Short-range ordered Co(OH)2/TiO2 for boosting sulfite oxidation: Performance and mechanism

Abstract

Catalysis of magnesium sulfite (MgSO3) oxidation is crucial for the flue gas desulfurization by magnesium oxide. Here, a short-range ordered Co(OH)2/TiO2 hybrid with a direct Z-scheme band structure, was fabricated for the reaction of MgSO3 oxidation. The abundant defects of Co(OH)2/TiO2 induced the generation of more surface adsorbed oxygen species, and therefore greatly facilitated the formation of the key radical of SO5− to enhance MgSO3 oxidation. The oxidation rate of MgSO3 was enhanced 6.1-fold higher than the uncatalyzed benchmark with this neat Co(OH)2/TiO2 catalyst. Moreover, the oxidation rate of MgSO3 could be further improved 11.3-fold by the assistance of light irradiation, which broadened the pathways for MgSO3 oxidation by inspiring more active radicals (O2−, OH, SO4−, SO5−) and photogenerated holes to participate into MgSO3 oxidation. The photogenerated holes were proved to play key role to accelerate reaction by directly oxidized MgSO3 or inducing active radicles, and the highly efficient utilization of photogenerated holes was guaranteed by the Z-scheme charge transfer in the Co(OH)2/TiO2 interface. The results provided by this study could serve as an environmentally friendly approach to improve the overall performance of wet desulfurization.