Photocorrosion Inhibition of Semiconductor-Based Photocatalysts: Basic Principle, Current Development, and Future Perspective

Graphene Oxide Coated Zinc Oxide Core–Shell Nanofibers for Enhanced Photocatalytic Performance and Durability

Recently, heterogeneous structured semiconductor photocatalysts have received significant interest in promoting global cleaning from the environmental pollution. Herein, we report the synthesis of graphene oxide (GO) wrapped zinc oxide (ZnO) core–shell nanofibers (ZnO@G CSNFs) by the simple core–shell electrospinning and subsequent annealing for efficient photocatalytic performance and stability. The heterostructured catalyst consisted of ZnO forming an enclosed core part while the GO was positioned on the surface, serving as a protective shell. Field emission scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction were used to confirm the synthesis of the desired product. Enhanced photocatalytic activity ZnO@G CSNFs was found compared to the corresponding ZnO NFs. Similarly, incorporation of GO into the ZnO nanofiber in a core–shell format significantly suppressed the photocorrosion. This study highlights the usefulness of using GO as the coating material to boost the photocatalytic performance of ZnO-based photocatalysts.

Manganese-Doped Zinc Oxide Nanostructures as Potential Scaffold for Photocatalytic and Fluorescence Sensing Applications

Herein, we report the photocatalytic and fluorescence sensing applications of manganese-doped zinc oxide nanostructures synthesized by a solution combustion technique, using zinc nitrate as an oxidizer and urea as a fuel. The synthesized Mn-doped ZnO nanostructures have been analyzed in terms of their surface morphology, phase composition, elemental analysis, and optical properties with the help of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and UV-Visible (UV-Vis) spectroscopy. A careful observation of the SEM micrograph reveals that the synthesized material was porous and grown in very high density. Due to a well-defined porous structure, the Mn-doped ZnO nanostructures can be used for the detection of ciprofloxacin, which was found to exhibit a significantly low limit of detection (LOD) value i.e., 10.05 µM. The synthesized Mn-doped ZnO nanostructures have been further analyzed for interfering studies, which reveals that the synthesized sensor material possesses very good selectivity toward ciprofloxacin, as it detects selectively even in the presence of other molecules. The synthesized Mn-doped ZnO nanostructures have been further analyzed for the photodegradation of methyl orange (MO) dye. The experimental results reveal that Mn-doped ZnO behaves as an efficient photocatalyst. The 85% degradation of MO has been achieved in 75 min using 0.15 g of Mn-doped ZnO nanostructures. The observed results clearly confirmed that the synthesized Mn-dopedZnO nanostructures are a potential scaffold for the fabrication of sensitive and robust chemical sensors as well as an efficient photocatalyst.

A novel green approach based on ZnO nanoparticles and polysaccharides for photocatalytic performance

Novel green photocatalysts based on ZnO in the presence of arabic gum (AGZ) or karaya gum (KGZ) were synthesized by a sol-gel method for photocatalytic performance. The materials were characterized by XRD, FTIR spectroscopy, SEM, nitrogen adsorption/desorption, and PL and diffuse reflectance spectroscopy. Photocatalytic test was performed using methylene blue (MB) dye as the target pollutant under visible light. The reuse of photocatalysts and Artemia saline bioassays were investigated. The ZnO nanoparticles showed a hexagonal structure and the values of the band gaps were 2.95 (AGZ) and 2.98 eV (KGZ). The PL results demonstrated emission bands at 440, 473 or 478 and 549 nm. The textural properties indicated the presence of typically mesoporous materials. The MB discoloration efficiency was 81.5% and 91.0% for AGZ and KGZ, respectively. The photocatalytic activity of AGZ and KGZ was maintained after the third run. The ˙OH radicals are the main species involved in the MB discoloration. The MB discoloration from the photocatalysts showed no toxicity; therefore, they are considered to be promising materials for the degradation of the dye in the photocatalytic process.

Visible-Light Photocatalysts and Their Perspectives for Building Photocatalytic Membrane Reactors for Various Liquid Phase Chemical Conversions

Photocatalytic organic synthesis/conversions and water treatment under visible light are a challenging task to use renewable energy in chemical transformations. In this review a brief overview on the mainly employed visible light photocatalysts and a discussion on the problems and advantages of Vis-light versus UV-light irradiation is reported. Visible light photocatalysts in the photocatalytic conversion of CO2, conversion of acetophenone to phenylethanol, hydrogenation of nitro compounds, oxidation of cyclohexane, synthesis of vanillin and phenol, as well as hydrogen production and water treatment are discussed. Some applications of these photocatalysts in photocatalytic membrane reactors (PMRs) for carrying out organic synthesis, conversion and/or degradation of organic pollutants are reported. The described cases show that PMRs represent a promising green technology that could shift on applications of industrial interest using visible light (from Sun) active photocatalysts.

Controllable growth of MoS2 nanosheets on TiO2 burst nanotubes and their photocatalytic activity

MoS2 nanosheets were grown on TiO2 nanotubes by the simple hydrothermal method for the first time. The layer-by-layer growth of MoS2 nanosheets led to a significant increase in the specific surface area of TiO2/MoS2 burst tube composites compared with TiO2 burst tubes, a significantly enhanced ability to separate photo-induced carriers, and synergistic adsorption and visible light catalytic activity of dye molecules. The maximum adsorption (q max) of MB was 72.46 mg g-1. In addition, 94.1% of MB could be degraded after 30 minutes of visible light irradiation. The microsurface morphology, structure, chemical composition, element valence and band width of TiO2/MoS2 nanocomposites were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The mechanism of photocatalytic reaction was studied via free radical capture experiments.

A novel application of In2S3 for visible-light-driven photocatalytic inactivation of bacteria: Kinetics, stability, toxicity and mechanism

Photocatalytic bacterial inactivation under visible light emerges as a new alternative to control microbial contamination by utilizing free and renewable sunlight. However, the exploration of highly effective and safe visible-light-driven (VLD) photocatalysts remains an important step toward accessing this new technology. Herein, an eco-friendly photocatalyst, namely Indium Sulfide (In₂S₃), was fabricated through a facile hydrothermal method for VLD photocatalytic inactivation of bacteria. The energy band gap of the as-prepared In₂S₃ was measured as 2.25 eV. As expected, the obtained In₂S₃ photocatalyst showed remarkable inactivation efficiency toward E. coli under fluorescent tubes irradiation. The photocatalytic inactivation kinetic was perfectly fitted by a mathematical model for bacteria inactivation. In addition, In₂S₃ exhibited high stability and could be reused. The leakage of In³⁺ was not significant and showed no toxic effect to the bacteria. Based on the results of scavenger study and ESR technology, the dominant reactive species causing In₂S₃ VLD photocatalytic bacterial inactivation were proposed as O₂^-, h⁺, H₂O₂ and e^-, rather than OH. The SEM study suggested that the damages to the intracellular components occurred prior to the destruction of cell wall. This study provides novel application of In₂S₃ for VLD photocatalytic inactivation of bacteria as well as comprehensive insight into the inactivation mechanism.

Suppressing the Radiation-Induced Corrosion of Bismuth Nanoparticles for Enhanced Synergistic Cancer Radiophototherapy

The level of tumor killing by bismuth nanoparticles (BiNPs) as radiosensitizers depends strongly on the powerful particle-matter interaction. However, this same radiation leads to the structural damage in BiNPs, consequently weakening their specific physicochemical properties for radiosensitization. Herein, we studied the radiation-induced corrosion behavior of BiNPs and demonstrated that these damages were manifested by the change in their morphology and crystal structure as well as self-oxidation at their surface. Furthermore, artificial heterostructures were created with graphene nanosheets to greatly suppress the radiation-induced corrosion in BiNPs and enhance their radiocatalytic activity for radiotherapy enhancement. Such a nanocomposite allows the accumulation of overexpressed glutathione, a natural hole scavenger, at the reaction interfaces. This enables the rapid removal of radiogenerated holes from the surface of BiNPs and minimizes the self-radiooxidation, therefore resulting in an efficient suppression of radiation corrosion and a decrease of the depletion of reactive oxygen species (ROS). Meanwhile, the radioexcited conduction band electrons react with the high-level H₂O₂ within cancer cells to yield more ROS, and the secondary electrons are trapped by H₂O molecules to produce hydrated electrons capable of reducing a highly oxidized species such as cytochrome c. These radiochemical reactions together with hyperthermia can regulate the tumor microenvironment and accelerate the onset of cellular redox disequilibrium, mitochondrial dysfunction, and DNA damage, finally triggering tumor apoptosis and death. The current work will shed light on radiosensitizers with an enhanced corrosion resistance for controllable and synergistic radio-phototherapeutics.

Functional Supported ZnO/Bi2MoO6 Heterojunction Photocatalysts with 3D-Printed Fractal Polymer Substrates and Produced by Innovative Plasma-Based Immobilization Methods

Inorganic photocatalysts became an essential and powerful tool for the remediation of polluted water. However, important limitations of photocatalysts in their colloidal form, especially nanosized, remain. For instance, their separation from water after use and recovery, which can be particularly demanding, time- and energy-wise. Considering such aspects, supported catalysts bear significant advantages. However, efforts still have to be made to develop processes that allow the permanent and efficient immobilization of inorganic photocatalysts in sustainable conditions, in order to maintain the advantages of supported catalysts over colloidal ones. Herein, we report the use of an aqueous-phase plasma-aided grafting (APPAG) process to produce functional and efficient hybrid photocatalysts. More specifically, based on cold plasma discharge (CPD), ZnO/Bi₂MoO₆ heterojunctions were permanently immobilized on polymer supports generated by 3D-printing, with fractal-inspired designs. Three different approaches of the APPAG process have been successfully used for the immobilization of the inorganic phase, that is core-shell-assisted direct grafting, indirect grafting and in situ complexation-assisted precipitation (ISCAP). Noticeably, the latter technique has never been reported before to our knowledge. These three immobilization routes rely on different strategies and yield to distinct morphological specificities, but all allow using mild synthesis conditions and producing stable, active, permanently immobilized coatings of photocatalysts. Regarding the preparation of the organic supports, two sorts of additive manufacturing (AM) technologies were employed, namely fused-deposition modeling (FDM) and liquid crystal diode (LCD)-based SLA (stereolithography). The use of fractal geometries combined with AM permits the production of supports with relatively high surface areas, in a single processing step. Overall, the three plasma-based immobilization methods revealed to be efficient and the performance of the different hybrid photocatalysts have later been assessed through the photodegradation of Rhodamine B dye under simulated sunlight irradiation and visible light only, with promising results.

Tailored Coupling of Biomineralized CdS Quantum Dots to rGO to Realize Ambient Aqueous Synthesis of a High-Performance Hydrogen Evolution Photocatalyst

Nanocomposite photocatalysts offer a promising route to efficient and clean hydrogen production. However, the multistep, high-temperature, solvent-based syntheses typically utilized to prepare these photocatalysts can limit their scalability and sustainability. Biosynthetic routes to produce functional nanomaterials occur at room temperature and in aqueous conditions, but typically do not produce high-performance materials. We have developed a method to produce a highly efficient hydrogen evolution photocatalyst consisting of CdS quantum dots (QDs) supported on reduced graphene oxide (rGO) via enzyme-based syntheses combined with tuned ligand exchange-mediated self-assembly. All preparation steps are carried out in an aqueous environment at ambient temperature. Size-controlled CdS QDs and rGO are prepared through enzyme-mediated turnover of l-cysteine to HS^- in aqueous solutions of Cd-acetate and graphene oxide, respectively. Exchange of cysteamine for the native l-cysteine ligand capping the CdS QDs drives self-assembly of the now positively charged cysteamine-capped CdS (CdS/CA) onto negatively charged rGO. The use of this short linker molecule additionally enables efficient charge transfer from CdS to rGO, increasing exciton lifetime and, subsequently, photocatalytic activity. The visible-light hydrogen evolution rate of the resulting CdS/CA/rGO photocatalyst is 3300 μmol h^-1 g^-1. This represents, to our knowledge, one of the highest reported rates for a CdS/rGO nanocomposite photocatalyst, irrespective of the synthesis method.

Rational Design of W-Doped Ag3PO4 as an Efficient Antibacterial Agent and Photocatalyst for Organic Pollutant Degradation

Bacterial and organic pollutants are major problems with potential adverse impacts on human health and the environment. A promising strategy to alleviate these impacts consists in designing innovative photocatalysts with a wider spectrum of application. In this paper, we report the improved photocatalytic and antibacterial activities of chemically precipitated Ag3PO4 microcrystals by the incorporation of W at doping levels 0.5, 1, and 2 mol %. The presence of W directly influences the crystallization of Ag3PO4, affecting the morphology, particle size, and surface area of the microcrystals. Also, the characterization via experimental and theoretical approaches evidenced a high density of disordered [AgO4], [PO4], and [WO4] structural clusters due to the substitution of P5+ by W6+ into the Ag3PO4 lattice. This leads to new defect-related energy states, which decreases the band gap energy of the materials (from 2.27 to 2.04 eV) and delays the recombination of e'-h• pairs, leading to an enhanced degradation process. As a result of such behaviors, W-doped Ag3PO4 (Ag3PO4:W) is a better visible-light photocatalyst than Ag3PO4, demonstrated here by the photodegradation of potential environmental pollutants. The degradation of rhodamine B dye was 100% in 4 min for Ag3PO4:W 1%, and for Ag3PO4, the obtained result was 90% of degradation in 15 min of reaction. Ag3PO4:W 1% allowed the total degradation of cephalexin antibiotic in only 4 min, whereas pure Ag3PO4 took 20 min to achieve the same result. For the degradation of imidacloprid insecticide, Ag3PO4:W 1% allowed 90% of degradation, whereas Ag3PO4 allowed 40%, both in 20 min of reaction. Moreover, the presence of W-dopant results in a 16-fold improvement of bactericidal performance against methicillin-resistant Staphylococcus aureus. The outstanding results using the Ag3PO4:W material demonstrated its potential multifunctionality for the control of organic pollutants and bacteria in environmental applications.

Anomalous Photoinduced Reconstructing and Dark Self-Healing Processes on Bi2O2S Nanoplates

We report an anomalous photoinduced reconstructing and dark self-healing process on Bi₂O₂S nanoplates by monitoring the time profile of open-circuit potential (OCP). When the light was switched on and off on the nanoplates, we observed pronounced and repeatable decrement-recovery cycles of the OCP signal, which are inexplicable by a rapid electron-hole separation-recombination process only as in a conventional semiconductor. It is proposed that upon irradiation, accumulation of photogenerated holes at the electrode surface caused oxidation of the S layers of Bi₂O₂S nanoplates into certain intermediates, which, when the light was turned off, were then reduced back to the original state by the electron back flow. Raman scattering spectroscopy provided te S-S vibrational signature of the intermediate, evidencing the hole oxidative dimerization of the S^2- species and the inverse reductive S-S dissociation process. The photophysics and photochemistry of semiconductor nanoplates reported here may inspire the development of energy devices, switches, and memristors.

A novel p-n Mn0.2Cd0.8S/NiWO4 heterojunction for highly efficient photocatalytic H2 production

Constructing a p-n heterojunction has been regarded as an effective way to restrain charge recombination and boost photocatalytic H2 production activity. Herein, a novel Mn0.2Cd0.8S/NiWO4 composite was fabricated by a hydrothermal process and which exhibited enhanced H2 production activity and excellent photostability. Particularly, the composite with 30 wt% of NiWO4 achieved the optimal H2 production rate of 17.76 mmol g-1 h-1, which was 2.9 times higher than that of Mn0.2Cd0.8S. The increased H2 production property was mainly due to the p-n heterojunction between Mn0.2Cd0.8S and NiWO4, which provided an efficient path for charge transfer and inhibited the photocorrosion of Mn0.2Cd0.8S. This work can offer technical support for the design and development of p-n heterojunctions that can be applied for photocatalytic H2 production.

Pt Deposites on TiO2 for Photocatalytic H2 Evolution: Pt Is Not Only the Cocatalyst, but Also the Defect Repair Agent

Pt, as a common cocatalyst, has been widely used in photocatalytic H2 evolution. However, the specific role of Pt in photocatalytic H2 evolution has not been thoroughly studied. In this paper, by employing three Pt sources with different charges (positive, negative and neutral), we systematically studied the charge effect of Pt sources on photocatalytic H2 evolution via TiO2 catalyst. According to the results of Raman, X-ray photoelectron spectroscopy (XPS), recycle experiments and photocurrent characterizations, it was found that TiO2 would produce electropositive defects during photocatalytic H2 evolution, inevitably leading to the decline of H2 production activity. Thanks to the electrostatic interaction, the electronegative Pt source not only promoted charge separation, but preferential deposited on electropositive defects, which acted as the defect repair agent, and thus resulted in the increased photocatalytic stability. This work may provide a new perspective for enhancing photocatalytic stability of hydrogen production.

Complementary behavior of doping and loading in Ag/C-ZnTa2O6 for efficient visible-light photocatalytic redox towards broad wastewater remediation

This work reports on the simple fabrication of a silver loaded and carbon doped zinc tantalate (Ag/C-ZnTa₂O₆) photocatalyst with visible light photocatalytic activity toward broad wastewater remediation, including high photo-reduction of Cr(vi) (98.4% in 210 min), excellent photo-oxidation of tetracycline hydrochloride (94.7% in 210 min), and superior photo-degradation of multiple dyes (>99.0% within 210 min). The optimal photocatalytic performance of Ag/C-ZnTa₂O₆ is mainly due to the excellent visible light absorption capacity and superior electron-hole separation efficiency, which is ascribed to the complementary behavior between carbon doping and silver loading. Particularly, the generation of defects due to C-doping is greatly inhibited by Ag-loading, and the SPR effect of Ag nanoparticles is enhanced due to the obstruction of Ag⁺ by C doping.

Kinetics of TiO2 photochromic response in different hole scavenging solvents

There has recently been a renewed interest in the photochromic properties and uses of TiO₂ as a potential candidate for smart windows. However, the surrounding medium of TiO₂ nanoparticles (NPs) is of equal importance, as it facilitates hole scavenging and, in turn, photochromism. Here, we investigated the impact of scavenging power on the photochromic properties of TiO₂. TiO₂ NP colloids in these solvents exhibit a photochromic response in a broad wavelength range from the visible to near-infrared region. We have shown that solvents such as ethanol have the best hole scavenging properties among the alcohols tested. The response can be further modified by the addition of a supplementary hole scavenger, such as hydroxylamine. The photochromism of TiO₂ is fully reversible and could be used for applications in smart windows.

A poly(3,4-propylenedioxythiophene)/carbon micro-sphere-bismuth nanoflake composite and multifunctional Co-doped graphene for a benchmark photo-supercapacitor

Efficient storage of sunlight in the form of charge is accomplished by designing and implementing a photo-supercapacitor (PSC) with a novel, cost-effective architecture. Sulfur (S)- and nitrogen (N)-doped graphene particles (SNGPs) are incorporated in a TiO2/CdS photoanode. The beneficial effects of SNGPs such as the high electrical conductance promoting fast electron transfer to TiO2, a suitably positioned conduction band that maximizes charge separation, and its' ability to absorb red photons translate into a power conversion efficiency of 9.4%, for the champion cell. A new composite of poly(3,4-propylenedioxythiophene)/carbon micro-sphere-bismuth nanoflakes (PProDOT/CMS-BiNF) is integrated with the photoanode to yield the PSC. The photocurrent produced under 1 sun irradiance is directed to the supercapacitor, wherein, the synergy between the faradaic and electrical double layer charge accumulation mechanisms of PProDOT and CMS-BiNF bestows storage parameters of an areal capacitance of 104.6 mF cm-2, and energy and power densities of 9 μW h cm-2 and 0.026 mW cm-2. An overall photo-conversion and storage efficiency of 6.8% and an energy storage efficiency of 72% exhibited by the PSC are much superior to those delivered by a majority of the PSCs reported in the literature on the otherwise highly efficient perovskite solar cell or the expensive Ru dye based solar cells.

Amorphous TiO2 as a multifunctional interlayer for boosting the efficiency and stability of the CdS/cobaloxime hybrid system for photocatalytic hydrogen production

The construction of both highly efficient and stable hybrid artificial photosynthetic systems comprising semiconductors as photosensitizers and abundant metal-based molecular complexes as cocatalysts for photocatalytic H2 generation remains challenging. Herein, we report an effective and stable CdS/cobaloxime hybrid system prepared by inserting an amorphous TiO2 (a-TiO2) interlayer with adjustable thickness and by covalently-surface-attaching molecular cobaloxime catalysts. This hybrid system displayed outstanding photocatalytic H2 production and reached a maximum rate of ∼25 mmol g-1 h-1, which was ∼20.8 times that of pure CdS and 1.7 times that of the CdS/cobaloxime system without an a-TiO2 interlayer (CdS/Co). More importantly, 6 nm a-TiO2 uniformly coated CdS nanorods (CdS NRs) exhibited exceptional 200 h long-term catalytic behaviour under ≥420 nm visible light irradiation. However, the H2 production performance of the CdS/Co hybrid system decreased significantly over 10 h. Density functional theory (DFT) calculations indicated that the a-TiO2 surface can provide abundant bonding sites for the effective immobilization of molecular catalysts. Moreover, Mott-Schottky electrochemical measurements and femtosecond transient absorption spectroscopy revealed that the a-TiO2 interlayer had favourable band levels that could fasten the photoexcited electron transfer from CdS to molecular cobaloxime and could extract holes with intraband electronic states generated by defects, thus prohibiting CdS photocorrosion and improving the stability of the hybrid system. This study proposes a strategy for designing multifunctional interlayers for the effective immobilization of molecular catalysts, beneficial regulation of photoinduced charge carriers, and improvement of the stability as well as facilitation of the construction of artificial photosynthetic hybrid systems with high efficiency and durability.

Hot electron and thermal effects in plasmonic catalysis of nanocrystal transformation

Plasmonic metal nanoparticles have the ability to harvest visible light and cause effective energy conversion, and they are considered as promising catalysts to drive chemical reactions. Although plasmonic catalysis has been widely used to mediate the reaction of organic molecules, the mechanism of contribution of thermal and hot carriers remains unclear. The catalysis of hot carriers is normally proposed as the dominant role of plasmonic catalysis, while the contribution of plasmonic thermal effects is often ignored, since the molecules on the metal surface are unstable at high temperatures. Here, plasmon catalytic nanocrystal transformation including oxidation reaction and optimization of the crystal structure is employed to investigate the plasmonic contributions of hot electron and thermal effects in plasmonic catalysis. It is found that the transformation rate and the corresponding product are very different with and without the assistance of hot electron catalysis. The thermal effect plays a dominant role in plasmon-catalyzed material transformation, and hot electrons can promote the oxidation reaction by facilitating the generation of active oxygen. The investigation provides insight into the specific role of hot electron and thermal effects in plasmonic catalysis, which is critically important for exploiting the highly localized fast plasmonic thermal effect and for designing energy-efficient plasmonic catalysts.

Polypropylene/ZnO Nanocomposites: Mechanical Properties, Photocatalytic Dye Degradation, and Antibacterial Property

Nanocomposite materials were prepared by compounding polypropylene (PP) with zinc oxide (ZnO) nanoparticles, using a twin-screw extruder. The compound was molded by injection molding to form dumbbell-shaped specimens. The influence of ZnO nanoparticle content on the morphology, mechanical properties, chemical structure, photocatalytic activity, and antibacterial properties of the obtained nanocomposites was investigated. The morphological images showed that the ZnO nanoparticles were well distributed in the PP matrix. Characterizations of the mechanical properties and chemical structures before and after sunlight exposure found that at the shortest exposure time, crosslinks could occur in the nanocomposites, which resulted in improved mechanical properties. However, sunlight exposure with the time period longer than 18 weeks caused the reduction of the mechanical properties, due to degradation of the PP matrix. It was found that PP with 2% ZnO could achieve the photocatalytic degradation of methylene blue up to 59%. Moreover, the result of antibacterial tests indicated that the nanocomposites had better antibacterial properties than neat PP.

Role of Nanomaterials in the Treatment of Wastewater: A Review

Water is an essential part of life and its availability is important for all living creatures. On the other side, the world is suffering from a major problem of drinking water. There are several gases, microorganisms and other toxins (chemicals and heavy metals) added into water during rain, flowing water, etc. which is responsible for water pollution. This review article describes various applications of nanomaterial in removing different types of impurities from polluted water. There are various kinds of nanomaterials, which carried huge potential to treat polluted water (containing metal toxin substance, different organic and inorganic impurities) very effectively due to their unique properties like greater surface area, able to work at low concentration, etc. The nanostructured catalytic membranes, nanosorbents and nanophotocatalyst based approaches to remove pollutants from wastewater are eco-friendly and efficient, but they require more energy, more investment in order to purify the wastewater. There are many challenges and issues of wastewater treatment. Some precautions are also required to keep away from ecological and health issues. New modern equipment for wastewater treatment should be flexible, low cost and efficient for the commercialization purpose.

Preparation of a Ti0.7W0.3O2/TiO2 nanocomposite interfacial photocatalyst and its photocatalytic degradation of phenol pollutants in wastewater

A Ti_0.7W_0.3O₂/TiO₂ nanocomposite interfacial photocatalyst was designed and prepared for the photocatalytic degradation of phenol pollutants in wastewater. The detailed properties of the Ti_0.7W_0.3O₂/TiO₂ nanocomposite interface (NCI) were analyzed by XRD, SEM, EDX, DRS, UPS and XPS technologies, showing that anatase TiO₂ nanospheres (NSs) were uniformly dispersed on the surface of rutile Ti_0.7W_0.3O₂ nanoparticles (NPs) and formed the nanocomposite interface. The DRS and UPS results of 5 wt% Ti_0.7W_0.3O₂/TiO₂ NCI indicated a greatly broadened light response range with a wavelength shorter than 527 nm and a shorter band gap energy of 2.37 eV. The conduction band of TiO₂ NSs, Ti_0.7W_0.3O₂ NPs and 5 wt% Ti_0.7W_0.3O₂/TiO₂ NCI were measured based on the results of the valence band and band gap energy obtained via XPS and DRS, and then the energy level diagram of Ti_0.7W_0.3O₂/TiO₂ NCI was proposed. The photocatalytic degradation of phenol at Ti_0.7W_0.3O₂/TiO₂ NCI with different loading ratios of Ti_0.7W_0.3O₂ NPs was investigated under optimum conditions (i.e., pH of 4.5, catalyst dosage of 0.45 g L^-1 and phenol initial concentration of 95 ppm) under the illumination of ultraviolet visible light. Also, 5 wt% Ti_0.7W_0.3O₂/TiO₂ NCI exhibited the highest photocatalytic activity, with the initial rate constant (k) calculated as 0.09111 min^-1. After recycling six times, Ti_0.7W_0.3O₂/TiO₂ NCI showed good stability and recyclability. The involvement of superoxide radicals in the initial reaction at Ti_0.7W_0.3O₂/TiO₂ NCI was evidenced by the use of a terephthalic acid (TA) fluorescent probe. Besides, UV-Vis spectroscopy, UHPLC-MS and GC-MS technologies were used to analyze the main intermediates in the photocatalytic degradation of phenol. The probable photocatalytic degradation mechanism of phenol at Ti_0.7W_0.3O₂/TiO₂ NCI was also proposed.

Enhanced visible-light-driven photocatalytic H2 production and Cr(vi) reduction of a ZnIn2S4/MoS2 heterojunction synthesized by the biomolecule-assisted microwave heating method

Photocatalytic applications of flower-like ZnIn₂S₄/MoS₂ composite, synthesized by biomolecule-assisted microwave heating method, in H₂ evolution and Cr(vi) reduction reactions.

Controllable photodeposition of nickel phosphide cocatalysts on cadmium sulfide nanosheets for enhanced photocatalytic hydrogen evolution performance

As efficient cocatalysts in photocatalytic processes, transition metal phosphides are usually synthesized in harsh and tedious conditions. So to achieve their simple and controllable loading on photocatalyst surface is especially valuable.

Tri-functional molecular relay to fabricate size-controlled CoOx nanoparticles and WO3 photoanode for an efficient photoelectrochemical water oxidation

Heterojunction and element doping to couple light-harvesting semiconductors with catalytic materials have been widely employed for photoelectrochemical (PEC) water splitting.

Interlayer Photoelectron Transfer Boosted by Bridged RuIV Atoms in GaS Nanosheets for Efficient Water Splitting

Photocatalytic water splitting over layered nanosheet (NS) catalysts has caught a lot of attention for renewable hydrogen fuel production. However, the weak van der Waals interlayer interactions make it a great challenge to realize an effective dissociation of photogenerated excitons and efficient charge transfer across the interior of layered catalysts during the photocatalysis process. Here, we propose an intercalation strategy of high-valence Ru^IV atoms to render two-dimensional GaS NS photocatalysts with rapid electron-hole dissociation and long photocarrier lifetime in visible-light-driven water splitting. Experimental and theoretical results unravel that the intercalated single-site Ru, confined in interlayer of GaS NSs, with a hexagonal structural configuration of "Ru₁-S₆", can serve as an electron-trapped high-speed channel toward simultaneously accelerating electron-hole pairs dissociation and promoting photoelectron transportation through the van der Waals interlayer. Consequently, the as-developed Ru-intercalated GaS NSs can give a notable H₂ production rate of 340 μmol g^-1 h^-1 under visible-light irradiation and an apparent yield of 7% at 420 nm, 38 times that of pure GaS NSs. This study opens up a feasible way for a new design of highly active layered photocatalysts toward high-efficiency solar energy conversion.

New carbon/ZnO/Li2O nanocomposites with enhanced photocatalytic activity

Our study was focused on the synthesis of photocatalytic materials for the degradation of organic dyes based on the valorization of biomass resources. The biochar resulted from pyrolysis process of cherry pits wastes was activated by CO₂ flow. Activated and inactivated carbon was used to obtain carbon-based photocatalysts impregnated with different zinc salt precursors. The activation of carbon had no significant influence on the photodegradation process. The doping procedure used Li₂CO₃ and Zn(CH₃COO)₂ of different concentrations to impregnate the biochar. The carbon-ZnO-Li₂O based nanomaterials were analysed by TEM and SEM, while the presence of hexagonal wurtzite ZnO was investigated by XRD. The solid samples were analysed by PL at 360 nm excitation fixed wavelength to correlate their morphology with the optical and photocatalytic properties. The presence of Li atoms led to photocatalytic activities of the doped ZnO similar to the undoped ZnO obtained at higher concentrations of zinc acetate precursor.

Synthesis of MgAC-Fe3O4/TiO2 hybrid nanocomposites via sol-gel chemistry for water treatment by photo-Fenton and photocatalytic reactions

MgAC-Fe₃O₄/TiO₂ hybrid nanocomposites were synthesized in different ratios of MgAC-Fe₃O₄ and TiO₂ precursor. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray fluorescence spectrometry (XRF), electron spin resonance spectrometry (ESR), Brunauer-Emmett-Teller (BET), photoluminescence (PL), and UV photoelectron spectroscopy (UPS) were used to characterize the nanocomposites. The increase of MgAC-Fe₃O₄, in the hybrid nanocomposites’ core-shell structure, led to the decrease of anatase TiO₂ peaks, thus reducing the photo-Fenton and photocatalytic activities. According to the obtained data, MgAC-Fe₃O₄ [0.05 g]/TiO₂ showed the best photo-Fenton and photocatalytic activities, having removed ~93% of MB (photo-Fenton reaction) and ~80% of phenol (photocatalytic reaction) after 20 and 80 mins, respectively. On the pilot scale (30 L), MgAC-Fe₃O₄ [0.05 g]/TiO₂ was completely removed after 27 and 30 hours by the photo-Fenton and photocatalytic activities, respectively. The synergistic effect gained from the combined photo-Fenton and photocatalytic activities of Fe₃O₄ and TiO₂, respectively, was credited for the performances of the MgAC-Fe₃O₄/TiO₂ hybrid nanocomposites.

A polyaniline-coated ZnS/ZnO/FTO photoelectrode for improving photocorrosion prevention and visible light absorption

To enhance the absorption of visible light for wide-bandgap semiconductors, methods such as sensitizing with nanoparticles or quantum dots and bandgap engineering using dopants have been reported.

Application of metal oxide semiconductors in light-driven organic transformations

Herein, we provide an up-to-date overview of metal oxide semiconductors (MOS) as versatile and inexpensive photocatalysts to enable light-driven organic transformations.