Molybdenum Dioxide Nanoparticles Anchored on Nitrogen-Doped Carbon Nanotubes as Oxidative Desulfurization Catalysts: Role of Electron Transfer in Activity and Reusability

Electron transfer between metal-oxides and supports considerably affects the oxidative desulfurization (ODS) performance of catalysts, while this is far from being well understood. Herein, molybdenum dioxide with oxygen vacancies (V-O-MoO2) catalysts derived from Mo-based metal-organic frameworks are anchored on electron-rich nitrogen-doped carbon nanotubes (NC) to obtain excellent ODS activity and reusability. Results show that either dibenzothiophene (DBT) or 4,6-dimethyldibenzothiophene (4,6-DMDBT) is removed 100% on the composite catalyst (V-O-MoO2@NC) within 40 min of reaction when cumene hydroperoxide is chosen as an oxidant. After five cycles of reaction, DBT and 4,6-DMDBT removal still exceeded 99.5 and 95.0%, respectively. Results from density functional theory calculations and characterizations confirm that the strong electron-donating effect of NC on V-O-MoO2 can promote the dispersion of V-O-MoO2 and reduce the bond energy of the Mo-O bond, leading to exposure of active sites and enrichment of oxygen vacancies (V-O). Furthermore, the strong interfacial electrostatic interaction caused by the electron transfer from NC to V-O-MoO2 can reduce the leaching of active sites of the catalyst. This study provides a versatile strategy of constructing strong electronic interaction between metal-oxide and support via anchoring on NC for the design of high-performance ODS catalysts.

Automated summary

The electron transfer between metal-oxides and supports greatly impacts the performance of catalysts in oxidative desulfurization (ODS), with molybdenum dioxide with oxygen vacancies (V-O-MoO2) catalysts anchored on electron-rich nitrogen-doped carbon nanotubes (NC) showing excellent ODS activity and reusability. By promoting dispersion of V-O-MoO2 and reducing the bond energy of the Mo-O bond, the strong electron-donating effect of NC on V-O-MoO2 enhances exposure of active sites and enriches oxygen vacancies, leading to effective desulfurization.