Changjian Lin

High Efficiency Dye-Sensitized Solar Cells Based on Hierarchically Structured Nanotubes

Dye-sensitized solar cells (DSSCs) based on hierarchically structured TiO(2) nanotubes prepared by a facile combination of two-step electrochemical anodization with a hydrothermal process exhibited remarkable performance. Vertically oriented, smooth TiO(2) nanotube arrays fabricated by a two-step anodic oxidation were subjected to hydrothermal treatment, thereby creating advantageous roughness on the TiO(2) nanotube surface (i.e., forming hierarchically structured nanotube arrays-nanoscopic tubes composed of a large number of nanoparticles on the surface) that led to an increased dye loading. Subsequently, these nanotubes were exploited to produce DSSCs in a backside illumination mode, yielding a significantly high power conversion efficiency, of 7.12%, which was further increased to 7.75% upon exposure to O(2) plasma.

p-n Heterojunction photoelectrodes composed of Cu2O-loaded TiO2 nanotube arrays with enhanced photoelectrochemical and photoelectrocatalytic activities

Cu2O/TiO2 p–n heterojunction photoelectrodes were prepared by depositing different amounts of p-type Cu2O nanoparticles on n-type TiO2 nanotube arrays (i.e., forming Cu2O/TiO2 composite nanotubes) via an ultrasonication-assisted sequential chemical bath deposition. The success of deposition of Cu2O nanoparticles was corroborated by structural and composition characterizations. The enhanced absorption in the visible light region was observed in Cu2O/TiO2 composite nanotubes. The largely improved separation of photogenerated electrons and holes was revealed by photocurrent measurements. Consequently, Cu2O/TiO2 heterojunction photoelectrodes exhibited a more effective photoconversion capability than TiO2 nanotubes alone in photoelectrochemical measurements. Furthermore, Cu2O/TiO2 composite photoelectrodes also possessed superior photoelectrocatalytic activity and stability in the degradation of Rhodamine B. Intriguingly, by selecting an appropriate bias potential, a synergistic effect between electricity and visible light irradiation can be achieved.

Inorganic-modified semiconductor TiO2 nanotube arrays for photocatalysis

Semiconductor photocatalysis is a promising physicochemical process for the photodegradation of organic contaminants and bacterial detoxification. Among various oxide semiconductor photocatalysts, TiO2 has garnered considerable attention because of its outstanding properties including strong oxidizing activity, chemical and mechanical stability, corrosion resistance, and nontoxicity. This Review briefly introduces the key mechanisms of photocatalysis, highlights the recent developments pertaining to pure TiO2 nanotube arrays and TiO2 nanotube arrays modified by non-metals, metals and semiconductors, and their applications in the photocatalytic degradation of organic dyes. The improved photocatalytic efficiencies of modified TiO2 nanotube arrays are compared with unmodified counterparts. Current challenges and prospective areas of interest in this rich field are also presented.

An Integrated Power Pack of Dye-Sensitized Solar Cell and Li Battery Based on Double-Sided TiO2 Nanotube Arrays

We present a new approach to fabricate an integrated power pack by hybridizing energy harvest and storage processes. This power pack incorporates a series-wound dye-sensitized solar cell (DSSC) and a lithium ion battery (LIB) on the same Ti foil that has double-sided TiO(2) nanotube (NTs) arrays. The solar cell part is made of two different cosensitized tandem solar cells based on TiO(2) nanorod arrays (NRs) and NTs, respectively, which provide an open-circuit voltage of 3.39 V and a short-circuit current density of 1.01 mA/cm(2). The power pack can be charged to about 3 V in about 8 min, and the discharge capacity is about 38.89 μAh under the discharge density of 100 μA. The total energy conversion and storage efficiency for this system is 0.82%. Such an integrated power pack could serve as a power source for mobile electronics.

Effects of the Structure of TiO2 Nanotube Array on Ti Substrate on Its Photocatalytic Activity

bNational Institute of Standards and Technology, Gaithersburg, Maryland 20899-8621, USA A novel oriented TiO2 nanotube TN array on Ti substrate was fabricated by using an electrochemical method. The structure and surface morphology of the TN array was examined by Raman spectroscopy and scanning electronic microscopy, respectively. The photocatalytic activity of the TN arrays was evaluated by the removal of methylene blue in aqueous solution. The effects of structure and morphology of the TN array on its photocatalytic activity were investigated. It was observed that the crystal structure, morphologies, and nanotube sizes were greatly influenced by anodization voltage and calcination temperature. The shift of absorption edges shorter wavelengths were ascribed to the quantum effect of the tube wall thickness. The TN arrays prepared at 20 V and calcined at 450°C have the highest photocatalytic activity due to an increase in the anatase crystal phase and an increase in surface area. When the calcination temperature was higher than 450°C, the photocatalytic activity of the TN array decreased, which was ascribed to excessive rutile content and a decrease in surface area resulting from the sintering and growth of TiO2 crystallites.

Nitrogen-doped TiO2 nanotube array films with enhanced photocatalytic activity under various light sources

Highly ordered nitrogen-doped titanium dioxide (N-doped TiO(2)) nanotube array films with enhanced photocatalytic activity were fabricated by electrochemical anodization, followed by a wet immersion and annealing post-treatment. The morphology, structure and composition of the N-doped TiO(2) nanotube array films were investigated by FESEM, XPS, UV-vis and XRD. The effect of annealing temperature on the morphology, structures, photoelectrochemical property and photo-absorption of the N-doped TiO(2) nanotube array films was investigated. Liquid chromatography and mass spectrometry were applied to the analysis of the intermediates coming from the photocatalytic degradation of MO. The experimental results showed that there were four primary intermediates existing in the photocatalytic reaction. Compared with the pure TiO(2) nanotube array film, the N-doped TiO(2) nanotubes exhibited higher photocatalytic activity in degradating methyl orange into non-toxic inorganic products under both UV and simulated sunlight irradiation.

Direct Growth of TiO2 Nanosheet Arrays on Carbon Fibers for Highly Efficient Photocatalytic Degradation of Methyl Orange

NSF; BES DOE; Chinese Scholars Council; National Basic Research Program of China [2012CB932900]

Ultrasound aided photochemical synthesis of Ag loaded TiO2 nanotube arrays to enhance photocatalytic activity

This work presents a novel approach for preparing TiO(2) nanotube array photocatalyst loaded with highly dispersed Ag nanoparticles through an ultrasound aided photochemical route. The Ag content loaded on the array was controlled by changing the concentration of AgNO(3) solution. The Ag-TiO(2) nanotube arrays were characterized by SEM, XRD, XPS and UV-vis absorption. The effects of Ag content on the photoelectrochemical (PEC) property and photocatalytic activity of TiO(2) nanotube array electrode were studied. The results showed that Ag loading significantly enhanced the photocurrent and photocatalytic degradation rate of TiO(2) nanotube array under UV-light irradiation. The photocurrent and photocatalytic degradation rate of Ag-TiO(2) nanotube array prepared in 0.006 M AgNO(3) solution were about 1.2 and 3.7 times as that of pure TiO(2) nanotube array, respectively.

High efficiency perovskite solar cells: from complex nanostructure to planar heterojunction

Perovskite solar cells have garnered great attention in recent years as promising high performance next-generation solar cells with long-term stability at low cost. Since the seminal work of Miyasaka and others in 2009, the power conversion efficiency (PCE) of perovskite-based dye-sensitized solar cells (DSSCs) has rapidly increased from 3.8% to 15% over the past four years, exceeding the highest efficiency of conventional organic dye-sensitized DSSCs. Recently, the perovskite has been demonstrated to act successfully as an active layer in simple planar-heterojunction solar cells with no need of complex nanostructured DSSC architectures, leading to an attractively high PCE of 15.4% at a competitive low manufacturing cost. In this Feature Article, we aim to review the recent impressive development in perovskite solar cells, and discuss the prognosis for future progress in exploiting perovskite materials for high efficiency solar cells.

Hierarchically structured nanotubes for highly efficient dye-sensitized solar cells.

Hierarchical TiO2 nanotube arrays grown on Ti foil are yielded by subjecting electrochemically anodized, vertically oriented TiO2 nanotube arrays to hydrothermal processing. The resulting DSSCs exhibit a significantly enhanced power conversion efficiency of 7.24%, which is a direct consequence of the synergy of higher dye loading, superior light-scattering ability, and fast electron transport.