Optimal Photocatalytic Efficiency Research Articles

​The structural regulation of photosensitive unit and conjugation in COFs for efficient photocatalytic H2 evolution.

The photosensitive unit and conjugation play a significant role in photocatalytic performance of covalent organic frameworks (COFs). In this work, a series of COFs that introduced the phenyl phenanthridine as photosensitive unit with different planarity of linkages were synthesized and the common regulation between them for photocatalysis hydrogen evolution reaction (HER) was also studied. The results indicate that DHTB-PPD, with 2/3 planarity linkages (β-ketoenamine/imine is 2/3) and the phenyl phenanthridine as building blocks, shows the narrowest bandgap and the strongest charge separation efficiency. Therefore, it shows the highest H2 production rate of 12.13 mmol g-1 h-1. The optimal photocatalytic efficiency of DTHB-PPD can be attributed to the combined effect of the photosensitive unit and the long-range ordering of the COF skeleton. According to The Density Functional Theory (DFT), the O site on β-ketoamine is the most possible H2 generation site, but the photocatalytic efficiency of TP-PPD, with the highest skeletal conjugation and the highest proportion of β-ketoamine is not the most efficient photocatalyst, indicating that the long-range ordering of COFs is important on photocatalytic performance. Thus, these findings provide valuable guidance for the structural design of COFs photocatalysts.

Development and analysis of novel Sm doped LaSiO for photocatalytic degradation and electrochemical sensing of heavy metals

This study explores the synthesis of La10Si6O27:Sm3+ nanoparticles (LSNP) with varying samarium (Sm3+) concentrations (0–8 mol%) using eco-friendly solution combustion method with urea as a fuel. Using powder X-ray diffraction (PXRD), we determined that the nanoparticles typically measure between 15 and 17 nm and display a spherical morphology. These rare earth (RE)-doped nanoparticles were employed as a novel photocatalyst for the degradation of malachite green (MG) dye, exhibit unprecedented photocatalytic efficiency. The release of OH radicals during the degradation process was found to vary with the chemical structure and concentration of the photocatalyst, with the 6 mol% LSNP formulation showing a significant advancement under both UV and sunlight. Electrochemical assessments revealed that these nanoparticles exhibit excellent cyclic stability and robust performance. Notably, the specific capacitance of the nanoparticles increased with the samarium concentration, reaching a peak of 261.3 F/g in 0.1 M HCl. Furthermore, graphite-modified electrodes incorporating these nanoparticles showed significant potential as sensitive materials for detecting mercury and lead in concentrations as low as 1–6 mM, underscoring the versatility and functional adaptability of the synthesized nanoparticles in environmental and electrochemical applications. The prepared La10Si6O27:Sm3+ nanoparticles The nanoparticles demonstrated an optimal photocatalytic efficiency of 95.5 % under UV light and 88.15 % under sunlight at 6 mol% Sm3+ doping. Additionally, a peak specific capacitance of 261.3 F/g was achieved in 0.1 M HCl.

Attached meso-tetra (4-carboxyphenyl) porphyrin copper (II) to BiOCl for enhanced photocatalytic performance in antibiotics degradation

Bismuth oxychloride (BiOCl) has been considerably accepted as a photocatalyst due to its excellent photoelectrochemical properties, low cost and corrosion resistance. However, its further application has not progressed due to limited visible-light utilization and quick recombination of photoexcited carriers. In this work, a series of meso-tetra (4-carboxyphenyl) porphyrin copper (II) (CuTCPP) hybridized BiOCl composites (CuTCPP/BiOCl) were synthesized to use as an efficient visible-light responsive photocatalyst for the degradation of antibiotics pollutants in the wastewater systems. The characterization results confirmed that the 2D fusiform-shaped CuTCPP nanosheets were successfully inserted into hierarchical flower-like BiOCl. The photocatalytic degradation of several typical antibiotics (tetracycline, enrofloxacin and ciprofloxacin) demonstrated that CuTCPP/BiOCl showed better photocatalytic activities than pure BiOCl. Further, 0.5 wt% CuTCPP/BiOCl manifested the optimal photocatalytic efficiency for decomposing the antibiotics, and its degradation rate constant was about 2.84 times higher than that of pristine BiOCl. The significantly improved photocatalytic performance was mainly due to the promotion of visible light harvesting and enhanced separation of photogenerated carriers after the introduction of the macrocyclic CuTCPP. The radical substances determination confirmed that active •O2−, h+ and •OH existed in the photocatalytic removal of antibiotic, in which •O2− was the main reactive oxidizing species. The excellent degradation efficiency of CuTCPP/BiOCl reveals its great potential as photocatalysts for use in the alleviation of antibiotic contaminants and wastewater purification.

Sodium titanate nanostructured modified by green synthesis of iron oxide for highly efficient photodegradation of dye contaminants

Abstract In this study, sodium titanate (ST)/iron oxide (Fe2O3) was successfully prepared as a novel binary photocatalyst for the first time to enhance the photocatalytic activity. The prepared photocatalyst was used in the photodegradation of methylene blue (MB) dye under sunlight and a tungsten lamp. The green synthesis method using orange peel extract was employed to prepare Fe2O3, while the hydrothermal method was used to synthesize ST. To achieve optimal photocatalytic efficiency, the loading of Fe2O3 onto ST was carefully controlled. The average crystallite size of ST, Fe2O3, and ST@Fe2O3 (with a 1:1 wt% ratio) was 999.8, 81.9, and 104 nm, respectively, using the Williamson–Hall (W–H) model. Optical analysis revealed that ST@Fe2O3 had a smaller direct bandgap (2.54 eV) compared to ST@0.3 Fe2O3 (2.70 eV) and ST@0.5 Fe2O3 (3.24 eV). The photodegradation of MB was analyzed considering the weight of the photocatalyst, the irradiation time, and the dye concentration. In-depth explanations of stability and kinetic models were also provided. Remarkably, the ST@Fe2O3 photocatalyst demonstrated superior performance compared to the other evaluated photocatalysts, completely degrading MB dye within just 60 min of solar light exposure. Incorporating Fe2O3 into ST effectively reduces the recombination of photo-produced electron/hole (e/h) pairs and broadens the response range of the solar spectrum. Based on these findings, ST@Fe2O3 appears to have a promising future as a practical photocatalyst for degrading various dye pollutants in wastewater.

A novel recyclable photocatalytic composite TiO2NTs@Bi25FeO40 for tetracycline mineralization

Titanium dioxide nanotubes (TiO2NTs) are prepared by anodizing Ti substrates, which is a good solution to the problem that powdered materials are more difficult to recycle. Hence, a novel recyclable TiO2NTs@Bi25FeO40 (TiO2/BFO) photocatalyst was prepared by anodic oxidation combined with hydrothermal deposition. The photocatalytic ability of TiO2NTs prepared at different factors and Bi25FeO40 compound was evaluated. The TiO2/BFO showed the optimal photocatalytic efficiency, which the removal ratio of tetracycline hydrochloride (TC-HCl) higher than that of TiO2NTs under visible-light irradiation. UV–vis diffuse reflectance spectra (DRS) analysis proved that the band gap of TiO2/BFO was narrower than that of TiO2NTs. The narrow band gap of TiO2/BFO results in a broadening of its light absorption region. Meanwhile, the combination of free radical quenching experiments and EPR measurement showed that ·O2− was the main active radical in the photocatalytic process, and the presence of Bi25FeO40 effectively promoted the generation and transfer of electrons. Mechanistic analysis showed that a unique II-type heterojunction electron transfer structure was formed between TiO2NTs and Bi25FeO40, which promoted the photogenerated electron-hole separation and improved the photocatalytic oxidation activity. The preparation of TiO2/BFO provided a new strategy for synthesizing more efficient and environmentally friendly photocatalyst.

Monoclinic α-Bi2O3 nanorods by microwave-assisted synthesis: Photocatalytic and antioxidant properties

Nanotechnology has emerged as a new route for addressing most environmental and medical challenges, hence this field of research continues to generate research interest. Herein, Bi2O3 was synthesized by a microwave-assisted thermal process. X-ray diffraction (XRD) result confirmed that a nanocrystalline monoclinic crystal structure of the α-phase was formed, and both the Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analysis confirmed that the synthesized α-Bi2O3 were rod-like in shape. The length of the nanorods was in the range of 60–160 nm, with an average dimension of 101.5 nm, while the width has an average value of 23 nm. A band gap energy value of 2.75 eV was obtained from the absorption spectroscopy, and they absorbed light in the UV to visible range, with an absorption maximum of around 345 nm. Photocatalytic activity of the nanorods under UV irradiation was investigated by assessing the degradation of Bromocresol green (BG) as a model pollutant. The degradation process of the dye molecules was studied at different concentrations (20–80 mg/L), varied photocatalyst dosage (0.025, 0.05, 0.075, and 1.0 g), and a range of solution pH (3, 6, 9, and 12). About 75 % optimum photocatalytic efficiency was achieved at pH 6 after 3 h. In addition, the results showed that an increase in catalyst dosage and concentration of dye molecules contributed to promoting the degradation effect. Moreover, the photocatalyst was found to be stable after 4 consecutive cycles, with negligible loss of efficiency. The antioxidant potency of the nanorods was assessed by evaluating their free radical scavenging capabilities across 4 different assays: 1,1-diphenyl-2-picrylhydrazyle (DPPH), Nitric oxide (NO), Hydrogen peroxide (HP) radical inhibition, and Reducing power (RP). The results from the IC50 values indicated the sample exhibited better inhibition of HP (25.22 µg/mL), followed by RP (28.22 µg/mL), NO (29.37 µg/mL), and DPPH (32.72 µg/mL) respectively. However, the standard Ascorbic acid exhibited IC50 values of 16.25, 24.50, 25.07, and 28.40 µg/mL for DPPH, RP, HP, and NO, respectively. These unique properties of the nanorods showed that they have good antioxidant potential that is comparable with that of Ascorbic acid used as the standard.

Photocatalytic Oxidization Based on TiO2/Au Nanocomposite Film for the Pretreatment of Total Phosphorus (TP)

Phosphorus, an essential rare element in aquatic ecosystems, plays a key role in maintaining ecosystem balance. However, excess phosphorus leads to eutrophication and algal proliferation. To prevent eutrophication, the pretreatment and measuring of the concentration of total phosphorus (TP) is crucial. Compared to conventional TP pretreatment equipment (autoclave), a lab-on-a-chip detection device fabricated using micro-electromechanical system technology and titania (TiO2) as a photocatalyst is more convenient, efficient, and cost-effective. However, the wide bandgap of TiO2 (3.2 eV) limits photocatalytic activity. To address this problem, this paper describes the preparation of a TiO2/Au nanocomposite film using electron-beam evaporation and atomic-layer deposition, based on the introduction of gold film and TiO2 to a quartz substrate. The photocatalytic degradation properties of TiO2/Au nanocomposite films with thicknesses of 1, 2, 3, and 4 nm were assessed using rhodamine B as a pollutant. The experimental results demonstrate that the deposition of gold films with different thicknesses can enhance photocatalytic degradation efficiency through synergetic reactions in the charge separation process on the surface. The optimal photocatalytic efficiency is achieved when the deposition thickness is 2 nm, and it decreases with further increase in the thickness. When the photocatalytic reaction time is 15 min, the lab-on-a-chip (LOC) device with a 2-nm-thick gold layer and autoclave exhibits a similar TP pretreatment performance. Therefore, the proposed LOC device based on photocatalytic technology can address the limitations of conventional autoclave equipment, such as large volumes, long processing times, and high costs, thereby satisfying the growing demand for on-site evaluation.

Addressing the synchronized impact of a novel strontium titanium over copolymerized carbon nitride for proficient solar-driven hydrogen evolution

Currently, novel technologies are highly prerequisite as an outstanding approach in the field of photocatalytic water splitting (PWS). Previous research has shown that copolymerization technology could improve the photocatalytic performance of pristine carbon nitride (CN) more efficiently. As this technology further allows the charge carrier recombination constraints, due to novel monomer-incorporated highly abundant surface-active sites of metals in polymeric carbon nitride-based heterojunction. However, in present study, a novel previously unexplored thiophenedicarboxaldehyde (TAL) conjugated, strontium-titanium (SrTiO3) induced and CN based heterojunction, i.e., SrTiO3/CN-TAL10.0, was prepared for solar-driven hydrogen evolution reaction (HER). This heterojunction effectively enables the proficient isolation of photoinduced charge carriers and enhanced the charge transport over the surface junction, by enhancing the optical absorption range and average lifetime of photogenerated charges. The incorporation of TAL within the structure of CN via copolymerization highly increases the photocatalytic activity, as well as maintaining its photostability performance. The SrTiO3 concentration and the proportion of TAL among CN can be precisely controlled to provide the optimal photocatalytic efficiency with a maximum HER of 285.9 µmol/h under visible light (λ = 420 nm). Based on these results, our optical analysis shows that coupling of SrTiO3 and TAL monomer in the structure of CN considerably reduce the band gap of superior sample from (3.42 to 2.66 eV), thereby, signifying the outstanding photocatalytic performance of SrTiO3/CN-TAL10.0. Thus, this study provide a new guideline in order to develop the multidimensional photocatalysts with proper functioning for sustainable energy conversion and production.

In situ synthesis of donut-like Fe-doped-BiOCl@Fe-MOF composites using for excellent performance photodegradation of dyes and tetracycline

A series of donut-like nanostructured heterojunction materials are first synthesized via one-step solvothermal method to improve the photocatalytic efficiency for the environmental pollutants. The unique donut-like Fe-doped-BiOCl@Fe-MOF heterojunction with uniform size guarantees suitable surface area and many active sites for the model pollutant. The optimal photocatalytic efficiency is shown in degradation of RhB (99.0 %, 90 min) and TC (90.4 %, 90 min) solution, which had higher photocatalytic efficiency than a variety of similar materials previously reported. The result revealed that the enhancing photocatalytic activity is mainly depended on the synergistic effect of Fe-MOF and Fe-doped BiOCl. The possible mechanism is further studied, which shown h+ and O2− are the primary active species in the degradation process of RhB and TC solution. Meantime, Fe-doped BiOCl@Fe-MOF with the excellent reusability and stability. After the fourth cycle, the degradation rate of RhB solution can still be as high as 86.4 %. In this work, we provide a higher efficiency heterojunction photocatalytic material by varying the organic ligand content.

Fabrication of Ti-doped Bi2S3/NiO p-n heterojunction with enhanced visible-light–driven photocatalytic activity

The present work is focused on the hydrothermal synthesis of Bi2S3, Tix-doped Bi2S3 (x = 0.3, 0.6, and 1 %), NiOy/Bi2S3 (y = 1, 3, and 5 %), and 0.6 %Ti-doped Bi2S3/1%NiO, which showed a high photocatalytic activity in the range of visible light. It can be attributed to the high BET surface area and p-n junction formed between n-type Bi2S3 and p-type NiO, resulting in the efficient separation/transition of photogenerated electron-hole pairs and a decreased recombination rate. Furthermore, Ti (IV) doping increased the band gap of Bi2S3, improving the transfer rate of photo-induced electrons and extending the lifetime of charge carriers. It is noteworthy that the amount of both the Ti and NiO components plays a crucial role in increasing photocatalytic activity. Among the synthesized samples, the 0.6 % Ti-doped Bi2S3/1%NiO nanocomposite represented the optimum photocatalytic efficiency by eliminating 80 % of methylene blue (MB, 20 mgL-1) after 500 min visible light illumination. In 180 min, only 63 % of the total organic carbon (TOC) from the MB solutions was removed under optimal circumstances. In general, the photocatalytic process of Ti-doped Bi2S3/ NiO p-n heterojunction was proved by the formation of •OH and •O2– radicals during the degradation reaction, confirmed by scavenger tests and Mott-Schottky studies. Moreover, gas chromatography-mass spectrometry (GC–MS) was employed to investigate the degradation products and determine the smaller resulting fragmented compounds. Furthermore, the design of new p-n heterojunctions as the photocatalyst for removing the azo dyes will aid the treatment of environmental contaminants, especially water purification.

Effect of Bismuth on the Structure, Magnetic and Photocatalytic Characteristics of GdFeO3

In this paper, a series of Gd1-xBixFeO3 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) nanoparticles have been readily synthesized by a green and facile sol–gel method. It gradually changed from the orthorhombic structure (space group Pbnm) to the rhombohedral perovskite structure (space group R3c). Weak ferromagnetic behavior was effectively induced by Bi3+, with reduced magnetization. It was closely related with the lattice distortion of the perovskite structure and modified interactions between Fe-O-Fe. Boosted photocatalytic activities of Gd1-xBixFeO3 were observed for the removal of methylene blue (MB) under the visible light irradiation. In particular, Gd0.5Bi0.5FeO3 showed the optimum photocatalytic efficiency, in which the degradation efficiency reached 82.1% after 180 min of visible light illumination, with good stability and repeatability. The improved performance was mainly ascribed to enhanced visible light absorption, decreased optical band gap from 2.21 to 1.8eV and stronger charge transfer efficiency. A possible photocatalytic mechanism is also proposed according to the band structure. The results indicate that this system will be a promising candidate for the degradation of organic pollutant as a novel magnetically recoverable photocatalyst.

MOF templated to construct hierarchical ZnIn2S4-In2S3 hollow nanotube for enhancing photocatalytic performance

3D (Three-dimensional) hollow porous structured materials received a lot of attention due to their significant benefits in photocatalytic reactions. In this study, 3D ZnIn2S4-In2S3 hollow hierarchical porous nanotubes were synthesized by a one-step MOF (metal–organic framework) templating strategy as efficient catalysts for photocatalytic hydrogen evolution in water. The dynamic process between the internal collapse of In-MIL-68 and the growth of ZnIn2S4 crystals with attached outer edges led to the one-step in situ preparation of hollow ZnIn2S4-In2S3 heterojunction catalysts. Crucially, In-MIL-68 simultaneously induced the formation of In2S3 hollow porous nanotubes and the construction of ZnIn2S4-In2S3 hierarchical heterojunction with ultrathin nanosheets. The optimal photocatalytic efficiency was obtained by adjusting the relative composition of the two-component heterojunction, and the optimized ZnIn2S4-In2S3-10 showed hydrogen evolution efficiency of 5.01 mmol·h−1·g−1 under visible light irradiation in the absence of co-catalysts and a high AQY (the apparent quantum yield) of 16.23 % at 420 nm, which was noticeably higher than the photocatalytic efficiency of the one-component and two-step synthesized In2S3-ZnIn2S4. Both theoretical and experimental results demonstrated that the construction of heterojunction and the forming of hollow porous nanotubes enhanced visible light absorption and promoted the separation and transfer of photogenerated carriers, thereby increasing the photocatalytic activity of the prepared materials. Meanwhile, ZnIn2S4-In2S3 hierarchical hollow nanotubes exhibited good stability and reusability, offering a new way to fabricate MOF-based hollow hierarchical photocatalysts.

Construction of CdSe/ZnIn2S4 Z-Scheme heterojunction for enhanced photocatalytic degradation of tetracycline

ZnIn2S4 as an energy band narrow photocatalyst has attracted extensive attentions in water remediation, but the fast carrier recombination efficiency hinders its further utilization. An effective strategy is to boost photocarrier separation and enhance photocatalysis performance by building heterojunction. Here, a simple in-situ deposition method is used to create a unique CdSe/ZnIn2S4 heterojunction structure. By varying the CdSe content, CdSe/ZnIn2S4 composites can be synthesized with diffident photocatalytic properties. The optimal photocatalytic efficiency of CdSe/ZnIn2S4 composite is obtained when 1.0 % CdSe addition, while an overdose of CdSe QDs results in a deterioration of photocatalytic efficiency. 93 % tetracycline (TC) degradation could be attained. And the degradation rate is 1.9 and 2.3 times higher than pure ZnIn2S4 and CdSe. In addition, the CdSe/ZnIn2S4 photocatalytic mechanism complies with the Z-Scheme. In the photodegradation process, the superoxide radicals (·O2–) and holes (h+) are the primary active agents.

Deoxidation regulation of SiC surface and its effect on enhancing photocatalytic performance

In this study, the surface of SiC was deoxidized by a simple NaOH etching treatment at room temperature. The synthesized SiC catalysts were tested for the removal of MB dyes under UV irradiation. Strong alkali corrosion thinned the thickness of the blocking silicon oxide layer and also led to the presence of more electrophilic centers (consisting of polar > CO groups) on the surface. Compared with unetched SiC, the optimal photocatalytic efficiency of EC1T10-SiC was 43.11 % higher than the photocatalytic efficiency of EC0T10-SiC after UV irradiation for 75 min. Quenching experiments show that superoxide radicals (O2−) are the main reactive species in this process. A possible enhanced mechanism was proposed based upon oxidation layer thinning that favors photogenerated electron transport and polar centers (>Cδ+=Oδ-) favorable for photogenic electron migration. This study presents a simple method for controlling the surface structure of silicon carbide to achieve excellent photocatalytic performance. This method is environmentally friendly, easy to implement, and suitable for practical applications.

Facile synthesis of Y2O3/CuO nanocomposites for photodegradation of dyes/mixed dyes under UV- and visible light irradiation

Yttrium oxide/CuO nanocomposite with different concentrations of Y2O3 were synthesized by a combustion technique. The structural, morphology, and photocatalytic properties were investigated using X-ray diffraction, SEM and photodegradation studies respectively. Scanning electron microscopy images reveal the porous nanocomposite morphology with significant aggregation. The photocatalyst degraded both carmine and methylene blue (MB). An attempt was made to discover the optimal circumstances of degradation, including time of contact, H2O2 concentration, and light exposure. Under UV irradiation, 2.5% Y2O3 -CuO nanocomposite demonstrated optimum photocatalytic efficiency of up to 55.68% in 70 min, with a rate constant of around 0.0079 min−1 for MB. However, the photocatalytic efficiency of the 1% Y2O3/CuO nanocomposite increased to 87.95% in 70 min, with a rate constant of about 0.01826 min−1 for carmine under UV irradiation. The findings demonstrated that UV light increased the reaction rate more than visible light. Furthermore, the research showed that carmine is degraded faster than MB. Cyclic experiments showed the Y2O3/CuO nanocomposite stability over repeated use. The photocatalytic reaction species trapping studies were performed with 1% Y2O3/CuO nanocomposite and UV light.

Synthesis of La2Ti2O7/Bi5O7I photocatalysts with improved photocatalytic activity for degradation of CIP under visible light

• Novle La 2 Ti 2 O 7 /Bi 5 O 7 I composite photocatalysts were synthesized. • The photocatalyst exhibited much higher performance for CIP degradation under visible light. • The apparent rate constant for CIP degradation was 57.7 times and 12.3 times as that of La 2 Ti 2 O 7 and Bi 5 O 7 I. • The mechanism on the enhanced performance was discussed deeply. The La 2 Ti 2 O 7 /Bi 5 O 7 I (LB) composite photocatalyst was synthesized by an in-situ growth method. The microstructure, optical properties, and energy band structure of the prepared photocatalysts were studied by a series of characterization methods. The photocatalytic activity was studied by degrading ciprofloxacin (CIP) under visible light. The effects of hybrid ratio (La 2 Ti 2 O 7 /Bi 5 O 7 I) on photocatalytic activity were investigated. The results showed that the composite photocatalyst exhibited better photocatalytic activity than the corresponding single component (La 2 Ti 2 O 7 or Bi 5 O 7 I). Among them, the LB-2 composite photocatalyst showed the optimal photocatalytic efficiency (reaction rate constant of 0.09403 min −1 ), which was 57.7 times and 12.3 times as that of La 2 Ti 2 O 7 and Bi 5 O 7 I, respectively. The enhanced activity of the composite photocatalyst was mainly ascribed to the formed heterojunction between La 2 Ti 2 O 7 and Bi 5 O 7 I. Finally, according to the data analysis and energy band theory, the possible charge transfer mechanism of La 2 Ti 2 O 7 /Bi 5 O 7 I composite photocatalyst was proposed. The degradation mechanism of CIP was also proposed based on the intermediates detected by LC-MS.

2D Ti3C2 decorated Z-scheme BiOIO3/g-C3N4 heterojunction for the enhanced photocatalytic CO2 reduction activity under visible light

The development of photocatalytic technology can not only reduce CO2 emissions, but also realize the effective utilization of solar energy, thus alleviating the global energy crisis. In this work, BiOIO3/g-C3N4 Z-scheme heterojunction modified by Ti3C2 nanosheets was designed and fabricated through hydrothermal method and electrostatic self-assembly strategy. The g-C3N4/BiOIO3/Ti3C2 (4 wt%) photocatalytic system exhibited the optimal photocatalytic efficiency, reaching 5.88 and 1.55 μmol/g/h for CO and CH4, respectively, and the CO production rate was 6.6 folds as high as that of bare g-C3N4. Various characterization techniques were utilized to research the physicochemical properties of as-prepared photocatalysts. Z-scheme heterojunction formed between g-C3N4 and BiOIO3 and the decorating of 2D Ti3C2 co-catalyst were responsible for the boosted photocatalytic behavior. Z-scheme heterojunction could prevent the recombination of charge carriers, the co-catalyst Ti3C2 acted as electron sink could achieve quick shift of photo-induced electrons and supply numerous active sites for photocatalytic reaction.

2D-Bi4NbO8Cl nanosheet for efficient photocatalytic degradation of tetracycline in synthetic and real wastewater under visible-light: Influencing factors, mechanism and degradation pathway

A 2D-Bi4NbO8Cl nanosheet (BNOCF) photocatalyst was fabricated using molten salt or flux method and was employed to degrade tetracycline (TCH) under visible light irradiation. The as-synthesized photocatalyst was characterized by a wide range of studies and compared with bulk-Bi4NbO8Cl (BNOCS). The BNOCF photocatalyst displayed 2.2 times higher degradation efficiency as compared to BNOCS. The enhanced efficiency could be attributed to the 2D architecture, with increased surface area and reduced charge recombination rate. The effect of various parameters was studied, and the optimal photocatalytic efficiency (96.5%) of BNOCF was obtained at a dosage of 1 g L−1, TCH concentration of 10 mg L−1, pH 4.4, and the light intensity of 10 mW cm−2. The effects of coexisting inorganic salts and real wastewater sources were also studied. A detailed study showed that a complex between BNOCF and TCH led to TCH degradation by inducing strong visible-light absorption. The radical trapping experiments showed that •O2− was primarily responsible for the degradation of TCH. Based on these findings, the photocatalytic mechanism was proposed. The inorganic ions like CO32-, Cl- and SO42- were found to hinder the degradation efficiency of BNOCF slightly. Excellent degradation efficiency (95.9%) was achieved towards TCH present in a real wastewater sample. The catalyst efficiently mineralized 34.6% TCH in 1 h, and after four recycling tests, was found quite stable. The intermediate products of TCH degradation over BNOCF were detected, and plausible degradation pathways were proposed. This study proves that BNOCF possesses tremendous potential as a visible-light-reactive photocatalyst in prospective wastewater treatment applications.

Metal-Organic Frameworks With Variable Valence Metal-Photoactive Components: Emerging Platform for Volatile Organic Compounds Photocatalytic Degradation

With their outstanding diversities in both structures and performances, newly emerging metal-organic frameworks (MOFs) materials are considered to be the most promising artificial catalysts to meet multiple challenges in the fields of energy and environment. Especially in absorption and conversion of solar energy, a variety of MOFs can be readily designed to cover and harvest the sun irradiation of ultraviolet (UV), visible and near-infrared region through tuning both organic linkers and metal nodes to create optimal photocatalytic efficiency. Nowadays, a variety of MOFs were successfully synthesized as powerful photocatalysts for important redox reactions such as water-splitting, CO2 reduction and aqueous environmental pollutants detoxification. MOFs applications in indoor-air VOCs pollutants cleaning, however, are less concerned partially because of limited diffusion of both gaseous pollutant molecules and photo-induced active species in very porous MOFs structures. In this mini-review, we focus on the major breakthroughs of MOFs as photocatalysts for the effective removal of indoor-air VOCs such as aldehydes, aromatics and short-chain alcohols. According to their nature of photoactive centers, herein MOFs photocatalysts are divided into two categories to comment, that is, MOFs with variable valence metal nodes as direct photoactive centers and MOFs with non-variable valence metal nodes but after combining other photoactive variable valence metal centers as excellent concentrated and concerted electron-transfer materials. The mechanisms and current challenges of the photocatalytic degradation of indoor-air VOC pollutants by these MOFs will be discussed as deeply as possible.

Photo-Fenton interfacial phenomena on graphene oxide: Computational and experimental investigations

For optimum photocatalytic efficiency, besides appropriate band positions, the molecules to be reduced should adsorb on the nucleophilic sites, and those to be oxidized should effectively interact with the electrophilic sites of a photo-excited photocatalyst. The present research investigates the photocatalytic properties of graphene oxide (GO) materials from this novel perspective. We combine density functional theory (DFT) calculations, large-scale classical molecular dynamics (MD), and experimental studies for comprehending the Fenton (in the dark) and visible light photo-Fenton catalytic activities of two GO materials for orange-G (OG) dye degradation. DFT and time-dependent density functional theory (TD-DFT) calculations located a GO model's nucleophilic and electrophilic functionalities in the ground and photo-excited states. Then large-scale classical MD simulations in an aqueous medium gave information about how different reactants interact with varying oxygen functionalities on the GO structure. The photo-Fenton activities of two GO samples with different visible range bandgaps were experimentally evaluated for OG degradation along with these computational studies. The GO photocatalysts efficiently degraded the target dye. Finally, the experimental and computational results are combined to shed light on critical aspects of heterogeneous Fenton and photo-Fenton interfacial phenomena operating on a typical GO structure.