High Temperature Electrolysis of CO2 for Fuel Production

Abstract

High temperature CO2 electrolysis to produce CO and O2 was studied with the goal of developing an efficient and practical method for producing fuel from solar energy. Electrolysis of CO2 at temperatures of 660°C–1400°C is performed on an electrolyte-supported cell composed of 8% YSZ electrolyte and Pt/YSZ cermet electrodes. The cell was operated at CO2 concentrations between 42%–99.9% with a balance of CO. This is the first published example of electrolysis measurements conducted at a temperature greater than 1000°C. The average specific differential resistances of the test cell during CO2 electrolysis, including lateral electrode resistance, were 53.8 Ohm·cm2 at temperatures between 660–670°C, 5.2 Ohm·cm2 at 950°C, 3.9 Ohm·cm2 at 1250°C, and 4.8 Ohm·cm2 at 1400°C. These measurements show an order of magnitude resistance reduction as temperature increases from 660°C to 1250°C, with the lowest cell resistance at 1250°C. The drop in performance as the temperature increases from 1250°C to 1400°C is primarily due to electrode sintering. Furthermore, it was determined that ppm levels of O2 present in the CO2/CO mixture on the cathode side of the cell increase cell resistance.