Selective Ethylene Production from Carbon Dioxide Electroreduction via Gas Diffusion Electrode Engineering

Electrochemical conversion of carbon dioxide into value-added hydrocarbons and oxygenates, compounds that contain oxygen atoms, offers a promising chemical means of storing intermittent electricity from renewable energy sources. This capability would reduce dependence on fossil fuels and mitigate the negative impact of anthropogenic carbon dioxide emissions.

Copper is a promising metal electrocatalyst capable of converting carbon dioxide into hydrocarbons such as ethylene. However, state-of-the-art copper catalysts exhibit low selectivity and low production rates of a single target product. Mechanistic pathways for the electrochemical conversion of carbon dioxide on heterogeneous copper catalysts are sensitive to extrinsic factors such as the local reaction microenvironment.

This research project focuses on customizing the microenvironment within a gas diffusion electrode to simultaneously increase current and energy efficiencies as well as the yield for the carbon dioxide-to-ethylene conversion. The outcomes of this research project will address the national interest in producing sustainable alternative fuels and chemicals from greenhouse gases such as carbon dioxide.

The research efforts will be complemented by outreach activities designed to communicate the outcomes of renewable energy research to diverse audiences, including undergraduate researchers, middle school students, and teachers, especially those groups that are underrepresented in STEM fields.

To deliver the electrochemical conversion of carbon dioxide into chemicals at industrially relevant production rates, systems will need to transition from conventional H-type glass cells to modular and scalable solid-state electrolyzers incorporating gas diffusion electrodes. The gas diffusion electrode is the critical component that determines the performance of gas-fed electrolyzers.

Control over the local reaction microenvironment, such as the partial pressure of gas reactants, water concentration, and pH value, around the copper catalyst within the gas diffusion electrode could potentially steer the activity and selectivity towards ethylene generation. This research project aims to manipulate the local reaction microenvironment by finely tuning the macro- and micro-structures of the gas diffusion electrode.

The investigators will characterize relationships between macro- and micro-structures of the gas diffusion electrode and carbon dioxide reduction performance through a series of experimental measurements and characterizations as well as multiscale numerical modeling. At first, the macro- and micro-structures of the gas diffusion electrode will be studied in a custom flow cell that features a flow liquid electrolyte between the cathode and ion exchange membrane.

The project will translate optimized gas diffusion electrode structures into a membrane electrode assembly-type cell that achieves higher energy efficiency at elevated current densities. The outcomes of this research project will advance our understanding of the interplay between reactant species transport and carbon-carbon coupling reaction kinetics.

Such knowledge can be applied to improving carbon dioxide-to-ethylene conversion with simultaneously high production efficiencies and rates.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.