Abstract
New niobate Ca0.5Nb3O8.1.5H2O was elaborated by soft chemistry via Ca2+ → H+ exchange between calcium nitrate and niobic acid H3ONb3O8. The compound was identified by X-ray diffraction using the Rietveld refinement; it was characterized by thermal analysis (TG), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. The layered compound resembles closely to the orthorhombic niobate KNb3O8. Two optical transitions indirectly (3.10 eV) and directly (3.34 eV) allowed were obtained from the diffuse reflectance. The photo-electrochemical properties are studied for the first time. The oxide exhibits n type conductivity with a flat band potential (Efb) of -0.12 VSCE and an electrons density (ND) of 6.51 × 1015 cm−3. The valence band formed from Nb5+: 4d orbital, is positioned at 7.59 eV below vacuum (2.84 VSCE). As application, Rhodamine B (Rh B, 10 ppm) a hazardous dye was successfully oxidized on Ca0.5Nb3O8.1.5H2O by •OH radicals under solar light; a conversion rate of 48% was obtained after 140 min. and the Rh B discoloration follows a first order kinetic with a half-life of 150 min.
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