Faqi Zhan

In situ synthesis of g-C3N4/WO3 heterojunction plates array films with enhanced photoelectrochemical performance

g-C3N4/WO3 heterojunction plate array films with enhanced photoelectrochemical (PEC) performance were successfully synthesized through a combination of hydrothermal and dipping-annealing methods. Urea aqueous solutions were prepared as the precursors to in situ synthesize g-C3N4 nanoparticles on the surface of WO3 platelets. The PEC performances of the photoanodes were investigated by the photocurrent density and incident photon-to-current conversion efficiency (IPCE). As-prepared g-C3N4/WO3 heterojunction films achieved a maximum photocurrent density of 2.10 mA cm−2 at +2.0 V (vs. RHE), which was almost 3-fold higher than that of the pure WO3 film (0.78 mA cm−2) under illumination. And the highest IPCE value increased from 25.1% to 53.1% after the g-C3N4 nanoparticles deposition. The enhanced PEC performance was attributed to the increased carriers density, better electron transport properties, longer electron lifetime and effective charge separation at the interface of heterojunction, which were confirmed by Mott–Schottky and electrochemical impedance spectroscopy (EIS). This study demonstrates that the low-dimensional morphological structure and in situ formation of heterojunction structure are expected to provide a promising photoanode for photoelectric catalysis.

Preparation of DyVO4/WO3 heterojunction plate array films with enhanced photoelectrochemical activity

In this work, DyVO4/WO3 heterojunction plate arrays were first fabricated on FTO using a hydrothermal method for WO3 vertical plate arrays and a dipping–annealing process for the deposition of DyVO4 nanoparticles. The samples were characterized by various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Photoelectrochemical activities were investigated by linear sweep voltammetry (LSV) and incident photon to current conversion efficiency (IPCE). The DyVO4/WO3 heterojunction electrode exhibited a maximum photocurrent density of 0.78 mA cm−2 at +1.2 V (vs. Ag/AgCl), while the photocurrent density of pure WO3 was just 0.49 mA cm−2 under illumination. And the highest IPCE value increased from 27.4% to 54.1% after the DyVO4 nanoparticle deposition. The enhanced PEC performance was attributed to the longer electron lifetime, increased carrier density and high charge separation efficiency at the interface of heterojunction, which were confirmed by electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. The study demonstrates that metal orthovanadates may be good heterojunction candidates to couple with WO3 to provide promising photoanodes for water splitting.

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.

S-C3N4 Quantum Dot Decorated ZnO Nanorods to Improve Their Photoelectrochemical Performance

S-doped C3N4 quantum dots (SCNQDs) were synthesized successfully by a low-temperature solid-phase method. The as-synthesised SCNQDs were decorated on ZnO nanorods by a dipping method. The ZnO nanorod films were prepared through a two-stage method, including pulse electrodeposition for depositing ZnO seed layer on fluorine doping SnO2 glass (FTO) and chemical bath for growing ZnO nanorods on the ZnO seed layer. The prepared samples were characterized via scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS). The photoelectrochemical performances of the prepared samples were estimated using linear sweep voltammograms, electrochemical impedance spectra (EIS), Mott–Schottky, transient photocurrent and incident photon-to-current conversion efficiency (IPCE). The results show that the light absorption edge of the prepared SCNQDs increases from 326nm (CNQDs) to 349nm after S doping. The CNQD deco...