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Covalent organic frameworks (COFs) are nanoporous crystalline polymers with densely conjugated structures. This work discovers that imine-linked COFs exhibit remarkable photodegradation efficiency to azo dyes dissolved in water. Visible light generates different types of radicals from COFs, and superoxide radicals break N N bonds in dye molecules, resulting in 100% degradation of azo dyes within 1 h. In contrast, these dyes cannot be degraded by conventionally used photocatalysts, for example, TiO2. Importantly, the COF photocatalysts can be recovered from the dye solutions and re-used to degrade azo dyes for multiple times without loss of degradation efficiency. This work provides an efficient strategy to degrade synthetic dyes, and we expect that COFs with designable structures may use as new photocatalysts for other important applications.

A kind of CdS/Cd-BiOCl immobilized films photocatalyst was prepared. The optical and physicochemical properties of the CdS/Cd-BiOCl photocatalysts were analysed, and the detailed characterization revealed CdS/Cd-BiOCl films photocatalyst with good charge carrier separation effect. The reusabilities and photocatalytic properties of the samples were studied. The 15%CdS/Cd-BiOCl photocatalyst exhibited superior performance in photocatalytic degradation of tetracycline (TC) and favorable stability under visible light irradiation. As for the photodegradation rate of TC, 15%CdS/Cd-BiOCl exhibited an excellent photodegradation activity, which is 4.06 and 9.53 times higher than that of CdS/Cd and BiOCl, respectively. The results showed that dominant active species are •O2− and •OH radicals during photodegradation. The charge transfer in Z-scheme CdS/Cd-BiOCl films photocatalyst could synchronously generate conduct band (CB) electrons in BiOCl and valence band (VB) holes in CdS, and metal Cd served as electron mediator. This work can be a reference for the design of film photocatalysts and new insight for photodegradating towards contaminants.

In this study, the photocatalytic activity of Nd-TiO2 photocatalysts obtained by common hydrothermal method were evaluated by practical experiments and theoretical calculations based on Density functional theory (DFT). The synthesized photocatalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) to study their physical/chemical properties. At the same time, the photoelectronic performance was also investigated. The photodegradation ability of as-prepared photocatalysts and the effect of Nd doped amount and photocatalysts dosage were investigated by the photodegradation of phenol (30 mg/L) under 400 W metal halide lamp (UV-Vis). The effect of Nd on electronic properties of TiO2 and adsorption ability of phenol were discussed. Results show that the red-shift wavelength of 0.5 mol%Nd-TiO2, indicating its absorption capacity is stronger than pristine TiO2 in the same wavelength range. The result of DFT calculations demonstrate that the optical bandgap of Nd-TiO2 is profoundly reduced, thus the light absorption ability is promoted, which will be responsible for the enhanced photocatalytic performance of Nd-TiO2. 0.5 mol%Nd is an optimum value for photodegradation phenol, and phenol can be completely degraded by 0.5 mol%Nd-TiO2 for 210 min, the higher catalytic performance is derived from the efficient separation of e–/h+ pairs. Moreover, the adsorption energy calculations of phenol on TiO2 (101) and Nd-TiO2 (101) demonstrate that the Nd doping can significantly enhance the adsorption ability of phenol on catalyst surfaces because of the formation of Nd–O bonds. At last, the stability measurement through four recycles exhibits that 0.5 mol%Nd-TiO2 possesses excellent stability.

The ZrSn composites materials were prepared in one pot by chemical co-precipitation method. SnO2 was incorporated to ZrxOy modifying the molar percentage from 1 to 5 mol%. The ZrSn composites were characterized by different techniques: XRD, FTIR, DRS, SEM, N2 physisorption and HR-TEM. The ZrSn composites were dried at 80 °C and thereafter were evaluated in the photodegradation of phenol under UV irradiation. The percentages of degradation and mineralization were determined after a reaction time of 150 min by UV–Vis spectroscopy and Total Organic Carbon analysis (TOC), respectively. The composite containing SnO2 in a 3 mol% showed the highest photoactivity with a 72% of photodegradation, a higher value compared with the obtained with TiO2-P25 (62%). Finally, a possible reaction mechanism was proposed based on certain studies, which allows to follow the formation of the active species •OH, •O2− and h+. The formation of the •OH specie was measured by fluorescence spectroscopy whereas the inhibition of the species •O2− and h+ was determined by UV–Vis spectroscopy. The results showed that the ZrSn composites not promotes the hydroxyl radical formation. In addition, the holes capture showed a full-loss of the photoactivity while the minimization of (•O2−) radicals in the reaction media results in a decrement of the photoactivity. The formation of heterojunctions and the presence of localized states in the synthesized composites offer an excellent alternative for a fast photodegradation of phenol.

Ag/CeO2/SBA-15 hybrid photocatalysts were synthesized and their catalytic activities were investigated in the photodegradation of Congo red (CR) under different conditions. The results of X-ray diffraction (XRD) analysis, Rietveld refinement, X-ray photoelectron spectroscopy (XPS) analysis, and DRS-UV-vis characterization confirmed that oxygen defects were created in CeO2 layer and its concentration decreased on increasing of ceria loading of the catalysts. Ag0/Ag+ and Ce3+/Ce4+ couples coexisted in the Ag/CeO2/SBA-15 catalysts, resulting from the electrons transferring from Ag0 nanoparticles (AgNPs) to Ce4+ around the oxygen defects in CeO2. The values of surface Ag0/Ag+ and Ce3+/Ce4+ ratios were correlated well with the variation of oxygen defect concentration and the photocatalytic activity. The catalysts with the lower CeO2 content, i.e. 5~10 wt%, exhibited the better photocatalytic activity due to the formation of a greater number of oxygen defects and more electrons transferring between AgNPs and CeO2. CR could be photodegraded with a higher conversion under acidic than basic condition, following the first order kinetics. A four-stage reaction mechanism consisting of the primary, secondary, aromatic ring opening, and mineralization steps was proposed. This work also confirms that the combination of computer simulation technique for the crystalline structure refinement with the catalytic experiments can gain new insights into the reaction mechanism and help to better understand the photocatalytic behaviors.

BiVO4 coupled to N-Doped TiO2 were obtained using the sol gel method assisted by microwave. Double modifications of TiO2 by doping with nitrogen and BiVO4 were induced to improve the UV visible response of TiO2 and improves the separation of generated charge carriers. The structural and morphological analyses support the formation of uniform BiVO4 and N-TiO2 heterostructures, with the surface area significantly increased by approximately 2.5 times in comparison with the bare TiO2. Doping with N and BiVO4 shifted the TiO2 band gap energy from 3.2 eV to around 2.4 eV. The photocatalytic activities of the catalysts were evaluated in the degradation reaction of Rhodamine B and Ofloxacin in aqueous solution. The resulting structures showed superior photocatalytic activity compared to their individual counterparts. More than 98% and 92% of Rhodamine B and Ofloxacin, respectively, could be degraded with the most active BiVO4/N-TiO2 catalyst under visible light radiation. The enhanced photocatalytic activity displayed by the heterostructures could be explained in terms of higher absorption of visible light due to the synergistic effect of N-doping of TiO2 and BiVO4 coupling and improved charge separation due to the formation of an n–n junction at the interface of N-TiO2 and BiVO4 semiconductors. The showed enhance photocatalytic response for the degradation for both pollutants was attributed to electrons and holes from photo-oxidation by ROS, confirmed by carrier scavenger experiments. The separation efficiency of photoinduced charge carriers was further affirmed by photoluminescence and electrochemical studies. The structures were stable even after the third catalytic cycle, indicating their efficiency in potential treatments of pollutants. Finally, based on experimental and test results, a reaction mechanism was proposed.

The major findings in this report are (i) development of nanocomposite photocatalyst working through Z-scheme charge transfer pathway across the heterojunction, (ii) utilization of direct sunlight as the photo-source, (iii) prospect of ligand-hole in photocatalysis through enhanced sub-band gap absorption. The photocatalysts, namely LaNiO3, g-C3N4 and LaNiO3/g-C3N4 nanocomposites were synthesized via facile route and were characterized for their structure, morphology, microstructure, texture, elemental mapping and surface oxidation states by using several physicochemical techniques. The photocatalytic performance of the nanocomposite was tested through the degradation of hazardous azo dye pollutants, namely reactive black 5 and methylene blue as well as the colorless antibiotic-pollutant tetracycline hydrochloride in aqueous solution in presence of natural sunlight with excellent recycling activity. The 10%LaNiO3/g-C3N4 nanocomposite sample shows best catalytic activity, degrading respectively 94%, 98.6% and 88.1% of reactive black 5, methylene blue and tetracycline hydrochloride in 60 min, 180 min and 120 min. The photocatalytic activity of the nanocomposite phase is several times superior to that of the pure phases. The improvements of photocatalytic activity of g-C3N4 in the nanocomposite have been rationalized through the construction of direct Z-scheme heterojunction and suppression of electron-hole pair recombination efficiency. The enhanced photo-absorption of the nanocomposite can possibly be related to sub-bandgap absorption, which is associated to the midgap state originated from ligand-hole formation or defects in the structure. The photodegradation process is mediated through the formation of super oxide radical (˙O2¯) and hole (h+) as the main responsible species.

Due to the massive discharge of antibiotics in water, it is an urgent matter to remove antibiotics from waste water. The photocatalysts with high stability and activity have attracted extensive attention from researchers. By an in-situ polymerization method, polypyrrole (PPy) was modified on the surface of TiO2 (named as TiO2/PPy). By one-step reduction method, NiCoP was grafted on the surface of TiO2/PPy (named as TiO2/PPy/NiCoP) to synthesize the photocatalyst of TiO2/PPy/NiCoP for degradation of tetracycline (TC) antibiotic. The characterization results revealed that NiCoP was deposited on the surface of TiO2/PPy successfully. The photocatalytic experiment results illustrated that 83.2% of TC could be degraded at natural pH with 20 mg of TiO2/PPy/NiCoP in 50 mL of TC solution (10 mg/L) under visible light irradiation. The high catalytic activity is attributed to the attachment of NiCoP on the surface of TiO2/PPy which can enlarge the light response range of TiO2 effectively. Scavenger studies revealed that the degradation of TC was dominated by •O2− and h+. The photodegradation efficiency of TC with TiO2/PPy/NiCoP still reached over 74% after 5 consecutive cycles, indicating the potential applications in practical wastewater.

Zinc oxide-hydroxyapatite composites were prepared using wet impregnation method. Firstly, a natural phosphate ore rich in silica and calcium phosphate was sieved to separate silica phase from phosphate phase. Then, through a chemical precipitation method, a pure hydroxyapatite (HAP) was obtained, which was used as a support for ZnO immobilization and applied for the photodegradation of two toxic contaminants: a transparent molecule (caffeine) and dye molecule (rhodamine B). During the present work two weight ratio percentages of zinc oxide were used: 25 wt.% and 50 wt.% of ZnO relative to HAP. The samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), X-ray Fluorescence (XRF), BET surface area (SBET), Scanning Electron Microscopy (SEM-EDS) and by Transmission Electron Microscopy (TEM-STEM). The immobilization of ZnO on HAP surface followed by thermal treatment at 400 °C for 2 h to get a homogenous dispersion of ZnO on the hydroxyapatite support. At high ZnO impregnation percentage, photodegradation performances of ZnO-HAP under UV illumination were fast and superior than the ZnO photocatalyst alone. The results showed that due to the presence of HAP, the conversion of both molecules became faster and greater, since it promotes the synergic phenomena of adsorption and photocatalysis. The toxicity of the treated substrate solutions obtained in the corn kernels germination test indicated a low toxicity after the photodegradation processes, probably due to a high mineralization degree.

To date, developing an efficient and economical method for the removal of sulfonamides is essential but yet challenging. This paper proposes a facile method to synthesize an efficient photocatalytic material denoted as CNZn heterojunction through in situ surface modification of g-C3N4 on ZnO nanoparticles. The as-obtained photocatalyst of CNZn has a three-dimensional (3D) spherical ZnO nanoparticles architecture wrapped on two-dimensional (2D) g-C3N4 nanosheets. Furthermore, other physicochemical properties of the novel photocatalyst were also analyzed in detail using X-ray diffraction, photoluminescence emission spectra, and UV–vis diffuses reflectance. The effects of catalyst dosage and solution pH on sulfamethoxazole (SMZ) degradation efficiency was also investigated. The optimized CNZn heterojunction exhibited 1.61-fold and 2.23-fold higher degradation efficiency for SMZ when compared to g-C3N4 and ZnO alone under the same experimental conditions. Compared with sulfafurazole (SFZ) and sulfadimidine (SDD), we found that SMZ was more easily photodegradated under visible-light irradiation (λ > 400 nm) due to the different molecular structure. The results of the trapping experiments revealed that both holes and superoxide radicals are the main active substances involved in the mechanism of SMZ photodegradation. Furthermore, the possible enhanced photocatalytic mechanism for SMZ degradation by the use of a CNZn heterojunction photocatalyst is proposed in this study. The results of this study provide an excellent reference for the construction of high-performance photocatalysts in the future.

The semiconductor-based photocatalysts with local surface plasmon resonance (LSPR) effect can extend light response to near-infrared region (NIR), as well as promote charge-carriers transfer, which provide a novel insight into designing light-driven photocatalyst with excellent photocatalytic performance. Here, we designed cost-effective wide-spectrum Zn2In2S5/W18O49 composite with enhanced photocatalytic performance based on a dual-channel charge transfer pathway. Benefiting from the synergistic effect of Z-scheme heterostructure and unique LSPR effect, the interfacial charge-carriers transfer rate and light-absorbing ability of Zn2In2S5/W18O49 were enhanced significantly under visible and NIR (vis-NIR) light irradiation. More reactive oxygen species (ROS) were formed by efficient molecular oxygen activation, which were the critical factors for both Escherichia coli (E. coli) photoinactivation and tetracycline (TC) photodegradation. The enhancement of molecular oxygen activation (MOA) ability was verified via quantitative analyses, which evaluated the amount of ROS through degrading nitrotetrazolium blue chloride (NBT) and p-phthalic acid (TA). By combining theoretical calculations with diverse experimental results, we proposed a credible photocatalytic reaction mechanism for antibiotic degradation and bacteria inactivation. This study develops a new insight into constructing promising photocatalysts with efficient photocatalytic activity in practical wastewater treatment.

The hydrophobic ionic liquids/water two-phase system was developed to prepare CuO nano particles. The catalytic activity of the synthesized CuO was investigated by photodegradation of 4-nitrophenol (4-NP) in the presence of H2O2 under visible light irradiation. The optical properties of the synthesized CuO were characterized by ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy (DRS). Experimental results indicated that the band gap energy (Eg), conduction band edge potential (ECB) and valence band edge potential (EVB) of the synthesized CuO were 1.37 eV, 0.625 eV and 1.995 eV, respectively. A degradation efficiency of 4-NP (4.8 mmol L−1) as high as 95.3% could be achieved under the conditions of pH 6.0, 0.48 g L−1 of CuO dosage, 1.4% of H2O2 dosage and 90 min of degradation time. The synthesized CuO exhibited poor catalytic activity under alkaline conditions due to the disassociation of 4-NP, which elevated the repulsion between CuO and the 4-NP anions. The synthesized CuO nano particles exhibited higher catalytic activity compared with the catalysts reported in literature. Furthermore, the synthesized CuO nano particles could be reused at least six times without decreasing their catalytic activity. Compared with the traditional hydrothermal method, mild operating conditions and time saving are the advantages of the developed method for the preparation of CuO.

Photocatalytic processes are promising and ecofriendly approaches to degrade organic pollutants in water. However, the rapid bulk and surface recombination of photogenerated electron-hole (e-h) pairs is the main impediment to the application of photocatalysts. In this paper, TiO2/CuO nanofilms were fabricated and optimized by doping TiO2 with Cr via reaction magnetron sputtering. The morphology, crystalline phase, surface chemical composition, and optical features of the nanofilms were investigated via SEM, XRD, Raman spectroscopy, AFM, XPS, and UV–vis spectroscopy. The experimental results showed that Cr modification led to the production of TiO2 crystals with an increased surface area of the {0 0 1} facet and more surface oxygen vacancies (OVs). Cr-doped TiO2/CuO showed superior photocatalytic activity, degrading 94.1% of rhodamine B (RhB) over 120 min. Furthermore, the Cr-doped TiO2/CuO nanofilm maintained good photocatalytic performance after four cycles of photocatalytic degradation without obvious changes in the morphology or crystal structure. Capture experiments demonstrated that superoxide anion radicals were the main active substance, and a possible mechanism of the photodegradation reaction was proposed.

The development of photocatalysts for efficient photodegradation of emerging water pollutants is a subject of global concern in recent years. In this study, the photophysical properties of TiO2 were modified by doping with different concentrations of boron (B-TiO2) and nitrogen (N-TiO2) by following a sol-gel route of synthesis. The type and concentration of dopants were optimized to achieve maximum degradation of acetaminophen (ACT) and monocrotophos (MCP) in aqueous solutions. UV DRS analysis shows that the bandgap of TiO2 (3.2 eV) reduced up to 2.96 and 2.27 eV in B-TiO2 and N-TiO2 samples, respectively. The presence of dopants inside the crystal lattice of doped TiO2 was confirmed with X-ray diffraction (XRD), Micro Raman, Fourier Transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy(XPS). The XRD data confirmed that the presence of these dopants promotes the rutile phase transformation in TiO2 to various extents. The doping of B decreased the surface area and pore volume of TiO2, whereas N doping had increased these properties.The XPS spectra showed the formation of Ti-O-B and Ti-O-N type linkage, indicating the presence of interstitial B and substitutional N atoms in TiO2 crystal lattice.The B doped samples exhibit more enhancement in photodegradation efficiency as compared to N doped samples. Under optimized conditions, 5% B-TiO2 showed 95% and 71% degradation of ACT and MCP, respectively. The degradation pathway for both ACT and MCP involving their intermediates was discussed through Mass spectrometry analysis. The cost-effectiveness of the most efficient doped catalysts and commercial catalysts were compared with the ACER tool and turnover frequency.

In this study, water-dispersible graphitic carbon nitride (g-C3N4) photocatalysts were successively prepared through the chemically oxidative etching of bulk g-C3N4 that was polymerized thermally in different calcination atmospheres such as air, CO2, and N2. The different calcination atmospheres directly influenced the physicochemical and optical properties of both bulk and water-dispersible g-C3N4, changing the photocatalytic degradation behavior of methylene blue (MB) and tetracycline hydrochloride (TC-HCl) for water-dispersible g-C3N4. The bubble-burst process in the thermal polymerization of thiourea produced defective edges containing C=O groups that preferred substituting the C-NHx groups over bulk g-C3N4. In the oxygen-free N2 atmosphere among the different calcination atmospheres, more C=O functional groups were generated on the defective edges of bulk g-C3N4, resulting in the highest N vacancy of the tri-s-triazine structure. During the successive chemical oxidation, S- or O-containing functional groups were introduced onto water-dispersible g-C3N4. The water-dispersible g-C3N4 photocatalyst from the oxygen-free N2 atmosphere (NTw) contained the most O- and S- functional groups on the g-C3N4 surface. Consequently, NTw exhibited the highest photocatalytic activity in the MB and TC-HCl photodegradation because of its slowest recombination process, which was ascribed to the unique surface properties of NTw such as abundant functional groups on the defective edges and N-deficient property.

Exploiting efficient and recyclable photocatalysts is a vital matter for environmental purification. Herein, cerium vanadate (CeVO4) sub-microspheres and silver nanowire (AgNW)@CeVO4 with core-shell architecture as photocatalysts are rationally constructed by hydrothermal approach. The AgNW@CeVO4 photocatalyst obtained by depositing CeVO4 on the surface of Ag NWs possess one dimensional continuous structure, which expand the optical absorption range and reduce the band gap of CeVO4 photocatalyst. Moreover, the resultant AgNW@CeVO4 photocatalyst demonstrates superior photocatalytic performance in the degradation of rhodamine B, methylene blue, and 4-nitrophenol pollutants upon solar light irradiation, compared with pure CeVO4. The excellent photocatalytic activity can be ascribed to the introduction of Ag NWs, which afford rapid charge transport channels and reservoir for the electrons in the AgNW@CeVO4 heterostructure to promote separation of electron–hole pairs. The first-principles investigations reveal increase of adsorption energy of oxygen molecules on the CeVO4 surface with the presence of Ag. Meanwhile, Ag NWs can further improve the photocatalytic efficiency of the AgNW@CeVO4 based on the plasmonic effect. More importantly, the good structural stability and recyclability of AgNW@CeVO4 are observed due to the strong synergistic effect, which ensures long-term usability of photocatalyst and great promise in water purification. This work can offer valuable reference into designs and construction of Ce-based heterojunction photocatalysts for environmental remediation.

Multi-functionalized and co-doped TiO2/C nanocomposites were derived from the pyrolysis of Ti-MOFs at 800 °C under different gaseous atmospheres and their photocatalytic performance were investigated. The gaseous atmosphere during pyrolysis plays a critical role in determining the structural, textural, optical and physicochemical properties of the derived TiO2/C composites due to the synergistic effect of nitrogen-containing species, carboxylate and sulfur functionalized porous carbon as well as N/S co-doped TiO2 nanoparticles. All the Ti-MOFs derived TiO2/C composites exclusively possess homogeneously distributed TiO2 nanoparticles in a functionalized disc-like porous carbon matrix and demonstrate much enhanced adsorption and photodegradation performance than commercial TiO2 under the same conditions. The adsorption of methylene blue (MB) in dark on these TiO2/C composites are dominated with pseudo second-order kinetic model and the high adsorption capacity of MB in dark on composite TiO2/C derived from MIL-125(Ti) in argon is due to its high surface area with predominant mesoporous carbon matrix in the composite. The composite N-O-TiO2/C derived from NH2-MIL-125(Ti) in water vapor exhibited the highest photodegradation activity with 99.7% MB removal in 3 hours under visible light due to the optimal anatase/rutile phasejunction, together with the formation of photoactive oxygen-rich N-O like interstitial/intraband states above the valence band of TiO2, as well as the presence of N-containing species and -OH/-COOH multi-functional groups with superhydrophilic nature of the composite. This simple one-step and easily modifiable approach can be further employed to modulate homogeneously dispersed multi-functionalized and co-doped metal oxide/carbon nanocomposites for various environment and energy-related applications.

In recent years, photocatalytic technology has attracted wide attention in environmental treatment, exploring non-toxic and metal-free photocatalysts is imminent to meet sustainable development. However, semiconductors with wide spectral response are rarely studied and applied in the field of photocatalysis. Herein, a new narrow band-gap polymer PFBDT-DPP (P3) with wide absorption from 500 to 860 nm was synthesized and further constructed heterostructure with g-C3N4 for photocatalytic sterilization and degradation of organic pollutant Rhodamine B (RhB). The optimal antibacterial rate for Escherichia coli reached 99.8% after 190 min of light irradiation and for Staphylococcus aureus reached 96.8% after 120 min of irradiation, and the highest degradation efficiency of RhB by P3/g-C3N4 was 98.9% within 60 min light irradiation, while g-C3N4 displayed an unsatisfactory sterilization and photodegradation performance. This is mainly attributed to the broadened light absorption range and enhanced carrier separation efficiency of P3/g-C3N4. This work could provide a new strategy to fabricate metal-free photocatalysts with high utilization of sunlight and excellent photocatalytic performance.

The pure TiO2 and lanthanum (La3+)-doped titanium dioxide (TiO2) nanofibers were synthesized by electrospinning method followed via calcination at different temperatures (from 400 °C to 700 °C). Structures of the nanofibers were characterized by X-ray diffraction, scanning electron microscopy, TEM images and diffuse reflectance spectroscopy. The size of the nanofiber diameters was determined to be 129 and 101 nm, for pure TiO2 and (0.1%)La3+:TiO2 materials, respectively. The prepared nanofibers possess a crystalline structure, and wide distribution of the band-gaps, in the 2.867–3.210 eV range. Effects of La3+-dopant content, calcination temperature, and different doses of photocatalysts on the photodegradation efficiency were studied. The optimal level of La3+ and the optimal temperature of calcination were 0.1% La3+ and 600 °C, respectively. The photocatalytic degradation of methylene blue (91%, with a rate constant of 2.179×10−2 min−1) and ciprofloxacin (CIP) (99.5%, with a rate constant of 1.981×10−2 min−1) pollutants was highest on the (0.1%)La3+:TiO2 annealed at 600 °C, after 300 min irradiation under visible light. This photocatalyst displayed sustainable efficiency for CIP degradation up to five consecutive uses.

As a response to the everyday growing concern about wastewater treatment, some new mesoporous TiO2/ZnFe2O4 and TiO2/ZnFe1.98La0.02O4 catalysts were synthesized during this research. The ultrasound template-assisted sol-gel method was employed in the synthesis, using conventional calcination and microwave treatment for pore directing agent removal. The as-prepared samples were characterized from the structural, optical, morphological and textural points of view, confirming the presence of spinel ferrites and TiO2 anatase crystals in the nanocomposites. The synthetized powders exhibit promising characteristics for their use in adsorption and light activated degradation of organic pollutants. The photodegradation experiments of model pollutant basic blue 9 (methylene blue) dye were performed at laboratory scale and the optimum experimental parameters were determined as 0.4 g/L catalyst and 30 mg/L initial dye concentration, under UV light irradiation, visible irradiation and natural sun light irradiation. The conventionally calcined lanthanum doped TiO2/ZnFe1.98La0.02O4 system exhibited the highest efficiencies of 97%, 70% and 91% for dye removal from the solution, under UV light, visible light and natural sun light irradiation, respectively. Moreover, the catalytic activity was similar for up to four consecutive cycles. A lower yield of organic pollutant removal was observed in wastewater treatment plant (WWTP) effluent. The obtained results show that the newly synthesized catalysts are good candidates for the removal of water pollutants through adsorption and photocatalysis.

Nonylphenol (NP) residues, as a typical endocrine disrupting chemical (EDC), frequently exist in sewage, surface water, groundwater and even drinking water, which poses a serious threat to human health due to its bioaccumulation. In order to remove NP, a series of MIL-100(Fe)/ZnFe2O4/flake-like porous carbon nitride (MIL/ZC) was synthesized through in-situ synthesis at room temperature. High performance of ternary MIL/ZC is used to degrade NP under visible light irradiation. The results show that 30MIL/ZC2 (20 wt.% ZnFe2O4) ternary composite had the best photocatalytic activity (99.84%) when the dosage was 30 mg. Further mechanism analysis shows that the excellent photocatalytic activity of 30MIL/ZC2 could be ascribed to the double charge transfer process between flake-like porous carbon nitride (PCN) and other catalysts in the ternary heterojunction, and the separation of photogenerated electron-hole pairs was more effective. In addition, the 30MIL/ZC2 also showed high stability after five cycles of the photodegradation reaction. Furthermore, the active substance (•O2−) was considered to be the main active substance in the NP degradation process. Based on the research results, the possible photocatalytic reaction mechanism of 30MIL/ZC2 ternary composite was proposed and discussed in detail.

Copper oxide nanoparticle (NPs) was prepared by a green Chemistry approach. The synthesized NPs were characterized by XRD, SEM, FT-IR, and UV–Vis spectrophotometer. The XRD peaks matches with the standard X-ray diffraction patterns confirming monoclinic crystal phase. FT-IR absorption exhibits the existence of metal oxygen stretching bond at 422 cm−1. SEM study shows that the particles were highly porous in nature having irregular shape and are agglomerated. EDX spectrum confirms the presence of Cu and O in the synthesized NPs. The band gap was found to be 1.65 eV from UV– Vis studies. An enhanced photo degradation of Rose Bengal dye was indicated by synthesized NPs.

This study synthesized UiO-66 (Zr) in situ on wood via a one-step solvothermal method. UiO-66/wood was successfully prepared and its catalytic performance for the ofloxacin (OFX) photodegradation under simulate sunlight was also explored. UiO-66/wood exhibited a better catalytic performance, and its degradation rate constant was about 1.2 and 1.5 times than that of UiO-66 and wood, respectively. The effects of solution initial concentration, pH of the system and dosage of the photocatalyst were explored. Additionally, the active species trapping experiments and UV–vis diffused reflectance spectra measurements were conducted to investigated the photocatalytic mechanism of the UiO-66/wood composite, superoxide radical (O2•–) and hydroxyl radical (•OH) were the main reactive species. In addition, the possible degradation pathways of OFX were analyzed by LC-MS. Meanwhile, the UiO-66/wood showed outstanding stability and reusability after 4 cycles experiments. The removal performance of UiO-66/wood towards real samples showed it has potential in actual application .

During the last decade, there is a growing interest in developing efficient photocatalysts with a visible light sensitivity. Herein, visible-light-driven photoactivity of CrFeO3 prepared by nitrate route was studied. The photocatalysis was evaluated through the Ni2+ reduction. The X-ray diffraction (XRD) is characteristic of a single phase crystallizing in the ilmenite structure with a good crystallinity. It was characterized by the SEM, TEM/HRTEM, FTIR spectroscopy and thermal analysis (TG). The optical and dielectric constants are determined from the diffuse reflectance data. The refractive index (n), extinction coefficient (k), relaxation time (τ), dissipation factor (tan δ) and optical conductivity are extracted. The forbidden band Eg (= 1.65 eV), was computed and confirmed by different methods. The electrical conductivity (σ) augments exponentially with 1000/T and activation energy of 0.22 eV was calculated. The p-type conduction is evidenced from the capacitance measurements with a flat band potential (Efb = −0.38 VAg/AgCl) and a hole concentration (NA = 5.87 × 1018 cm−3). The novel hetero-system CrFeO3/TiO2 showed improved efficiency by 47% compared to CrFeO3. An optimal mass ratio CrFeO3/TiO2 (25%/75%) gives to a Ni2+ reduction of 88% at pH ∼ 7.2 within 4 h irradiation for an initial Ni2+ concentration of 15 mg/L. A first order kinetic was found from the Ni2+ photoreduction with a half photocatalytic life of 61 min−1 and a higher photodegradation under sunlight is obtained. More interestingly, the photocatalyst showed a good stability and recyclability after four runs.

In this paper, it was used a monolithic-type structured photoreactor with a high surface area calcined brass as a substrate for TiO2-P25. The TiO2 immobilization over the monoliths was carried out by the washcoating process. The films were characterized via XRD and diffuse reflectance. The monoliths were tested at a recirculation reactor using a solar simulator as an energy source and their efficiency was evaluated at Reactive Black 5 (RB5) textile dye photodegradation. It was investigated the effect of the impregnated catalyst mass, the monolith size, the initial dye concentration and the reaction medium pH. The preliminary tests of the brass calcination temperature (500, 600, and 700 °C) showed the formation of ZnO and CuO semiconductors at the brass surface, thus suggesting that the monoliths can act as photocatalysts. Furthermore, the brass calcined at 500 °C showed the greater formation of both oxides (ZnO and CuO) and greater photocatalytic efficiency. The TiO2/brass monolith presented more than 59 % of degradation for an initial dye concentration of 12.5 mg.L−1. In regarding to stability test, the system set forth a decrease at RB5 degradation efficiency of 62 % and presented an adherence of 77.5 % after 5 cycles of monoliths reuse. Therefore, the brass monolithic systems with immobilized TiO2 showed to be a feasible alternative for textile effluent treatment.

The introduction of oxygen-defects has been a versatile strategy to enhance photocatalysis efficiency. In this work, a 2D/3D Bi/BiO2-x/Bi2WO6 heterojunction photocatalyst with rich oxygen-defective was in sequence prepared through a facile solvothermal method, which displays favorable photocatalytic activity towards organic contaminants under visible-NIR light irradiation. The enhancement in photocatalytic performance can be attributed to the synergistic effect between oxygen-vacancy-rich heterojunction and the localized surface plasmon resonance induced by metallic Bi. The functional group interaction, surface morphology, crystal structure, element composition, and tuned bandgap were investigated by FT-IR, SEM, Raman shift, ICP-MS, and XPS technique. The spectrum response performance of the photocatalyst was verified by UV-visible DRS analysis. Results of photodegradation experiments toward organic contaminants showed that the prepared photocatalyst can degrade 90% of phenol in 20 mins under visible-NIR light irradiation, both Z-scheme heterojunction and the introduction of Bi metal contribute to the enhancement in the photocatalytic activity. The results of the DFT calculation suggest that the valence band-edge hybridization within BiO2-x and Bi2WO6 can effectively enhance the photocatalytic performance by increasing the migration efficiencies of electron-hole pairs. Moreover, a possible mechanism was proposed on the results of EIS, ESR and GC-MS tests. This work offers a novel insight for synthesizing efficient visible-NIR light photocatalysis by activating the semiconductors with Bi metal.

Conjugated microporous polymer (CMP) is an emerging organic semiconductor with π-conjugated skeletons, and the bandgap of CMP can be flexibly modulated to harvest visible light. Based on the diversity and adjustability of monomers in CMP, we designed and synthesized donor-accepter (D-A) type BTN-CMP through Sonogashira-Hagihara cross-coupling polymerization, further in-situ constructing series of inorganic/organic Z-scheme BW/BTN-n composite in the presence of Bi2WO6. After optimization, the tetracycline hydrochloride (C0=10 mg·L-1) degradation efficiency reached 84 % with BW/BTN-2 as catalyst in 90 min under visible light irradiation, the apparent rate constant k1 is 0.017 min-1, which is 1.7 and 5.7 times higher than bare Bi2WO6 and BTN-CMP. X-ray photoelectron spectra and UV-Vis diffuse spectra showed that the enhanced photocatalytic activity originated from the tight heterojunction between Bi2WO6 and BTN-CMP, which can extend the light absorption range and facilitate the separation and transport of photogenerated charges in the interface of heterojunction. The active species trapping experiments and electron spin resonance technique revealed that h+ was the dominant active species during the photodegradation process of tetracycline hydrochloride (TCH). The present study demonstrated the feasibility to construct inorganic/organic composite for the photocatalytic degradation of environmental pollutants.

In this study, we studied the effect of starting ligands such as 1,4-benzenetdicarboxylic (H2BDC), 1,3,5-benzenetricarboxylic (H3BTC), and 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoic (H3TATB) acids on the photocatalytic activity of three bismuth-based MOFs (Bi-MOF) obtained via a microwave-assisted solvothermal process. Different shapes and sizes of ligands displayed different structure properties from the corresponding Bi-MOF. Specifically, Bi-MOF composed of Bi3+ and H3TATB (Bi-TATB) exhibits the largest specific surface area of 355 m2/g, highest surface-oxygen vacancy amount, a more vigorous light absorption intensity with a broader range of visible light absorption and red-shifted absorption edge than that of Bi-MOF composed of Bi3+ and H2BDC (Bi-BDC) and Bi-MOF composed of Bi3+ and H3BTC (Bi-BTC), suggesting the extension in the photocatalytic activity for Bi-TATB. The reason is attributed to the difference in their structural features. Compared with H2BDC and H3BTC ligands in Bi-BDC and Bi-BTC, H3TATB ligands in the structure of Bi-TATB contained more delocalized π electrons. This outcome may facilitate the ligand-to-metal charge transfer (LMCT) and decrease the electronic bandgap of the Bi-TATB, thus contributing to the enhanced photocatalytic rate. The enhanced photocatalytic activity of Bi-TATB was further confirmed by the photodegradation of rhodamine B (RhB) under LED light irradiation, which is 99.1% of RhB removal after 180 min of light irradiation. The as-synthesized Bi-TATB showed promising photocatalytic activity for the degradation of organic dye with an excellent recyclable catalytic efficiency. With the above understanding, Bi-MOF was finally used for the photocatalytic O2 evolution from water under LED light irradiation. The Bi-TATB had a maximum photocatalytic O2 evolution rate of 691 μmol h−1. To the best of the author’s knowledge, there has been no research on both the photocatalytic degradation of organic model dye pollutants and photocatalytic O2 evolution studies using Bi-MOFs with different organic linkers. The results should open an alternative approach of ligand selection that could increase the applicability of Bi-MOF in the field of catalysis.

Designing recyclable photocatalysts with high activity and stability has drawn considerable attention in the fields of sewage treatment. Herein, a series of heterojunctions constructed by zirconium-based metal–organic frameworks (UiO-66-NH2) and tungsten trioxide (WO3) is immobilized on carbon cloth via a facile solvothermal method, resulting in highly recyclable photocatalysts. Multiple characterization techniques, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy, verify the successful synthesis of UiO-66-NH2 nanospheres on the surface of needlelike WO3 modified carbon cloth. Results show that the optimal heterojunction photocatalyst exhibits excellent photocatalytic degradation efficiency for the removal of tetracycline (TC) from water, for which nearly 100% of TC is degraded within 60 min under visible light. Trapping experiments and electron spin resonance (ESR) spectra analyses demonstrate that the superoxide radicals O2– and photogenerated hole h+ play a dominant role in the degradation process. Excellent photocatalytic activity is dominantly attributed to the effective separation of photoinduced carriers in this type-Ⅱ heterostructure system. Moreover, the possible photocatalytic oxidation degradation pathway is confirmed by analyzing intermediates using liquid chromatography mass spectrometry (LC-MS). This study offers a highly efficient strategy to design recyclable heterojunction photocatalysts for the degradation of refractory antibiotics in sewage.

A straightforward, high-yield route was followed to produce visible light active BiVO4 (BV)-based catalysts through the novel, green approaches: metathesis and metathesis-assisted molten salts. The catalysts prepared at room temperature (BV-RT) and 350 °C for 12 h (BV350/12) exhibited spherical-like and highly crystalline plate-like particles, respectively. A novel BV catalyst was prepared by adding graphite oxide, GO/BV. The synthesis conditions affected crystallite size, crystallinity, optical edge, energy gap, specific area characteristics, and photocatalytic activity. GO/BV achieved 100% rhodamine B (RhB) degradation irradiated (300 min) with low-power blue LEDs. The initial reaction rate (-r0) of RhB using the GO/BV was 4.57, 3.42 and 1.31-fold faster than BV-RT, BV350/12, and BV350/2. Catalyst dosage and RhB initial concentration on the photoactivity of GO/BV were analyzed. Trapping experiments established that holes and hydroxyl radicals are the main oxidative species causing RhB degradation, and the mechanism was postulated based on GO/BV. Reusability tests confirmed GO/BV chemical stability. GO/BV reached 74% photodegradation of methylene blue (MB). The photodegradation of the RhB + MB mixture using GO/BV showed that the coexistence of MB diminished the RhB degradation to 86%.

In this work, a S-scheme ZnO/Zn3(PO4)2 heterojunction photocatalyst was fabricated by a simple co-precipitation manner under reflux condition. The ZnO/Zn3(PO4)2 heterostructured nanocomposite was employed for the degradation of tetracycline antibiotic under UV and visible light irradiation. The structure, composition, morphology, and optical properties of the as-synthesized ZnO/Zn3(PO4)2 products were characterized by XRD, EDS, FESEM, TEM, UV–Vis DRS, and PL measurements. The hybrid ZnO/Zn3(PO4)2 nanoparticles exhibited the highest photocatalytic efficiency in the degradation of tetracycline under ultraviolet (97%) and visible (82%) light irradiation, which was ∼1.5 times more than sole Zn3(PO4)2 nanostructures. The promoted light harvesting and generated heterojunction interfaces between ZnO and Zn3(PO4)2 can obviously reduce the recombination rate of charge carriers in the ZnO/Zn3(PO4)2 heterostructure. Moreover, a reasonable photocatalytic mechanism of the UV and visible light-induced degradation of antibiotic over ZnO/Zn3(PO4)2 nanocomposites is suggested. The results indicated that under UV, the mechanism follows from the S-scheme in the presence of •O2− and •OH as predominant species, while upon visible, the type-II heterojunction utilizing •O2− as prevailing radical is possible.

Developing durable photocatalysts with highly efficient antibiotics degradation is crucial for environment purification. Herein, tetra (4-carboxyphenyl) porphyrin (TCPP) was loaded onto the surface of Bi2MoO6 microspheres to gain hierarchical organic–inorganic TCPP/Bi2MoO6 (TCPP/BMO) heterojunctions via a facile impregnation strategy. The catalytic properties of these catalysts were comprehensively investigated through the photodegradation of tetracycline hydrochloride (TC) under visible light. Among all the TCPP/BMO heterojunctions, the highest photodegradation rate constant (0.0278 min−1) was achieved with 0.25 wt% TCPP (TCPP/BMO-2), which was approximately 1.15 folds greater than that of pristine Bi2MoO6 and far superior to pure TCPP. The extremely high photocatalytic performance is attributed to the interfacial interaction between TCPP and Bi2MoO6, which favors the efficient separation of charge carriers and the enhancement of visible-light absorbance. TCPP/BMO-2 possesses high mineralization capability and good recycling performance. Photo-induced O2–, h+, and OH were mainly responsible for the degradation of TC. The degradation pathways of TC and toxicity of degradation intermediates were analyzed based on the intermediates detected by the high performance liquid chromatography-mass spectrometer (HPLC–MS) and the toxicity assessment by the quantitative structure–activity relationship (QSAR) prediction. A possible photocatalytic mechanism over TCPP/BMO is proposed. This work offers an insight in developing the porphyrin-based organic–inorganic heterojunctions for effectively remedying pharmaceutical wastewater.

Semiconductor-based photocatalysis represents a promising technology for removing antibiotic given its cost effectiveness and environmental compatibility. However, finding suitable photocatalysts and semiconductors for practical applications can be challenging. This work aims to investigate the photocatalytic performance of as-synthesized photocatalysts under broad-spectrum from visible (Vis) to near-infrared (NIR) sunlight. In this work, a step-scheme (S-scheme) heterojunction photocatalyst, i.e., CuS/S–C3N4, was prepared, employing a single-step hydrothermal route. The synthesized photocatalyst showed excellent crystallinity and high purity content. The CuS loading provided a better NIR light response-ability and improved photocatalytic activity for CuS/S–C3N4. The 2 wt% CuS/S–C3N4 produced the highest tetracycline (TC) photodegradation rate, up to about 95% efficiency under Vis + NIR light irradiation. The result also showed that the 2 wt% CuS/S–C3N4 sample had a first-order kinetic constant (k) that was 6.2-fold higher than the pure S–C3N4 sample under Vis + NIR light irradiation. However, too much CuS content led to the presence of inactive sites on S–C3N4, which hampered the light absorption ability, thus leading to inadequate photocatalytic activity. In addition, the 2 wt% CuS/S–C3N4 sample also showed high photocatalytic stability and insignificant change of the composite structure before and after the experiments. In short, we can enhance the CuS/S–C3N4 photocatalytic activity by increasing the light response range and the separation efficiency of light-induced electrons and holes. Consequently, we have developed a novel strategy and experimental basis for S-scheme heterojunction to be fully utilized under broad-spectrum sunlight.

The photo-catalyzed oxidation process of Brown HT dye was studied in the aqueous solution of the dye, using an irradiation source (ultraviolet rays UV) with the use of manganese oxide (MnO) and nickel oxide (NiO) catalysts, where the effect of increasing the weight of the catalyst in the range of 0.05–0.8 g was studied using a fixed concentration of dye 20 ppm, The best weight gave the highest dissociation rate of the dye 0.1 g from MnO and 0.075 g from NiO, and at the best weight the effect of many factors on it was studied, including pH, change of initial dye concentration, and temperature. The effect of changing the pH in the range (2–10) was studied, and the best pH gave the highest rate of dissociation of the dye at pH = 2 in the presence of MnO and pH = 4 in the presence NiO when using UV as an irradiation source. The effect of changing the initial concentration of the dye in the range of 10–50 ppm was studied, as the higher the concentration, the lower the dissociation rate. Accordingly, there is an inverse relationship between the initial concentration and the dissociation rate. The effect of changing the temperature in the range (298–323) K was studied. It was found that the higher the temperature, the greater the dissociation rate. Accordingly, the relationship is direct between temperature and reaction speed, and the activation energy for each reaction was calculated using the Arrhenius equation.

As competitive photocatalysts, Cu2O nanoparticles meet with severe photogenerated carries recombination and insufficient light absorption, leading to the poor photocatalytic performance. Herein, the truncated Cu2O-Au (CA) binary and Cu2O-Au-TiO2 (CAT) ternary octahedra with Au nanoparticles (Au NPs), preferentially supported on the (110) and (100) planes of Cu2O, are synthesized for efficient photocatalytic degradation reactions. The photodegradation rates of MO of CA1 (Cu2O-Au containing 1 wt % Au) and CAT are as high as 95.61% and 96.5% under 60 min of visible light irradiation, respectively. On the one hand, the synergistic function of localized surface plasmon resonance (LSPR) of Au NPs and Schottky barrier accelerate the separation and transfer of photogenerated carriers. On the other hand, a Z-scheme electron transfer system is constructed in CAT to promote the photodegradation performance. According to the finite-difference-time-domain (FDTD) simulation result, there is a strong electric field enhancement at the contact sites between Au, Cu2O and TiO2, which accelerates the electron transfer to a large extent and separates the electron-hole pairs. Therefore, this work may provide an approach for the synthesis and applications of multiple heterostructure catalyst.

Recently environmental pollution due to industrial effluents is a major concern for researchers, so the development of natural dyes is widely accepted due to their low cost, biodegradability, low toxicity, and non -carcinogenic nature and also replaces existing hazardous chemicals in industries. Many plants and fruit extracts can be used as natural dyes, but their efficiency depends on photostability and photo degradation activity. Herein reported extraction of natural dye from Basella Alba fruit using different solvents and photo stability was investigated under UV and visible light. To enhance the stability of extracted pure dye, zinc oxide nanoparticles were added and it acts as an excellent photostabilizer that shows better performance over betalain dye. UV visible spectrum of pure dye shows an absorbance peak of 480 nm and functional groups of both dye and zinc oxide were identified by FTIR spectrum. The structure and surface morphology of the synthesized nanoparticle was confirmed by UV–Visible, XRD, SEM-EDAX and TEM analysis. The crystalline structure of zinc oxide was confirmed by XRD and composition was analyzed by EDAX studies. The wurtzite type structure of zinc nanoparticle was confirmed by XRD. The external morphology of prepared zinc oxide nanoparticles is captured using FESEM. The HRTEM and SAED images are confirmed the crystalline structure of the synthesized material. The photostability and photodegradation studies were performed under UV light and at various temperatures like 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C. These results clearly show a piece of evidence for the usage of nanoparticles for enhancing photostability of natural dyes.

In this work, rare-earth single atoms (La, Er) were decorated on the surface of 2D-TiO2 nanosheets by an impregnation-calcination strategy. The formation of rare-earth single atoms was certified by AC HAADF-STEM and XAS. TiO2 decorated with rare-earth single atoms (La1-TiO2 and Er1-TiO2) exhibited outstanding photocatalytic activity than pure 2D-TiO2 nanosheets (2D-TiO2) towards gas-phase degradation of O-xylene. Compared with 2D-TiO2, the rare-earth single atoms greatly improved the adsorption capacity of O-xylene without increasing their specific surface area. This is because rare-earth single atoms provide additional adsorption sites and reduce the adsorption energy of O-xylene. In addition, the hybrid orbital formed by the combination of rare-earth single atom and oxygen atom is beneficial to the rapid transmission and separation of photo-induced electrons, thereby improving the performance of photocatalytic degradation. In addition, in-situ DRIFTS and GC-MS were used to reveal the photocatalytic oxidation mechanism. Interestingly, the results showed that the La1-TiO2 and Er1-TiO2 samples can reduce the types of intermediates and simplify the reaction route, implying that the single atoms play an important role in the modulation and thorough mineralization of intermediate products. This work shows that the rare-earth single atom decorated 2D-TiO2 nanosheets have great potential in photocatalytic air pollution control.

Light-induced degradation (LID) strongly depends on experimental conditions, among which the presence of oxygen is a major parameter. Elucidating LID processes is of high concern to many areas of interest, e.g., for the conservation of cultural heritage, safety and shelf life of food, and UV-disinfection methods for water purification. Recently, we presented a new, fully automated tool to study molecular photodegradation in solution. The tool employs a gas-permeable liquid-core waveguide (LCW) as a light-exposure cell with in-situ absorption spectroscopy for real-time monitoring, coupled on-line to liquid chromatography (LC) with diode-array (DAD) and mass spectrometry (MS) for characterization of the photodegradation products. The current work reports on the assessment of the potential of the LCW in a tube-in-tube geometry for studying the role of oxygen in photodegradation processes, using Riboflavin and Eosin Y as model compounds. The LID results obtained for Riboflavin and Eosin Y using the LCW set-up were in line with reported data obtained with conventional approaches. On-line LC-MS analysis allowed semi-quantitative monitoring of LID differences under oxic and anoxic circumstances. An increase in degradation by 9% and 30% for Riboflavin and Eosin Y, respectively, was observed after 10 min under anoxic conditions. Moreover, for the first time, the fully debrominated species of Eosin Y (i.e. fluorescein), was identified as a photodegradation product in solution. The presented set-up can be highly useful for the investigation of photodegradation mechanisms and kinetics in solution, including the role of oxygen while increasing analytical efficiency and reducing time spent in the lab.

In this present work, reduced graphene oxide (RGO) coupled with hydrothermally grown sodium niobate nanorods (NaNbO3-NRs) have been successfully synthesized. The photocatalytic performance of RGO/NaNbO3-NRs photocatalyst demonstrated faster photodegradation of organic methylene blue (MB) dye than bare NaNbO3-NRs. A ∼6 fold enhancement in the photocatalytic activity of RGO/NaNbO3-NRs nanocomposite than that of NaNbO3-NRs has been demonstrated towards the degradation of MB dye under similar light illumination. Furthermore, the potentiality of the fabricated NaNbO3-NRs and RGO/NaNbO3-NRs nanocomposite photoanodes have been investigated for photoelectrochemical (PEC) water splitting. The fabricated RGO/NaNbO3-NRs nanocomposite photoanode showed ∼4 times higher photocurrent density than the NaNbO3-NRs photoanode. The electrochemical impedance spectroscopy (EIS) and Mott-Schottky (MS) measurements demonstrated that coupling of RGO nanosheets in the RGO/NaNbO3-NRs nanocomposite reduced the charge transfer resistance (Rct) at the photoanode/electrolyte interface, increased the donor density (Nd), and reduced flat band potential (Vfb) of the RGO/NaNbO3-NRs, thus significantly improving the PEC performance of the RGO/NaNbO3-NRs nanocomposite. The enhancement in the PEC measurements of RGO/NaNbO3-NRs nanocomposite is attributed to the extended absorption of the visible portion of the solar spectra and increased mobility of the photogenerated charge transport in the RGO nanosheets, which improve the separation efficiency and reduce the recombination process. The possible charge transfer mechanism has been proposed responsible for the enhanced photocatalytic and PEC water splitting performance.

The current era of nanotechnology has provided numerous impressive opportunities to purify ever-increasing water impurities. Of them, photodegradation of industrial dyes is one of the best strategies to solve this problem effectively using cost-effective photocatalysts. MXene has been considered as an efficient photocatalytic material however, its transport properties suffer due to the re-stacking of its flakes. Moreover, a very low bandgap of MXene causes electron/hole recombination which is a major drawback of a photocatalyst. Herein, we explored 2D/2D composite nanoarchitectures to stop this re-stacking in MXene by applying Zinc oxide nanoflakes (ZnO NFKs) with Ti3C2Tx (MXene) to solve this outstanding issue. The as-synthesized composite nanoarchitectures not only degraded the 99.9% Methylene Blue (MB) dye within 40 min but also demonstrated excellent antibacterial activity. We hope the work presented here will be a great help for the young researchers exploring the hybrid 2D-2D composite nanoarchitectures for various applications.

Constructing favorable heterointerface to facilitate photogenerated carrier transport is an effective way to improve the photocatalytic activities of semiconductor catalysts. However, the fabrication of atomic-level interface remains a challenge due to the difficulties in constructing intimate interface contact. Herein, a unique atom-to-atom TiO2/ZrTiO4 heterointerface with the potential formation of Ti–O–Ti(Zr) bonds between TiO2 and ZrTiO4 was constructed through the in-situ formation of the two components using a one-step sol-gel method. The resulting photocatalyst exhibited superior photocatalytic activity and high stability, i.e., about 97% of Rhodamine B was degraded after visible light irradiation for 90 min for three consecutive photodegradation cycles. By further analyses such as refined X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS), Raman microscope (Raman), photoluminescence (PL), and photoelectrochemical spectra (TP and EIS), it revealed that the atom-to-atom heterointerface of TiO2/ZrTiO4 with stronger interaction forces would greatly accelerate the charge separation as well as provide generous defect sites, boosting the number of photogenerated carriers available at reaction sites, thus contribute to the improvement of photocatalytic performance. The present work demonstrates a new approach of in-situ construction for interface engineering TiO2 based catalyst, providing design guidelines for heterointerface photocatalytic structures.

In this work, modified g-C3N4 was fabricated successfully by calcination of ionic liquid (IL) and urea. The addition of IL changed the polymerization mode of urea, induced the self-assembly of urea molecules, modified the morphological structure of the tightly packed g-C3N4, and extended the electron conjugation system. When using 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) as a modifier, the heteroatom Cl could be inserted into the g-C3N4 to optimize the electronic structure. The results of characterizations indicate that the unique structure of modified g-C3N4 has an expanded electron delocalization range, introduces an interlayer charge transmission channel, promotes the charge transmission, reduces the band gap, enhances the absorption of visible light, and inhibits electron-hole recombination. Modified g-C3N4 showed excellent photocatalytic performance for the degradation of rhodamine B and tetracycline. Furthermore, the effect of different anions in 1-butyl-3-methylimidazolium salts ([Bmim]Cl, [Bmim]Br, [Bmim][BF4], and [Bmim][PF6]) on the structure and function of g-C3N4 are discussed.

Bisphenol A (BPA) is an endocrine disruptor, and removing it from contaminated water is a major environmental concern. Herein, graphene derivatives such as graphene (G), graphene oxide (GO), and reduced graphene oxide (rGO) supported silica-zirconia (SZ) were successfully synthesized for photodegradation of BPA. The photodegradation of BPA was ordered as follows: rGO/SZ (88%)>GO/SZ (63%)>G/SZ (58%)>SZ (55%). This is because rGO has bigger regions for π-π stacking and less negatively charged carboxyl groups, which BPA has a higher adsorption affinity than GO. In addition, the highest degradation is predominantly due to the high number of carbon-support interactions and defects sites, including oxygen vacancy. This encouraged effective mobility of charge carriers and subsequently enhanced photoactivity. In this study, the rGO/SZ catalyst was chosen to optimize further the reaction parameters including catalyst dosage, pH and initial concentration of BPA. According to the analysis of variance, the catalyst dosage was the most important variable in the degradation of BPA, followed by pH and initial concentration. The optimum BPA degradation predicted from response surface methodology is 88% at conditions of 8.09 mg L−1 using 0.469 g L−1 of rGO/SZ at pH 6.1, which is reasonably close to the predicted value (89.8%). The rGO/SZ catalyst was found to be stable even after five cycles in the reusability testing.

The development of highly efficient sunlight assisted photocatalysts has been acknowledged as a promising strategy for the enhanced degradation of antibiotics. In this work, effectual fabrication of a novel Bi2WO6/NH2-MIL-88B(Fe) heterostructure was carried through solvothermal route. The structural, morphological and compositional analysis was done by employing number of analytical techniques, namely XRD, FTIR, HRTEM, FESEM, XPS, PL and BET surface area. The prepared Bi2WO6/NH2-MIL-88B(Fe) heterostructure was utilized as an efficient photocatalyst towards decomposition of a typical antibiotic tetracycline (TC) in aqueous medium. It was found that Bi2WO6/NH2-MIL-88B(Fe) heterostructure exhibited improved degradation efficiency of about 89.4% within 130 min of solar illumination than pristine NH2-MIL-88B(Fe) under optimized parameters i.e. initial drug solution of 10 mg/L concentration at pH 4 with 0.35 g/L dose of catalyst. Moreover, adsorption studies, kinetics and isotherms of adsorption on TC were also investigated. Results revealed that adsorption kinetics followed pseudo 2nd order model and isotherm data fitted well with Freundlich model (R2 = 0.99803) as compared to Temkin and Langmuir. The ameliorating photocatalytic capability could be primarily accredited to the heterojunction created among Bi2WO6 and NH2-MIL-88B(Fe) which facilitated the charge transfer and thus determines high catalytic efficiency. The enhanced photocatalyic effect was further verified by electrochemical impedance and photocurrent studies. The prepared composite also exhibited longer carrier lifetime (140.72 ns) compared to pure MOF (132.05 ns) and Bi2WO6 (136.39 ns). Further, based on the radical trapping investigations, role of superoxide radicals was dominant and detailed mechanism was proposed for the photocatalytic degradation process. The major intermediates formed during the course of reaction were also examined using LCMS analysis. The photodegradation was also carried over simulated hospital wastewater by the prepared heterostructure and 60.5% TOC was obtained under solar light in 390 min. Moreover, the synthesized heterostructure showed good recyclability up to three cycles depicting good stability.

Construction of heterojunction with reusability is one of the effective ways to avoid secondary pollution and strengthen photocatalysis. Herein, a magnetically recyclable Z-scheme Bi4O5I2/NiFe2O4 heterojunction photocatalyst was successfully fabricated by a two-step hydrothermal method. Through adjusting the theoretical molar proportion of NiFe2O4 to Bi4O5I2, it was verified that the optimal composite could decompose 98.5% Rhodamine B (RhB, 10 mg/L) within 60 min under simulative sunlight and 98.1% RhB within 80 min under visible light. According to the characterizations, the superior performance was mainly associated with the small band gap energy (2.44 eV) and efficient separation of photo-generated electrons and holes caused by the formation of heterojunction. Meanwhile, the enlarged specific area (27.6 m2/g) provided many adsorptive sites and active sites to improve the reaction further. Moreover, the trapping experiment indicated that the photodegradation involved O2–, OH and h+. After confirming the reliable activity, reusability and stability of the photocatalyst, an inferred mechanism was shown. In summary, the design of this magnetically recyclable Z-scheme Bi4O5I2/NiFe2O4 heterojunction photocatalyst can become a new choice to purify wastewater.

Background The photocatalytic activity of a series of UIO-66 modified MOFs viz. UiO-66-NO2 [ 1 ], UiO-66-NH2 [ 2 ] and UiO-66-NO2/UiO-66-NH2 [ 3 ] materials for photocatalytic degradation of model aromatic dye Rhodamine B [Rh B] have been assessed. Methods The photocatalysis experiments indicated that the most efficient photocatalyst for the Rh B degradation is 3 which achieved 95.5% degradation under UV light irradiation and displayed excellent recyclability and reusability when compared to 1 and 2. The trapping experiments indicated that O2˙− radical anion is main ROS generated during the photocatalysis play major role in the Rh B degradation. The LC-MS experiments and band gap calculations have been performed which suggested initial protection of xanthene unit and confirmed the major contribution of O2˙− radical anion generated by ligand to ligand transition in 3 for photodegradation of Rh B. Significant Findings This facile approach inculcating benefits of mixed ligands in multivariate metal-organic framework, lays a new pathway to design effective photocatalytic systems for safe and sustainable degradation of aromatic dyes. This strategy led to suppression in rate of hole-electron pair recombination that concomitantly uplifted photocatalytic efficiency over single component counterparts.

The development of porous adsorbent materials from renewable resources for water and wastewater treatment has received considerable interest from academia and industry. This work aims to synthesize composite hydrogel from the combination of guar gum (a neutral galactomannan polysaccharide) and TiO2. The TiO2-embedded guar gum hydrogel (TiO2@GGH) was utilized to remove methylene blue through adsorption and photodegradation. The presence of TiO2 particles in the hydrogel matrix (TiO2@GGH) was confirmed by scanning electron microscopy-energy dispersive X-ray and X-ray photoelectron spectroscopy analysis. The mercury intrusion and N2 sorption isotherm indicate the macroporous structure of the TiO2@GGH composite, showing the presence of pore sizes ~420 μm. The dye removal efficiency of the GGH and TiO2@GGH was evaluated in batch mode at ambient temperature under varying pH. The effect of UV radiation on the dye removal efficiency was also assessed. The results demonstrated that the highest dye removal was recorded at pH 10, with the equilibrium condition achieved within 5 h. UV radiation was shown to enhance dye removal. The maximum adsorption capacity of TiO2@GGH is 198.61 mg g−1, while GGH sorbent is 188.53 mg g−1. The results imply that UV radiation gives rise to the photodegradation effect.

Gd2O3 nanoparticles modified g-C3N4 photocatalytic composites were synthesized by a simple one-step hydrothermal method. The structure, morphology, optical properties of the prepared photocatalyst were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM) and X-ray photoelectron spectroscopy (XPS). The result demonstrates that gadolinium is mainly dispersed on the surface of g-C3N4 in the form of Gd2O3, and does not destroy the lattice structure of g-C3N4. Besides, the gadolinium can cause the red shift of the absorption edge of light, narrow the band gap, and increase the separation efficiency of the photogenerated electron and hole of g-C3N4. Especially, the specific surface area of g-C3N4 can be significantly increased. Furthermore, g-C3N4/Gd-0.05 displays the highest photodegradation performance when it is used for degradation of methyl orange (MO), methylene blue (MB) and Rhodamine B (RhB). The photodegradation rate of g-C3N4/Gd-0.05 composites is 72.4% for MO, 95.5% for RhB, 100% for MB after 120 min under visible light (λ > 420 nm) irradiation. Narrow band gap promotes the separation of photogenerated electron and hole, which enhances the photocatalytic activity of g-C3N4. It is noted that g-C3N4/Gd-0.05 exhibits excellent photocatalytic stability by the photocurrent and the cyclic photodegradation of MO.

Background Development of human society has led to various environmental problems and energy crisis. Methods In this paper, Bismuth oxychloride (BiOCl) with a 3D network structure was prepared via a simple one-step sodium dodecylbenzenesulfonate (SDBS) assisted hydrothermal method and used for CO2 reduction and antibiotic degradation. Consideration was given to the influence of addition of SDBS in the preparation process on the microscopic morphology and energy band structure of the photocatalyst. Significant findings The results of the present study indicate that the formation of the 3D network structure helps to expose the {001} facets of BiOCl and promotes the generation of more oxygen vacancies. As-prepared BiOCl-0.6, i.e., 0.78 g of Bi(NO3)3·5H2O with 0.6 g SDBS, demonstrating the highest photocatalytic reduction performance of CO2. The production of CO by BiOCl-0.6 can reach 59.5 and 20.1 µmol g−1 after 4 h of UV-vis/vis illumination, which is ten times higher than the control BiOCl. In addition, BiOCl prepared with a 3D network structure also showed efficient antibiotic (oxytetracycline hydrochloride, OTC) degradation ability. When the initial concentration of OTC was 20 mg/L, OTC was completely removed after 45 min of UV-vis irradiation, and 77.2% of OTC was removed after 90 min of photocatalytic reaction under visible light. In the photodegradation process, photogenerated holes (h+) and superoxide radical (·O2−) play an important role.