Syngas production via Ce0.8Zr0.2O2-based thermochemical co-splitting of H2O and CO2 and partial oxidation of methane: Achieving a 2:1 H2/ CO ratio

Solar-driven thermochemical splitting of H2O and CO2 presents an enticing avenue for converting solar energy into chemically storable energy. In particular, isothermal cycling processes integrating partial oxidation of methane have shown promise in enabling reactions at moderate temperatures and enhancing reactivity and solar-to-fuel conversion efficiency. The ability to maintain a syngas with an H2:CO ratio of 2:1 through the reduction of metal oxides by CH4, followed by co-splitting of H2O and CO2 during the oxidation process to preserve this ratio, holds significant importance for subsequent industrial applications. This study delves into the characterization and evaluation of the partial oxidation of methane in tandem with the co-splitting of H2O and CO2 within Ce0.8Zr0.2O2. Gas production ratios were explored under diverse H2O and CO2 feed ratios in a fixed- bed configuration operating under an isothermal condition of 900 degrees C. Furthermore, cyclic stability experiments comprising up to 100 cycles were conducted to assess the material's performance across repeated redox processes. The results unveil that various oxygen sources (H2O, CO2, or a combination thereof) facilitate the swift recovery of oxygen vacancies within the material. Noteworthy is the generation of a syngas with an H2/CO ratio of 2 during the oxidation stage when the H2O/CO2 ratio reaches 5. Importantly, this optimal ratio is maintained even after 100 redox cycles, underscoring the material's enduring reaction performance.