Adsorption and photocatalytic oxidation of dimethyl sulfide and ethyl mercaptan over layered K_1-2xMn_xTiNbO₅ and K_1-2xNi_xTiNbO₅

 Layered K_1-2xM_xTiNbO₅(M = Mn, Ni) was prepared by ion-exchange of KTiNbO₅ obtained by the solidstate method with Mn²⁺ and Ni²⁺. The crystal structure and optical property of the as-prepared K_1-2xM_xTiNbO₅ were studied by using powder X-ray diffraction and ultraviolet (UV)-visible light diffuse reflection spectroscopy. The adsorption feature and photocatalytic oxidation activity of dimethyl sulfide (DMS) and ethyl mercaptan (EM) over the as-prepared K_1-2xM_xTiNbO₅ were evaluated using infrared spectroscopy. K_1-2xM_xTiNbO₅ showed a higher interval between sheets and a stronger absorbance to visible light than KTiNbO₅. After ion-exchange with Mn²⁺ and Ni²⁺, the bandgap energy of KTiNbO₅ was shifted from 3.35eV to 2.97eV and 2.45eV, respectively, whereas the weak interaction between K_1-2xM_xTiNbO₅ and DMS/EM was little affected by the exchanged cation. The photocatalytic oxidation activity of K_1-2xM_xTiNbO₅ for DMS or EM depended on the special cation. K_1-2xMn_xTiNbO₅ emerged a photocatalytic activity only under ultra-light irradiation, which converted DMS to sulfoxide and sulfone, and EM to sulfonic acid. However, K_1-2xNi_xTiNbO₅ emerged the photocatalytic activity under visible light besides under ultra-light irradiation; EM was converted to sulfonic acid by visible irradiation, but to sulfate and carbonate by UV radiation.