Experimental and theoretical studies of natural mineral attapulgite supported iron-based oxygen carriers in chemical looping hydrogen production

The low-priced and efficient oxygen carrier is the key to the successful operation of chemical looping hydrogen production (CLH) technology, and also the premise and foundation of its large-scale application. In this study, a novel iron-based oxygen carrier based on natural mineral attapulgite (ATP) was first applied to CLH. The effects of support on the performance of iron-based oxygen carrier and its mechanism in the CLH process were investigated. The results showed the Fe2O3 with ATP as support had more superior activity and stability than those supported by expanded perlite, kaolin or Al2O3. In particular, Fe6ATP4 exhibited a high hydrogen yield at 850 degrees C which was twice as high as that of Fe2O3/Al2O3. The excellent reaction performance of Fe2O3/ATP was validated by both experimental and theoretical methods. Density functional theory (DFT) calculations revealed that the electrons in Fe2O3/ATP system have stronger delocalization than those of Fe2O3/Al2O3. Moreover, XPS showed there were more defect oxides or hydroxyl groups on the surface of ATP-supported Fe2O3, which further facilitated the reduction reaction.