Combined Experimental and Density Functional Theory Study on the Mechanism of Catalytic Oxidation of Methanol over CeO₂ with Various Exposed Crystal Facets

Catalytic oxidation is an effective method for removing methanol emitted from industrial production and the combustion of methanol as a clean energy source. In this work, the mechanism of the catalytic oxidation of methanol on CeO₂ with various morphologies (nanorods, nanoparticles, and nanocubes) and hence different exposed crystal facets was studied by various designed experiments and density functional theory (DFT) calculation. It was demonstrated that the oxidation of methanol on the CeO₂ surface follows the reaction pathway of CH₃OH → -CH₃O → HCHO → HCOOH → CO + H₂O → CO₂. The activation of O₂ was the rate-determining step of the entire catalytic oxidation reaction. CeO₂ nanorod-exposed (111) and (100) facets exhibited superior catalytic activity due to their rich oxygen vacancies and surface O_ads compared with the CeO₂ nanoparticle mainly exposed (111) facet and the CeO₂ nanocube mainly exposed (100) facet. When considering the specific surface area, nanocubes had the highest specific activity as the (100) facet has a stronger ability for O₂ activation than the (111) facet. These findings clarified the reaction pathway and rate-determining step of methanol oxidation on CeO₂-based catalysts and provided valuable insights into the development of high-performance catalysts for oxygen-containing VOC oxidation.