Ethane Oxidative Dehydrogenation over TiO2 and M/TiO2 Catalysts: Unraveling the Surface Structure Evolution, Oxygen Species Type, and Role of Doped Metal in Tuning Catalytic Performance

Abstract

TiO₂ has better catalytic performance toward alkane oxidative dehydrogenation (ODH) due to adjustable surface oxygen species; however, identifying the dynamic evolution process of the TiO₂ surface structure and its effect on the type of surface oxygen species is still challenging. In this work, the combined methods of density functional theory calculations and kinetic Monte Carlo simulations were employed to fully investigate the catalytic performance of ethane ODH over TiO₂ and 15 types of single-atom metal-doped TiO₂ (M/TiO₂) catalysts. The results clearly unravel the evolution mechanism of the TiO₂ surface structure and the type of surface oxygen species formed during the evolution process in tuning ethane ODH catalytic performance. Surface oxygen vacancies enhance catalytic performance with unsaturated Ti_4CN as the active site, while surface-adsorbed oxygen species limit catalytic performance. Single-atom metal-doped TiO₂ can change the O₂(g) adsorption mode and dissociation activity to adjust the type of surface oxygen species and further regulate the catalytic performance by tuning electronic properties of adsorbed oxygen atoms. Interestingly, the screened V/TiO₂–O* catalyst exhibits high C₂H₄(g) production activity and selectivity at the optimal temperature of 873.15 K and a C₂H₆(g) partial pressure of 0.2 bar, which thoroughly eliminates the negative effect of adsorbed oxygen species over the TiO₂ catalyst in the process of ethane ODH due to more charge transfer from V to the adsorbed oxygen atom. This work provides the theoretical basis and structural clue for designing an alkane ODH catalyst by regulating the types and electronic properties of surface oxygen species over metal oxide.