Large Ultrathin Anatase TiO2 Nanosheets with Exposed {001} Facets on Graphene for Enhanced Visible Light Photocatalytic Activity

Abstract

Tailored synthesis of well-defined anatase TiO 2 nanocrystals with a high percentage of reactive facets has attracted widespread attention due to the scientific and technological importance. Here, high-quality nanosized anatase ultrathin TiO 2 nanosheets, mainly dominated by {001} facets, were grown on graphene nanosheets by a simple one-pot solvothermal synthetic route. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of as-prepared TiO 2 /graphene composites for degradation of methylene blue (MB) under visible-light irradiation at λ ≥ 400 nm was investigated. The results show that TiO 2 /graphene nanocomposites have a higher photocatalytic activity than pure TiO 2 and P25. This enhanced photocatalytic activity suggests that the photoinduced electrons in TiO 2 prefer transferring to the graphene efficiently. As a consequence, the electron transfer via Ti–O–C between TiO 2 and C interaction greatly retards the recombination of photoinduced charge carriers and prolongs the carrier lifetime, thus contributing to the enhancement of photocatalytic performance. The amount of graphene is an important factor affecting the photocatalytic activity of TiO 2 /graphene nanocomposites. The optimum amount of graphene is ca. 1 wt %, at which the TiO 2 /graphene sample displays the highest reactivity. Furthermore, the photodegradation rate does not show an obvious decrease during five successive cycles, indicating that our TiO 2 /graphene nanocomposites are stable visible-light photocatalysts.