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Nickel phosphide (Ni2P) was used as an excellent water oxidation cocatalyst for photoelectrochemical (PEC) water splitting, which could significantly promote the hole injection efficiency and suppress the back reaction of water oxidation over a Ti4+ doped Fe2O3 photoanode. [ABSTRACT FROM AUTHOR]

In this study, well-crystallized mesoporous anatase TiO spheres (TiO-MS) were prepared via a simple sol-gel process followed by subsequent hydrothermal treatment and then used as photoelectrode for quantum-dot-sensitized solar cell (QDSC) application. The mesoporous structure exhibits efficient QD loading and good light-scattering properties for light harvesting. In the meantime, both surface photovoltage technique based on lock-in amplifier and transient photovoltage measurement reveal that the QDs-sensitized mesoporous TiO sphere photoelectrode is conducive to promote the separation of photo-induced charges and reduce the charge recombination owing to the efficient charge transfer. As a result, the QDSCs based on mesoporous TiO spheres photoelectrode shows a power conversion efficiency of 1.34 %, which is significantly higher than that derived from P25 nanoparticle electrode. The relation between the performance of QDSCs and their photovoltage characterization was also discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] CdS QDs were attached to TiO2 nanorod arrays via a one-step in situ hydrothermal route. [•] GSH molecule could link the CdS QDs onto the surface of TiO2 nanorods. [•] The photoanode exhibited a maximum η of 0.278% with the J sc of 1.95mAcm−2. [ABSTRACT FROM AUTHOR]

The TiO2-B nanobelt (NB)/TiO2nanoparticle (NP) sandwich-type structure photoelectrode, with controllable nanobelt length, has been used to fabricate high-efficiency dye-sensitized solar cells (DSSCs), which combine the advantages of the rapid electron transport in TiO2-B NBs and the high surface area of TiO2NPs. The results indicate that the sandwich-type photoelectrode achieves higher photoelectrical conversion efficiency when compared with the TiO2nanoparticulate electrode. Increasing the length of TiO2-B NBs has been demonstrated to improve the photoelectric conversion efficiency (η). DSSCs with the longest (10 μm) TiO2-B NBs yield the highest ηof 7.94%. The interfacial electron transport of DSSCs with different lengths of TiO2-B NBs has been quantitatively investigated using the photovoltage transient and the electrochemical impedance spectra, which demonstrates that the DSSCs with longest TiO2-B NBs display the highest electron collection efficiency and the fastest interfacial electron transfer. [ABSTRACT FROM AUTHOR]

Abstract: Carbon-doped anatase TiO2 was prepared by a facile hydrothermal process without adding additional carbon source. The as-prepared sample shows highly efficient photocatalytic activity, which only requires 4min and is about 11 times higher than that of Degussa P25 TiO2 in degradation of methyl orange (MO) dye under UV light irradiation. Moreover, a highly visible-light activity is also observed. UV–vis diffuse reflectance spectra and X-ray photoelectron spectroscopy confirm that the carbon atoms are incorporated into the interstitial positions of TiO2 lattice and form a strong interaction with titanium atoms and extend photoresponding range to 700nm. Surface photovoltage spectra (SPS) and transient photovoltage (TPV) suggest that the presence of interstitial carbons induce several localized occupied states in the gap, enhance the separation extent and restrain the recombination of the photo-induced electron and hole carriers in TiO2. [Copyright &y& Elsevier]

Abstract: In this study TiO2 nanotube arrays were fabricated by potentiostatic anodization of titanium sheet. The X-ray diffraction (XRD) pattern and field emission scanning electron microscopy (FE-SEM) image indicated the TiO2 nanotube arrays were of pure anatase form and highly ordered. The properties of the photo-generated charges in the nanotube arrays were investigated by transient photovoltage (TPV) technique and surface photovoltage (SPV) technique based on lock-in amplifier with dc bias, in comparison with the commercial powder derived film. The separation processes of the photo-induced charges in the system of TiO2 nanotubes on Ti have been demonstrated to be correlated with the incident light intensity, surface trapping states, and the interfacial electric field between Ti and TiO2. The results also show that the highly ordered nanotube film could generate much stronger SPV responses under external electric field than the commercial powder derived film. [Copyright &y& Elsevier]

Abstract: Water-soluble anatase TiO2 nanocrystals (NCs) were synthesized by a simple sol–gel method. The reaction time is greatly reduced even under mild conditions. High-resolution transition electron microscopy (HRTEM), X-ray diffraction (XRD) and UV–vis were used to characterize the synthesized NCs and proved that the NCs are anatase phase and about 2 nm with near spherical shape. Surface photovoltage spectroscopy (SPS) experiments show that the synthesized anatase NCs have good photovoltaic properties compared with that of poly(vinyl pyrrolidone) (PVP) coated NCs synthesized by the similar method. [Copyright &y& Elsevier]

Abstract: Crack-free and transparent Zn2TiO4 single crystals of 4–6mm in diameter and 30mm in length have been grown by the optical floating zone method. The powder X-ray diffraction (XRD) results show that the as-grown crystals have the spinel-type Zn2TiO4 structure. XRD2 measurements on Zn2TiO4 wafers cut perpendicular to the growth direction display only one peak at 42.7°, which indicates that the Zn2TiO4 single crystals grow along the 〈400〉 direction (a-axis). The formation of bubble inclusions was effectively suppressed by lowering rotation rate. Transmission polarized-light microscopy results showed that as-grown crystals were free of low angle grain boundaries. [ABSTRACT FROM AUTHOR]

CuInS 2 and CdS quantum dots (QDs) are sequentially assembled onto mesoporous TiO 2 film to prepare a CuInS 2 /CdS co-sensitized photoelectrode for QD-sensitized solar cell (QDSC) application. Our results show that the performance of a QDSC is strongly dependent on the order of CuInS 2 and CdS respected to the TiO 2 . When CuInS 2 is in between TiO 2 and CdS, the power conversion efficiency could reach 0.90%, while the efficiency decreased dramatically when the CuInS 2 QDs were on top of the layer (0.08%). Surface photovoltage (SPV) measurement revealed that the charge transfer from the cosensitizers toward the TiO 2 is much more efficient in the TiO 2 /CuInS 2 /CdS electrode rather than in the TiO 2 /CdS/CuInS 2 electrode. From the information on time-resolved photoluminescence (TRPL) technique, it was found that the average photoluminescence (PL) lifetime of TiO 2 /CuInS 2 /CdS electrode is shorter than that of the TiO 2 /CdS/CuInS 2 electrode, suggesting the higher carrier transfer rates between the heterointerfaces of CuInS 2 /CdS and TiO 2 /QDs. This study reported herein propose an innovative route to investigate the role of heterointerface in the carrier transfer mechanism and enable better design of highly efficient QDSCs. [ABSTRACT FROM AUTHOR]

To better understand the behavior of photogenerated charges in the composite photocatalyst interface is beneficial to the designing of effective photocatalyst for photocatalytic reaction. In our work, the separation and transfer process of photogenerated charges in NiO/TiO 2 nanotube arrays (NiO/TiO 2 NTAs) has been studied by surface photovoltage (SPV) spectroscopy and transient photovoltage (TPV) measurement. Through the experimental results analysis, we find that an interfacial electric field is formed at NiO/TiO 2 NTAs interface, which is attributed to the work function difference between NiO and TiO 2 NTAs. The photogenerated holes in TiO 2 can transfer to the NiO layer along the interface electric field under the ultraviolet irradiation. A large amount of photogenerated holes can be separated effectively and then prolonged the holes lifetime to participate in the photocatalytic oxidation reaction. The above results show that the favorable hole-collecting process of NiO in the surface of TiO 2 NTAs is the main factor being responsible for the increase the photocatalytic efficiency. [ABSTRACT FROM AUTHOR]

Abstract: A water–dichloromethane interface-assisted hydrothermal method was employed to grow rutile TiO2 nanowires (NWs) on electrospun anatase TiO2 nanofibers (NFs), using highly reactive TiCl4 as precursor. The water–dichloromethane interface inhibited the formation of rutile NWs in water phase, but promoted the selective radial growth of densely packed rutile NWs on anatase NFs to form a branched heterojunction. The density and length of rutile NWs could be readily controlled by varying reaction parameters. A formation mechanism for the branched heterojunction was proposed which involved (1) the entrapment of rutile precursor nanoparticles at water–dichloromethane interface, (2) the growth of rutile NWs on anatase NFs via Ostwald ripening through the scavengering of interface-entrapped rutile nanoparticles. The heterojunction formed at anatase NF and rutile NW enhanced the charge separation of both under ultraviolet excitation, as evidenced by photoluminescence and surface photovoltage spectra. The branched TiO2 heterostructures showed higher photocatalytic activity in degradation of rodamine B dye solution than anatase NFs, and the mixture of anatase NFs, and P25 powders, which was discussed in terms of the synergistic effect of enhanced charge separation by anatase–rutile heterojunction, high activity of rutile NWs, and increased specific area of branched heterostructures. [Copyright &y& Elsevier]

Abstract: Zn-doped TiO2 microspheres have been synthesized by introducing a trace amount of zinc nitrate hexahydrate to the reaction system. Scanning electron microscope (SEM), field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) have been utilized to characterize the samples. Both surface photovoltage spectroscopy (SPS) technique based on lock-in amplifier and transient photovoltage (TPV) measurement reveal that the slight doping of Zn can promote the separation of photo-generated charges as well as restrain the recombination due to the strong interface built-in electric field and the decreasing of surface trap states. The photovoltaic parameters of dye-sensitized solar cells (DSSCs) based on Zn-doped TiO2 are significantly better, compared to that of a cell based on undoped TiO2. The relation between the performance of DSSCs and their photovoltaic properties is also discussed. [Copyright &y& Elsevier]

Abstract: The N-doped anatase TiO2 photocatalysts were prepared via solvothermal and ethylenediamine reflux treatment, followed by the sequential calcination in air and NH3/N2 atmosphere. The resulting photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and UV–vis diffuse reflectance spectra. The results revealed that the prepared N-doped anatase TiO2 had characteristics of small crystallite size, large surface area, high crystallinity and visible light response. The prepared N-doped anatase TiO2 photocatalysts showed much higher photocatalytic activity than N-doped Degussa P25 for the degradation of phenol under both ultraviolet and visible light irradiation, owing to more highly oxidizing hydroxyl radical which was the main oxidative species responsible for the degradation of phenol. [Copyright &y& Elsevier]

Abstract: Titania–silica mixed oxide (TiO2–SiO2) was prepared from the alkoxides: titanium tetrabutoxide (TBOT) and tetraethyl orthosilicate (TEOS), by using an ammonia–water solution as the hydrolysis catalyst. Variables included synthesis route, aging time, the type of alcohol, and calcination temperature. The materials were then evaluated as photocatalysts for the decomposition of n-heptane. Experimental results revealed: (1) the photoactivity of TiO2–SiO2 prepared via the route that Ti sol and Si sol were simultaneously and slowly added, was significantly enhanced due to its good homogeneity. However, for pure TiO2 the route that Ti sol was slowly added into ammonia–water solution was effective in inhibiting the growth of crystalline size and therefore improving the photoactivity; (2) longer aging time promoted the hydrolysis of TEOS. As a result, the intimate interaction between titania and silica (Ti–O–Si hetero linkages) were strengthened and the photoactivity was increased; (3) TiO2–SiO2 prepared by using ethanol as the solvent had the best combination of crystalline size, crystallinity, and homogeneity, thus, it exhibited the best photoactivity among the mixed oxides prepared via different alcohols; (4) 600°C calcined TiO2–SiO2 possessed excellent photoactivity as compared with that calcined at 400 or 800°C due to the good crystallinity and the synergism between Ti–O–Si hetero linkages and surface hydroxyl groups. [Copyright &y& Elsevier]

Mercurochrome-sensitized composite TiO2/SnO2 and ZnO/SnO2 photoelectrochemical cells (DSC) have been fabricated from the mixture of the SnO2 particles and the semiconductor colloid (TiO2, ZnO). The influence of the mixed ratio on the performances of the composite semiconductor photoelectrochemical cells was studied. Comparing the composite TiO2/SnO2 and ZnO/SnO2 cells with the corresponding TiO2 and ZnO cells, the incident photon-to-current conversion efficiency of the composite cells was improved greatly. The photovoltage spectra (SPS) indicated that the dye molecule was adsorbed mainly by the TiO2 and ZnO particles respectively in the composite cells. The energy barriers between the different semiconductors contributed to the improvement of the short-circuit photocurrent. The possible transport mechanism of the photogenerated electrons in composite cells was percolation through the SnO2 particles. [Copyright &y& Elsevier]

Abstract: The photovoltaic properties of nanoporous TiO2 film treated with Al3+ ions have been investigated by the spectral and transient photovoltage (PV) technique. The performances of the dye-sensitized solar cells (DSSCs) with different amounts of aluminum oxide were compared. The results showed that with increased amount of aluminum oxide, the spectral PV responses blue shift (with the exception of the 0.1wt%) and the time of the transient PV maximum increase. The performances of the corresponding cells were improved. These results indicated the dependence of the DSSCs performances on the charge dynamics in the corresponding nanoporous TiO2 film. [Copyright &y& Elsevier]