Boosting the performance of Co-doped CeO2 catalyst in the catalytic oxidation of toluene by modulating oxygen vacancies

Abstract

Metal doping is one of the most effective strategies to enhance redox capacity and modulate the oxygen vacancies in Ce-based catalysts. This manuscript reports a Co-doped CeO2 catalyst (Co0.2Ce0.8 (W/E = 1/1)) for the catalytic oxidation of toluene fabricated by a facile co-precipitation method. The appropriate ratio of deionized (DI) water/ethanol in the reaction solvent contributed to the mesocrystallization of the CeO2 phase and the highly uniform dispersion of the Co-O-Ce mixed bond in the catalyst. The feasible lattice distortion induced the generation of richer oxygen vacancies in both the surface and bulk of the catalyst. Meanwhile, the efficient cycle of Co2+ + Ce4+ ↔ Co3+ + Ce3+ enhanced the redox property of the catalyst. As revealed by in situ DRIFTS studies, the as-formed surface oxygen vacancies promoted the adsorption and partial oxidation of toluene. The oxygen vacancies in the bulk of the catalyst improved the migration of lattice oxygen, accelerating the mineralization of the aromatic ring. Thus, the excellent low-temperature oxidation of toluene by Co0.2Ce0.8 (W/E = 1/1), reducing T90 to 192 °C, was attributed to the synergism between the catalyst’s surface and bulk oxygen vacancies.