Transient Photocurrent Density Research Articles

Facile fabrication of Co2P/TiO2 nanotube arrays photoelectrode for efficient methylene blue degradation

The TiO2 nanotube arrays (NTAs) modified by various contents of Co2P were synthesized through a two-step anodization-hydrothermal approach to degrade methylene blue (MB). Co2P nanoparticles (NPs) were uniformly deposited on the nozzle of TiO2 NTAs and used as a cocatalyst to transfer the holes, which could accelerate the separation of photogenerated carriers. The experimental results showed that the light absorption capacity, photocurrent density and degradation rate of TiO2 NTAs were improved after Co2P modification, and that the transient photocurrent density of 1.5-Co2P/TiO2 NTAs was about 3.22 times higher than that of pure TiO2 NTAs. Besides, 1.5-Co2P/TiO2 NTAs also exhibited excellent activity during the photoelectrocatalytic degradation of MB. The trapping experiment was conducted to investigate the physicochemical properties of 1.5-Co2P/TiO2 NTAs. It was found that the enhanced activity might be attributed to the effective synergistic contribution of O2− and OH.

Enhanced catalytic performance of Ag2O/BaTiO3 heterostructure microspheres by the piezo/pyro-phototronic synergistic effect

Abstract The introduction of a built-in electric field by using ferroelectric materials is an efficient way to modulate the carrier generation and transportation behavior of photocatalysts. Here, we propose a hydrothermal-synthesized Ag2O/BaTiO3 heterostructure composite, whose photocatalytic performance can be largely enhanced by a four-way coupling effect among piezoelectricity, pyroelectricity, semiconductor and photoexcitation, referred as the piezo/pyro-phototronic synergistic effect. The photoelectrochemical (PEC) test of Ag2O/BaTiO3 shows a high photocurrent density of 3.48 mA/cm2 at 1.5 VSCE, which is 1.5 and 1.3 times as high as that of pristine BaTiO3 and Ag2O, respectively, and the transient photocurrent density of the composite at 0.5 VSCE is 20 times higher than that of the pure BaTiO3. Under varying temperature field and ultrasonic excitation condition, the photocatalytic degradation efficiency of the Ag2O/BaTiO3 composite is enhanced greatly when compared to that under only light illumination condition. This enhancement can be attributed to the attraction and release process of photogenerated carriers during the varying temperature field and ultrasonic excitation cycling. These results indicate that the ferroelectric heterostructure composites can act as a promising photocatalyst in wastewater treatment field under different environmental conditions.

Few-Layer Black Phosphorus Nanosheets: A Metal-Free Cocatalyst for Photocatalytic Nitrogen Fixation.

Exploiting an appropriate strategy to prepare fine crystal quality black phosphorus nanosheet (BPNS) catalyst is a major challenge for its practical application in catalysis. Herein, we address this challenge by developing a rapid electrochemical expansion strategy for scale preparation of fine crystal quality BPNSs from bulk black phosphorus, which was demonstrated to be an active cocatalyst for photocatalytic nitrogen fixation in the presence of CdS as a photocatalyst. The transient photocurrent and charge density studies show that the BPNSs can efficiently accelerate charge separation of CdS, leading to the enhanced photocatalytic activities of BPNS/CdS nanocomposites for nitrogen fixation. The 1.5% BPNS/CdS photocatalyst exhibits the highest photocatalytic activity for nitrogen fixation with an NH3 evolution rate of 57.64 μmol·L-1·h-1. This study not only affords a rapid and simple strategy for scale synthesis of fine crystal quality BPNSs but also provides new insights into the design and development of black phosphorus-based materials as low-cost metal-free cocatalysts for photocatalytic nitrogen fixation.

Architecting a Double Charge-Transfer Dynamics In2S3/BiVO4 n-n Isotype Heterojunction for Superior Photocatalytic Oxytetracycline Hydrochloride Degradation and Water Oxidation Reaction: Unveiling the Association of Physicochemical, Electrochemical, and Photocatalytic Properties.

To surmount incompatibility provoked efficiency suppression of an anisotype heterojunction and to pursue an improved intrinsic photocatalytic activity by manipulating oriented transfer of photoinduced charge carriers, an In2S3/BiVO4 (1:1) n–n isotype heterojunction was fabricated successfully through a simple two-step calcination method, followed by a wet-chemical deposition method. The formation of an n–n isotype heterojunction was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV–visible diffuse reflectance spectroscopy. The photocatalytic efficiency of the In2S3/BiVO4 catalyst was examined over degradation of oxytetracycline hydrochloride (O-TCH) and oxygen (O2) evolution reaction. Consequently, an n–n In2S3/BiVO4 isotype heterojunction exhibits a superior O-TCH degradation efficiency (94.6%, 120 min) and O2 evolution (695.76 μmol, 120 min) of multiple folds as compared to the pure BiVO4 and In2S3 solely. This is attributed to the proper band alignment and intimate interfacial interaction promoted charge carrier separation over the n–n isotype heterojunction. The intimate interfacial contact was confirmed by transmission electron microscopy (TEM), high-resolution TEM, and field emission scanning electron microscopy analysis. The proper band alignment was confirmed by Mott–Schottky analysis. The photoelectrochemical linear sweep voltammetric study shows a superior photocurrent density (269 μA/cm2) for In2S3/BiVO4 as compared to those for pristine BiVO4 and In2S3, which is in good agreement with the photocatalytic results. Furthermore, the superior charge antirecombination efficiency of the n–n isotype heterojunction was established by photoluminescence, electrochemical impedance spectroscopy, Bode analysis, transient photocurrent, and carrier density analysis. The improved photostability of the heterojunction was confirmed by chronoamperometry analysis. An orderly corelationship among physicochemical, electrochemical, and photocatalytic properties was established, and a possible mechanistic pathway was presented to better understand the outcome of the n–n isotype heterojunction. This study presents an effective way to develop new n–n isotype heterojunction-based efficient photocatalysts and could enrich wide applications in other areas.

Graphite carbon nitride coupled S-doped hydrogenated TiO2 nanotube arrays with improved photoelectrochemical performance

With the goal of improving the photoelectrochemical performances of titanium dioxide nanotube arrays (TiO2 NTAs), graphitic carbon nitride (g-C3N4)/S-doped hydrogenated TiO2 NTAs (g-C3N4/H-S-TiO2 NTAs) nanocomposite were fabricated by a feasible method. Photoelectrochemical tests showed that the photoelectric conversion efficiency of g-C3N4/H-S-TiO2 NTAs4 was up to 1.47%, which is about 5.44 times than that of TiO2 NTAs. The g-C3N4/H-S-TiO2 NTAs4 exhibited higher transient photocurrent density (1.64 mA/cm2) with good stability than TiO2 NTAs (0.29 mA/cm2). Furthermore, g-C3N4/H-S-TiO2 NTAs4 had a more negative open circuit potential and optimal photoelectric stability than other photoelectrodes. The possible photoelectric mechanism of g-C3N4/H-S-TiO2 NTAs was proposed. Photoelectrochemical characterizations demonstrated that hydrogenation, S-doping and the introduction of g-C3N4 have synergistic effects on the improvement of the photoelectrochemical performances of TiO2 NTAs.

Carbon membrane bridged ZnSe and TiO2 nanotube arrays: Fabrication and promising application in photoelectrochemical water splitting

In this work, a cascade structure among ZnSe, carbon membrane and TiO2 NTAs was constructed precisely. This carbon membrane bridged ZnSe and TiO2 composite exhibits excellent H2 evolution activity, the H2 evolution rate of ZnSe/C/TiO2 NTAs (866.76 μmol/cm2) is about 6.95 times higher than that of pure TiO2 NTAs (124.64 μmol/cm2) after 200 min irradiation. The introduction of carbon membrane can greatly facilitate the electron transfer from ZnSe to TiO2, ZnSe/C/TiO2 ternary composite exhibits the highest transient photocurrent density (1.05 mA/cm2) and the lowest impedance (677.6 Ω) among all the samples. Besides, the contact between TiO2 and electrolyte is improved after introducing carbon membrane, therefore C/TiO2 NTAs shows more positive flat band potential of (1.86 V) compared with TiO2 NTAs (0.50 V). It is also found that pure carbon powder can achieve H2 production under visible light irradiation, its sensitization effect can further improve photocurrent density of the composite under 500 nm light radiation, the electrons produced in carbon film can inject into TiO2, and holes from TiO2 can quickly transfer to carbon film, leading to excellent H2 evolution efficiency.

Dependence of stability and electronic and optical properties of perovskite quantum dots on capping ligand chain length.

Methylammonium lead bromide (MAPbBr3) perovskite quantum dots (PQDs) passivated with capping ligands with different chain length, including butylamine-valeric acid (BUTY-VA), octylamine-caprylic acid (OCTY-CA), and dodecylamine-lauric acid (DODE-LA), are investigated to determine an optimized capping layer thickness for maximizing both electronic and antimoisture properties of perovskite materials in optoelectronic devices. The photoluminescence quantum yield (PLQY) is observed to be chain length dependent, where the PLQY of BUTY-VA, OCTY-CA, and DODE-LA MAPbBr3 PQDs is 82% ± 4%, 68% ± 7%, and 18% ± 2%, respectively. Electrochemical impedance spectroscopy (EIS) measurements of each PQD film reveal that there is a slight increase in conductivity from reducing the capping ligand chain length from 8 carbon atoms (OCTY-CA) to 4 carbon atoms (BUTY-VA). Using the Butler-Volmer equation, the charge transfer factor β for BUTY-VA and OCTY-CA MAPbBr3 PQD films in a tetrabutylammonium hexafluorophosphate-dichloromethane electrolyte solution was calculated to be 0.36 and 0.31, respectively. From an Arrhenius analysis, the activation energy (Ea) for charge transport between the PQD film and the electrolyte was calculated to be 77 and 90 meV for BUTY-VA and OCTY-CA MAPbBr3 PQD films, respectively. Moreover, passivating PQDs with capping ligands with 12 carbon atoms (DODE-LA) almost completely insulates the PQDs and diminishes charge transport. This is also observed in transient photocurrent density measurements. The results suggest that the inter-PQD distance in this solid film is too long for effective tunneling to occur. However, using BUTY-VA capping ligands to improve electronic properties of PQD solid film comes with a cost of stability.

Preparing a photocatalytic Fe doped TiO2/rGO for enhanced bisphenol A and its analogues degradation in water sample

For extending the light response to visible spectrum, an approach to efficient photocatalysts in sustainable energy technology has been a hot research topic. In this work, Fe doped TiO2/rGO (Fe-TiO2/rGO) was synthesized via one-step hydrothermal deposition method. The presence of Fe-Ti bond and Ti3+ in the photocatalyst was confirmed by XPS, EXAFS and Raman analyses. The batch experiments showed that as-synthesized Fe-TiO2/rGO nanocomposites exhibited high photocatalytic performance for bisphenol A (BPA) and its analogues degradation under visible light irradiation (λ ≥ 420 nm). Moreover, Fe-TiO2/rGO presented high photocatalytic activity at a high BPA concentration of 95 ppm as well as a wide pH value of 4.5–8.5. Additionally, the extended visible light absorption range Fe-TiO2/rGO was demonstrated by low temperature electron spin resonance, UV–vis diffuse reflectance spectra, the transient photocurrent density and electrochemical impedance spectroscopies measurements. The radical quenching and ESR active species trapping experiments implied the main role of superoxide radicals on the high efficient photodegradation of BPA. These findings are crucial for designing TiO2-based photocatalysts with high performance for degradation of persistent organic pollutants in wastewater treatment.

Solvothermal ion exchange preparation of Bi11VO19 to sensitize TiO2 NTs with high photoelectrochemical performances

Ag3VO4 nanograss was deposited on the surface of vertically grown TiO2 nanotube arrays (TiO2 NTs) by a successive ion layer adsorption and reaction (SILAR) method, and the Ag3VO4 nanograss was further transformed into Bi11VO19 by the solvothermal ion exchange method. The formation of Bi11VO19 was influenced by solvothermal intervals, and the TiO2 NTs/Bi11VO19 exhibited outstanding visible light response and photoelectrochemical activity. The TiO2 NTs/Bi11VO19 (3) prepared with solvothermal treatment for 3 h showed the optimal photoelectric conversion and photoelectrocatalytic (PEC) properties. The transient photocurrent density, photovoltage and charge carrier concentration achieved 9.53 mA/cm2, −0.29 V and 1.36 × 1020 cm−3, respectively. Furthermore, the PEC rate constants of TiO2 NTs/Bi11VO19 (3) for the MO, RhB and MB degradation achieved 3.56 × 10−3, 9.01 × 10−3 and 2.30 × 10−2 min−1, respectively. The PEC removal efficiency of Cr(VI) was 86.62%. The outstanding photoelectric activity drives the TiO2 NTs/Bi11VO19 photoelectrode prospective applications in waste-water purification and solar cells.

Basic properties and photo-generated carrier dynamics of bismuth vanadate composites modified with CQDs, MWCNTs and rGO

Three types of carbon materials with different dimensions were successfully combined with bismuth vanadate (BiVO4) using different methods, resulting in BiVO4/carbon quantum dots (CQDs), BiVO4/hydroxylated multiwalled carbon nanotubes (MWCNTs) and BiVO4/reduced graphene oxide (rGO). First, analysis of the basic morphology and elemental characterization of the materials were performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DRS). Second, the effects of conductivity on the separation and recombination efficiency of the photo-generated carriers were investigated using photoluminescence spectroscopy (PL), transient fluorescence, electron spin resonance (ESR), transient photocurrent density (TPD) and electrochemical impedance spectroscopy (EIS). These results showed the addition of carbon promoted the separation of photo-generated carriers. Transient fluorescence measurements showed the separation and recombination of carriers was an ultrafast kinetic process and the photo-generated carriers exhibited the following three recombination mechanisms during fluorescence decay: bulk recombination, surface migration and defect recombination. In this study, photocatalytic carrier separation was improved by the addition of carbon materials, which resulted in improved photocatalytic degradation. Examination of the kinetic process of carbon-modified BiVO4 composites resulted in a deeper understanding of the composite process of the photo-generated carriers and the development of a better research method for improving photocatalytic degradation effects.

Synthesis of SnS/TiO2 nano-tube arrays photoelectrode and its high photoelectrocatalytic performance for elimination of 2,4,6-trichlorophenol

In this study, SnS decorated TiO2 nano-tube array (SnS/TiO2 NTAs) photoelectrode, which was applied for degradation of 2,4,6-trichlorophenol under simulated visible light illumination, was synthesized by anodization combined with electrodeposition strategy. Afterwards, series of the systematical physicochemical properties were measured. Results show that SnS/TiO2 NTAs photoelectrode exhibited improved visible light range of 650 nm and transient photocurrent density of 0.119 mA cm−2, as well as higher photo-generated charge separation efficiency, because of the synergistic effect between TiO2 and SnS. Also, the enhanced charge separation and photoelectrocatalysis (PEC) mechanism were further confirmed by photoluminescence spectroscopy and visible light assisted PEC efficiency for degradation of 2,4,6-trichlorophenol. It is worth mentioning that SnS/TiO2 NTAs photoelectrode displayed excellent stability and reusability, for the degradation efficiency of repeated experiments were all over 90% after 5 runs. All these results indicated SnS/TiO2 NTAs photoelectrode has great potential for the degradation of organic pollutants in waste water treatment.

Facile synthesis of Ti3+ self-doped and sulfur-doped TiO2 nanotube arrays with enhanced visible-light photoelectrochemical performance

Titanium dioxide nanotube arrays (TiO2 NTAs) has shown its promising properties for use as a photoelectrode material. However, the efficiency in this regard is restricted by the wide band gap of TiO2. In this study, a facile method was employed to prepare Ti3+ self-doped and sulfur-doped (S-doped) TiO2 NTAs (H-S-TiO2 NTAs). The Ti3+ and S co-doping greatly improved the photoelectrochemical performances of TiO2 NTAs. The optimized H-S-TiO2 NTAs showed obviously red-shifted compared with the optimized TiO2 NTAs. The saturation photocurrent density and the photoelectric conversion efficiency of the optimized H-S-TiO2 NTAs reached 1.97 mA/cm2 and 1.18%, which were 3.72 and 4.92 times higher than that of the optimized TiO2 NTAs, respectively. Furthermore, the optimized H-S-TiO2 NTAs exhibited the highest transient photocurrent density (1.08 mA/cm2) with excellent photoelectric response characteristics, indicating that the transfer efficiently of photogenerated carriers was increased in the optimized H-S-TiO2 NTAs. On the basis of research results, such enhanced performances could prove that the Ti3+ self-doping and S-doping had synergistic effects. The established S-doping as well as introduced Ti3+ self-doping of TiO2 NTAs resulted in enhanced visible-light absorption and rapid electron transfer rate.

Synthesis of PbS/TiO2 nano-tubes photoelectrode and its enhanced visible light driven photocatalytic performance and mechanism for purification of 4-chlorobenzoic acid

In this study, highly ordered TiO2 nano-tubes (TiO2 NTs) were synthesized by anodization. Subsequently, PbS nanoparticles were successfully decorated onto the surface of TiO2 NTs by successive ionic layer adsorption and reaction strategy in the presence of lead acetate (Pb(Ac)2) and thiourea. Afterwards, morphologies and chemical structures of PbS/TiO2 NTs photoelectrode were systematically studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results showed that PbS nanoparticles were uniformly dispersed on the surface of TiO2 NTs, and a small amount of PbS nanoparticles gathered together. Besides, their optical properties were investigated by ultraviolet–visible diffuse reflectance spectroscopy (DRS), transient photocurrent density, open potentials, electrochemical impedance spectroscopy (EIS) and Mott-schottky measurements. Compared with the pristine TiO2 NTs photoelectrode that only could utilize ultraviolet light, The PbS/TiO2 NTs photoelectrode presented absorption properties of visible light, which improved the utilization of solar energy. What’s more, the photocatalytic degradation performance of PbS/TiO2 NTs photoelectrode was studied by using 4-chlorobenzoic acid as the target pollutant, finding that 80.37% of 4-chlorobenzoic acid could be removed within 7 h. After these, based on the electrochemical and fluorescence spectra, the enhanced photocatalytic performance mechanism of PbS/TiO2 NTs was proposed. In addition, the PbS/TiO2 NTs possessed excellent stability for 4-chlorobenzoic acid degradation after consecutive utilization for five cycles. This study illustrated that the novel PbS/TiO2 NTs photoelectrode was a promising photocatalyst with many potential applications, which could be used in sewage treatment process. Most importantly, this study provided a theoretical support for the practical application of photocatalytic technology.

Supersonically sprayed iron oxide nanoparticles with atomic-layer-deposited ZnO/TiO2 layers for solar water splitting

We demonstrate a promising Fe2O3/ZnO/TiO2 photoanode for photoelectrochemical water splitting. Passivation of the Fe2O3 surface with thin layers of ZnO and TiO2 enhances the water splitting photocurrent density of Fe2O3. The increased photoelectrochemical activity of the hematite-based structure with heterojunctions, compared to that of bare Fe2O3, results from improved charge separation during water oxidation. The multilayered Fe2O3 film exhibits a seven-fold improvement in photocurrent density (to 4.25 mA cm−2) compared with bare Fe2O3, due to suppression of electron–hole recombination. The transient photocurrent density and impedance were evaluated to assess the effect of the passivation layer thickness and achieve a high photocurrent at low potential (0.7 V vs. Ag/AgCl) through improved light harvesting of the Fe2O3 film with an ultrathin ZnO/TiO2 overlayer.

Synthesis of 3D Bi2S3/TiO2 NTAs photocatalytic system and its high visible light driven photocatalytic performance for organic compound degradation

In the present study, Bi2S3/TiO2 nano-tube arrays (Bi2S3/TiO2 NTAs) photoelectrode was fabricated by anodization and electrodeposition strategy. Besides, the deposition time and electric current density during photoelectrode construction process was optimized as 90 min and −0.8 A⋅cm−2, MB removal and mineralization efficiency within 30 min was 82.3% and 57.4%, severally. Afterwards, physicochemical properties of the resulting Bi2S3/TiO2 NTAs were studied through SEM, XRD, XPS and DRS measurements. Photoelectrochemical (PECH) performance was determined by transient photocurrent density (TPR) and electrochemical impedance spectroscopy (EIS). Results indicated that Bi2S3/TiO2 NTAs photoelectrode was constructed successfully and with enhanced photocatalytic performance. Additionally, OH radical and e- played the dominant parts in the photocatalystic process confirmed via scavenging experiments. At last, enhanced photocatalytic mechanism of Bi2S3/TiO2 NTAs reaction system was proposed. The consequence would be attributed to the special 3D microstructure formation and the construction of Z-scheme photocatalytic system of Bi2S3/TiO2 NTAs, which both could improve photocatalytic performance via effective photogenerated electron-hole separation and electron transfer process.

Photovoltaic and capacitance performance of low-resistance ZnO nanorods incorporated into carbon nanotube-graphene oxide nanocomposites

Nanocomposites of hexagonal ZnO nanorods incorporated into carbon nanotube-graphene (ZnO/CNT-GO) were prepared using a simple hydrothermal approach. The structure, light absorption, surface texturing, and morphology characterizations have established the strong interaction between ZnO, carbon nanotubes, and graphene oxide components because of the presence of well-dispersed ZnO nanorods with an aspect ratio of 3.4 (L × D = 75 × 22 nm). The assembled dye-sensitized solar cell of a ZnO/CNT-GO photoanode exhibited a superior performance, with a power conversion efficiency of 7.73%, surpassing those of its ZnO/CNT (5.07%) and ZnO/GO (3.96%) counterparts. Although CNT-GO exhibited a higher incident photon-to-current conversion efficiency (IPCE) and lower photoluminescence (PL) intensity than those of the ZnO/CNT-GO composite, it presented a lower conversion efficiency of 5.60%. This can be attributed to the presence of structural defects at the CNT/GO interface, which resulted in lower electronic conductivity (0.25 × 10−3 Ω−1 cm−1 vs. 0.8 × 10−3 Ω−1 cm−1 for ZnO/CNT-GO) and optical performance. The ZnO/CNT-GO composite showed a superior Isc value of 17.6 mA/cm2 but a lower Voc value of 0.63 V in comparison to those of its ZnO/GO analog (3.9 mA/cm2, 0.8 V); it also showed a manifested increase in surface area and pore radius values (227.5 m2/g, 58.9 Å) toward the dye absorption. The electrochemical capacitance performance obtained via using charge-discharge and impedance spectroscopy revealed an excellent specific capacitance in the order of ZnO/CNT-G (290 F/g) > CNT-G (275 F/g) > ZnO/G (230 F/g) > ZnO/CNT (183 F/g) at 1.0 A g−1. This is attributed to the synergistic effect of ZnO within the CNT/GO nanocomposite and affirms its charge collection efficiency toward the improvement of dye-sensitized solar cells. The formation of a p/n junction between CNT/G and ZnO nanorods, as evidenced by the Mott-Schottky analysis, played a vital role in the improvement of solar cell devices based on the narrowing of the band gap (Eg = 2.64 eV), ease of electronic transfer, transient photocurrent density, as well as framework mesoporosity.

A facile strategy to synthesize Pd/TiO2 nanotube arrays with high visible light photocatalytic performance

Novel Pd/TiO2 nanotube arrays (Pd/TNTAs) were fabricated by introducing Pd nanoparticles onto TNTAs via a facile deposition–reduction method. Pd nanoparticles can uniformly distribute over the inner and outer surfaces of TiO2 nanotubes by controlling the Pd loading. The hybrid prepared by two deposition–reduction cycles (Pd/TNTAs-2) showed the best visible light absorption and the highest transient photocurrent density compared with the pure TNTAs and other Pd/TNTAs. The Pd/TNTAs-2 sample also showed the best photocatalytic activity and recyclability toward the degradation of Rhodamine B (RhB). As much as 99.7% of RhB could be removed over the Pd/TNTAs-2 film within 2 h under visible light irradiation, which is about three times higher than that over P25 films. The enhancement is attributed to the surface plasmon resonance of Pd nanoparticles and the effective interaction between Pd nanoparticles and TiO2 nanotubes, which improves the charge transfer and reduces the recombination rate of the photogenerated electron–hole pairs.

Construction of BiOCOOH/g-C3N4 composite photocatalyst and its enhanced visible light photocatalytic degradation of amido black 10B

Abstract The application of semiconductor photocatalysts in wastewater treatment has received increasingly attentions because of its potential utilization of solar energy. In this study, a novel visible-light-driven (VLD) BiOCOOH/g-C3N4 composite photocatalyst was successful synthesized by a facile hydrothermal method. Afterwards, physicochemical properties of the resulting samples were investigated through X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface areas, UV–visible diffuse reflectance spectroscopy (UV–vis DRS), transient photocurrent density, Mott-Schottky (M−S) and electrochemical impedance spectroscopy (EIS) measurement. Furthermore, the visible light photocatalytic (PC) performance was evaluated through the degradation of amido black 10B dye. All results indicated that the combination of g-C3N4 and BiOCOOH could exhibited greatly visible light absorbance and photo-generated charge separation efficiency, thereby resulting in the enhanced PC performance of BiOCOOH/g-C3N4 composite photocatalyst. The optimal Bi/C molar rate in BiOCOOH/g-C3N4 composite was determined to be 1/1, and the corresponding photodegradation rate for amido black 10B was 0.01794 min−1, which was nearly 2.19 and 5.73 folds higher than that of pure g-C3N4 and BiOCOOH. The possible mechanism of the PC reaction was also discussed in detail. Furthermore, BiOCOOH/g-C3N4 composite photocatalyst performed good reusability and stability even after four recycle utilization.

Construction of Bi 2 O 3 /g-C 3 N 4 composite photocatalyst and its enhanced visible light photocatalytic performance and mechanism

Abstract To improve the photocatalytic (PC) performance of g-C3N4 nano-material, a novel Z-scheme Bi2O3/g-C3N4 composite photocatalyst was synthesized by heat treatment method. Subsequently, the morphologies, chemical structures, optical and photoelectrochemical (PECH) properties of as-obtained photocatalysts were investigated through X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface areas, UV–visible diffuse reflectance spectroscopy (UV–vis DRS), transient photocurrent density, Mott-Schottky (M-S) and electrochemical impedance spectroscopy (EIS) measurement. Furthermore, the PC efficiency was evaluated by degradation of amido black 10B dye. All results indicated that as-fabricated Bi2O3/g-C3N4 photocatalytic system displayed superior PC performance under visible light illumination, which was mainly ascribed to the intense visible light absorbance and the migration of photo-generated carriers adopted a Z-scheme mechanism. Moreover, the degradation of amido black 10B for 3 wt.%Bi2O3/g-C3N4 were about 1.41 and 1.42 times than that of pure g-C3N4 and pure Bi2O3, respectively.

Flower-like Bi2WO6/ZnO composite with excellent photocatalytic capability under visible light irradiation

The photocatalytic ability of ZnO is improved through the addition of flower-like Bi2WO6 to prepare a Bi2WO6/ZnO composite with visible light activity. The composite is characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy with UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and N2 adsorption-desorption isotherms. After modification, the band gap energy of Bi2WO6/ZnO is reduced from 3.2 eV for ZnO to 2.6 eV. Under visible light irradiation, the Bi2WO6/ZnO composite shows an excellent photocatalytic activity for degrading methylene blue (MB) and tetracycline. The photo-degradation efficiencies of (0.3:1) Bi2WO6/ZnO for MB and tetracycline are approximately 246 and 4500 times higher than those of bare ZnO, respectively, and correspondingly, the photo-degradation rates for the two pollutants are approximately 120 and 200 times higher than those with bare ZnO, respectively. Moreover, the photocatalyst of (0.3:1) Bi2WO6/ZnO exhibits a higher transient photocurrent density of approximately 4.5 μA compared with those of bare Bi2WO6 and ZnO nanoparticles. The successful recombination of Bi2WO6 and ZnO enhances the photocatalytic activity and reduces the band gap energy of ZnO, which can be attributed to the effective separation of electron–hole pairs. Active species trapping experiments display that [O2]− is the major species involved during photocatalysis rather than •OH and h+. This study provides insight into designing a meaningful visible-light-driven photocatalyst for environmental remediation.