a Schematic representation of the flow cell electrolyzer. b Faradaic efficiencies as a function of applied geometric current density for CuO NS with catalyst loading of 1 mg cm−2 in 1 M KHCO3. c The partial current density of C2H4. d Stability test at a geometric current density of 300 mA cm−2, displaying the Faradaic efficiencies as a function of time. e Plots of C2+ partial current densities in a flow-cell system (compared with references)4,43,46,63,64,65,66,67,68.