Solar Thermochemical CO2 Splitting Utilizing a Reticulated Porous Ceria Redox System

摘要

Solar-driven thermochemical cycles based on metal oxide redox reactions can split H2O and CO2 to produce H2 and CO (syngas), the precursors to the catalytic synthesis of conventional liquid fuels for the transportation sector. Among a variety of metal oxides, ceria has emerged as an attractive redox active material because of its ability to rapidly conduct O~(2-) contributing to fast redox kinetics. The two-step H2O/CO2 splitting cycle based on non-stoichiometric ceria is represented by High-temperature reduction: CeO2 = CeO_(2-δ) + 1/2δO2(1) Low-temperature oxidation with H2O: CeO_(2-δ)+ δH2O = CeO2 + δH2 (2) Low-temperature oxidation with CO2: CeO_(2-δ) +δCO2 = CeO2 + δCO (3) In the solar reduction step, ceria is thermally reduced to a non-stoichiometric state. At equilibrium, the oxygen deficiency δ reaches 0.06 at 1500°C and 10~(-5) bar O2 partial pressure. In the subsequent non-solar oxidation step, the reduced ceria is re-oxidized with H2O and/or CO2 below about 1400°C to form H2 and/or CO.