(309c) Electrochemical Plasma-Activated CO2 Reduction at a Plasma-Water Interface

The development of technologies and processes to decarbonize chemical and fuel production is key to reducing global anthropogenic greenhouse gas emissions. Electrochemical carbon dioxide reduction enables a sustainable pathway to circularize these carbon-based chemical products by upgrading recovered carbon dioxide using renewable energy sources. Demonstrations of electrochemical CO₂ reduction have successfully yielded chemicals like ethanol and ethylene, but their performance has been limited by dependence on elevated temperature or pressure to achieve high yields and limited ability to generate higher order carbon products. Non-thermal carbon dioxide plasma can be generated at ambient temperature and pressure and contains energetically excited gas species that, when introduced to an electrocatalyst, could participate in reaction pathways that have higher activation barriers and lead to the generation of higher order carbon species. Further, plasma discharges over water in an electrochemical cell generate plasma-activated water species, introducing solvated electrons and secondary reactive oxygen and carbon species that may participate in electrocatalytic reactions towards a wider variety of possible products.

In this work, we investigate how the use of plasma-activated carbon dioxide at a water interface impacts electrochemical product generation. We design a novel non-thermal plasma electrode to discharge carbon dioxide plasma into water in an electrochemical cell with a Cu nanoparticle electrocatalyst. We demonstrate enhanced production of C₃ products and generation of C₄ products (which are not generated with electrocatalysis alone) with plasma pre-activation of CO₂. Through experiments designed to probe the reaction mechanism, we hypothesize that the synergistic effect of plasma activation of gaseous and aqueous carbon species and electrocatalytic conversion enables C-C coupling towards higher order products. Results indicate the potential for a plasma-water electrochemical system to generate value-added products which are challenging to produce in traditional electrochemical processes at ambient pressure and temperature.