Engineering the NiNC Catalyst Microenvironment Enabling CO2 Electroreduction with Nearly 100% CO Selectivity in Acid

CO2 electrolysis in acid has emerged as a promising route to achieve high CO2 utilization due to the inhibition of undesired carbonate formation that generally occurs in alkaline or neutral conditions. However, the efficiency and stability of this system need to be further improved through tailoring of the electrocatalyst and its working environment. Here, a working microenvironment of structurally engineered NiNC catalyst for acidic CO2 electrolysis is probed and optimized by adding hydrophobic poly(tetrafluoroethylene) (PTFE) nanoparticles in the catalytic layer of gas-diffusion electrodes. The PTFE-modified electrode delivers nearly 100% CO Faradaic efficiency at an industry-relevant current density of 250 mA cm-2 , and a high single-pass CO2 utilization of 75.7% at a current density of 200 mA cm-2 under 20 sccm CO2 gas flow rate. Moreover, compared to a conventional electrode without added PTFE, the PTFE-modified electrode exhibits a substantially enhanced water-flooding-resistant ability. Mechanistic investigations reveal that a moderate PTFE modification can optimize the local CO2 /H2 O ratio in the catalytic layer, favoring the reduction of the diffusion layer thickness and the formation of a highly active and stable solid-liquid-gas interfacial microenvironment.