Visible-light photocatalytic activity and deactivation mechanism of Ag3PO4 spherical particles.
ABSTRACT Ag(3)PO(4) spherical particles were synthesized by a facile precipitation method using silver nitrate and Na(2) HPO(4) as precursors. The as-prepared samples had a high photocatalytic activity toward Rhodamine B (RhB) degradation under visible-light illumination. With increasing recycling times the photocatalytic activity first increased and then decreased. Based on systematic characterization of particles by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis absorption spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), a possible mechanism responsible for the improvement and subsequent decline of the photocatalytic performance of Ag(3)PO(4) is proposed. Ag(3)PO(4) spherical particles recycled for four times showed the highest photocatalytic activity because, according to our mechanism, Ag nanoparticles deposited on Ag(3)PO(4) acted as electron trapping centers to prevent photogenerated electron-hole pairs from recombination. A further increase in the recycle times decreases the photocatalytic activity owing to the shielding effect by Ag layers on the surface of Ag(3)PO(4). The results presented herein shed new light on the photostability of Ag(3) PO(4) spherical particles and are potentially applicable to other photocatalytically active composites.
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ABSTRACT: Visible light photocatalytic H(2) production through water splitting is of great importance for its potential application in converting solar energy into chemical energy. In this study, a novel visible-light-driven photocatalyst was designed based on photoinduced interfacial charge transfer (IFCT) through surface modification of ZnS porous nanosheets by CuS. CuS/ZnS porous nanosheet photocatalysts were prepared by a simple hydrothermal and cation exchange reaction between preformed ZnS(en)(0.5) nanosheets and Cu(NO(3))(2). Even without a Pt cocatalyst, the as-prepared CuS/ZnS porous nanosheets reach a high H(2)-production rate of 4147 μmol h(-1) g(-1) at CuS loading content of 2 mol % and an apparent quantum efficiency of 20% at 420 nm. This high visible light photocatalytic H(2)-production activity is due to the IFCT from the valence band of ZnS to CuS, which causes the reduction of partial CuS to Cu(2)S and thus enhances H(2)-production activity. This work not only shows a possibility for substituting low-cost CuS for noble metals in the photocatalytic H(2) production but also for the first time exhibits a facile method for enhancing H(2)-production activity by photoinduced IFCT.Nano Letters 11/2011; 11(11):4774-9. · 13.03 Impact Factor
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ABSTRACT: Delafossite structured alpha-AgGaO(2) powder was successfully synthesized through a cation exchange reaction. alpha-AgGaO(2) has a band gap of 2.4 eV, absorbs visible light up to 520 nm, and effectively decomposes 2-propanol to CO2 via acetone by irradiating with either UV light (300-400 nm) or visible light (420-530 nm). The values of the quantum efficiency are similar (ca. 0.6%) under light irradiations with wavelengths of 365, 390, 430, 470, and 510 +/- 10 nm, but steeply decrease with wavelengths longer than 530 +/- 10 nm, which support a 2.4 eV band gap. In contrast, the other polymorph, alpha-AgGaO(2) powder, which has a band gap of 2.1 eV, shows a negligible activity when irradiating with either UV light or visible light. The higher oxidation activity of alpha-AgGaO(2) is probably due to its larger band gap, which is formed at the top of its valence band in a lower energy region as compared to alpha-AgGaO(2). Moreover, the first-principle calculations of alpha-AgGaO(2) and alpha-AgGaO(2) clearly indicate that alpha-AgGaO(2) has a remarkably larger dispersed valence band as compared to alpha-AgGaO(2), which is advantageous to the photocatalytic activity due to the efficient hole conduction.The Journal of Physical Chemistry B 12/2006; 110(46):23274-8. · 3.61 Impact Factor
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ABSTRACT: Graphene, a single layer of graphite, possesses a unique two-dimensional structure, high conductivity, superior electron mobility and extremely high specific surface area, and can be produced on a large scale at low cost. Thus, it has been regarded as an important component for making various functional composite materials. Especially, graphene-based semiconductor photocatalysts have attracted extensive attention because of their usefulness in environmental and energy applications. This critical review summarizes the recent progress in the design and fabrication of graphene-based semiconductor photocatalysts via various strategies including in situ growth, solution mixing, hydrothermal and/or solvothermal methods. Furthermore, the photocatalytic properties of the resulting graphene-based composite systems are also discussed in relation to the environmental and energy applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation and photocatalytic disinfection. This critical review ends with a summary and some perspectives on the challenges and new directions in this emerging area of research (158 references).Chemical Society Reviews 08/2011; 41(2):782-96. · 24.89 Impact Factor