By adding CeO2 into Ni/CaO dual functional materials, the oxygen vacancies are largely enhanced, which promotes ICCU performance (CO2 conversion is increased from 23% to 50%) (https://doi.org/10.1016/j.apcatb.2018.11.040). The dispersion of Ni is also significantly enhanced, resulting in the high stability of materials during ICCU cycles. As shown in the following figure, the CeO2-promoted Ni/CaO shows great stability for 20 cycles of ICCU, while Ni/CaO indicates some deactivation.
20 cycles of ICCU using (a) Ca1Ni0.1; (b) Ca1Ni0.1Ce0.033 (https://doi.org/10.1016/j.apcatb.2018.11.040)
The experimental procedures are:
“In a typical experiment, 250 mg powdered DFMs was loaded into the tube fixed by the quartz wool. The sample received a pre-reduction at 650 °C in a flow of 5% H2 balanced with N2 for 3 h with the heating rate of 10 °C min−1. After reduction, the carbonation reaction was conducted in 15% CO2 balanced with N2 (100 mL min−1) for 25 min. Subsequently, the DFMs were regenerated under 5% H2 in N2 (100 mL min−1) after the fixed reactor was purged by N2 for 5 min. With the further increase of temperature to 700 °C and then 750 °C, the carbonation reaction was carried out in 15% CO2 balanced with N2 (100 mL min−1) for 25 min. After the fixed reactor was purged by N2 for 5 min, the regeneration of DFMs was performed under 5% H2 in N2 (100 mL min−1).”
The provision of extra oxygen vacancies by adding Fe and Co species into CaO is also reported by Shao et al. (https://doi.org/10.1039/D0EE03320K). Over 90% CO2 conversion and 100% CO selectivity have been obtained. In addition, MgO is used as CaO stabilizer, and the authors report a stable high-temperature CO2 capture capacity of 9.0–9.2 mmol g−1.