Improving efficiency by enhancing mass transfer at CO reduction cathodes

Transforming CO₂ to commodity chemicals to close the carbon cycle is possible through first converting CO₂ to CO in a solid oxide cell, then reducing the CO to multicarbon products like ethylene. However, CO reduction electrolysis suffers from poor energy efficiency due to high full cell voltages, low reactant conversion rates, and parasitic reactions which decrease product selectivity.  These losses are most prominent at the cathode side, which comprises the carbon fiber gas diffusion layer and a thick, porous catalyst layer containing copper catalyst and Teflon nanoparticles to balance hydrophilicity and hydrophobicity. We have built a 2D computational model that fully couples the kinetics of multiple electrochemical reactions, ion transport, mass transfer in porous media by viscous and diffusive mechanisms, and an overall material balance. Changing key parameters such as the flow rate, pressure, temperature, and catalyst loading has allowed us to identify tradeoffs between figures of merit like faradaic efficiency and CO conversion. High energy efficiency can be achieved when a high partial pressure of CO and high CO conversion are simultaneously maintained. We will also present a sensitivity analysis and model validation against experimental results.