Wang Zeshan, Li Yuelun, Wang Yuxin, Li Tao, Zheng Jiahao, Huang LiNan, Zuo Huicong, Tian Dong, Wang Hua, Li Kongzhai
Engineering Research Center of Metallurgical Energy Conservation and Emission Reduction, Ministry of Education, Kunming University of Science and Technology, Kunming 650093, China.
Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China.
Phys Chem Chem Phys. 2025 Jan 2;27(2):868-884. doi: 10.1039/d4cp03370a.
The density functional theory (DFT) method is used to investigate the effect of low oxygen vacancy formation energy on the catalytic performance of chemical looping dry reforming of methane (CL-DRM) when metal ions are co-substituted on CeO(111) surfaces. The results show that the oxygen vacancy formation energy is extremely low with a value of -2.05 eV when Zn and Nd are co-substituted on the CeO(111) surface. For the CH conversion process in CL-DRM, the reaction paths are found to be CH → CH → CH → CH → C → CO paths on the pristine as well as on the Zn and Nd co-substituted surfaces. The critical rate-limiting step for both pristine and co-substituted surfaces is the dehydrogenation of CH to form CH and H with activation energies of 1.62 and 1.00 eV, respectively. This indicates that the surface co-substituted with Zn and Nd promotes the CH conversion process more effectively than the clean surface. However, the desorption process of syngas on the co-substituted surface requires high energy, and CO is easily peroxidized to CO before desorption, reducing the selectivity of CO to the detriment of syngas production. For the CO cleavage process in CL-DRM, it is difficult for CO to generate enough energy on the co-substituted surfaces to overcome the activation energy of the reaction. The formation of oxygen vacancies is facilitated by an extremely low oxygen vacancy formation energy, which in turn enhances the adsorption of reaction intermediates in the CL-DRM process onto the oxygen carrier. Nevertheless, an excessive accumulation of oxygen vacancies can drive the oxygen carrier into a hyperactivated condition, which may inhibit the desired reaction pathways and reduce the efficiency and selectivity of the CL-DRM process. The present study is of great importance for the design concept of oxygen carriers in CL-DRM and the application potential of oxygen vacancy regulation.
采用密度泛函理论（DFT）方法，研究了金属离子共掺杂在CeO(111)表面时，低氧空位形成能对甲烷化学链干重整（CL-DRM）催化性能的影响。结果表明，当Zn和Nd共掺杂在CeO(111)表面时，氧空位形成能极低，为-2.05 eV。对于CL-DRM中的CH转化过程，在原始表面以及Zn和Nd共掺杂表面上，反应路径均为CH→CH→CH→CH→C→CO路径。原始表面和共掺杂表面的关键速率限制步骤均为CH脱氢形成CH和H，活化能分别为1.62和1.00 eV。这表明，Zn和Nd共掺杂的表面比清洁表面更有效地促进了CH转化过程。然而，合成气在共掺杂表面上的解吸过程需要高能量，并且CO在解吸前容易过氧化为CO，降低了CO的选择性，不利于合成气的生产。对于CL-DRM中的CO裂解过程，CO在共掺杂表面上难以产生足够的能量来克服反应的活化能。极低的氧空位形成能促进了氧空位的形成，这反过来又增强了CL-DRM过程中反应中间体在氧载体上的吸附。然而，氧空位的过度积累会使氧载体进入超活化状态，这可能会抑制所需的反应路径，降低CL-DRM过程的效率和选择性。本研究对于CL-DRM中氧载体的设计理念以及氧空位调控的应用潜力具有重要意义。
