Transient Photocurrent Research Articles

Fabrication and Self-Assembly Behavior of BPEF and BBPEF Composite Langmuir-Blodgett Films with Photovoltaic Conversion Properties.

The LB films prepared through the Langmuir-Blodgett (LB) technique are of significant importance for the fabrication of functional films such as optoelectronic materials and sensors. In this study, 9,9-bis (4-(2-hydroxy-ethoxy) phenyl) fluorene (BPEF) and 9,9-bis [3-phenyl-4-(β-hydroxy-ethoxy) phenyl] fluorene (BBPEF) were combined with saffron T (ST), methylene blue (MB) and Rhodamine B (RhB) dyes by LB technique to prepare ordered composite films. The nanostructures and morphologies of the composite films were analyzed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). It was found that the films exhibited distinct aggregation morphologies. The UV-VIS absorption spectra showed that the concentration of dye molecules had a significant effect on the spectral characteristics. The contact Angle test shows that the prepared composite films are hydrophobic. The photovoltaic conversion performance of LB composite films was studied by transient photocurrent response experiments. It was found that BPEF/dye and BBPEF/dye composite films exhibited significant responses in photocurrent. In particular, BPEF/RhB and BBPEF/RhB composite films demonstrated excellent photoresponsive performance. This study used LB technology in combination with BPEF and BBPEF to demonstrate enhanced photocurrent and stable performance of LB film, which provided ideas for expanding the application range of materials.

Resolving the Trap Distribution of Chalcogenide-Based Heterojunctions via Optical Injection Deep Level Transient Spectroscopy.

Chalcogenide semiconductors have emerged as promising candidates for next-generation optoelectronics, mainly benefiting from their cost-effective processability, chemical versatility, and excellent stability. However, the device performance is limited by the complex defect characteristics, necessitating a detailed understanding of the defect density, types, and distribution. This study employs optical injection deep level transient spectroscopy to characterize the trap features of antimony bismuth sulfide-based heterojunctions. Photoexcitation offers the possibility to determine the spatial distribution of traps. It reveals distinct distributions of hole and electron traps. Short-wavelength light (570 nm) detects hole traps near the hole transport layer, while long-wavelength light (830 nm) identifies electron traps near the electron transport layer. Additional intermediate-wavelength tests (670 and 755 nm) and light field distribution simulation further elucidate the trap distribution. Transient absorption and transient photocurrent also support the non-uniform trap distribution within the chalcogenide-based photodiodes.

Preparation of Bi@Ho3+:TiO2/Composite Fiber Photocatalytic Materials and Hydrogen Production via Visible Light Decomposition of Water

Using electrospun nanofibers doped with TiO2 and rare-earth ion Ho3+ as the matrix, and sodium gluconate as the reducing agent, Bi(NO3)3 was reduced using hydrothermal technology to produce Bi@Ho3+:TiO2 composite fiber materials. The materials’ phase, morphology, and photoelectric properties were characterized using various analytical testing methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), and transient photocurrent (IP). During the hydrothermal process, it was confirmed that Bi3+ was reduced by sodium gluconate to form pure Bi nanoparticles, which combined with Ho3+:TiO2 nanofibers to form heterojunctions. By leveraging the surface plasmon resonance (SPR) effect of metallic Bi and the abundant energy level structure and 4f electron transition properties of rare-earth Ho3+, the TiO2 nanofibers underwent dual modification, effectively enhancing the photocatalytic activity and stability of TiO2. Under visible light irradiation, the rate of hydrogen production through water decomposition reached 43.6 μmol·g−1·h−1.

Synthesis of leek-based N,S self-doped CQDs/TiO2 and its application in the photocatalytic degradation of organic pollutants

In this work, N,S self-doped CQDs (N,S-CQDs/TiO2) were synthesized from leeks via a microwave method, and a new leek-based N,S-CQDs/TiO2 composite photocatalytic material was prepared by roasting. The structural characteristics, optical properties, and electrical properties of the N,S-CQDs/TiO2 composites were characterized by Scanning electron microscope (SEM), Transmission electron microscope (TEM), X-ray powder diffraction (XRD), Solid ultraviolet–visible diffuse reflectance (UV–vis-DRS), Fourier transform infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transient photocurrent response, and Electrochemical impedance spectroscopy (EIS). In addition, the catalytic degradation effect of N,S-CQDs/TiO2 was evaluated by the photocatalytic degradation of Rhodamine B (RhB) and ibuprofen (IBU). The experimental results showed that the photocatalytic degradation effect of leek-based N,S-CQDs/TiO2 was significantly better than that of TiO2, and N,S-CQDs/TiO2 with 1.86 wt% N,S-CQDs (1.86-N,S-CQDs/TiO2), which demonstrated optimal photocatalytic degradation. The photocatalytic degradation rate of RhB (20 mg/L) was 94.65 % within 120 min of high-voltage mercury lamp irradiation, which was 41.15 % higher than that of TiO2(53.50 %), and the degradation rate was 80.10 % after four cycles. After 180 min, the photocatalytic degradation rate of IBU (10 mg/L) was 96.92 %, which was 26.39 % higher than that of TiO2 (70.53 %), and the degradation rate could still reach 78.94 % after four cycles. In this work, the photocatalytic degradation mechanisms of RhB and IBU by N,S-CQDs/TiO2 were explored by free radical capture and ESR free radical detection experiments. This study may serve as an important reference for enhancing the photocatalytic degradation effect by using biomass self-doped CQDs/TiO2 composite photocatalytic materials, and as a reference for the photocatalytic treatment of organic pollutants in water.

Facilistic preparation of zinc oxide nanoarrays on nickel foam via a one-step chemical bath method for photocatalysis

One-dimensional ZnO nanoarrays (ZnO NAs) were prepared on nickel foam using a one-step chemical bath deposition method. SEM and XRD confirmed the successful preparation of ZnO nanoarrays. TEM and Raman spectroscopy confirmed the preferential orientation of the ZnO nanorods along the (002) crystal plane. The Ni/ZnO NAs composites exhibited excellent photocatalytic degradation activity for ciprofloxacin (CIP) under UV light. UV–visible diffuse reflectance and transient photocurrent response characterization revealed that compared with ZnO nanorod powder, the Ni/ZnO NA composites increased the light absorption and reduced the complexation rate of photogenerated electron-hole pairs, thus improving the photocatalytic efficiency. In addition, the electron work functions of the two substances were calculated by using the crystal faces of Ni (111) and ZnO (002), and the calculation results confirmed the electron transfer paths. Electron transfer pathways further confirmed the possible reaction mechanism of Ni/ZnO NA degradation of CIP. Finally, Mott–Schottky tests were used to investigate the structure of the energy bands of the material and reveal its photocatalytic mechanism.

(Invited) Parameter Prediction in Colloidal Quantum Dot Solar Cells Using Residual Neural Networks Trained on Experimental Data

Colloidal quantum dots (CQDs) are an attractive third-generation material for photovoltaics, especially as infrared materials for multi-junction solar cells. Characterization and materials parameter prediction both play a critical role in the rising efficiencies in this field. However, there are numerous materials properties that need to be measured in order to fully characterize a device, leading to high research costs and slow development times. Here, we leverage recent advancements in machine learning (ML), along with a recently-demonstrated multimodal spectral characterization method [1], to predict complex materials parameters in CQD solar cells from simple current density-voltage (JV) curves, using an algorithm trained on experimental data.[2]Past work ML prediction of materials properties has focused on using simulated data due to the difficulty in collecting enough experimental data to fully train an algorithm. While it is not feasible to fabricate thousands of devices in a typical research lab, it is possible to measure several thousand points on a single device. We used a micrometer-resolution 2D characterization method with millimeter-scale field of view to acquire enough training data using only a handful of devices, while learning the spatial relationships between materials parameters. Photoluminescence, trap state density, transient photovoltage, transient photocurrent, and carrier mobility were predicted (Figure 1) by five different residual neural networks, each using a ResNet block and containing over 300k learnable parameters. The design of the networks were based on the ResNet50 architecture [3]. We also implemented a novel neighborhood approach to reduce errors and account for spatial correlations in device behavior, leading to insights into transport mechanisms and correlation lengths in CQD thin films. This method could be used to study a wide range of material systems and devices, ultimately leading to a universal prediction model that greatly simplifies the characterization process for optoelectronic devices and accelerates development times.

Electro-photocatalyst effect of N-S-doped carbon dots and covalent organic triazine framework heterostructures for boosting photocatalytic degradation of phenanthrene in water

In the present study, we introduce a covalent organic triazine framework polymer (COTF-P) using 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) with triazine-based amine. The resulting dark red COTF-P illustrated potential behavior as a photocatalyst under visible light. Due to the inadequate solar energy capture and ultrafast charge recombination of the resulting COTF-P, the prepared COTF-P has been decorated with CQDs (N-CQD and N-S-CQD) to build a Z-scheme CQDs/COTF-P heterojunction photocatalyst and utilizes as photocatalyst for the breakdown of phenanthrene (PHE) exposed to visible light. The prepared COTF-P and CQDs/COTF-P were fully characterized, analyzing the textural (N2 isotherms), structural (XRD and FTIR), chemical (EDX and XPS), morphological (FESEM and TEM), optical (DRS-UV-Vis and photoluminescence), and electrochemical properties (EIS impedance, transient photocurrent, and flat band potential). The prepared N-S-CQD/COTF-P heterojunction displayed optimum activity for the photocatalytic oxidation of PHE from water, owing to an enhanced separation of the photogenerated charges and lower bandgap value, 2.1 vs. 1.9 eV. The N-S-CQD/COTF-P heterojunction showed acceptable stability in terms of activity and structural properties after 5 cycles of reuse. The mechanism of activation highlights the importance played by superoxide radicals and hydroxyl radicals. This project sheds light on the potential use of CQDs for the decoration of polymers, extending the absorbance in the visible region and boosting the migration of charge, which boosts the activity of the resulting material.

Photoactive Donor–Acceptor Covalent Organic Framework Material for Synergistic Cyclization Approach to Imidazole Derivatives

ABSTRACTAs one of the most potential platforms for heterogeneous catalysis, two‐dimensional porphyrin‐based covalent organic frameworks (COFs) have attracted great research interests. In this work, following the correlation of COF structure and their performance, a type of donor–acceptor 2D COF (Por‐COF‐Zn) based on porphyrin and thiophene units was designed and easily constructed by one‐pot method using 5,10,15,20‐tetra‐(4‐aminophenyl)porphyrin (TAPP), thieno[3,2‐b]thiophene‐2,5‐dicarbaldehyde, and zinc acetate. The as‐synthesized COF material is tested to show high crystallinity and good thermal and chemical stability. The Brunauer–Emmett–Teller (BET) measure results show that the specific surface area of Por‐COF‐Zn is 413.6 m2g−1, and the pore volume is 0.279 cm3g−1. Transient photocurrent response and EIS measurement also demonstrate that Por‐COF‐Zn exhibits an efficient separation of photogenerated electron/hole pairs. The photocatalytic performance of the resulted COF was further evaluated by using intramolecular cyclization of N‐phenyl‐o‐phenylenediamine and benzaldehyde to form benzimidazole derivative. The catalyst system exhibited good to high conversion efficiency, moderate substrate applicability, and excellent stability and recyclability for the catalytic cyclization approach of benzimidazoles. The catalytic mechanism should be contributed to the synergistic effect of organic framework and metallic zinc. Our current work also provides valuable information for understanding COF‐based photocatalytic systems and further highlight new insights to meet new challenges of heterogeneous photocatalysis.

Vanadium as a Ti-like mediator boosting electronic transmission in Fe-based MOFs for photocatalytic sterilization

Efficient metal–organic frameworks (MOFs) photocatalytic bactericidal catalysts are urgently needed in water purification. Herein, a Fe-MOF (MIL-88B-NH2(V1Fe5) with promoted electron transport was achieved by vanadium (V) ions doping and V/Fe ratio optimization, showing excellent photocatalytic bactericidal activity against E. coli under visible light irradiation (99.92%). The efficient antibacterial mechanism, V as a Ti-like mediator boosting electronic transmission in MIL-88B-NH2(V1Fe5), was revealed by its band structure, transient photocurrent, electrochemical impedance spectroscopy, and scavenger quenching experiments. The enhancement of photocatalytic bactericidal performance of Fe-MOFs by V–ion-doping was confirmed by two other Fe-MOFs, MIL-53-NH2(V1Fe5) and MIL-101-NH2(V1Fe5), with the same metal ions and ligands, both of which have higher performance than the corresponding undoped MOFs. Among them, MIL-88B-NH2(V1Fe5) exhibits the highest photocatalytic bactericidal activity due to its suitable metal clusters ([M(μ 3-O)] cluster) and topological structure (three-dimensional rhomboid network structure). This work demonstrated the amplification effect of V ion doping on electron transport in Fe-MOFs photocatalysts.

Physics-Based Artificial Neural Network Assisting in Extracting Transient Properties of Extrinsically Triggering Photoconductive Semiconductor Switches.

In this paper, a physics-based ANN assisting method for extracting transient properties of extrinsically triggering photoconductive semiconductor switches (ET-PCSSs) is proposed. It exploits the nonlinear mapping of ANN between transient current (input) and doping concentration (output). According to the basic laws of photoelectric device operating, two types of ANN models are constructed by gaussian and polynomial fitting. The mean absolute error (MAE) of forecasting transient photocurrent can be less than 10 A under low triggering optical powers, which verifies the feasibility of ANN assisting TCAD applied to PCSSs. The results are comparable to computation by Mixed-Mode simulation, yet even thousands of seconds of CPU runtime cost are saved in every period. To improve the robustness of the Poly-ANN predictor, Bayesian optimization (BO) is implemented for minimizing the curl deviation of photocurrent-time curves.

Room-temperature electrodeposition of Cu2O layers and its low-temperature annealing for photoelectrochemical water splitting applications

Cuprous oxide layers were obtained on a conductive glass substrate via room-temperature electrochemical deposition from the electrolyte containing 0.4 M CuSO4, 3 M lactic acid (pH = 12) at −0.5 V vs. SCE for various durations (from 0.25 to 3 h). Physicochemical properties of as-received FTO/Cu2O materials were characterized using SEM, PXRD, and UV–Vis DRS. The photoelectrochemical (PEC) properties of the obtained electrodes were evaluated in detail by analyzing the influence of the energy of monochromatic radiation, and the applied polarization on the resulting photocurrent transients. It was found that Cu2O crystals are getting bigger and sharper with prolonged electrosynthesis duration and a slight decrease in the band gap energy from 2.4 to 2.1 eV with increasing deposition duration was observed. Moreover, this trend was also reflected in PEC properties of resulted material, higher photocurrents were generated by the material deposited for 3 h. More importantly, this PEC response was enhanced by low-temperature (100 °C, 200 °C) annealing. Thermal treatment at 100 °C led to a noticeable improvement in the photoactivity of the samples. Further increasing post-treatment temperature to 200 °C resulted in a further six-fold increase in photocurrents. Finally, the calculated values of accumulated and dissipated charges indicated significantly lower surface recombination after thermal treatment.

Visible Light-Driven Photocatalytic CH4 Production from an Acetic Acid Solution with Cetyltrimethylammonium Bromide-Assisted ZnIn2S4

Photocatalytic methods have been popular in energy production and environmental remediation. Designing high-efficiency photocatalysts is still challenging in converting solar energy into chemical fuels. Herein, a series of surfactant-assisted ZnIn2S4 (ZIS) photocatalysts were synthesized by utilizing the one-pot hydrothermal method. Photocatalytic methane production from an acetic acid solution was carried out under LED light (450 nm) irradiation, and the evolved gas was analyzed by the GC-FID system. Reaction factors (surfactant amount, catalyst dose, reaction temperature, substrate concentration, and reaction pH) were optimized for photocatalytic production. With the increase in cetyltrimethylammonium bromide (CTAB) amount, CH4 production gradually increased. The ZIS-3.75 photocatalyst exhibited the highest photocatalytic CH4 production rate (0.102 µmol g−1·h−1), which was approximately 1.8 times better than that of pure ZIS (0.058 µmol g−1·h−1). The presence of CTAB reduced the charge transfer resistance and improved photocurrent response efficiency. Structure and morphology were characterized by XRD, FTIR, SEM, TEM, and N2 adsorption–desorption isotherm analysis. Optical properties were investigated by UV-DRS and PL spectroscopic techniques. The electrochemical evaluation was measured through EIS, Mott–Schottky, and transient photocurrent response analysis. The CTAB-modified catalyst showed excellent stability and reusability, even after five irradiation cycles. Methane production was enhanced by lowering the photogenerated charge transfer resistance and boosting the dispersion of ZIS-3.75 under visible light (450 nm) irradiation.

Anchoring Cu2O onto WO3 by adsorption-ascorbic acid reduction: A p-n junction with improved photocatalytic and photoelectrochemical properties

Tungsten trioxide is a promising photoelectric material owing to its abundant structures and unique properties, but the serious photogenerated charge recombination limits its photocatalytic and photoelectrochemical performance. Herein, 0D Cu2O was anchored onto 3D WO3 in-situ via a facile adsorption-ascorbic acid reduction method at room temperature. The coupling of WO3 with Cu2O produces improved charge separation efficiency, thereby the photocatalytic degradation rate and transient photocurrent of optimal WO3/Cu2O are 2.7 and 1.6 times higher than those of WO3, respectively. The enhanced performance is ascribed to the formation of a p-n heterojunction, which was demonstrated by experimental characterizations and theoretical calculation.

Preparation and performance of g-C3N4/g-C3N5 homojunction photocatalyst activated peroxymonosulfate for ceftriaxone sodium degradation

As the overuse of antibiotics increasingly contaminates the environment, one of modern chemistry's objectives is to identify high-performance photocatalytic materials to degrade antibiotics. This study initially utilized NH4Cl as a gas template to synthesize porous lamellar g-C3N4 (CNS) through a high-temperature calcination process. Building upon this, a homojunction catalyst, CNS/g-C3N5 (S-CN), was developed via a secondary sintering technique using different amount of 3-amino-1,2,4-triazole addition to evaluate its efficacy in activating peroxymonosulfate (PMS) for degrading the antibiotic ceftriaxone sodium. Under neutral conditions, the photocatalytic system composed of S-CN catalysts prepared by 50 mg of 3-amino-1,2,4-triazole addition and PMS (S3-CN/PMS) exhibited degradation rates that were 3.37 and 8.11 times higher than those of the CNS/PMS and g-C3N5/PMS, respectively. At a pH of 8, the S3-CN/PMS system attained a 99.7 % degradation efficiency within 75 min. Based on results from UV–visible diffuse reflectance spectroscopy (DRS), transient photocurrent response, electrochemical impedance spectroscopy (EIS), photoluminescence spectroscopy and radical scavenging experiments, this high efficiency is attributed to a homojunction Z-type charge transfer mechanism that enhances the separation of photogenerated carriers. Furthermore, the study found that the optimal PMS addition was 20 mg and the optimal pH was 8. Chloride ions promoted the reaction, while other ions decreased the reaction rate. In conclusion, this paper provides valuable insights for the morphological modification of carbon nitride homojunction materials and the efficient activation of PMS for pollutant degradation.

In2S3-modified ZnIn2S4 enhanced photogenerated carrier separation efficiency and photocatalytic hydrogen evolution under visible light

ZnIn2S4 (ZIS) has limited photocatalytic hydrogen production due to low visible light utilisation and insufficient separation efficiency of photogenerated carriers. This study utilized a simple hydrothermal method to prepare In2S3/ZnIn2S4 (INS/ZIS) heterojunctions. The addition of In2S3 (INS) improves the separation and movement of photogenerated charges, and makes better use of visible light. The material was analysed using SEM, TEM, XRD, XPS and photoelectrochemical tests. Results from the transient photocurrent (TPR) and photoluminescence (PL) experiments show a photocurrent density of approximately 1.8 μA/cm2, which is 3 times greater than the ZIS (0.6 μA/cm2) density, when the INS mass is 5 %. And at this time, INS/ZIS boasts the most effective photogenerated carrier separation. The hydrogen photocatalytic generation test results showed that the photocatalytic hydrogen production rate of 5-INS/ZIS (5690 μmol/g/h) was 8.4 and 66.9 times higher than that of pure ZIS (710 μmol/g/h) and INS (89 μmol/g/h), respectively. The enhanced activity is due to the creation of type II heterojunctions, which improve the separation and transfer of light-generated charges. The research presents an innovative approach to creating composites based on ZIS.

In situ loading of Ag2MoO4 nanoparticles onto oxygen-doped porous g-C3N4 for enhanced photocatalytic H2 evolution

Photogenerated carriers transfer and separation from the substance itself to produce spatial isolated electron-hole pairs is crucial for the utilization of composite photocatalysts in the field of photocatalytic hydrogen (H2) evolution. Herein, novel oxygen-doped porous graphitic carbon nitride (g-C3N4) micro-sheets decorated with Ag2MoO4 have been fabricated by a facile calcination method followed by in situ deposition strategy. The physicochemical properties of the obtained Ag2MoO4/OC3N4 composites were characterized via SEM, TEM, EDS, XRD, N2 adsorption-desorption, XPS, UV–vis DRS, PL, transient photocurrent response, and EIS, as well as DFT calculation. In addition, the effects of Ag2MoO4 content, type of scavengers, pH value of reaction solution and dosage of scavenger on photocatalytic H2 production were investigated. The results show that the modification of ammonium acetate thermal polymerization with urea could enhance the porosity of g-C3N4 and its specific surface area. The Ag2MoO4 nanoparticles are highly dispersed on the OC3N4 surface, reducing the charge transfer resistance at their interfaces. The OC3N4 photocatalyst achieves H2 yield of 8629.11 μmol/g over 2 h, which is about 1.46 times higher than that of C3N4. The H2 production amount over the optimal Ag2MoO4/OC3N4 composite photocatalyst (50 mg) is further enhanced to 16619 μmol/g, which is 1.93 and 180 times higher than that of OC3N4 and Ag2MoO4, respectively. The S-scheme charge transfer mechanism of Ag2MoO4/OC3N4 is proposed based on the DFT calculation. This work provides a facile and easy strategy to develop g–C3N4–based photocatalysts through adjusting chemical composition and photocatalytic properties.

Preparation of SnOx/N-GQDs composites with oxygen-rich vacancies for enhanced photoelectric properties

SnOx with oxygen-rich vacancies and SnOx/N-GQDs (Nitrogen-doped graphene quantum dots) composites were prepared by high temperature annealing and hydrothermal method, respectively. The annealing process introduced a large number of oxygen vacancies and produced defect energy levels in the band gap. The existence of the defect level effectively reduced the band gap of SnOx, enlarged the optical absorption range, and improved the light utilization. The introduction of N-GQDs also improved the carrier density and electron transport rate, and extended the carrier lifetime (τ = 7.44 ms). I-T (Transient photocurrent response) analysis results showed that when the mass ratio of Sn/SnO2 was 1:4 and N-GQDs doping content was 1 wt%, the transient photocurrent response of SnOx/N-GQDs could reach 5.51 × 10−4 A/cm2, which was 25 times higher than that of pure SnO2, and the photocurrent response value maintained 80.1 % within 500 s. EIS (Electrochemical impedance) and M-S (Mott-Schottky) analyses indicated that the appropriate amount of oxygen vacancies and N-GQDs were beneficial to reducing the charge transport resistance, inhibiting the electron-hole pair recombination, and increasing the carrier density of SnOx. The results show that SnOx/N-GQDs composites present the improved photoelectric properties with the addition of oxygen vacancies and N-GQDs, which provides a new idea for promoting the properties of semiconductors.

Electrocoagulation-photocatalysis sequential combined method for the removal of anticancer drugs from pharmaceutical wastewater using NH2-MIL-125(Ti)/cobalt ferrite nanorods composite photocatalyst

This research reports that the novel NH2-MIL-125(Ti)/cobalt ferrite nanorods composite photocatalyst based on metal-organic framework (MOF) has been synthesized by the microwave heating method. Herein, the sequential electrocoagulation (EC)-photocatalysis combination method was used to remove the chemical oxygen demand (COD), doxorubicin hydrochloride (DOX), and 5-Fluorouracil (5-FU) antineoplastic drugs from wastewater by the composite photocatalyst under a simulated sunlight irradiation. The synthesized photocatalysts were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Brauner-Emmet-Teller surface area analyzer, vibrating sample magnetometer, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, transient photocurrent response, and electrochemical impedance spectroscopy. In the EC process, three-level, three-factor Box-Behnken design was used to investigate the interaction effects of pH (3−8), time (10–60 min), and current density (100–200 A/m2) on the removal of contaminants. The maximum experimental removal efficiencies of COD, DOX, and 5-FU were 68.2 %, 21.1 %, and 24.5 %, respectively, under EC time of 60 min, pH of 5.98, and current density of 176.77 A/m2. About 99.2 % COD, 93.8 % DOX, and 97.0 % 5-FU were removed from pharmaceutical wastewater using NH2-MIL-125(Ti)/ cobalt ferrite nanorods photocatalyst under cobalt ferrite content of 0.288 g, reaction time of 58.48 min, pH of 7.54, and catalyst dosage of 0.5 g/L. The obtained results demonstrated that the combined process of EC and photocatalysis in the presence of MOFs-based photocatalysts is an effective treat strategy for the pharmaceutical wastewater.

Two new selenidostannates TM-Sn-Se (TM = transition metal) photoelectrocatalytic materials

In recent decades, chalcogenides have appealed extensive attention due to potential applications in photoelectric materials. Two selenidostannates, [Fe1.11Zn0.89(en)3]2Sn2Se6 (1, en = ethylenediamine) and [Co1.24Zn0.76(en)3]2Sn2Se6 (2) were synthesized by solvothermal method with ethylenediamine and ethylene glycol as the solvents, both consisting of complexes in which the two different transition metals occupied the same position and [Sn2Se6]4− anions. Transition metal complexes (TMCs) can combine photoelectric properties with inorganic skeletons to extend their compound properties. Therefore, we investigated the photocurrent response of both compounds and found higher transient photocurrent densities. The band gaps of compounds 1 and 2 were calculated to be 2.31 eV and 2.17 eV, respectively, indicating that two compounds have potential semiconductor properties. In addition, we also studied the photodegradation efficiency of compounds 1 and 2 and found that the degradation efficiency of two compounds could be achieved 84.5 % and 55.9 %, which indicated that the compounds have excellent photocatalytic properties. The field of photoelectrocatalytic research on selenidostannates is broadened.

Hydrogel composites based on chitosan and CuAuTiO2 photocatalysts for hydrogen production under simulated sunlight irradiation

This study explored the photocatalytic hydrogen evolution reaction (HER) using novel biohydrogel composites comprising chitosan, and a photocatalyst consisting in TiO2 P25 decorated with Au and/or Cu mono- and bimetallic nanoparticles (NPs) to boost its optical and catalytic properties. Low loads of Cu and Au (1 mol%) were incorporated onto TiO2 via a green photodeposition methodology. Characterization techniques confirmed the incorporation of decoration metals as well as improvements in the light absorption properties in the visible light interval (λ > 390 nm) and electron transfer capability of the semiconductors. Thereafter, Au and/or Cu NP-supported TiO2 were incorporated into chitosan-based physically crosslinked hydrogels revealing significant interactions between chitosan functional groups (hydroxyls, amines and amides) with the NPs to ensure its encapsulation. These materials were evaluated as photocatalysts for the HER using water and methanol mixtures under simulated sunlight and visible light irradiation. Sample CuAuTiO2/ChTPP exhibited a maximum hydrogen generation of 1790 μmol g−1 h−1 under simulated sunlight irradiation, almost 12-folds higher compared with TiO2/ChTPP. Also, the nanocomposites revealed a similar tendency under visible light with a maximum hydrogen production of 590 μmol g−1 h−1. These results agree with the efficiency of photoinduced charge separation revealed by transient photocurrent and EIS.