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Invited Talk: Cerium-Vanadium Metal Oxides for Syngas Production Via Solar Thermochemical Redox Cycles

Authors: 
Lipinski, W., The Australian National University
Riaz, A., The Australian National University
Tsuzuki, T., The Australian National University
Lowe, A., The Australian National University
Developing durable redox materials with fast and stable redox kinetics under high-temperature operating conditions is a key challenge for an efficient industrial-scale production of synthesis gas via two-step solar thermochemical redox cycles. CeO2 possesses a high phase stability with moderately high and stable redox kinetics during the reduction and oxidation reactions. Materials with a high degree of catalytic activity improve the syngas yield. V2O5 is well-known for its catalytic activity in redox processes such as electrolysis, gas sensing and hydrocarbon oxidation. Here, the effects of V and Ce concentrations (each varying in the 0–100% range) in vanadia–ceria multi-phase systems are investigated for synthesis gas production via thermochemical redox cycles of CO2 and H2O splitting coupled to methane partial oxidation reactions. Stable redox rates are observed in pure CeO2, while pure V2O5 is characterized by the highest syngas yield at the cost of irregular kinetic rates between cycles. Incorporation of vanadium in CeO2 improves the syngas yield without impacting the stability of redox rates. 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. The structural and chemical analysis of the mixed metal oxides provides insights into the phase transformation in V2O5 due to cerium and vanadium interactions.