Electrochemical CO<sub>2</sub> Reduction: Tailoring Catalyst Layers in Gas Diffusion Electrodes
Kai junge Puring, Daniel Siegmund, Jana Timm, Florian Möllenbruck, Steffen Schemme, Roland Marschall, Ulf‐Peter Apfel
Abstract
Abstract The electrochemical conversion of CO 2 into commodity chemicals or fuels is an attractive reaction for sustainable CO 2 utilization. In this context, the application of gas diffusion electrodes is promising due to efficient CO 2 mass transport. Herein, a scalable and reproducible method is presented for polytetrafluoroethylene (PTFE)‐bound copper gas diffusion electrodes (GDEs) via the dry‐pressing method and compositional parameters are emphasized to alter such electrodes. The assembly of the catalytic layer plays a critical role in the electrode performance, as elevated bulk hydrophobicity coupled with good surface wettability is observed to offer highest performance in 0.5 m KHCO 3 . With optimized electrodes, formate, CO, and H 2 are obtained at a current density of 25 mA cm −2 as main products in 1 m KOH in faradaic efficiencies (FEs) of 27%, 30%, and 36%. At 200 mA cm −2 , an altered product composition with ethylene (33% FE) and ethanol (9% FE) along with H 2 (33% FE) is observed. In addition, n ‐propanol is observed with 7% faradaic efficiency. The results indicate that the composition of the GDE has a severe influence on the electrode performance and setting proper hydrophobicity gradients within the electrode is key toward developing a successful electrochemical CO 2 reduction.