Concentration-Dependent Solar Thermochemical CO₂/H₂O Splitting Performance by Vanadia-Ceria Multiphase Metal Oxide...

The effects of V and Ce concentrations (each varying in the 0-100% range) in vanadia-ceria multiphase systems are investigated for synthesis gas production via thermochemical redox cycles of CO₂ and H₂O splitting coupled to methane partial oxidation reactions. The oxidation of prepared oxygen carriers is performed by separate and sequential CO₂ and H₂O splitting reactions. Structural and chemical analyses of the mixed-metal oxides revealed important information about the Ce and V interactions affecting their crystal phases and redox characteristics. Pure CeO₂ and pure V₂O₅ are found to offer the lowest and highest oxygen exchange capacities and syngas production performance, respectively. The mixed-oxide systems provide a balanced performance: their oxygen exchange capacity is up to 5 times higher than that of pure CeO₂ while decreasing the extent of methane cracking. The addition of 25% V to CeO₂ results in an optimum mixture of CeO₂ and CeVO₄ for enhanced CO₂ and H₂O splitting. At higher V concentrations, cyclic carbide formation and oxidation result in a syngas yield higher than that for pure CeO₂.