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

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.