Single-pass CO2 conversion efficiency. The electrochemical single-pass CO2 conversion efficiency (%) of CP|CoPL was calculated by dividing the rate of CO formation (mol min -1 ) by the flow rate of CO2 (mol min -1 ) and multiplying the product by 100. The flow rate of CO2 was obtained by transforming ml min -1 to mol min -1 using the ideal gas law equation (pV = nRT),