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In the present study, a nanocomposite material g-C3N4/Fe-TiO2 has been prepared successfully by a simple one-step hydrothermal process and its structural properties were thoroughly studied by various characterization techniques, such as X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR) spectrum, X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectrometry (UV-vis DRS). The performance of the fabricated composite material towards the removal of phenol from aqueous phase was systematically evaluated by a photocatalytic approach and found to be highly dependent on the content of Fe3+. The optimum concentration of Fe3+ doping that showed a dramatic enhancement in the photocatalytic activity of the composite under visible light irradiation was observed to be 0.05% by weight. The separation mechanism of photogenerated electrons and holes of the g-C3N4/Fe-TiO2 photocatalysts was established by a photoluminescence technique in which the reactive species generated during the photocatalytic treatment process was quantified. The enhanced photocatalytic performance observed for g-C3N4-Fe/TiO2 was ascribed to a cumulative impact of both g-C3N4 and Fe that extended its spectrum-absorptive nature into the visible region. The heterojunction formation in the fabricated photocatalysts not only facilitated the separation of the photogenerated charge carriers but also retained its strong oxidation and reduction ability. [ABSTRACT FROM AUTHOR]

In the present work, a novel photocatalytic fuel cell (PFC) system involving a dual heterojunction photoelectrodes, viz. polyaniline/TiO2 nanotubes (PANI/TiO2 NTs) photoanode and CuO/Co3O4 nanorods (CuO/Co3O4 NRs) photocathode, has been designed. Compared to TiO2 NTs electrode of PFC, the present heterojunction design not only enhances the visible light absorption but also offers the higher efficiency in degrading Rhodamine B-a model organic pollutant. The study includes an evaluation of the dual performance of the photoelectrodes as well. Under visible-light irradiation of 3 mW cm-2, the cell composed of the photoanode PANI/TiO2 NTs and CuO/Co3O4 NRs photocathode forms an interior bias of +0.24 V within the PFC system. This interior bias facilitated the transfer of electrons from the photoanode to photocathode across the external circuit and combined with the holes generated therein along with a simultaneous power production. In this manner, the separation of electron/hole pair was achieved in the photoelectrodes by releasing the holes and electrons of PANI/TiO2 NTs photoanode and CuO/Co3O4 NRs photocathode, respectively. Using this PFC system, the degradation of Rhodamine B in aqueous media was achieved to an extent of 68.5% within a reaction duration of a four-hour period besides a simultaneous power generation of 85 μA cm-2. [ABSTRACT FROM AUTHOR]

The deposition of MnO 2 spheres on a TiO 2 nanotube arrays substrate are achieved via a sequential chemical bath deposition (SCBD) method for an application of anode materials in supercapacitors. The electrochemical performance of the MnO 2 –TiO 2 composite electrode is observed to show a strong dependence on the MnO 2 loading mass, which could be adjusted by repeating the SCBD treatment for several cycles. The optimized doses of MnO 2 loaded MnO 2 –TiO 2 and MnO 2 –Ti samples are compared in terms of their areal capacitance studies and the former is of 175 and 101 mF cm −2 at a scan rate of 10 and 100 mV s −1 , respectively, which are 1.52-fold and 1.51-fold of that of the latter sample at corresponding scan rates. The enhancement in areal capacitance has been accounted to the progressive effect of the TiO 2 tubular substrate on the capacitive behavior of the loaded MnO 2 rather than the different MnO 2 loading mass on these two substrates. Impedance analysis reveals this enhanced electrochemical activity is owing to the tubular structure of the TiO 2 substrate provides an increased reaction area and facilitates the contact of electrolyte with the active MnO 2 material. This work justified the suitability of using the TiO 2 nanotube arrays for constructing high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract: TiO2 nanotube arrays are modified by a facile cathodic reduction process treatment and the results are discussed in terms of their electrochemical activity and conductivity. The instrumental characterizations such as X-ray photoelectron spectroscopy and Raman spectroscopy indicate that the formation of oxygen vacancies in the lattice and introduction of hydroxyl groups on the surface of TiO2 take place. The capacitance of the modified sample is found to be 13 times larger than the pristine TiO2 nanotube arrays. This work reveals a feasible and simple method to improve electrochemical activity and conductivity of TiO2 for supercapacitors application. [Copyright &y& Elsevier]

Carbon nano-onions/titanium dioxide (CNOs/TiO2) photocatalyst was synthesized by a simple sol-gel method and characterized by the methods of X-ray diffraction (XRD), scanning electronic microscope (SEM), X-ray photoelectron spectroscopy (XPS), specific surface area (BET method), Fourier transform infrared (FTIR), thermogravimetric analysis (TG), differential scanning calorimeter (DSC), UV-Vis diffuse reflectance spectra (UV-Vis DRS), and high-performance liquid chromatography (HPLC). The photocatalytic activity of CNOs/TiO2 photocatalyst was assessed by testing the degradation rate of Rhodamine B (RhB) under visible light irradiation. The results showed that the optimum photocatalytic activity was achieved when the mass ratio of CNOs to TiO2 was 10%. The aforementioned specific CNOs/TiO2 photocatalyst resulted in a maximum RhB degradation efficiency of 78% (10 mg/L of RhB in 220 min). CNOs enhance the photocatalytic efficiency of TiO2 and improve the separation quantity of CNOs/TiO2 catalyst from aqueous media. CNOs can be used as a modification agent to develop high-performance photocatalysts for the removal of organic pollutants. [ABSTRACT FROM AUTHOR]

A silicon dioxide/carbon nano onions/titanium dioxide (SiO2/CNOs/TiO2) composite was synthesized by a simple sol-gel method and characterized by the methods of X-ray diffraction (XRD), scanning electronic microscope (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FTIR), thermogravimetric analysis (TG), differential scanning calorimeter (DSC) and UV-Vis diffuse reflectance spectra (UV-Vis DRS). In this work, the photocatalytic activity of the SiO2/CNOs/TiO2 photocatalyst was assessed by testing the degradation rate of Rhodamine B (RhB) under visible light. The results indicated that the samples exhibited the best photocatalytic activity when the composite consisted of 3% CNOs and the optimum dosage of SiO2/CNOs/TiO2(3%) was 1.5 g/L as evidenced by the highest RhB degradation rate (96%). The SiO2/CNOs/TiO2 composite greatly improved the quantum efficiency of TiO2. This work provides a new option for the modification of subsequent nanocomposite oxide nanoparticles. [ABSTRACT FROM AUTHOR]

The fabrication of TiO 2 @MnO 2 nanotube arrays (NTAs) structure is accomplished via a pulsed electrodeposition technique. The successful preparation of this structure is owing to the high current pulse used, which creates a sufficient nucleation trend on the wall of the entire TiO 2 nanotube layer, that results in the continuous deposition of MnO 2 along the nanotube walls. The synthesized TiO 2 @MnO 2 NTAs sample is found to exhibit excellent electrochemical behavior with high specific capacitance of 425.0 F g −1 and areal capacitance of 150.9 mF cm −2 , ranking in the top level ever achieved by a MnO 2 -TiO 2 composite. Furthermore, a symmetric supercapacitor device is assembled using two strips of the TiO 2 @MnO 2 NTAs electrode that yielded energy density as high as 7.4 Wh kg −1 , a much higher value than most of the values reported for symmetric MnO 2 //MnO 2 supercapacitors. The remarkable electrochemical properties of the TiO 2 @MnO 2 NTAs sample make it an attractive candidate for the application of constructing high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract: Due to the complexity of dye-sensitized solar cell modules, the conversion efficiency increased slightly over the years of development. The TiO2 photoelectrode, as core part in the module, plays an important role in the overall performance. Here, we conducted series of associative experiments on modification of the TiO2 photoelectrode to achieve a better performance. The paste was prepared using conventional P-25 powder, and the conversion efficiency was found to be increased from the initial 1.41% to 2.48% by optimizing paste additives. Further, a merchandised paste with smaller particle size was introduced to fabricate a double-layer cell with the P-25 paste, followed by a surface treatment with TiCl4. The final result was observed to be quite satisfactory with a sharp increase in the conversion efficiency of 6.51%. [Copyright &y& Elsevier]

Semiconductor doping is an effective strategy for improving the light absorption efficiency and the photogenerated carrier transport in photocatalysts. However, bulk defects induced by doping act as recombination centers, accelerating the recombination of carriers, which is detrimental to the photocatalytic performance. In this study, a novel electric-assisted photocatalytic technique was developed to reduce the recombination of the carriers trapped by the defects. The technique involves applying a low external voltage to a self-doped TiO 2 nanotube film, without any electrolyte and counter electrode. The remarkable improvement in the charge carrier dynamics under the electric assistance is attributed to the significant promotion of photogenerated electron fluxes and prevention of charge recombination. The electric-assisted photocatalytic technique is compatible with a liquid- or a gas-phase reactive system, e.g., water splitting, H 2 O 2 synthesis, and CO 2 photoreduction. The technique is sufficiently advanced to allow scale-up of the photocatalytic process from laboratory scale to industrial-scale. [Display omitted] • An advanced technique of electric-assisted photocatalysis in self-doped TNTs. • Reduced recombination of the carriers trapped by a low external voltage. • Compatibility of electric assistance with a liquid- or a gas-phase reactive system. [ABSTRACT FROM AUTHOR]

A visible-light driven Photocatalytic Fuel Cell (PFC) system comprising WO 3 /TiO 2 and CuO/TiO 2 nanotube array materials as photoanode and photocathode, was established with a dual objective of degrading an organic water pollutant and generating electric power as well. Under illumination, the Fermi level of WO 3 /TiO 2 nanotube arrays photoanode was higher than that of CuO/TiO 2 nanotube arrays photocathode. Arising an interior bias (0.18 V) induced the transfer of electrons from the photoanode across the external circuit to the photocathode and combination with the holes produced therein with electric power generation. In this manner, the separation of electron/hole pair was achieved in the photoelectrodes by releasing the holes of WO 3 /TiO 2 nanotube arrays photoanode and electrons of CuO/TiO 2 nanotube arrays photocathode. Using this PFC based system, the degradation of an organic water pollutant, Rhodamine B, was successfully accomplished with determining its decolorization and the variation in total organic carbon (TOC) content. The decolorization and TOC removal were obtained to the extent of 100% and 57%, respectively at 4 h reaction time. The stability of the photoelectrodes for scaling up applications could also be confirmed by the repeated several experimental runs using the electrodes. The proposed photoelectrocatalytic system provides a self-sustained and energy-saving methodology for wastewater treatment with a parallel energy production. [ABSTRACT FROM AUTHOR]

In this study, a simple electrochemical reduction approach is reported to enhance the photoelectrochemical performance of TiO2 nanotube arrays towards degrading water contaminants such as Rhodamine B, phenol and E. coli K-12. The results obtained from X-ray diffraction and X-ray photoelectron spectroscopy demonstrate that oxygen vacancies i.e., Ti3+ self-doping, were formed in the lattices of TiO2 nanotube arrays during the electrochemical reduction process of pristine TiO2 nanotube arrays at different negative potentials ranging from −1.2 to −1.5V. Comparing the pristine TiO2 nanotube arrays, the treatment TiO2 nanotube arrays samples by electroreduction process were found to be showing enhanced photoelectrocatalytic activity in the UV and visible regions in the entire potential window tested. Further, the photocurrent density of self-doped TiO2 nanotube arrays sample prepared at −1.3V was 250% higher than that of the pristine TiO2 under visible-light illumination. Impedance analysis revealed that the electrical conductivity of the nanotubes significantly enhanced after self-doping. The photoelectrocatalytic activity of the self-doped TiO2 nanotube increased dramatically due to the enhanced electrical conductivity and absorption in the visible light region, as well as an accelerated charge transfer rate between the interface of solid and electrolyte. [ABSTRACT FROM AUTHOR]

A binary component catalyst consists of single atoms (SAs– Pt and Au) anchored on self-doped TiO 2 nanotubes (TNTs), was developed for photocatalytic CO 2 reduction. The defects introduced TNTs substrate was stabilized with atomic Pt and Au via strong metal support interactions (MSI), due to which, the covalent interactions facilitated an effective transfer of photo-generated electrons from the defective sites to the SAs, and in turn an enhanced separation of electron–hole pairs and charge-carrier transmission. The Pt–Au/R-TNTs with 0.33 wt% of SA metals, exhibited a maximum of 149 times higher photocatalytic performance than unmodified R-TNT and a total apparent quantum yield (AQY) of 17.9%, in which the yield of CH 4 and C 2 H 6 reached to 360.0 and 28.8 μmol g−1 h−1, respectively. The metals loading shifted the oxidation path of H 2 O from •OH generation into O 2 evolution, that inhibited the self-oxidization of the photocatalyst. • A binary component SAC developed for photocatalytic CO 2 reduction. • Enhanced separation of electron–hole pairs and charge-carrier transmission by MSI. • A high photocatalytic performance with a total apparent quantum yield of 17.9%. [ABSTRACT FROM AUTHOR]