DFT insights into oxygen vacancy formation and chemical looping dry reforming of methane on metal-substituted CeO₂ (111) surface

The oxygen vacancy formation energy and chemical looping dry reforming of methane over metal-substituted CeO₂ (111) are investigated based on density functional theory calculations. The calculated results indicate that among the various metals that can substitute for the Ce atom in the CeO₂(111) surface, Zn substitution results in the lowest oxygen vacancy formation energy. For the activation of CH₄ on CeO₂ (111) and Zn-substituted CeO₂ (111) surfaces, the calculated results illustrate that the dissociation process of CH_3(ads) is very difficult on pristine surfaces and unfavorable for CHO_(ads) on substituted surfaces. Furthermore, the dissociative adsorption of CO and H₂ on the Zn-substituted CeO₂ (111) surface requires high energy, which is unfavorable for syngas production. This work demonstrates that excessive formation of oxygen vacancy can lead to excessively high adsorption energies, thus limiting the conversion efficiency of the reaction intermediates. This finding provides important guidance and application prospects for the design and optimization of oxygen carrier materials, especially in the field of chemical looping dry methane reforming to syngas.