Regulating surficial oxygen vacancies in Cu/Ca composites to enhance CO2 capture via CeO2 and Al2O3 co-doping in combined Cu/Ca technology

In this study, a stabilizer doping strategy combined with surficial oxygen vacancy regulation was developed to improve the performance of Cu/Ca composites. CeO2, known for creating numerous oxygen vacancies, was doped in Cu/Ca composites for the first time. Four synthesis approaches, including co-precipitation, reverse coprecipitation, Pechini, and solution combustion, were explored to prepare Ce-doped Cu/Ca composites. Of these, composites prepared via the Pechini method with a Ce/Cu/Ca molar ratio of 10:45:45 demonstrated the best CO2 capture performance, achieving a CO2 uptake capacity of 0.096 gCO2/gmaterial in the tenth cycle. This was ascribed to its highest porosity and surficial oxygen vacancy concentration. To further improve CO2 capture performance and reduce high costs related to the cerium precursor, a secondary stabilizer (MgO, Al2O3, or ZnO) was introduced to the Ce-doped Cu/Ca composites. Among these, Al2O3 was the most effective, significantly enhancing CO2 capture stability. The optimal Ce/Al co-doped Cu/Ca composite, with a Ce/Al/Cu/Ca molar ratio of 5:5:45:45, achieved a CO2 uptake capacity of 0.084 gCO2/gmaterial in the 20th cycle, maintaining 90% of its initial capacity. X-ray photoelectron spectrometer (XPS) and electron paramagnetic resonance (EPR) analysis indicated that co-doping CeO2 and Al2O3 facilitated the formation and retention of high surficial oxygen vacancy concentrations in the Cu/Ca composites, promoting both O2- mobility and CO2 diffusion during the carbonation reaction.