Breaking symmetry: enhanced propane dehydrogenation via asymmetric oxygen vacancies from vanadium doped ZrO2 catalysts

Abstract

Zirconia, ZrO₂, has attracted considerable attention due to its outstanding catalytic performance in the propane dehydrogenation (PDH) reaction, primarily attributed to the high reactivity of coordinatively unsaturated zirconium sites (Zr_cus) around oxygen vacancies. As an effective strategy for modulating the active sites on the zirconia surface, metal doping has been found to significantly optimize its catalytic performance. In current work, DFT calculations and microkinetic simulations were combined to systematically investigate the catalytic mechanism of vanadium-doped ZrO₂ in the PDH reaction. V doping caused the significant changes of both geometry and electronic structure regarding of Zr_cus, and in particularly V doping induced the formation of an asymmetric oxygen vacancy, where the adjacent V and Zr_cus sites exhibit significant asymmetric electron distribution, thereby effectively enhancing catalytic activity. Specifically, V doping not only significantly reduces the energy barrier for C–H bond activation in propane but also facilitates hydrogen molecule desorption. Moreover, the reaction mechanism is also altered by V doping compared with pristine catalyst as the strong rate dependence on the product desorption observed on undoped surface is largely reduced after V doping which is benefit for product formation. This study provides important guidance for designing highly efficient and environmentally friendly PDH catalysts.