Recovering carbon losses in CO2 electrolysis using a solid electrolyte reactor

The practical implementation of electrochemical CO2 reduction technology is greatly challenged by notable CO2 crossover to the anode side, where the crossed-over CO2 is mixed with O2, via interfacial carbonate formation in traditional CO2 electrolysers. Here we report a porous solid electrolyte reactor strategy to efficiently recover these carbon losses. By creating a permeable and ion-conducting sulfonated polymer electrolyte between cathode and anode as a buffer layer, the crossover carbonate can combine with protons generated from the anode to re-form CO2 gas for reuse without mixing with anodic O2. Using a silver nanowire catalyst for CO2 reduction to CO, we demonstrated up to 90% recovery of the crossover CO2 in an ultrahigh gas purity form (>99%), while delivering over 90% CO Faradaic efficiency under a 200 mA cm−2 current. A high continuous CO2 conversion efficiency of over 90% was achieved by recycling the recovered CO2 to the CO2 input stream. Crossover of CO2, in the form of carbonate, from the cathode to the anodic compartment places a major limitation on carbon efficiency in traditional CO2 electrolysis cells. Here, the authors place a porous solid electrolyte layer between the compartments, where protonation of carbonate during CO2 electrolysis allows recovery of over 90% of the lost CO2 gas.