Tailored
fabrication of nonstoichiometric semiconductor nanocrystals
with tunable electronic structures has attracted considerable attention
owing to their scientific and technological importance. In this work,
we have developed a novel and facile approach to prepare stable Sn2+ self-doped SnO2‑x
nanocrystals
with a large surface area via a synproportionation reaction of Sn4+ with metal tin under mild conditions. The effects of Sn2+ doping concentration in SnO2‑x
lattice on the nanoparticle size, band structure, and photodegradation
of methyl orange (MO) were investigated in detail. It is found that
the obtained deep-yellow colored Sn2+ self-doped SnO2‑x
sample shows exceptionally higher
visible-light photocatalytic performance than stoichiometric SnO2, which is only sensitive to UV light due to its intrinsic
large band gap. To the best of our knowledge, this is the first experimental
example that self-doped metal oxide nanocrystals have been utilized
as an effective photocatalyst for the degradation of pollutants within
15 min under visible-light irradiation (λ ≥ 400 nm).
The superior photodegradation activity of the Sn2+ self-doped
SnO2‑x
can be ascribed to the incorporation
of Sn2+ into the lattice matrix and accompanying oxygen
vacancies, which can result in significant narrowing of the band gap
and enhancement in the visible-light absorption capability, notably,
the efficient separation of the photogenerated electron–hole
pairs in SnO2‑x
, which has been
further confirmed by remarkable enhancement of the photocurrent response.
Moreover, strong photo-oxidation capability for high content •OH
radical formation over SnO2‑x
(ca.
25 times higher than SnO2 sample) also contributes to the
improvement of photocatalytic performance. Our synthetic approach
could be extended to design other nonstoichiometric semiconductor
nanostructures with tunable band structure, highly efficient visible-light
photocatalytic activity, and enhanced photoelectric conversion properties
in the future.
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