Electroreduction of Carbon Dioxide (CO2) at Oxalate and Polypyrrole Modified Copper Surfaces

Abstract

The electrochemical conversion of CO₂ into useful chemicals remains an active area of investigation, especially towards higher order C₂ and C₃ products such as ethylene, ethanol and n-propanol. Herein we demonstrate that oxalate modified copper surfaces on porous gas-diffusion substrates (GDE) can be used to modify the selectivity of the electrochemical CO₂ reduction reaction (eCO₂RR) towards higher order chemicals using a flow-type electrochemical cell at near-neutral pH and industrially viable current densities. This multi-layer composite cathode consisting of a Teflon substrate, coated with copper, and then modified with copper oxalate. With modified copper surfaces, we demonstrate up to 79% selectivity to C₂₊ products at varying current densities ranging from 50 up to 250 mA/cm² representing a shift in electrocatalytic behavior as compared to the pristine copper/Teflon cathode. The oxalate modified copper surface enables further modification by a conductive polymer such as polypyrrole, tunable to varying thickness, demonstrating the ability to perform oxidative electropolymerization on copper-based GDE and subsequently use them for eCO₂RR. We also investigate the changes occurring to these electrodes with respect to particle/grain size, morphology and surface chemistry using SEM, XRD and XPS.