Hydrogen production through dry reforming of biogas using a porous electrochemical cell: Effects of a cobalt catalyst in the electrode and mixing of air with biogas

This paper reports the performance of porous Gd-doped ceria (GDC) electrochemical cells with Co metal in both electrodes (cell No. 1) and with Ni metal in the cathode and Co metal in the anode (cell No. 2) for CO2 decomposition, CH4 decomposition, and the dry reforming reaction of a biogas with CO2 gas (CH4 + CO2 → 2H2 + 2CO) or with O2 gas in air (3CH4 + 1.875CO2 + 1.314O2 → 6H2 + 4.875CO + 0.7515O2). GDC cell No. 1 produced H2 gas at formation rates of 0.055 and 0.33 mL-H2/(min m2-electrode) per 1 mL-supplied gas/(min m2-electrode) at 600 °C and 800 °C, respectively, by the reforming of the biogas with CO2 gas. Similarly, cell No. 2 produced H2 gas at formation rates of 0.40 mL-H2/(min m2) per 1 mL-supplied gas/(min m2) at 800 °C from a mixture of biogas and CO2 gas. The dry reforming of a real biogas with CO2 or O2 gas at 800 °C proceeded thermodynamically over the Co or Ni metal catalyst in the cathode of the porous GDC cell. Faraday's law controlled the dry reforming rate of the biogas at 600 °C in cell No. 2. This paper also clarifies the influence of carbon deposition, which originates from CH4 pyrolysis (CH4 → C + 2H2) and disproportionation of CO gas (2CO → C + CO2), on the cell performance during dry reforming. The dry reforming of a biogas with O2 molecules from air exhibits high durability because of the oxidation of the deposited carbon by supplied air.