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

Abstract

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.