Electrochemical CO2 Reduction: Tailoring Catalyst Layers in Gas Diffusion Electrodes

• Published in: Advanced sustainable systems (Online) Vol. 5; no. 1
• Main Authors: Junge Puring, Kai, Siegmund, Daniel, Timm, Jana, Möllenbruck, Florian, Schemme, Steffen, Marschall, Roland, Apfel, Ulf‐Peter
• Format: Journal Article
• Language: English
• Published: 01.01.2021
• Subjects: carbon dioxide; copper; electrocatalysis; ethylene; gas diffusion electrodes
• ISSN: 2366-7486; 2366-7486
• DOI: 10.1002/adsu.202000088

The electrochemical conversion of CO2 into commodity chemicals or fuels is an attractive reaction for sustainable CO2 utilization. In this context, the application of gas diffusion electrodes is promising due to efficient CO2 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 KHCO3. With optimized electrodes, formate, CO, and H2 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 H2 (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 CO2 reduction. A method for adjusting the fine balance between hydrophobicity and hydrophilicity of gas diffusion electrodes for the electroreduction of CO2 is presented. The bulk hydrophobicity of the catalyst is decoupled from its surface hydrophobicity using a facile ionomer coating. This enables good surface wettability of the catalyst layer while retaining bulk hydrophobicity needed for efficient CO2 reduction.