Climate Change is a phenomenon driven by anthropogenic activities, such as the combustion of fossil fuels, which results in large amount of greenhouse gas emissions. To address this issue, clear objectives must be established. One of the primary goals of the United Nations Conference (COP 28) is to reduce greenhouse gas emissions by 43% by 2030 while limiting the global temperature increase to 1.5°C. Among the various CO₂ mitigation strategies, Carbon Capture and Utilization (CCU) to produce useful and renewable chemicals is particularly promising, as it fosters the development of new carbon-neutral techniques using renewable energy sources.

Currently, various approaches have been developed to activate and convert CO₂. Among these, the electrochemical reduction of CO₂ offers an attractive solution, as it combines the reduction of CO₂ emissions with the production of value-added products such as formic acid or formate [1]. The gas diffusion electrode (GDE), the most common and effective configuration for CO₂ electrochemical reduction to formic acid and formate, consists of three layers: (i) a carbonaceous support, (ii) a microporous layer, and (iii) a catalytic layer. While the catalytic layer has been extensively studied, the microporous layer plays a crucial role by imparting hydrophobic properties, preventing flooding, and enhancing contact between the CO₂ stream and the catalyst [2].

The most common material used for the microporous layer is carbon black, produced through the incomplete combustion of petroleum-derived hydrocarbons. However, these materials have drawbacks that impact both the environment and human health. Therefore, this study focuses on evaluating the performance of GDEs made from biomass materials sourced from phytoremediation processes to create an environmentally friendly microporous layer for the GDEs.

The carbon materials used to fabricate the GDEs were synthesized from three different lignocellulosic species: Phragmites australis, Cladium mariscus and Typha domingensis. These materials were initially subjected to hydrothermal carbonization with a biomass-to-water ratio of 130 g L^-1 (200 ºC, 2 h under self-generated pressure). The resulting hydrochar was then further processed through either pyrolysis or chemical activation (with KOH). These materials have demonstrated their effectiveness in generating H₂O₂ [3] and have the potential to help mitigate climate change by enabling the CO₂ electrochemical reduction to formate.

The best results were obtained with a mixture of biomass materials and Vulcan XC-72R (50% wt), achieving a formate concentration of 1.8 g·L⁻¹ at 90 mA·cm⁻². The experiment demonstrated a high Faradaic efficiency of nearly 80% and slightly lower energy consumption compared to Vulcan XC-72R alone, based on absolute cell potentials. In conclusion, these new materials combined with Vulcan XC-72R (50% wt) could help reduce soil contamination and mitigate the impact of climate change through CO₂ electrochemical reduction to formate, achieving results comparable to those of the microporous layer made with carbon black.