Incessant interest has been shown in the synthesis of graphene (GR)-semiconductor nanocomposites as photocatalysts aiming to utilize the excellent electron conductivity of GR to lengthen the lifetime ...of photoexcited charge carriers in the semiconductor and, hence, improve the photoactivity. However, research works focused on investigating how to make sufficient use of the unique electron conductivity of GR to design a more efficient GR-semiconductor photocatalyst have been quite lacking. Here, we show a proof-of-concept study on improving the photocatalytic performance of GR-TiO(2) nanocomposites via a combined strategy of decreasing defects of GR and improving the interfacial contact between GR and the semiconductor TiO(2). The GR-TiO(2) nanocomposite fabricated by this approach is able to make more sufficient use of the electron conductivity of GR, by which the lifetime and transfer of photoexcited charge carriers of GR-TiO(2) upon visible light irradiation will be improved more efficiently. This in turn leads to the enhancement of visible-light-driven photoactivity of GR-TiO(2) toward selective transformation of alcohols to corresponding aldehydes using molecular oxygen as a benign oxidant under ambient conditions. It is anticipated that our current work would inform ongoing efforts to exploit the rational design of smart, more efficient GR-semiconductor photocatalysts for conversion of solar to chemical energy by heterogeneous photocatalysis.
The g-C3N4 photocatalyst was synthesized by directly heating the low-cost melamine. The methyl orange dye (MO) was selected as a photodegrading goal to evaluate the photocatalytic activity of ...as-prepared g-C3N4. The comparison experiments indicate that the photocatalytic activity of g-C3N4 can be largely improved by the Ag loading. The strong acid radical ion (SO4 2− or NO3 −) can promote the degrading rate of MO for g-C3N4 photocatalysis system. The MO degradation over the g-C3N4 is mainly attributed to the photoreduction process induced by the photogenerated electrons. Our results clearly indicate that the metal-free g-C3N4 has good performance in photodegradation of organic pollutant.
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The efforts to produce photocatalysts operating efficiently under visible light have led to a number of plasmonic photocatalysts, in which noble metal nanoparticles are deposited on the surface of ...polar semiconductor or insulator particles. In the metal-semiconductor composite photocatalysts, the noble metal nanoparticles act as a major component for harvesting visible light due to their surface plasmon resonance while the metal-semiconductor interface efficiently separates the photogenerated electrons and holes. In this article, we survey various plasmonic photocatalysts that have been prepared and characterized in recent years.
Due to noble metal's surface plasmon resonance, plasmonic photocatalysts have great absorption in visible light and show high photocatalytic activities.
Nanoporous g-C3N4 (npg-C3N4) with high surface area was prepared by a bubble-templating method. A higher calcination heating rate and proportion of thiourea can result in a larger surface area and ...better adsorption and photodegradation activities of npg-C3N4. Compared with the bulk g-C3N4, the adsorption capacity for the target pollutants and photocatalytic degradation and photocurrent performances under visible light irradiation of npg-C3N4 were greatly improved. The optimal photodegradation activity of npg-C3N4 was 3.4 times as high as that of the bulk g-C3N4. The enhanced activities of npg-C3N4 can be attributed to the larger number of surface active sites, improved separation of photogenerated electron–hole pairs, and higher efficiency of charge immigration.
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Porous graphitic carbon nitride (g-C
3
N
4
) was prepared by a simple pyrolysis of urea, and then a g-C
3
N
4
-Pt-TiO
2
nanocomposite was fabricated
via
a facile chemical adsorption followed by a ...calcination process. The obtained products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance absorption spectra, and electron microscopy. It is found that the visible-light-induced photocatalytic hydrogen evolution rate can be remarkably enhanced by coupling TiO
2
with the above g-C
3
N
4
, and the g-C
3
N
4
-Pt-TiO
2
composite with a mass ratio of 70 : 30 has the maximum photoactivity and excellent photostability for hydrogen production under visible-light irradiation, and the stable photocurrent of g-C
3
N
4
-TiO
2
is about 1.5 times higher than that of the bare g-C
3
N
4
. The above experimental results show that the photogenerated electrons of g-C
3
N
4
can directionally migrate to Pt-TiO
2
due to the close interfacial connections and the synergistic effect existing between Pt-TiO
2
and g-C
3
N
4
where photogenerated electrons and holes are efficiently separated in space, which is beneficial for retarding the charge recombination and improving the photoactivity.
A visible-light-responsive g-C
3
N
4
-Pt-TiO
2
nanocomposite with efficient photogenerated carrier separation in space was fabricated.
