Eliminating the need for anodic gas separation in CO(2) electroreduction systems via liquid-to-liquid anodic upgrading

Electrochemical reduction of CO(2) to multi-carbon products (C(2+)), when powered using renewable electricity, offers a route to valuable chemicals and fuels. In conventional neutral-media CO(2)-to-C(2+) devices, as much as 70% of input CO(2) crosses the cell and mixes with oxygen produced at the anode. Recovering CO(2) from this stream adds a significant energy penalty. Here we demonstrate that using a liquid-to-liquid anodic process enables the recovery of crossed-over CO(2) via facile gas-liquid separation without additional energy input: the anode tail gas is directly fed into the cathodic input, along with fresh CO(2) feedstock. We report a system exhibiting a low full-cell voltage of 1.9 V and total carbon efficiency of 48%, enabling 262 GJ/ton ethylene, a 46% reduction in energy intensity compared to state-of-art single-stage CO(2)-to-C(2+) devices. The strategy is compatible with today’s highest-efficiency electrolyzers and CO(2) catalysts that function optimally in neutral and alkaline electrolytes.