Turning waste into value: fabrication of gas diffusion electrodes from biomass-derived materials for CO2 electroreduction to formate

Abstract

Climate change, driven predominantly by anthropogenic activities such as fossil fuel combustion, has led to significant greenhouse gas emissions. In response, the United Nations' COP28 has set an ambitious goal to reduce emissions by 43 % by 2030, with the aim of limiting global temperature rise to 1.5 °C. Among the various CO2 mitigation strategies, Carbon Capture and Utilization (CCU) is particularly promising, especially the electrochemical reduction of CO2 into valuable chemicals. This process not only curtails CO2 emissions but also facilitates the production of renewable chemicals such as formic acid and formate. Gas diffusion electrodes (GDEs) are central to CO2 electroreduction, with the microporous layer playing a critical role in preventing flooding and optimizing catalyst interaction. However, traditional carbon black-based microporous layers, such as those made from Vulcan XC-72R, raise environmental and health concerns. This study explores the use of biomass-derived materials, specifically lignocellulosic species, processed via hydrothermal carbonization, pyrolysis, and chemical activation. The results show that GDEs incorporating a biomass and Vulcan XC-72R (50 % wt) mixture achieve high formate concentrations (1.8 g·L-1) and Faradaic efficiency toward formate (80 %) at 90 mA·cm-2-performances that are comparable to or even superior to those of GDEs made solely with commercial Vulcan XC-72R. This demonstrates that these sustainable biomass-derived materials have great potential to effectively replace up to 50 % of carbon black materials and thereby reducing reliance on non-renewable resources, for the production of high-value chemicals from CO2.