of 19.2 mW cm−2 at 318 K. The latter power density is four times higher than reported values for other emerging non-metal batteries such as sulfur-air. Our overarching goal is to develop rechargeable flow batteries that utilize captured CO2 from industrial sources to store renewable energy.