Photocurrent Time Measurement Research Articles

Amino acid-mediated chiral Ag@Au with circularly polarized light induced photothermal and photodynamic synergistic photocatalytic disinfection

As the deterioration of the environment, microbiological contamination of drinking water is threatening human health. Therefore, it is crucial to investigate rapid, reliable, and safe sterilization techniques. In this study, chiral Ag@Au nanoparticles (L/D-NPs) were synthesized using an amino acid-mediated protocol. The L/D-NPs demonstrated outstanding photothermal and photodynamic capabilities when irradiated with linearly polarized (LP) light. The photothermal and photodynamic synergism demonstrated by L/D-NPs resulted in high sterilization capability against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). It was noteworthy that these results were chirality-independent. With the interaction of chirality-matched circularly polarized light (CPL) and chiral NPs, excellent sterilization performance could be achieved even at a much lower concentration. The mechanisms were investigated using Finite-Difference Time-Domain (FDTD) simulations and photocurrent-time measurements. In addition, under identical conditions, chiral NPs were found to maintain excellent sterilization performance for the complex microbial system of actual river water. This work offers novel guidance and insights into photocatalytic disinfection, including sterilization of water and public facilities.

Calcination synthesis of N-doped BiOIO3 with high LED-light-driven photocatalytic activity

Novel LED-light-active N-doped BiOIO3 was synthesized successfully by calcination treatment of the mixture of BiOIO3 and urea. It gave a fairly easy way to coordinate the control of bandgap engineering. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed the incorporation of nitrogen into the BiOIO3. In UV–vis diffuse reflection spectroscopy (UV–vis), photocurrent-time measurement (PT) and electrochemical impedance spectroscopy (EIS), the N-doped BiOIO3 exhibits enhanced visible-light absorption and improved photocurrent response compared to pure-BiOIO3. The photocatalytic activity of the samples was evaluated via photodegradation of rhodamine B (RhB), bisphenol A (BPA), tetracycline (TC) and ciprofloxacin (CIP) under LED light irradiation. The N-doped BiOIO3 showed higher photocatalytic activity than pure BiOIO3.

Enhanced photoelectric performance of CdSe by graphene quantum dot modification

CdSe/graphene quantum dots (GQDs) composites with varying contents of GQDs were prepared via a facile solvothermal process. The as-prepared CdSe, GQDs and CdSe/GQDs composites were investigated, and the results indicate that GQDs exhibit a transverse dimension of 10–15 nm and a topographic height of 1–2 nm. GQDs attached CdSe composites present well-defined lattice fringes with the interlamellar spacing of 0.34 and 0.21 nm ascribed to the (002), (220) crystal facets of GQDs and cubic CdSe, respectively. The performances of CdSe/GQDs composites were investigated by photocurrent-time measurements and electrochemical impedance spectra. The GQDs content plays a crucial part in promoting the photoelectric performance of CdSe/GQDs composites. With an increase of GQDs from 0.3 wt% to 1.2 wt%, the charge-transfer resistance reaches a minimum at a content of 0.9 wt% and displays a higher photocurrent density of 1.65 × 10−5 A cm−2, which is 13 times more than that of pristine CdSe.

Investigation of p-type Ca2Fe2O5 as a Photocathode for Use in a Water Splitting Photoelectrochemical Cell

Ca2Fe2O5 is a p-type oxide that has not been previously investigated as a photocathode for use in a water splitting photoelectrochemical cell. In this study, Ca2Fe2O5 was synthesized as a polycrystalline electrode, and its properties relevant to photoelectrochemical hydrogen production were investigated. Ca2Fe2O5 electrodes were prepared by thermally annealing electrodeposited FeOOH films with a solution of Ca(NO3)2 drop-casted onto the electrode surface. The bandgap energy, band edge positions, flatband potential, photocurrent generation, and chemical and photoelectrochemical stabilities of Ca2Fe2O5 were examined. The results showed that Ca2Fe2O5 has an ideal bandgap and band positions that can enable the utilization of visible light for overall solar water splitting. Photocurrent–time measurements were also performed and the changes in morphology, crystallinity, and composition of the Ca2Fe2O5 electrodes before and after the photocurrent measurement were investigated. This made it possible to examine th...

Petal-like CdS nanostructures coated with exfoliated sulfur-doped carbon nitride via chemically activated chain termination for enhanced visible-light–driven photocatalytic water purification and H2 generation

Novel composite photocatalysts consisting of petal-like cadmium sulphide (CdS) nanoparticles and varying amounts of exfoliated sulfur-doped carbon nitride (SCN) were successfully prepared. The as-obtained materials were characterized by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflection spectroscopy, photoluminescence spectroscopy and photocurrent-time measurement. Results indicate a strong electric coupling interaction between SCN and CdS due to the heterojunction formed at the amine functionalities sites and oxidized chain terminations of SCN. Two typical pollutants like rhodamine B (RhB) and colorless bisphenol A (BPA) were used for the evaluation of photocatalytic activity. The best-performing CdS/SCN composite (i.e., CS5) synthesized exhibited enhanced visible-light-driven photocatalytic RhB efficiency of about 8.71 and 4.06 times higher than those of pure exfoliated SCN and CdS, respectively. As for BPA degradation, the CS5 composite was 9.00 and 3.61 times more efficient than that of exfoliated SCN and CdS, respectively. These excellent performances were found to be attributable to the remarkable charge carrier separation between CdS and exfoliated SCN with the aid of heterojunction interfacial structures. More importantly, the exfoliated SCN substantially reinforced the photostability of the CdS nanoparticles. Evaluation of the photocatalytic H2 evolution showed that the visible-light H2 production rate of the best-performing CS5 composite was also much greater than the constituents at 247.72 μmol h−1 g−1. Cyclic tests demonstrated the stability of the CS5 composite over repeated use. A possible mechanism was proposed to explain the photocatalytic reaction process. This study provides new insights into the preparation of highly efficient and stable sulfide-based composite photocatalysts, which are promising for implementation in wide-ranging environmental applications.

Plasmonic Bi nanoparticles and BiOCl sheets as cocatalyst deposited on perovskite-type ZnSn(OH)6 microparticle with facet-oriented polyhedron for improved visible-light-driven photocatalysis

Perovskite-type structure materials have attracted considerable attention in the field of solar cell and photocatalysis. In this study, novel plasmonic Bi nanoparticles and BiOCl sheets co-decorated ZnSn(OH)6 (ZSH) with various morphologies (hence exposure facets) was successfully synthesized via one-pot precipitation, hydrolysis and UV-photoreduction process. The as-obtained materials were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflection spectroscopy and photocurrent-time measurement. Results indicated that the cubic, 14-facets polyhedral and octahedral ZSH were decorated by plasmonic Bi particles and BiOCl sheets, which improved visible-light absorption, charge carrier separation and migration performance. Compared with pure ZSH, the composites showed enhanced photocatalytic activity, with the highest photocatalytic performance achieved by the octahedral ZSH decorated by Bi and BiOCl (i.e., ZSH-3-Bi). The photo-degradation rate of ZSH-3-Bi was about 81 times higher than that of pure octahedral ZSH. This phenomenon was mainly ascribed to the surface plasmon resonance effect for visible light absorption, the exposed {111} facets relative to other facets of octahedral ZSH, and the improved charge carrier separation efficiency due to the strong interfacial interaction of three components. The radical and hole trapping, and electron spin resonance spin-trap experiments verified that the OH, O2− and h+ were the main reactive species in this system, which were responsible for the decoloration and part mineralization of the RhB molecules. Therefore, this work provides new insights into the in situ fabrication of plasmonic Bi-based photocatalyst with facet-oriented polyhedron for full utilization of solar energy and wastewater treatment.

Synthesis and characterization of CeO2/TiO2 nanotube arrays and enhanced photocatalytic oxidative desulfurization performance

Well-aligned CeO2/TiO2 nanotube arrays photocatalyst was successfully prepared by anodization and microwave homogeneous synthesis technique. The nanocomposites were characterized by X-ray diffraction(XRD), Raman spectroscopy(RS), scanning electron microscopy(SEM), energy-dispersive spectrometry(EDS), transmission electron microscopy(TEM), UV–vis diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), photocurrent-time measurements, and electrochemical impedance spectroscopy(EIS). The TiO2 nanotube arrays showed enhanced optical properties with significant red shift after the introduction of CeO2 nanoparticles. Photocatalytic activities of the prepared samples were examined by the photocatalytic oxidation of benzothiphene (BT) under visible light irradiation. The CeO2/TiO2 nanotube arrays photocatalyst showed higher photocatalytic activity than that of TiO2 nanotube arrays. It was found that more than 90% of sulfur compounds in model oil were photocatalytic oxidized and removed by using CeO2/TiO2 nanotube arrays as photocatalyst.

Preparation and visible-light photocatalytic performances of g-C3N4 surface hybridized with a small amount of CdS nanoparticles

An efficient visible-light photocatalyst was successfully synthesized by surface-hybridizing graphitic carbon nitride (g-C3N4) using a small amount of cadmium sulfide (CdS) nanoparticles. The CdS/g-C3N4 nanocomposites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, electrochemical impedance spectroscopy, and photocurrent–time measurement. The photocatalytic activity of the CdS/g-C3N4 nanocomposites was investigated by evaluating the degradation of Rhodamine B (RhB) under visible-light irradiation. The effects of the CdS content on the nanocomposites, initial RhB concentration, pH value of the investigated system, and dosage of CdS/g-C3N4 nanocomposites on the visible-light photocatalytic activity were systematically investigated. The results revealed that the visible-light photocatalytic activity of g-C3N4-based photocatalysts was significantly improved by surface-hybridization of a small amount of CdS nanoparticles, increased as both CdS content on the nanocomposites and dosage of CdS/g-C3N4 nanocomposites increased, while increased at first and then decreased as both initial RhB concentration and pH value of the investigated system increased. The visible-light photocatalytic mechanism of the CdS/g-C3N4 nanocomposites was discussed.

G-C3N4 modified Bi2O3 composites with enhanced visible-light photocatalytic activity

Novel g-C3N4 modified Bi2O3 (g-C3N4/Bi2O3) composites were synthesized by a mixing-calcination method. The samples were characterized by thermogravimetry (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), UV–vis diffuse reflection spectroscopy (DRS), photoluminescence (PL) and photocurrent-time measurement (PT). The photocatalytic activity of the composites was evaluated by degradation of Rhodamine B (RHB) and 4-chlorophenol (4-CP) under visible light irradiation (>400nm). The results indicated that the g-C3N4/Bi2O3 composites showed higher photocatalytic activity than that of Bi2O3 and g-C3N4. The enhanced photocatalytic activity of the g-C3N4/Bi2O3 composites could be attributed to the suitable band positions between g-C3N4 and Bi2O3. This leads to a low recombination between the photogenerated electron–hole pairs. The proposed mechanism for the enhanced visible-light photocatalytic activity of g-C3N4/Bi2O3 composites was proven by PL and PT analysis.

Synthesis of carbon-doped g-C3N4 composites with enhanced visible-light photocatalytic activity

Novel visible-light-active carbon-doped graphitic carbon nitride composites (C/g-C3N4) were prepared by hydrothermal treatment of the mixture of g-C3N4 and glucose solution. The products were characterized by X-ray diffraction, transmission electron microscopy (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflection spectroscopy (UV–vis), and photocurrent–time measurement (PT). Compared to g-C3N4, the C/g-C3N4 showed enhanced visible-light absorption, adsorptivity and improved photocurrent response. C/g-C3N4 composites also showed enhanced performance for Methylene Blue (MB) photodegradation. The enhanced activity of the C/g-C3N4 composites is attributed to the synergistic effect between the doped carbon and g-C3N4.

Synthesis and photocatalytic activity of a bentonite/g-C3N4 composite

Novel bentonite/g-C3N4 composite photocatalysts were synthesized through a conventional calcination method and systematically characterized by thermogravimetric analysis (TG), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and photocurrent–time measurement (PT). The optimal sample bentonite/g-C3N4 (5.4%) composite shows an enhanced photocurrent value (about 8 times as high as that of g-C3N4) under visible light irradiation and high efficiency for the degradation of methylene blue (the photoreaction kinetics constant value is about 2.5 times that of g-C3N4) under visible light. Results show the improved photoactivity is mainly attributed to the electrostatic interaction between g-C3N4 and negatively charged bentonite, this leads to the efficient migration of the photogenerated electrons and holes of g-C3N4. This study reports an inexpensive and environmentally friendly photocatalyst for pollution degradation and prospective photoelectric materials.

Efficient degradation of RhB over GdVO4/g-C3N4 composites under visible-light irradiation

GdVO4/g-C3N4 composite photocatalysts were synthesized by a milling and heating method. The samples were characterized by X-ray diffraction (XRD), thermogravimetry and differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis diffuse reflection spectroscopy (DRS). The photocatalytic activities were evaluated in the degradation of rhodamine B aqueous solution. The result shows that g-C3N4 and GdVO4 present suitable band potentials, which induces a charge transfer at the heterojunction interfaces of the two semiconductors. The recombination of photogenerated electron–hole pairs is thus retarded and, consequently, the photocatalytic activity of GdVO4/g-C3N4 composites is enhanced. The 10wt.% GdVO4/g-C3N4 composite presents the highest photocatalytic activity of with a degradation rate of 0.0434min−1, which exceeded that of pure g-C3N4 by more than 3.1times. The proposed mechanism for the enhanced visible-light photocatalytic activity of GdVO4/g-C3N4 composites was further proven by photoluminescence (PL) spectroscopy, photocurrent–time measurement, and hydroxyl radicals trapping measurement.