Solar water-splitting with the defect pyrochlore type of oxides KFe0.33W1.67O6 and Sn0.5Fe0.33W1.67O6·xH2O

• KFe0.33W1.67O6 and Sn0.5Fe0.33W1.67O6 are prepared and characterized.
• The photo-induced reactive species are examined by radical quenchers.
• MB degradation and splitting of water are studied in the presence of these catalysts.

Defect pyrochlore of composition KFe0.33W1.67O6 (KFeW) was synthesized by ethylene glycol assisted sol–gel method. The divalent tin doped KFeW (SnFeW) was prepared by ion exchange process using acidified SnCl2. Structural, morphological and optical properties of both materials were characterized by XRD, TGA, SEM-EDS, BET surface analyses and UV–visible diffuse reflectance techniques. The composition of tin-doped KFeW was obtained from EDS and TGA profiles. The cubic lattice parameter 'a' was obtained from Rietveld refinement program, Fullprof.2k, by refining the d- lines of the KFeW. The optical properties of Fe3+ were investigated. Substitution of K+ by Sn2+ led to an absorption shift onset to longer wavelengths. The photocatalytic activities of both samples were evaluated by photodegradation of methylene blue, photooxidation of cyclohexene and solar water-splitting reactions. The mechanistic degradation pathway of methylene blue (MB) was studied in the presence of both photocatalysts.

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