Reaction activity and deep reduction reaction mechanism of a high index iron oxide surface in chemical looping combustion

Abstract

The possibility of morphological control of iron oxide as an oxygen carrier for chemical looping combustion was investigated using density functional theory and experiment. First, we calculated the reactivity of Fe2O3 with high- index facets [104] and low- index facets [001], as well as the deep reduction reaction mechanism of these two facets. Surface reaction results show that the activity of Fe2O3[104] for oxidizing CO is greater than that of Fe2O3[001]. Fe2O3[104] was reduced into iron oxide at lower oxidation state or into iron, which could then be regenerated after being oxidized by O2. The deep reduction reaction mechanism between oxygen carrier and CO shows that Fe2O3[104] can be completely reduced into Fe, and Fe2O3[104] exhibits high oxygen transfer ability. However, Fe2O3[001] can only be reduced to a limited extent, with a high energy barrier preventing further reduction, while it also exhibits limited oxygen transfer capacity. Results of experiments further verify the high reactivity and stability of Fe2O3[104].