Thesis presented December 12, 2023

Abstract:
Carbon dioxide capture and utilization (CCU) is a way to decarbonize industrial sector. This technology provides a valorization of cheap carbon feedstock by its transformation to carbonaceous value-added chemicals. Multiple CO₂ capture and utilization techniques exist to prevent the release of the greenhouse gas to the atmosphere. Here, we propose an integrated process of CO₂ capture sequenced by electroconversion to C-based products in electrochemical cell. Electrochemical CO₂ conversion is a promising method due to mild reaction conditions and possibility to power the reaction with electricity produced by renewable energy sources. This process necessitates the development of solvents capable to capture CO₂ and to play a role of electrolyte during electrochemical reduction reaction. At the same time, efficient catalytic materials are vital for selective CO₂ conversion to targeted product(s). The choice of capture solvent is usually based on CO₂ capture ability, chemical and electrochemical stabilities, environmental issue and cost. Economically affordable deep eutectic solvent (DES) electrolytes seem to be promising candidates for CO₂ capture and electroreduction because of good thermal and electrochemical stabilities, competitive CO₂ uptake and large electrochemical windows. In this work, we focused on the development of novel deep eutectic solvent electrolytes for CO₂ electroreduction with Pd-based electrocatalysts. Palladium proved its efficiency for selective conversion of carbon dioxide to C1 molecules such as carbon monoxide.
During the thesis, we synthesized and electrochemically tested multiple DESs and Pd-based electrocatalysts with different morphologies and particle sizes to get more insights into reaction mechanism of CO₂ electroreduction to C1 molecules. The implementation of different characterization techniques helped to study catalytic materials and DESs structures, to analyze gaseous and liquid reaction intermediates and products, and to understand main challenges of the studied system. Overall, this study is a one step forward the application of CO₂ER (carbon dioxide electrochemical reduction) for valorisation of carbon dioxide and climate change mitigation.

Keywords:
CO₂ electroreduction, decarbonization, CCU, palladium electrocatalyst, deep eutectic solvent electrolyte