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

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.