Structure and crystal phase transition effect of Sn doping on anatase TiO₂ for dichloromethane decomposition

Efficient removal of chlorinated volatile organic compounds (CVOCs) has received great attention because of the considerable harm that they cause to the environment and to human health. Developing novel catalysts and exploring the catalytic activation and deconstruction mechanism of CVOCs molecule are always the focus in this field. Here, a set of Sn doped TiO₂ catalysts were investigated for the decomposition of dichloromethane (DCM). Rietveld refinement of the XRD patterns showed that Sn ions can uniformly disperse into TiO₂ and induce the crystal transition of anatase. Meanwhile, such decorating can induce an increase in specific surface area and affect the surface oxygen vacancy concentration of these samples, which have been demonstrated by N₂ adsorption and XPS, respectively. Catalytic performance tests indicated that the Sn_0.2Ti_0.8O₂ has the best activity for DCM decomposition, and a lower CH₃Cl selectivity than that of pure TiO₂. Computational results suggested the dominant surface (110) of rutile Sn_0.2Ti_0.8O₂ is more beneficial for the adsorption/dissociation of DCM molecule than that of anatase TiO₂ (101). That's because the anchoring of DCM to Sn sites and electron enrichment on the surface bridge oxygen atoms of rutile Sn_0.2Ti_0.8O₂ (110) can promote the nucleophilic substitution process for breaking of CCl bonds.