Canjun Liu

In situ synthesis of Bi2S3 sensitized WO3 nanoplate arrays with less interfacial defects and enhanced photoelectrochemical performance

In this study, Bi2S3 sensitive layer has been grown on the surface of WO3 nanoplate arrays via an in situ approach. The characterization of samples were carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and ultraviolet–visible absorption spectroscopy (UV-vis). The results show that the Bi2S3 layer is uniformly formed on the surface of WO3 nanoplates and less interfacial defects were observed in the interface between the Bi2S3 and WO3. More importantly, the Bi2S3/WO3 films as photoanodes for photoelectrochemical (PEC) cells display the enhanced PEC performance compared with the Bi2S3/WO3 films prepared by a sequential ionic layer adsorption reaction (SILAR) method. In order to understand the reason for the enhanced PEC properties, the electron transport properties of the photoelectrodes were studied by using the transient photocurrent spectroscopy and intensity modulated photocurrent spectroscopy (IMPS). The Bi2S3/WO3 films prepared via an in situ approach have a greater transient time constant and higher electron transit rate. This is most likely due to less interfacial defects for the Bi2S3/WO3 films prepared via an in situ approach, resulting in a lower resistance and faster carrier transport in the interface between WO3 and Bi2S3.

Efficient Planar Perovskite Solar Cells with Reduced Hysteresis and Enhanced Open Circuit Voltage by Using PW12–TiO2 as Electron Transport Layer

An electron transport layer is essential for effective operation of planar perovskite solar cells. In this Article, PW12-TiO2 composite was used as the electron transport layer for the planar perovskite solar cell in the device structure of fluorine-doped tin oxide (FTO)-glass/PW12-TiO2/perovskite/spiro-OMeTAD/Au. A proper downward shift of the conduction band minimum (CBM) enhanced electron extraction from the perovskite layer to the PW12-TiO2 composite layer. Consequently, the common hysteresis effect in TiO2-based planar perovskite solar cells was significantly reduced and the open circuit voltage was greatly increased to about 1.1 V. Perovskite solar cells using the PW12-TiO2 compact layer showed an efficiency of 15.45%. This work can contribute to the studies on the electron transport layer and interface engineering for the further development of perovskite solar cells.

Enhancing photoelectrochemical activity of CdS quantum dots sensitized WO3 photoelectrodes by Mn doping

Mn-doped CdS quantum dots sensitized WO3 photoelectrodes were successfully synthesized by a combination of hydrothermal and chemical bath deposition (CBD) methods. To improve the stability of the photoelectrodes in an alkaline environment, the electrodes were treated with TiCl4 to form a nano-TiO2 buffer layer on the WO3 plate surface before depositing CdS quantum dots (QDs). The resulting electrodes were applied as photoanodes in the photoelectrochemical cell for water splitting. The photoelectrochemical (PEC) properties were investigated by the photocurrent density curves and incident photon-to-current conversion efficiency (IPCE). The as-prepared Mn-CdS QDs sensitized WO3 plate-like photoelectrodes exhibit a significant improvement in their photoelectrochemical performance compared with undoped photoelectrodes. To better understand the enhanced PEC properties, the electron transport properties and efficient electron lifetime were studied in detail using electrochemical impedance spectroscopy (EIS), transient photocurrent spectroscopy and intensity modulated photocurrent spectroscopy (IMPS). The results show that the Mn-CdS QDs/TiO2/WO3 photoelectrodes exhibit a higher electron transit rate and a longer electron lifetime. This is most likely due to the existence of electronic states in the mid-gap region of the Mn-CdS QD.

Epitaxial growth of Bi2S3 nanowires on BiVO4 nanostructures for enhancing photoelectrochemical performance

In this paper, a novel Bi2S3/BiVO4 heterojunction film was prepared by a facile drop-casting and hydrothermal method for the first time. The as-prepared films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet visible spectrometry (UV-Vis). Interestingly, the heterojunction film was formed by epitaxial growth of Bi2S3 nanowires on BiVO4 nanostructures and exhibited a good visible light absorption performance. Photoelectrochemical (PEC) hydrogen generation was demonstrated using the prepared films as photoanodes. The heterojunction photoelectrode showed an excellent PEC activity and generated a photocurrent density of 7.81 mA cm−2 at 0.9761 V vs. RHE (0.1 V vs. Ag/AgCl) in the electrolyte solution containing 0.35 M Na2SO3 and 0.25 M Na2S. The present study provides new insight into the design of highly efficient heterojunction photoelectrodes for hydrogen generation.

Photoelectrocatalytic reduction of CO2 into formic acid using WO3–x/TiO2 film as novel photoanode

Abstract A novel WO 3– x /TiO 2 film as photoanode was synthesized for photoelectrocatalytic (PEC) reduction of CO 2 into formic acid (HCOOH). The films prepared by doctor blade method were characterized with X-ray diffractometer (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The existence of oxygen vacancies in the WO 3– x was confirmed with an X-ray photoelectron spectroscopy (XPS), and the accurate oxygen index was determined by a modified potentiometric titrimetry method. After 3 h of photoelectrocatalytic reduction, the formic acid yield of the WO 3– x /TiO 2 film is 872 nmol/cm 2 , which is 1.83 times that of the WO 3 /TiO 2 film. The results of PEC performance demonstrate that the introduction of WO 3– x nanoparticles can improve the charge transfer performance so as to enhance the performance of PEC reduction of CO 2 into formic acid.