Solar-driven co-thermolysis of CO2 and H2O promoted by in situ oxygen removal across a non-stoichiometric ceria membrane

Abstract

We report on the first ever experimental demonstration of simultaneous thermolysis of CO₂ and H₂O with in situ separation of fuel and oxygen in a solar-driven membrane reactor. Gaseous CO₂/H₂O mixtures at molar ratios from 3 : 4 to 2 : 1 were fed to a mixed ionic–electronic conducting non-stoichiometric ceria (CeO_2−δ) membrane enclosed in a solar cavity receiver and exposed to simulated concentrated solar radiation of up to 4200 suns. Reaction rates were measured under isothermal and isobaric conditions in the range of 1723–1873 K and 0.2–1.7 Pa O₂, yielding a maximum combined CO and H₂ fuel production rate of 2.3 μmol cm⁻² min⁻¹ at 1873 K and 0.2 Pa O₂ at steady state, which corresponded to a conversion of reactants of 0.7%. Under all conditions tested, CO production was favored over H₂ production, as expected from theory. Experimental results followed the same trends as the thermodynamic equilibrium limits of membrane-assisted thermochemical fuel production.