Huizhen Yao

Simple synthesis method of Bi2S3/CdS quantum dots cosensitized TiO2 nanotubes array with enhanced photoelectrochemical and photocatalytic activity

A TiO2 nanotubes array film with nanowires directly formed on top (denoted as TiO2 NTWs) was prepared by an anodization method (potentiostatic anodization growth). Bi2S3 QDs were sensitized on the CdS/TiO2 NTWs array by a simple successive ionic layer adsorption and reaction (S-SILAR). A short-circuit photocurrent density of 2.16 mA cm−2 was obtained under an illumination of AM 1.5 G. The data of the photoelectrochemical performance test show that Bi2S3/CdS co-modification can boost the photocurrent density of the bare TiO2 NTWs by up to 308%. The photocatalytic activity was tested by treating rhodamine B (RhB) and methyl orange (MO) solutions, which were degraded completely after 240 min and 210 min, respectively. The present study shows the Bi2S3/CdS/TiO2 NTWs array can be applied in photocatalytic devices, and the greatest advantages are low-cost, easy reuse and recyclability.

The enhanced photoelectrochemical performance of CdS quantum dots sensitized TiO2 nanotube/nanowire/nanoparticle arrays hybrid nanostructures

This study aims at improving the photoelectrochemical performance mainly from two aspects: the increased number of heterojunctions and the advantages of nanotube/nanowire/nanoparticle arrays hybrid nanostructures. TiO2 nanoparticles porous layer was sensitized by CdS quantum dots (QDs), and coated on the top of the material, hydrogen-treated TiO2 nanotubes with nanowires, which was also sensitized by CdS QDs (This nanostructure is defined as CdS/H:TTWP). CdS/H:TTWP was successfully fabricated by the methods of electrochemical anodization, successive ionic layer adsorption and reaction (SILAR) and sol–gel. The data from the photoelectrochemical (PEC) performance test shows that the photocurrent density of CdS/H:TTWP is 7.6 mA cm−2 at −0.43 V vs. Ag–AgCl under AM 1.5 G illuminations.

Efficient improvement of photoelectrochemical activity for multiple semiconductor (CdS/PbS/ZnS) co-sensitized TiO2 photoelectrodes by hydrogen treatment

In the present work we report a simple and viable approach to improve the photoelectrochemical activity of TiO2 photoelectrodes. Firstly, a TiO2 nanotube array film with nanowires directly formed on top (denoted as TiO2NTWs) was prepared by a simple electrochemical anodization method on a titanium foil. Then the pristine TiO2NTWs were annealed in a hydrogen atmosphere (denoted as H*TiO2NTWs). Subsequently, the formation of a CdS, PbS, and ZnS quantum dot (QD) sensitized H*TiO2NTW photoelectrode was carried out by successive ionic layer adsorption and reaction (SILAR). The best performance of the photoelectrode was TiO2 NTWs annealed in hydrogen at 350 °C with 4 cycles of CdS plus 2 cycles of PbS and 3 cycles of ZnS. A maximum short-circuit photocurrent density of 3.62 mA cm−2 was obtained under an illumination of AM 1.5 G, which can boost the photocurrent density of the pristine TiO2NTWs by up to 503%. The enhancement was attributed to the extension of the light absorption range by hydrogen treatment and QD sensitization.

Hierarchical TiO2 nanoflowers/nanosheets array film: synthesis, growth mechanism and enhanced photoelectrochemical properties

The possible growth mechanism of a hierarchical TiO2 nanoflower/nanosheet (NFS) array was put forward in the work. The TiO2 NFS array film perpendicularly grown on transparent conductive fluorine-doped tin oxide (FTO) glass substrates was prepared via a one-step template-free hydrothermal method. The NFS array film was formed by the self assembly of nanosheets with exposed highly reactive {001} facets. Titanium butoxide and ammonium hexafluorotitanate ((NH4)2TiF6) were used as titanium precursor and morphology controlling agent, respectively. The growth process of TiO2 NFS array was investigated according to the SEM images and XRD patterns of the products at different reaction stages. The tractable morphology controlling agent played a key role in the preparation of pure anatase TiO2 and affected the thickness of the nanosheets. This study provides new insights into the synthesis of hierarchical anatase TiO2 nanostructures with a high percentage of {001} facets. In addition, the photoelectrochemical performance of the CdS QDs sensitized TiO2 NFS array film was assessed, indicating a variety of applications such as dye-sensitized or quantum dot-sensitized solar cells fields.

Synthesis of ZnO nanosheet array film with dominant {0001} facets and enhanced photoelectrochemical performance co-sensitized by CdS/CdSe

In this work, [110] oriented ZnO nanosheet (ZnONS) array films with a large percentage of high-energy {0001} surfaces were prepared for the first time with the assistance of sodium citrate. ZnONS array films possess prominent UV–visible absorption with an absorption edge at ~405 nm, indicating that the optical property of the semiconductor is dependent on a specific crystal structure and crystal plane. CdS and CdSe quantum dots (QDs) were assembled onto ZnONS array films to form a cascade structure of ZnONS/CdS/CdSe by the successive ionic layer adsorption and reaction method. The as-fabricated photoanode exhibits strong absorption in the visible spectrum up to 735 nm. With light illumination, the optimum photoanode yields a photocurrent of ~4.40 mA cm−2 at 0 V versus SCE, which is about 4.6 times of that of pure ZnONS samples. The excellent photoelectrochemical (PEC) properties of our photoanodes suggest that the QDs sensitized ZnONS array films with a large percentage of high-energy surfaces have potential applications in PEC solar cells.

Enhanced photovoltaic properties of perovskite solar cells by TiO2 homogeneous hybrid structure

In this paper, we fabricated a TiO2 homogeneous hybrid structure for application in perovskite solar cells (PSCs) under ambient conditions. Under the standard air mass 1.5 global (AM 1.5G) illumination, PSCs based on homogeneous hybrid structure present a maximum power conversion efficiency of 5.39% which is higher than that of pure TiO2 nanosheets. The enhanced properties can be explained by the better contact of TiO2 nanosheets/nanoparticles with CH3NH3PbI3 and fewer pinholes in electron transport materials. The advent of such unique structure opens up new avenues for the future development of high-efficiency photovoltaic cells.