Co-Electrolysis of Biohythane Using Solid Oxide Fuel Cell Technology

Abstract

Two-stage anaerobic digestion enables the production of biohythane, which is composed of 60/30/10 vol% CH4/CO2/H2 and is easier and more beneficial to utilize than conventional biogas (60/40 vol% CH4/CO2). This study has investigated co-electrolysis of biohythane with H2O and CO2 using an anode-supported solid oxide fuel cell. The kinetic performance of the cell was characterized using I-V curves and electrochemical impedance spectroscopy. The output gases from the anode were characterized using quadrupole mass spectrometry. The work has shown that addition of 10 vol% H2 to CH4/CO2 feedstocks markedly improves the overall performance of the cell in electrolysis mode. Co-electrolyzing with H2O gave the highest performance, highest syngas (H2 + CO) yield (87%) and highest H2/CO ratio (2.69). Co-electrolyzing with CO2 decreased the catalytic and electrochemical conversion of reactants, giving lower performance, lower syngas yields (79%) and lower H2/CO ratios (0.87). Enhanced performance with H2O was due to a mixture of increased catalytic and electrochemical conversion of reactants.