A microchanneled solid electrolyte for carbon-efficient CO2 electrolysis

The electrochemical reduction of CO2 is a promising route to convert carbon emissions into valuable chemicals and fuels. In electrolyzers producing multi-carbon products, 70%–95% of the supplied CO2 is converted to (bi)carbonates, limiting the carbon efficiency of electrochemical CO2 conversion. These (bi)carbonate anions can be lost to the aqueous electrolyte, converted back to gaseous CO2 and diluted in the anode tail gas, and/or combined with alkali metal cations from the electrolyte to form solid salt precipitates. Here, we report a microchanneled solid electrolyte that allows for the recapture and recycling of (bi)carbonate ions before reaching the anode, reducing CO2 loss to ∼3%. We demonstrate CO2 electroreduction to multi-carbon products with 77% selectivity without the use of alkali metal cations, by incorporating fixed quaternary ammonium cations. This system simultaneously achieves near-zero CO2 loss, high selectivity toward multi-carbon products, and stable operation at an industrially relevant current density over 200 h.