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Achieving highly effective water splitting based on conventional TiO 2 photoanode is challenging due to its poor visible light response and low electrical conductivity. Herein, a Bi 2 MoO 6 /TiO 2 heterojunction with a suitable band structure is constructed to broaden light absorption and accelerate oxidation kinetics. In particular, the highest photocurrent density (0.35 mA cm−2 at 1.23 V vs. RHE) of Bi 2 MoO 6 /TiO 2 is 2.1 times higher than that of pristine TiO 2. The integrated Bi 2 MoO 6 nanoflakes enrich more reactive sites and charge transfer tunnels. The surface hole injection efficiency and electron lifetime of Bi 2 MoO 6 /TiO 2 are 1.4 and 5.5 times larger than those of bare TiO 2 , respectively. Additionally, the activation energy and charge transfer resistance of Bi 2 MoO 6 /TiO 2 electrodes are decreased remarkably, dramatically promoting the separation of electron-hole pairs. This work offers a novel strategy for TiO 2 -based heterojunction with great potential for application in photoelectrochemical water splitting. [Display omitted] • Bi 2 MoO 6 /TiO 2 heterojunction prolongs electron lifetime and enlarges surface hole injection efficiency. • Bi 2 MoO 6 nanoflakes broaden light absorption, enrich reactive sites, and provide charge transfer tunnels. • The charge transfer resistance of Bi 2 MoO 6 /TiO 2 photoanode is decreased remarkably. • Twice enhancement on photocurrent density achieved by Bi 2 MoO 6 /TiO 2 heterojunction. [ABSTRACT FROM AUTHOR]

This work firstly introduced Si quantum dots (QDs) to modify TiO 2 nanotube arrays for photoelectrochemical water splitting. A systematic study using surface and optical characterization tools reveals the nature of the combination of Si QDs and TiO 2 nanotube arrays. Scanning electron microscopy and X-ray photoelectron spectroscopy results show that Si QDs were assembled on the surface of vertically aligned TiO 2 nanotube arrays. The UV–vis diffuse reflectance spectra indicate the improved visible light absorbance. The enhanced photoelectrochemical water splitting was demonstrated under visible light illumination and the photocurrent density was 1.6 times larger than that of pristine TiO 2 electrodes. Electrochemical impedance behavior was measured for the electrodes and the impedance is slightly reduced for the nanocomposite electrode with the presence of Si QDs. This work demonstrated that Si QDs would be a novel and effective choice for improving the utilization of visible light for TiO 2 nanotubes. [ABSTRACT FROM AUTHOR]

Abstract: Si–W codoped TiO2 nanotubes were synthesized using a one-step anodization process with the presence of silicotungstic acid in the electrolyte. X-ray photoelectron spectroscopy results indicated that the content of Si and W in the TiO2 nanotubes was proportional to the concentration of the silicotungstic acid in the solution. More absorption in the visible light region was observed for the resulted samples from the UV–vis diffuse reflectance spectra. An enhanced photoelectrochemical visible response was demonstrated for the codoped samples and the photocurrent was 2.5 times larger than that of pristine TiO2 nanotubes under visible light irradiation. More negative flat band potential and a higher carrier density were associated with the introduction of dopants Si and W. This work demonstrated a feasible and simple method to fabricate doped TiO2 with controlled doping content based on the corresponding additives in the anodization electrolyte. [Copyright &y& Elsevier]

Abstract: Homogeneous titanium nitride (TiN) thin film was produced by simple electrophoreic deposition process on Ti substrate in an aqueous suspension of nanosized TiN powder. Nitrogen-doped titanium dioxide (TiO2− x N x ) was synthesized by oxidative annealing the resulted TiN thin film in air. Photoelectrochemical measurements demonstrated visible light photoresponse for the electrode of annealed electrophoreic deposited TiN samples. It is found that the synthesized TiO2− x N x electrode showed higher photo potential under white and visible light illumination than the pure TiO2 electrode. The photocurrent under visible light illumination was also observed, which increased with the increase of deposition time of TiN thin films. [Copyright &y& Elsevier]

In this paper, Ta-TiO 2 nanotubes were prepared and characterized its photoelectrochemical performance. TiO 2 nanotube arrays were prepared by anodic oxidation of Ti and then Ta was introduced on the surface by direct current magnetron sputtering, followed by an annealing process. The chemical composition, morphology and crystal structure of the Ta-TiO 2 nanotubes were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), X-ray photoemission spectroscopy (XPS), UV–vis diffuse-reflection spectra (DRS), photoelectrochemical measurements and electrochemical impedance spectroscopy (EIS). Highly-uniform nanotube arrays with anatase phase were confirmed by SEM images and XRD patterns, respectively. The light absorption is extended to larger wavelength with the presence of Ta according to UV–vis DRS. Samples with different Ta content were prepared by adjusting the sputtering time and an optimum Ta content in TiO 2 was achieved with an improvement of photoconversion efficiency from 0.28% to 0.63%. The enhancement can be attributed to a decreased band gap, lower charge transfer resistance and higher charge carriers density, which was confirmed by EIS and Mott–Schottky measurements. This facile and environmentally-friendly technique can also be applicable for fabricating other metal-modified TiO 2 nanotubes for potential use in water splitting. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen-doped titanium dioxide thin films with visible light photoresponse were prepared by oxidation of sputtered TiNx films, whose nitrogen contents can be easily changed by controlling the volume ratio of N2/(Ar+N2) during reactive direct current (DC) magnetron sputtering process. The reference TiO2 sample was also deposited by the same method under Ar/O2 gas mixture. The as-prepared films were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoemission spectroscopy, UV–vis spectrophotometry and photoelecrochemical measurements. The formation of anatase type TiO2 is confirmed by XRD. SEM measurement indicates a rough surface morphology with sharp, protruding modules after annealing treatment. Optical properties reveal an extended tailing of the absorption edge toward the visible region due to nitrogen presence. The band gap of the N-doped sample is reduced from 3.36eV to 3.12eV compared with the undoped one. All the N-doped samples show red shift in photoresponse towards visible region and improved photocurrent density under visible irradiance is observed for the N-doped samples. [Copyright &y& Elsevier]

In this work, we have shown that aluminium acetylacetonate (Al(acac) 3 ) can be used as the catalyst to synthesize Ti 3+ self-doped TiO 2 (Ti 3+ -TiO 2 ) by sol–gel method in air. Ti 3+ -TiO 2 can be obtained directly and Al(acac) 3 is removed during the annealing process. Ti 3+ concentrates in the surface layer of powders, making a homojunction between Ti 3+ -TiO 2 in the surface layer and TiO 2 in the bulk. Based on the scheme of Zielger-Natta catalysts and the characterization of the sols and gels of samples, the synthesis mechanism of Ti 3+ is proposed as the combination of steric hindrance effect, Lewis acid-base reaction and crystal field effect and Al(acac) 3 acts as the catalyst in the reaction. Charge generation, charge transport and interface reactions, all of the three crucial strategies of photocatalytic are improved through the self-doped Ti 3+ , resulting in enhanced photocatalytic and photoelectrochemical activities. Compared with the reported methods, this work proposes a simple and novel route for the preparation of Ti 3+ -TiO 2 , which would facilitate the preparation and application of TiO 2 photocatalyst. [ABSTRACT FROM AUTHOR]

Abstract: Silicon-doped TiO2 thin films were fabricated by annealing titanium metal sheet embedded in SiO2 powders and characterized by X-ray photoemission spectroscopy and photoelectrochemical measurements. The results showed that the content of silicon in the doped TiO2 thin films was proportional to the annealing time and temperature. Enhanced visible light response, more negative flat band potential and higher carrier density were demonstrated by the electrochemical measurement. The technique proposed in this paper can be also applicable to fabricate other doped TiO2 thin films based on the corresponding oxide bath. [Copyright &y& Elsevier]