Low Temperature Synthesis of Large-Size Anatase TiO2 Nanosheets with Enhanced Photocatalytic Activities

Abstract

TiO₂ nanosheets have continuously been intriguing due to their high surface activities as photocatalyst but still challenging to synthesis large-scale 2D nanostructures. A special microstructure evolution of TiO₂ , ripening in aqueous solution at low temperature (≈4 °C), is found for the first time, i.e., from the initial aperiodic atom-networks gradually into low crystallized continuous spongy structure with small crystal facets and ultimately forming large-size anatase nanosheets with exposed (101) and (200) facets. Based on this finding, the synthesized anatase TiO₂ nanosheets possess monodispersed large-scale 2D nanostructure so as to exhibit appreciable quantum size effects and remarkable enhanced optical absorption capacity. Using photocatalytic reduction of Cr (VI) to Cr (III) as the probe reaction to evaluate photocatalytic activities of the TiO₂ nanosheets, the reductivity of Cr (VI) achieves 99.8% in 15 min under irradiation of 200-800 nm light. At the same time, an in situ Cr (III)-doping occurs spontaneously and triggers pronounced visible light driven photocatalysis, reducing 99% of Cr (VI) in 100 min under irradiation of 400-800 nm light.

Keywords: hexavalent chromium reductions; large-size nanosheets; low temperature-doping effects; photocatalysis; titanium dioxides.