A TiO2-boron doped diamond (TiO2-BDD) heterojunction was employed as a photocatalyst to simultaneously oxidize an azo dye C.I. reactive yellow 15 (RY15) and reduce hexavalent chromium (Cr(VI)). This heterojunction was fabricated first by depositing a BDD film on a Ti sheet in a hot filament chemical vapor deposition reactor, followed by covering a layer of TiO2 in a metal-organic chemical vapor deposition system. The morphology of this heterojunction was characterized by using a scanning electron microscope (SEM). X-ray diffraction (XRD), Raman spectroscopy, and current-voltage (I-V) measurement were used to characterize its structures. Additionally, the characterization of surface photovoltage showed that the TiO2-BDD heterojunction exhibited a higher photovoltage response and a better ability for charge separation than the photocatalyst of TiO2 directly deposited on a Ti sheet (TiO2-Ti). The photocatalytic experiments revealed that the kinetic constants for the oxidation of RY15 and the reduction of Cr(VI) were, respectively, increased by 85 and 71% when the photocatalyst of TiO2-Ti was replaced by the TiO2-BDD heterojunction. Meanwhile, a significant synergy was confirmed in the simultaneous oxidation of RY15 and reduction of Cr(VI). The enhanced photocatalytic ability of the TiO2-BDD composite could be attributed to the heterojunction. The possible photocatalytic mechanism was also discussed.

ZnIn2S4 film was fabricated on Ti substrate by a two-step approach including electrodeposition and annealing. The film obtained after electrodeposition was composed of Zn, In, and S. Then this precursor film was gradually converted to hexagonal phase ZnIn2S4 during the process of annealing in a nitrogen flow. The crystallographic structures and photoresponse ability of the film could be affected significantly by the annealing temperature. From diffuse reflection spectra, ZnIn2S4 film annealed at 500 degrees C exhibited the highest absorption intensity in visible light region among all the samples, resulting in a high photoresponse in the electrochemical measurement. The microstructures of ZnIn2S4 were characterized by transmission electron microscopy, and the results indicated that the interlayer distance was 0.295 nm, corresponding to d(104) space of hexagonal ZnIn2S4. Energy-dispersive X-ray spectra showed that the atomic ratio of Zn:In:S was 9.3:20.3:39.5, which was close to the stoichiometry ZnIn2S4. The photocatalytic ability of ZnIn2S4 was investigated by photoelectrocatalytic inactivation of Escherichia coli ( E. coli) with the initial concentration of approximately 3 x 10(8) colony forming units per milliliter. More than 3 logs of E. coli were killed within 60 min with the ZnIn2S4 film under visible light, and when the photocatalytic process was assisted by a 0.6 V positive potential, no surviving bacteria were detected after 60 min of inactivation.

The photochemical formation of Fe(II) and hydrogen peroxide (H 2O 2) coupled with humic acids (HA) was studied to understand the significance of iron cycling in the photodegradation of atrazine under simulated sunlight. The presence of HA significantly enhanced the formation of Fe(II) and H 2O 2, and their subsequent product, hydroxyl radical ( (*)OH), was the main oxidant responsible for the atrazine photodegradation. During 60 h of irradiation, the fraction of iron presented as Fe(II) (Fe(II)/Fe(t)) decreased from 20-32% in the presence of the Fe(III)-HA complex to 10-22% after adding atrazine. The rate of atrazine photodegradation in solutions containing Fe(III) increased with increasing HA concentration, suggesting that the complexation of Fe(III) with HA accelerated the Fe(III)/Fe(II) cycling. Using fluorescence spectrometry, the quenching constant and the percentage of fluorophores participating in the complexation of HA with Fe(III) were estimated by the modified Stern-Volmer equation. Fourier transform infrared spectroscopy (FTIR) offered the direct evidence that Fe(III)-carboxylate complex could be formed by ligand exchange of HA with Fe(III). Based on all the information, a possible reaction mechanism was proposed.

A single-step route was developed for the direct growth of tungsten oxide nanobelt arrays by heating a tungsten sheet without additional catalysts or reactants. X-ray diffraction and Raman analysis indicated that the tungsten oxide nanobelts were monoclinic. The surface photovoltage signal and photocurrent density of the tungsten oxide nanobelt arrays clearly suggested a high photoconversion ability. Further investigation demonstrated that the photoelectrocatalytic activity of the nanobelt arrays was higher than that of a tungsten oxide film when using phenol as the probe molecule.

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