Possibility of Morphological Control To Improve the Activity of Oxygen Carriers for Chemical Looping Combustion

Morphological control of transition-metal oxides has received great attention for the preferential exposure of catalytically active sites. However, in contrast to catalytic processes, structural damage and relaxation of metal-oxide-based oxygen carriers (OCs) occur during the chemical looping combustion (CLC) processes. To answer the doubt whether surface-controlled preparation to obtain active and efficient OCs for CLC is practical, we supported Fe2O3 with the high-index [104] surface on Al2O3 (denoted as Fe2O3[104]/Al2O3) as an OC via surface-controlled preparation and experimentally detected the reaction behavior between the probe model fuel gas CO and Fe2O3[104]/Al2O3 during CLC processes. The results showed that Fe2O3[104]/Al2O3 is more efficient than the reference Fe2O3/Al2O3 prepared via the traditional method of precipitation, as less carbon was deposited on the reduced Fe2O3[104]/Al2O3 than on the reduced Fe2O3/Al2O3. Then we theoretically revealed the detailed mechanisms of reactions between CO and different surfaces of Fe2O3 to further confirm the high activity and behavior of Fe2O3[104] as an oxygen carrier for CLC. Finally, the results of structural characterizations and reuse experiments verified the regeneration ability of Fe2O3[104]. These findings indicate that morphological control of oxygen carriers is very rewarding for CLC.