In situ highly dispersed loading of molybdenum dioxide with oxygen vacancies on N-doped graphene for enhanced oxidative desulfurization of fuel oil

Herein, molybdenum dioxide (MoO2) nanoparticles with a particle size of 1.78 nm was uniformly anchored on nitrogen-doped reduced graphene oxide (NrGO) with strong electron-donating effect by in situ annealing of the precursor composed of polyaniline-modified graphene oxide (PANI/GO) and ammonium molybdate. The as-prepared MoO2/NrGO catalyst at 800 °C showed the excellent oxidative desulfurization (ODS) activity and reusability. In the presence of H2O2, the DBT removal over MoO2/NrGO-800 could reach 99.8 % within 10 min at 60 °C, and it was almost still retained even after 8 cycles. The outstanding ODS performance is importantly ascribed to the following aspects. The electron transfer from electron-rich NrGO to MoO2 could not only weaken Mo-O bonds and improve the small size and dispersion of MoO2, resulting in more oxygen vacancies and exposed active sites, but also reduce the leaching of active sites due to the induced electronstatic interaction. Oxygen vacancies intrinsiclly facilitate the generation of active oxygen intermediates. Radical scavenger experiments and electron paramagnetic resonance (EPR) revealed that during the DBT oxidation over MoO2/NrGO-800, •OH radicals are the major active species, and electron transfer is still an important step.