Methanation of CO2 on Cu in a tubular co-ionic SOEC

Abstract

This work aims contributing to develop a cathode for CO2 methanation in tubular co-ionic (H+/O2- conducting) SOECs and to cell operation optimization to decrease energy input and costs for advancing process application. It studies the effect of temperature (325-550 ºC) and potential (from -2 to +2 V at 450 ºC) on CO2 conversion and selectivity to CH4 and CO, at bench scale, at atmospheric pressure and using high flowrates (42 NL/h) and realistic compositions (4H2/CO2 binary mix), over a Cu film (<2 mm) coated by electroless on an anode (Ni-BZCY)-supported solid electrolyte (BZCY) candle. CH4 preferentially forms over CO. CH4 selectivity increases with temperature up to 97.3% at 400 ºC, from which, CH4 and CO selectivity decreases and increases, respectively. The optimum potential is -0.5V, as maximizes CH4 selectivity (94.2%) and minimizes energy cost (0.002 kWh/kg CH4) with high CO2 conversion (32.5%) and low CO selectivity (5.8%), resulting in higher CH4 yield and lower CH4 purification cost.