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

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 Ti4CN 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.