Role of Binder in Cu2O Gas Diffusion Electrodes for CO2 Reduction to C2+ Products

The electrochemical CO 2 reduction reaction (CO 2 RR) to form C 2+ products was investigated to obtain high selectivity in liquid CO 2 -fed systems having the limitation of low current density. Over the past decade, flow cells with gas diffusion electrodes (GDEs) have emerged to achieve high current densities close to the industrial-relevance scale by overcoming gas diffusion limitations. However, key parameters of GDE design, including binders, were not sufficiently identified to enhance selectivity and current density for C 2+ products. Nafion, FAA-3, and polypyrrole were used to explore the effects of binder type and content on GDE properties such as porosity (gas permeability), ion conductivity, and electron conductivity for the modulation of the CO 2 RR on the Cu 2 O catalyst. The Cu 2 O GDEs with high binder content showed poor selectivity for C 2+ products because of their low exposure to the catalyst surface and decreased gas permeability. The anion exchange ionomer, FAA-3, showed high selectivity for C 2+ products and electrode stability resulting from the C–C coupling increase and suppression of the hydrogen evolution reaction, which was induced by OH – conductivity. In contrast, the cation exchange ionomer, Nafion, exhibited low electrode stability due to the loss of gas products through the catholyte and due to its excessive wettability.