Electrochemical CO₂ Reduction: Tailoring Catalyst Layers in Gas Diffusion Electrodes

Abstract

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.

Understanding the Effects of Anion Interactions with Ag Electrodes on Electrochemical CO2 Reduction in Choline Halide Electrolytes

“…We did not see any significant change in FE CO when recirculating the catholyte (Figure S18), which indicates that the Ag dissolution‐electrodeposition cycle is not a key mechanism in the CO 2 R flow‐cell. The small decrease in FE CO observed over a 1 h CO 2 R test in the recirculation experiments in both ChCl and ChBr could be due to electrowetting effects, which would allow catholyte to infiltrate the pores of GDE and inhibit CO 2 mass‐transfer rate to the catalyst layer [71,72] . Our flow‐cell results do demonstrate the choline‐based electrolytes can achieve very good CO 2 R performance, but cannot yet fully explain why the trends in results obtained in the H‐type cell and flow‐cell electrolyser are different.…”

Influence of the Fe : Ni Ratio in FexNi9‐xS8 (x=3–6) on the CO2 Electroreduction

“…The observed CO 2 R activity of an electrocatalyst depends not only on its intrinsic properties but is also heavily influenced by the electrolytic environment [20] . In the case of CO 2 reduction in organic electrolytes, the water content at the catalyst surface plays a major role in controlling the generation of H 2 and CO [3] . Therefore, we performed similar experiments in a proton‐poor electrolytic environment containing only 24 ppm of H 2 O at the start of electrolysis.…”

“…The electrochemical reduction of carbon dioxide (CO 2 R) driven by renewable energies to produce valuable commodity chemicals or fuels is commonly regarded as a highly promising strategy to establish a sustainable economy based on a closed carbon cycle. However, an effective development to an industrial scale with reasonable economic viability [1] is still impaired by major challenges including electrolyzer engineering [2] , electrode design [3,4] as well as the search for effective and durable catalyst systems [5] . For the latter, especially noble metal free formulations based on inexpensive and readily available elements are particularly desirable [6]…”

Crossing the Valley of Death: From Fundamental to Applied Research in Electrolysis

“…Consequently, the gas diffusion system (GDS) corresponds to a combination of GDL and MPL. The PTLs in combination with the CL represent the gas-diffusion electrode (GDE) (e.g., utilized in the electrochemical reduction of CO 2 26 ), whereas the membrane coated with the anode and cathode CL forms the catalyst coated membrane (CCM).…”