Assessment of Ce Zr Hf O2 based oxides as potential solar thermochemical CO2 splitting materials

Abstract In this paper, we report the synthesis, characterization, and assessment of CexZryHfzO2 (CZH) materials for solar thermochemical splitting of CO2 in up to 20 consecutive thermochemical cycles. CZH materials with different stoichiometries were synthesized by using the co-precipitation of hydroxides method. CZH materials acquired after calcination were characterized using powder X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and BET surface area. The thermochemical CO2 splitting ability of the derived CZH materials was assessed by performing multiple thermochemical cycles using a thermogravimetric analyzer. All CZH materials studied exhibit a higher activity than ceria modified with Hf or Zr alone. Thus a synergistic effect seems to be present. Among the different CZH materials examined, Ce0.895Zr0.046Hf0.053O1.988 (CZH5) was observed to be the most active exhibiting a sustained redox activity in terms of CO production/O2 release in the temperature range of 1000–1400 °C. Moreover, CZH5 was subjected to 20 consecutive thermochemical cycles during which no degradation could be observed. The results obtained indicate that CZH5 is a promising candidate for solar thermochemical conversion of CO2 as it is capable of producing stable amounts of O2 and CO in multiple thermochemical cycles.