Direct electrocatalytic CO2 reduction in a pressurized tubular protonic membrane reactor

Power-to-methane technology enables storage of renewable elec-tricity in chemical energy, which can be transported and converted us-ing existing infrastructure. The moderate energy efficiency of this pro-cess is associated with high reactor exothermicity and complex thermal integration. Proton-ceramic electrochemical cells (PCECs) enable ther-mal combination of methanation and electrochemically driven H2 steps via endothermic reactions, boosting energy efficiency and heat man-agement. Here, we report single-step methane production from CO2 in a tubular PCEC at 450 degrees C and less than 30 bar. The H2 reactant is sup-plied by electrochemical pumping of protons from H2 in the external chamber. The electrochemical cell consists of an -25-mm-thick electro-lyte (BaZr0.8Ce0.1Y0.1O3-8) supported on a BaZr0.8Ce0.1Y0.1O3-8/Ni com-posite acting as a methanation catalyst. The reaction was studied as a function of total pressure, H2/CO2 ratio, and current density, reaching CH4 yields greater than 99% above 20 bar. High pressure and a CO2- rich atmosphere ameliorated the electrochemical behavior because of higher electrolyte hydration and boosted electrode kinetics.