Electrochemical Reduction of CO2 in a Biphasic Continuous-Flow Electrolysis Reactor

Electrochemical conversion of carbon dioxide (CO₂) to carbon monoxide (CO) can simultaneouslymitigate anthropogenic greenhouse gas emissions and produce useful industrial chemicals. When combined with a renewable energy source, a reactor can recycle CO₂ into CO, which is the carbon source of synthesis gas, in a sustainable fashion. Through Fischer-Tropsch processing, syngas is processed into a range of liquid hydrocarbons that can be used as fuels or precursor materials. Electrochemical fuel generation processes are advantageous because they usually occur at mild conditions, near ambient pressure and temperature, in comparison to the thermochemical processes. In addition, the time scale for adjusting the applied voltage, which controls production rate, is small and, allows the process to be synced with periods of low cost electricity. These benefits along with decreasing energy prices, have contributed to a growing interest in synthesizing catalysts for energy-efficient CO₂ conversion to CO.

Pursuant to this goal, significant development has been made on identifying electrocatalysts that are of high activity, stability, and selectivity towards CO over the competing hydrogen (H₂) evolution side reaction. My research group has screened an array of precious metal catalysts and identified carbon supported gold nanoparticles as a superior material, achieving over 90% coulombic efficiency. However, we conducted these experiments in a small-scale electrochemical H-cell designed for catalytic studies. A more practical application is to deposit the catalyst onto a gas diffusion layer and then characterize the electrode performance in a reactor that has higher product yield. Drawing from fuel cell literature and electrolyzer designs, we developed a continuous-flow electrochemical reactor with gas phase reactant delivery, where the anode and cathode are bridged by the flowing electrolyte and the gaseous reactant permeates directly to the active catalyst site. Using this analytical platform, we aim to quantify performance of the system as a function of electrode preparation, cell configuration, and operating conditions. Optimization of the flow cell can inform future catalyst and electrode development, and serve as a bridge between academic pursuit and industrial scalability.