Tuning metal oxide-support interaction and crystal structure of prussian blue derived iron-based oxygen carriers for enhanced chemical looping CO2 conversion

Abstract

Iron-based oxygen carrier is a promising material for chemical looping CO2 conversion into value-added chemicals but suffers easy reactivity deactivation. Using self-templated metal–organic framework (MOF) to develop efficient iron-based oxygen carriers is an effective way. However, the effect of metal oxide-support interaction and crystal structure on the reactivity of MOF-derived iron-based materials is still unclear. Toward that end, a series of iron-based oxygen carriers are synthesized via selecting Prussian blue (PB) with different coating types (Al2O3, MgO, MgAl2O4, ZrO2) and synthesis environments (HCl concentration and PVP addition). Isothermal H2-CO2 redox cycles and characterization techniques are applied to interpret the structure-performance relationship. PB-derived Fe-Zr oxygen carrier shows the best activity (0.9 and 24.1 mmol[O]·s-1·kgFe2O3-1 for reduction and oxidation rates) with limited deactivation. The superior performance originates from: (i) no inactive intermedia formation from interaction between Fe2O3 and ZrO2; (ii) the presence of m-ZrO2 acted as an active promoter, comparing to other promoters and coprecipitated material, respectively. High HCl concentration and PVP addition are beneficial for enhancing redox reactivity. This study provides a useful way to optimize the interface and structure of MOF-derived oxygen carriers for improving redox activity and stability.