C─H Activation in Propane Dehydrogenation Over Spinel ZnAl ₂ O ₄ : The Role of Lattice‐Oxygen

ABSTRACT

Spinel oxide catalysts have shown promising potential for propane dehydrogenation (PDH), yet the nature of their active sites and the mechanism of oxygen vacancy modulation remains unclear. In this study, density functional theory (DFT) calculations combined with microkinetic simulations were employed to systematically investigate the PDH reaction mechanism on the AlO ₂ ‐terminated ZnAl ₂ O ₄ (100) surface. Two types of lattice‐oxygen sites (O1 and O2) were identified, with the O1 site exhibiting a lower oxygen vacancy formation energy. The introduction of oxygen vacancies induces local structural reconstruction on the surface, generating a new two‐coordinated oxygen (O3) accompanied by significant electron localization. Adsorption analysis reveals that defects moderately enhance propane adsorption while markedly weakening propylene adsorption, which facilitates rapid product desorption and suppresses deep dehydrogenation and coke formation. C─H activation barrier calculations demonstrate that, on both pristine and defective surfaces, active‐site configurations involving O2 sites consistently exhibit the lower reaction barriers, indicating that O2‐related sites serve as the dominant active centers for PDH. Microkinetic simulations further corroborate the trend that O2‐associated sites are the primary origin of high activity, and defect engineering reinforces this dominant trend. This work elucidates the structure–performance relationship of ZnAl ₂ O ₄ catalysts and proposes a modulation strategy of preferentially creating O1 oxygen vacancies to increase the population and spatial distribution of O2 active sites, providing a theoretical basis for the rational design of efficient spinel PDH catalysts.