CH₄ partial oxidation mechanism of LaFeO₃ oxygen carrier in chemical looping reforming

Density functional theory (DFT) calculations were employed to reveal the CH₄ partial oxidation mechanism of LaFeO₃ oxygen carrier during chemical looping reforming. The CH₄ partial oxidation reaction network was constructed by systematically studying the elementary reaction steps, including CH₄ adsorption activation, H₂ and CO formation, and oxygen diffusion. It was found that CH₄ undergoes a gradual dehydrogenation reaction to form H atoms, and the energy barrier (1.50 eV) of CH₃ dehydrogenation is the highest, which is the rate-limiting step. There are two possible paths for H₂ formation on the surface of oxygen carrier. It is the main route that the H atom from O-top site to Fe-top site bonds with another H atom on O-top site to form H₂ molecule. Due to its relatively low energy barrier (1.27 eV), the CO formation process is easier to occur. Oxygen diffusion needs to overcome an energy barrier of 1.35 eV, indicating that it occurs at high temperatures and the diffusion rate is low. By comparing the energy barrier of each elementary reaction, it was found that the H₂ formation is the rate-limiting step of CH₄ partial oxidation kinetics for LaFeO₃ oxygen carrier. The H migration is the key to limiting H₂ formation, and accelerating the H migration is the main approach to improve the performance of LaFeO₃ oxygen carrier. Based on DFT calculations, the H migration of A/B site doped LaFeO₃ oxygen carriers could be studied, which is expected to achieve the rapid screening of potential A/B site effective dopants and guide the design and development of high-performance LaFeO₃ oxygen carriers.