Investigation of CO2 Splitting on Ceria-Based Redox Materials for Low-Temperature Solar Thermochemical Cycling with Oxygen Isotope Exchange Experiments

Abstract

Surface exchange and bulk transport of oxygen are of high relevance for ceria-based redox materials, which are envisaged for future solar thermochemical splitting of carbon dioxide. Experimental investigations of oxygen isotope exchange on CeO2-δ, Ce0.9M3+0.1O1.95-δ (with M3+ = Y, Sm) and Ce0.9M4+0.1O2-δ (with M4+ = Zr) samples were carried out utilizing oxygen isotope enriched C18O2 gas atmospheres followed by Secondary Ion Mass Spectrometry (SIMS). Experimental data reveal promising results in terms of CO2 splitting when trivalent (especially Sm) doped ceria is employed. Reaction temperatures are lower than previously proposed/reported, due to the weak temperature dependency of the parameters and .The majorities of isotope exchange experiments show higher values of and for Sm-doped cerium dioxide, in comparison to Y-doped and Zr-doped ceria, as well as nominally undoped ceria. Apparant activation energies for both, K and D are lowest for Sm-doped ceria. Using Zr-doped cerium oxide shows various negative aspects. Zr-doping of ceria enhances the reducibility, but possible Zr-based surface alteration effects and dopant-induced migration barrier enhancement in Zr-doped ceria are detrimental for surface exchange and oxygen diffusion at lower temperatures of T ≤ 800 °C.