Polymer Membrane Gas-Diffusion Layer with Nanowire Catalyst Implemented in Zero-Gap CO ₂ Electrolyzer Prevents Salt Precipitation-Induced Failure

The formation of salt precipitates in zero-gap CO 2 electrolyzers is a notorious cause of operational instability as it hinders CO 2 feed to the catalyst. Salt formation is often related to electrowetting of carbon-based gas-diffusion layers (GDLs), and a proposed solution is to use nonconductive polymer membranes as a GDL instead. By combination of a PTFE membrane with a conductive Ag nanowire catalyst layer, a stand-alone gas-diffusion electrode (GDE) is obtained. We then introduce a modification of the CO 2 electrolyzer that permits the use of nonconductive GDL electrodes with membrane-only separation between cathode and anode. As a result, stable operation with high selectivity toward CO production is maintained for 100 h at −200 mA cm –2, whereas a carbon paper GDL suffers from fluctuating performance, with the flow channel eventually being blocked by salt precipitates. In effect, the use of nonconductive GDL substrates combined with suitable catalyst morphology enables stability in zero-gap CO 2 electrolyzers.