The best of both worlds: stacked catalytic layers for the electrocatalytic generation of CO in zero-gap electrolysers

Tailoring the properties of the catalytic layer (CL) and its architecture is crucial for enhancing both the efficiency and selectivity of CO2 electrolysers. Traditionally, CLs for CO2 reduction comprise of a single binder material or a combination that handles both ion conductance and the maintenance of a hydrophobic environment. In this work, we decouple these processes into two individual, stacked catalyst-containing layers. Specifically, a hydrophobic catalytic layer is placed on the gas diffusion layer to improve water management within the CL during CO2R in zero-gap electrolysers. Additionally, a second catalytic layer, bound by an ion-conducting binder, facilitates the conduction of OH- and HCO3-/CO32- during CO2R, thereby enhancing both ionic conductivity between the GDE and anion exchange membrane (AEM), as well as mechanical adhesion between different interfaces. Notably, we present a comprehensive stepwise optimization pathway for the CL, addressing both single and stacked CLs for CO2-to-CO conversion at current densities of 300 mA cm-2.