College of Electrical and Power Engineering, Taiyuan University of Technology
State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology

本研究基于密度泛函理论（DFT）计算揭示了化学链重整过程中LaFeO3载氧体的CH4部分氧化反应机理，通过系统研究CH4吸附活化、H2和CO形成以及氧扩散等基元反应步骤，构建了CH4部分氧化反应网络。研究发现，CH4发生逐步脱氢反应形成H原子，其中，CH3脱氢反应所需要克服的能垒（1.50 eV）最高，是CH4逐步脱氢反应的限速步骤。载氧体表面H2形成有两种路径，其中，H原子从O顶位迁移到Fe顶位，然后与另外O顶位的H原子成键形成H2分子是主要途径。由于其相对较低的能垒（1.27 eV），CO的形成过程较易发生。氧扩散需要克服1.35 eV的能垒，表明氧扩散过程需要在高温下进行且扩散速率较低。通过比较各基元反应能垒，发现H2形成是LaFeO3载氧体CH4部分氧化反应动力学的限速步骤，而H迁移是限制H2形成的关键，加快H迁移是增强LaFeO3载氧体性能的主要途径。基于DFT计算研究系列A/B位点掺杂LaFeO3载氧体的H迁移过程，有望实现潜在A/B位点有效掺杂剂的快速筛选，指导高性能LaFeO3载氧体的设计开发。

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.

山西省基础研究计划青年科学研究项目(202103021223077)资助

王娜娜, 冯于川, 郭欣, 马素霞. 化学链重整过程中LaFeO3载氧体的CH4部分氧化反应机理研究[J]. 燃料化学学报（中英文）, 2024, 52(4): 586-594.

WANG Nana, FENG Yuchuan, GUO Xin, MA Suxia. CH4 partial oxidation mechanism of LaFeO3 oxygen carrier in chemical looping reforming[J]. Journal of Fuel Chemistry and Technology, 2024, 52(4): 586-594.