| Summary: | 碩士 === 國立中正大學 === 化學研究所 === 89 === Here we report the syntheses and structural modification of two potential photocatalytic materials, KTiNbO5 (I) and K3Ti5NbO14(II). After treating with excess acid to ion-exchange K+ cations, their protonated forms were obtained. HTiNbO5 and H3Ti5NbO14 were then intercalated with alkylamines of various lengths to expand the interlayered spacings so as to introduce the precursor molecules, M(OEt)4 [M = Si, Ti], Ti(OiPr)4, or NH2(CH2)3Si(OEt)3, in between the layers. Subsequent calcinations resulted in the pillaring of SiO2 or TiO2 inside the two dimensional frameworks, as indicated by the expansion of d-spacings determined by X-ray powder diffraction data. As a consequence, microporous materials were fabricated.
As a consequence of pillaring, the maximum specific surface area (BET, N2) can be improved to 323 m2/g from less than 10 m2/g of the starting materials KTiNbO5 and K3Ti5NbO14. Silica- or titana-pillared titanoniobates, with larger surface areas, also exhibit better photocatalytic efficiency in the decomposition of salicylic acid than KTiNbO5 and K3Ti5NbO14.
HTiNbO5 and H3Ti5NbO14 can be exfoliated reversibly by shorter surfactants, namely ethylamine, or by tetrabutylammonium hydroxide, resulting in colloidal suspension of monolayers, with dimensions ranging from 0.01 to 1μm. Upon photodegrading a probe dye, Orange II, such suspension exhibited remarkably better catalytic activity than P-25 TiO2.
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