Abstract
Gas diffusion electrodes mediate the transport of reagents, products, and electrons in electrochemical reactors for CO2 reduction. Here, we show that the ionomer-to-electrocatalyst ratio in precursor catalyst inks does not necessarily remain unchanged after deposition on the GDE. We develop an X-ray fluorescence spectroscopic protocol to quantify Nafion content and show that small changes in GDE composition can substantially alter CO2RR product selectivity. These findings provide procedures for generating more reproducible CO2RR performance parameters in flow cells.