Reactivity of Ni, Cr and Zr doped ceria in CO2 splitting for CO production via two-step thermochemical cycle

This work focuses on modification and screening of ceria-based oxides for solar H2O/CO2 splitting via two-step thermochemical cycle. Ce1-xMxO2-δ (M = Zr, Ni, Cr; x = 0, 0.05, 0.10, 0.15, 0.20) were synthesized via sol-gel method and tested for CO2-splitting via two-step thermochemical cycles. Reduction was conducted at 1500 °C through a ramp rate of 10 °C/min and oxidation was performed at 1000 °C isothermally. Both Ni and Cr showed low solubility in ceria and no or very limited promoting effect on CO productivity. Cr could be reduced in the first reduction step but cannot be oxidized by CO2 in the following oxidation step. Zr doped sample showed advantages in both CO productivity and lattice stability. 15% Zr doped exhibited the best performance with the CO productivity of 315.40 μmol/g. However, the oxidation rate of Zr doped samples was much lower than that of pure ceria. Compromise between fuel productivity and fast kinetics should be made in practical application.