Theoretical screening method of oxygen carriers with high lattice oxygen activity towards CO oxidation

Abstract

The development of oxygen carriers with superior performance is crucial for chemical looping combustion. Here, the theoretical screening method based on two reactivity descriptors was proposed via the density functional theory calculations in order to screen the transition-metal-doped perovskite-type oxygen carriers. Experiments were conducted to comprehensively investigate the effects of transition-metal doping on the reaction characteristic of LaMnO₃ oxygen carrier with CO. The theoretical results indicate that the doping of Fe, Co, Ni and Cu can reduce the formation energy of oxygen vacancy on the LaMnO₃ surface. The substitution of Co and Cu can improve the reaction rate of CO oxidation, while CO oxidation is inhibited after the doping of Fe and Ni. Among them, Co-doped LaMnO₃ has the lowest activation barrier of 51.06 kJ/mol during CO oxidation. Experimental results demonstrate that Co- and Cu-doped LaMnO₃ show better activity than undoped LaMnO₃ at the lower temperatures, which is consistent with the theoretical screening results. Co doping can still improve the reaction rate of oxygen carrier at the higher temperatures. Moreover, the doping of Co can further enhance the oxygen release property of LaMnO₃. The weight loss of LaMnO₃ increases from 8.67 % to 9.09 % after Co doping. Co-LaMnO₃ also exhibits good sintering resistance and can be used as a promising oxygen carrier during chemical looping combustion. This work paves a new way to design and screen highly efficient oxygen carriers for chemical looping combustion.