Modification of Metal (Fe, Al) Doping on Reaction Properties of a NiO Oxygen Carrier with CO during Chemical Looping Combustion

Oxygen carriers can significantly enhance the performance of chemical looping combustion at low energy-cost CO2 capture. Based on the density functional theory, a microscopic model of the metal Fe, Al-doped NiO oxygen carrier was established. The results indicate that the intermediate state energy and the reaction energy reduce due to electronic interaction of the Al-doped surface. With the progress of the reaction, the NiO-Al surface promotes the oxidation process of CO, indicating that the activity of the NiO surface enhanced, which is attributed to the electronic and steric effects of the Al-O structure. For the decomposition of CO on the OC surface, doping with other atoms is beneficial to suppress the carbon deposition, which is related to the steric hindrance caused by doping with other atoms. Besides, doping with iron and aluminum atoms is more conducive to the movement of OC bulk crystal lattice oxygen to the surface, thereby promoting subsequent reactions. Therefore, it is feasible to improve the reactivity of the Ni-based OC by doping metal Al, and its modification effect is closely related to the characteristics of the components.