Tailored synthesis of well-defined anatase TiO2 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 TiO2 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 TiO2/graphene composites for degradation
of methylene blue (MB) under visible-light irradiation at λ
≥ 400 nm was investigated. The results show that TiO2/graphene nanocomposites have a higher photocatalytic activity than
pure TiO2 and P25. This enhanced photocatalytic activity
suggests that the photoinduced electrons in TiO2 prefer
transferring to the graphene efficiently. As a consequence, the electron
transfer via Ti–O–C between TiO2 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 TiO2/graphene
nanocomposites. The optimum amount of graphene is ca. 1 wt %, at which
the TiO2/graphene sample displays the highest reactivity.
Furthermore, the photodegradation rate does not show an obvious decrease
during five successive cycles, indicating that our TiO2/graphene nanocomposites are stable visible-light photocatalysts.
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