Film Photocatalyst Research Articles

Floating ZnO QDs-Modified TiO2/LLDPE Hybrid Polymer Film for the Effective Photodegradation of Tetracycline under Fluorescent Light Irradiation: Synthesis and Characterisation

In this work, mesoporous TiO2-modified ZnO quantum dots (QDs) were immobilised on a linear low-density polyethylene (LLDPE) polymer using a solution casting method for the photodegradation of tetracycline (TC) antibiotics under fluorescent light irradiation. Various spectroscopic and microscopic techniques were used to investigate the physicochemical properties of the floating hybrid polymer film catalyst (8%-ZT@LLDPE). The highest removal (89.5%) of TC (40 mg/L) was achieved within 90 min at pH 9 due to enhanced water uptake by the LDDPE film and the surface roughness of the hybrid film. The formation of heterojunctions increased the separation of photogenerated electron-hole pairs. The QDs size-dependent quantum confinement effect leads to the displacement of the conduction band potential of ZnO QDs to more negative energy values than TiO2. The displacement generates more reactive species with higher oxidation ability. The highly stable film photocatalyst can be separated easily and can be repeatedly used up to 8 cycles without significant loss in the photocatalytic ability. The scavenging test indicates that the main species responsible for the photodegradation was O2●−. The proposed photodegradation mechanism of TC was demonstrated in further detail based on the intermediates detected by LC-time-of-flight/mass spectrometry (LC/TOF-MS).

Nano-ZnO film photocatalysts in bench-scale continuous-flow mineralization of olive mill waste contaminants in water

Olive oil milling, widely practiced in Mediterranean countries, including Palestine, yields the so-called olive mill waste water (OMWW) or Zebar (Zibar). The waste contains minerals and organic materials (including phenols and polyphenols) which undergo continuous oxidation and cause environmental hazards if not well managed. This work basically aims at purifying surface waters, intentionally pre-contaminated with OMWW organic contaminants. Fate of other mineral ions present in the contaminated water is also investigated. ZnO nanoparticles, deposited as films onto glass reactor bottom (165 cm2 area), are described as catalyst for photodegradation of the organic contaminants, in a continuous flow reaction mode (gravity fed, typically at flow rate 3.5 mL/min). Two types of ZnO materials, namely commercial ZnO onto glass (C–ZnO/Glass) and synthetic ZnO supported onto clay and deposited on glass (Syn–ZnO/Clay/Glass), have been examined. The Syn–ZnO/Clay/Glass catalyst is slightly more efficient in removing organic contaminants (~ 43%), compared to the C–ZnO/Glass (41%) in 30 h. Different reaction parameters have been investigated, such as waste dilution factor, exposure duration, pH and catalyst recovery and reuse.

Effects of Ag Nanoparticles on Zinc Oxide Photocatalytic Performance

We used a sol–gel spin coating technique to synthesize nanocomposite thin films based on zinc oxide (ZnO) loaded with silver nanoparticles (NPs). We tested these ZnO/Ag NPs photocatalysts, with a thickness of about 100 nm, for the photodegradation of the indigo carmine dye solution. The study focused on the effects of Ag NPs on the ZnO matrix as well as the impact of their concentration on the photocatalytic performance of the nanocomposite. The study also highlighted the high stability of the photocatalytic performance of these nanocomposites. This work is a contribution in the search for non-toxic thin film photocatalysts that is usable under solar radiation for the treatment of contaminated wastewater. Innovation in the field of heterogeneous photocatalysis requires the use of solar resource with efficient results in terms of photocatalytic performance.

TiO2 doped HKUST-1/CM film in the three-phase photocatalytic ammonia synthesis system

Photocatalytic synthesis of ammonia from N2 and H2O at room temperature and atmospheric pressure is considered to be a safe, clean and sustainable method. Due to the low solubility and diffusion coefficient of nitrogen in water, the rate of ammonia synthesis is significantly hindered. As a result, we develop a kind of thin film photocatalyst, which can be used in gas-liquid-solid three phase reaction system to solve this problem. The catalyst bases on HKUST-1 thin film with high nitrogen adsorption performance and supported with TiO2 nanoparticles with photocatalytic nitrogen fixation performance. The constructed binary composite photocatalyst has a stable structure under a 300 W xenon lamp, which exhibits good photoelectric conversion performance. While characterizing the structure and photoelectric performance of the material, the performance of photocatalytic ammonia synthesis was investigated. The highest ammonia synthesis efficiency was 0.048 μmol·h−1·cm−2, and its performance was 2.8 times that of TiO2/CM catalyst under the same conditions. The thin film catalyst does't contain any N substance and won't interfere with the ammonia synthesis reaction. The preparation process is simplified by directly using the copper source in the CM without additional metal reagent. Moreover, it provides a new idea for the design of photocatalytic catalysts for ammonia synthesis.

NiO Decorated Ti/TiO2 Nanotube Arrays (TiO2NT)/TiO2/g-C3N4 Step-Scheme Heterostructure Thin Film Photocatalyst with Enhanced Photocatalytic Activity for Water Splitting

A new strategy to enhance the photocatalytic properties of graphitic carbon nitride is reported via constructing an effective NiO decorated Ti/TiO2NT/TiO2/g-C3N4 S-scheme heterostructure photocatalyst thin film (Ti/TiO2NT/TiO2/g-C3N4/NiO). This thin film photocatalyst can separate hydrogen gas and oxygen gas into different sides of the Ti substrate. Owing to the synergistic effect of the NiO as co-catalyst and the formation of Step-scheme (S-scheme) heterojunction between g-C3N4 and TiO2, the electrons and holes were successfully separated to their opposing active centers, which is beneficial to inhibiting the recombination of the charge carriers. The gas evolution rate of Ti/TiO2NT/TiO2/g-C3N4/NiO is 7.97 μmol h−1 cm−2 under the irradiation of high-pressure mercury lamp, which was 3 and 1.3 times as high as that of the Ti/TiO2NT/g-C3N4 and Ti/TiO2NT/TiO2/g-C3N4, respectively. Firstly, benefiting from the well-matched band structure, a direct S-scheme Ti/TiO2NT/g-C3N4 heterojunction thin film is constructed easily driven by the built-in electric field across the Ti/TiO2NT/g-C3N4 interface. Furthermore, the introduction of the TiO2 layer on the TiO2NT will broaden light absorption range and increase the heterojunction area, which in turn conduces to effective charge separation. In addition, NiO as a co-catalyst cannot only accelerate the charge separation but also provide plentiful catalytic sites and decompose H2O2 produced by g-C3N4. The thin film photocatalysts can be recycled again, which is different from traditional powdered photocatalysts. This work constructs a NiO decorated Ti/TiO2NT/TiO2/g-C3N4 S-scheme heterostructure photocatalyst thin film, and provides a new insight to promote photocatalytic activity of g-C3N4 under the synergetic impact of S-scheme heterostructure and NiO co-catalyst. A novel NiO decorated Ti/TiO2NT/TiO2/g-C3N4 S-scheme heterostructure photocatalyst thin film was fabricated to enhance photocatalytic activity for water splitting.

Fabrication of Graphitic Carbon Nitride‐Based Film: An Emerged Highly Efficient Catalyst for Direct C—H Arylation under Solar Light

Main observation and conclusionPhotoredox C—H bond formation can proceed in aerobic environment under solar light and has therefore become attractive. Nowadays, different types of expensive novel metal complexes and nanomaterials have been urbanized as photocatalysts for direct C—H bond formation in between derivatives of heteroarenes (HAs) and aryl diazonium salts. These photocatalysts, however, still suffer from poor stability, high cost, and decay. Herein, a graphitic carbon nitride‐based fluorescein isothiocyanate (g‐C3N4–FITC) film photocatalyst has been reported, which shows excellent light harvesting ability, and band gap suitability to catalyze the metal free direct C—H arylation of HAs under solar light at ambient temperature. Moreover, the g‐C3N4–FITC film photocatalyst can be reused four times without significant loss of activity, confirming the excellent photocatalytic stability. The current strategy to construct a g‐C3N4–FITC film photocatalyst for direct C—H arylation opens a new path towards replacing metal‐based catalysts in fine chemical synthesis.

Effect of polystyrene characteristic on photocatalytic hydrogen production by porous polystyrene photocatalyst film under simulated solar light irradiation

In this study, we developed a polystyrene-platinum/nitrogen-doped titanium dioxide/strontium titanate composite-polyvinylpyrrolidone (PS-PNS-PVP) photocatalyst film, which is applied in the process of photocatalytic hydrolysis under simulated sunlight to produce hydrogen, is developed. PS, which is cheap, non-toxic, with high UV resistance, and chemical inertness, is used as a carrier, and a highly effective hydrogen production of Pt/N–TiO2/SrTiO3 as a photocatalyst. The influence of the PS concentration on the stability, optical, and electrical properties of the photocatalyst film is discussed. In addition, the influence of the photocatalyst dispersion in the film on the activity under various photocatalyst concentrations was investigated. A polyvinylpyrrolidone pore-forming agent was then used to examine the effect on the photocatalyst film structure and optical properties, and the subsequent influence on photocatalytic hydrogen energy activity. Adjusting the PS concentration to 20 wt% produced good film-forming stability, and the photocatalyst dispersibility in the film under different photocatalyst concentrations. A photocatalyst concentration of 2.5 wt% resulted in good film dispersibility and the realization of added pore-forming agent. The modified photocatalyst film changed the film from a blind pore structure to a connecting void structure, increasing the film's porosity and hydrophilicity. This increased the number of photocatalytic sites, and the optimal hydrogen production of the photocatalyst film reached 21,333 μmol h−1 g−1.

An investigation of scale effect and applicability of compact light sources in microchannel reactors applied to pollutant abatement.

In this work, the performance of microreactors irradiated with conventional (fluorescent) and UV-LED light was evaluated. For this purpose, a microfluidic reactor with an equivalent diameter of 133.5 μm was used. In addition, the effect of scale variation on the performance of photochemical reactors was assessed using reactors with three internal diameters (600, 1200, and 2300 μm), 2 residence times (30 and 60 s), and two sources of UVA radiation (A with irradiance of 115 W m-2 and B with irradiance of 44 W m-2). Also, the relationship between the configuration of the photocatalyst film and the effect of the scale on the performance of photochemical reactors was experimentally and theoretically investigated. For both cases, methylene blue dye was used as a model pollutant and titanium dioxide (TiO2) as a photocatalyst deposited on the inner wall of the photocatalytic reactors. For the residence time of 30 s, the smaller the reactor diameter, the greater was the degradation (22, 18, and 6%, respectively, for lamp A and 17, 16, and 8 %, respectively, for lamp B). The influence of the diameter of the reactor was also observed for the residence time of 60 s, but only for the reactor with a 2300-μm internal diameter. The reactors with diameters 600 and 1200 μm only showed different results when illuminated with lamp B (33 and 28% of methylene blue conversion, respectively). Moreover, computational simulation results suggested higher efficiency as the reactor's diameter is decreased and an optimum thickness of photocatalyst film to maximize the performance of devices in which photocatalytic reactions are carried out.

Removal of naphthalene from aqueous solutions by phosphorus doped- titanium dioxide coated on silica phosphoric acid under visible light

In this research, titanium dioxide-phosphorus (TiO2-P) immobilized on silica phosphoric acid (SPA) was prepared by a simple modified sol-gel method with SPA as a precursor instead of phosphoric acid. TiO2-P thin film photocatalyst immobilized on SPA as a novel high-efficiency photocatalyst was investigated to remove naphthalene as a toxic compound from wastewater. The novel resulting photocatalyst were characterized by energy-dispersive X-ray (EDX) and X-ray diffraction pattern revealed nano-photocatalyst TiO2-P with the average size of 15-20 nm. EDX analysis showed the presence of phosphorus elements in the crystalline structure of TiO2 and diffuse reflectance spectroscopy showed the energy bandgap narrowing and transfer of photocatalytic activity of TiO2-P to the visible region. The excellent photocatalytic activity of TiO2-P/SPA compared with TiO2-N,S as thin films coated on glass microspheres. The results showed that the optimal pH, time, concentration, and efficiency removal of naphthalene for TiO2-P were 5, 50 min, 25 mg/L, and 92.12% and TiO2-N,S catalyst were 5, 60 min, 25 mg/L, and 88.47%, respectively (P < 0.05). The removal of chemical oxygen demand in pH 5 for TiO2-N,S was obtained 79.26% and for TiO2-P was obtained 81.64%. In this research, the ability to use immobilized TiO2-P in SPA can be used as a new, effective and practical method in the treatment of water and industrial wastewater containing naphthalene in the presence of visible light.

Immobilization of ZnO into polychlorotrifluoroethylene-co-acrylate matrix as hybrid film photocatalyst for effective degradation of methylene blue

Immobilization of ZnO into polychlorotrifluoroethylene-co-acrylate matrix as hybrid film photocatalyst for effective degradation of methylene blue

Interfacially synthesized 2D COF thin film photocatalyst: efficient photocatalyst for solar formic acid production from CO2 and fine chemical synthesis

Easy fabrication of multi-functional, free standing, centimeter sized, thin film photocatalyst for sustainable solar fine chemical synthesis and photoreduction of CO2 to formic acid under visible light.

Synchrotron infrared spectroscopic high-throughput screening of multi-composite photocatalyst films for air purification

Synchrotron-based infrared microscope was used for the high-throughput screening of Fe3+/Nb5+ doped TiO2 photocatalysts for air purification.

Effect of Ag NPs on the radiant absorption of photocatalyst film

<abstract> A composite film composed of Ag nanoparticles, Al₂O₃ and TiO₂ was prepared by cosputtering. Ag NPs were immersed in the Al₂O₃ host, TiO₂ was deposited onto the Ag/Al₂O₃ layer. The degradation of aqueous methylene blue under incident irradiation indicated that the Ag/Al₂O₃-TiO₂ composite film with the Ag-TiO₂ distance of 2nm or 5nm exhibited high degradation rate. Spectral absorptivity and radiant absorption distribution were analyzed through FDTD simulation to analyze the relationship between radiant absorption and photocatalytic activity. Results indicated that the spectrum and distribution of the radiant absorption in the composite film could be rationally regulated to improve photocatalytic activity. </abstract>

Anatase/brookite biphasic surface fluorinated Fe–TiO2 photocatalysts to enhance photocatalytic removal of VOCs under visible and UV light

Volatile organic compounds (VOCs) are categorized as a major group of indoor air pollutants with several adverse health effects on humans. Photocatalytic oxidation (PCO) is a promising in-situ air purification technology for removing indoor VOCs. However, the PCO application by using TiO2 photocatalyst is hindered at high humidity and under visible light irradiation. A facile hydrothermal treatment was used to fabricate biphasic anatase-brookite iron-doped TiO2 with different Fe contents (0.2–4 atomic%) to enhance photoactivity of TiO2 under visible and UV light irradiations. Surface fluorination was then applied to reduce the surface hydrophilicity of Fe–TiO2 photocatalyst with the optimum Fe content (FeTi-0.4%). Surface fluorination of FeTi-0.4% moderates the surface hydrophilicity to repel water molecules from adsorption. The performance of developed photocatalysts was studied toward degradation of gaseous methyl ethyl ketone (MEK) using ultraviolet (UV) and visible light irradiations. The results reveal that iron metal dopants and surface fluorination promoted the performance of synthesized photocatalysts. It was found that the best single-pass removal efficiency was obtained at RH = 20% on F–FeTi-0.4% with values of 54% using visible and 70% using UV illumination. To advance the degradation efficiency and lessen the by-product formation rate, three layers of F–FeTi-0.4% and FeTi-0.4% photocatalyst films were examined. The photocatalytic degradation efficiency for three layers of FeTi-0.4% and F–FeTi-0.4% photocatalyst films were respectively 72% and 80% under UV, and 50% and 60% under visible light illumination. This study provided an effective visible-driven photocatalyst for indoor air purification technology. The results revealed the high MEK removal efficiency under visible light as an environmentally sustainable source of energy, leading to lower indoor pollutions to protect human health.

Chitosan‐based fluorescein isothiocyanate film as a highly efficient metal‐free photocatalyst for solar‐light‐mediated direct CH arylation

SummaryDevelopment of ecofriendly and low‐cost highly efficient photocatalysis is of importance in the field of chemical synthesis. Currently, various metals‐based organic materials, metal oxide nanoparticles, and metal nanomaterials have been urbanized as light harvesting photocatalysts for direct carbon (C)‐hydrogen (H) arylation of aryl diazonium salts and heteroarenes. These light harvesting photocatalysts, however, still suffer from poor stability, reusability problem, high cost, or less selectivity. Herein, we report the fabrication of a novel chitosan‐based fluorescein isothiocyanate (CBFITC) film photocatalyst and demonstrate its tremendous photocatalytic activity, high yields (97 ± 0.015%), selectivity (99%), and reusability to catalyze the metal free solar‐light‐mediated direct CH arylation of aryl diazonium salts and heteroarenes at ambient temperature. Moreover, CBFITC film photocatalyst can be recycled more than five times without loss of activity, verifying this photocatalyst excellent light harvesting ability and stability. The present approach to fabricate a metal‐free film photocatalyst with the suitable band gap will be a new platform for efficient photocatalytic reaction and provide a new insight into the solar chemical synthesis.

Study on the synergistic effect of terbium-doped SnO2 thin film photocatalysts for dye degradation

The undoped and terbium (Tb)-doped SnO2 thin films are coated on the glass substrates using the nebulized spray pyrolysis (NSP) technique. The crystallite size is calculated using the Williamson-Hall method and is found to be decreased from 80 to 56 nm with the increase of Tb doping concentration. Atomic force microscope (AFM) images show the spheroidal shape of the grains. The elemental analysis of the samples was investigated by energy dispersive analysis of X-rays (EDX). An increase in absorbance and decrease in bandgap values provide more photon absorption which enhances the photocatalytic reaction. The PL studies reveal the creation of more defect levels by doping which provides more active sites for catalyzed reactions. The Tb doping with SnO2 improved the rate constant about 0.015/min, and a maximum photocatalytic dye degradation efficiency of 85% against methylene blue dye was observed. Therefore, the fabricated films found potential applications for photocatalysis that enable them to chemical industries.

Local surface plasma resonance effect enhanced Z-scheme ZnO/Au/g-C3N4 film photocatalyst for reduction of CO2 to CO

Local Surface Plasma Resonance (LSPR) effect enhanced Z-scheme ZnO/Au/g-C3N4 micro-needles film (3-ZAC) has been prepared for the photoreduction of CO2 into CO under UV–vis light irradiation. Photoreduction experiments show that 3-ZAC has the excellent photocatalytic performance and reusability. The CO production can be achieved 689.7 μmol/m2 after 8 h reaction time, which is 4.5 higher than that of the pure ZnO film. 13C isotope test shows that CO is produced from CO2 by photoreduction. DFT calculations confirm that build-in electric field formed at g-C3N4/ZnO interface effectively promoted the electron transfer efficiency in Z-scheme interface. FDTD simulations prove that Au NPs not only act as electron-transfer bridge, but also as LSPR excited source to speed up the separation of electron-hole pairs. In-situ FTIR technique was used to investigate the CO2 photoreduction process. The above characteristics together maximize the electron transfer efficiency, which causes the material has enhanced photocatalytic performance.

Photoelectroanalytical Oxygen Detection with Titanate Nanosheet – Platinum Hybrids Immobilised into a Polymer of Intrinsic Microporosity (PIM‐1)

AbstractThe polymer of intrinsic microporosity PIM‐1 is employed to disperse and deposit a Pt@titanate nanosheet photocatalyst film. The resulting microporous films allow electrolyte and oxygen permeation to give conventional oxygen reduction voltammetric responses on glassy carbon or on platinum disk electrodes in the dark. Preliminary data are presented showing that with pulsed light from a blue LED (385 nm) oxygen reduction at the electrode is effectively “switched off”. A mechanism is tentatively assigned as photocatalytic depletion of oxygen near the electrode. Photoelectrochemical current responses are observed in aqueous NaOH, NaCl, Na2HPO4 and shown to be light intensity and oxygen concentration dependent. Electroanalytical applications are suggested.

In situ growth of boron doped g-C3N4 on carbon fiber cloth as a recycled flexible film-photocatalyst

The development of feasible, highly stable and easily recycled metal-free photocatalysts has drawn great attention for wastewater purification. Herein, dip-coating followed with thermal polymerization is developed for in situ growth of boron doped graphitic carbon nitride (BCN) on carbon fiber cloth (CFc) as flexible film photocatalysts. HNO3 treatment on CFc is used to improve the surface hydrophilicity of CF, which is beneficial for the adsorption and nucleation of BCN precursor on CFc in aqueous solution. Boric acid not only works as the boron source but also causes a porous morphology of BCN due to the gasification of water generated from boric acid decomposition during heating process. Because of the close contact between CFc and BCN, CFc induces BCN to better crystalize. Furthermore, the film-photocatalyst exhibits high mechanical stability and recyclability. The porous sheet-like structures, together with the boron doping and CFc support, can improve light capture, charge separation and transport, and dye adsorption. Our work provides a thinking for component and morphology regulation of film-based flexible catalysts towards reusable photocatalysis under outdoor sunlight.

Photocatalytic degradation of the acetaminophen by nanocrystal-engineered TiO2 thin film in batch and continuous system

Un-biodegradable pharmaceuticals are one of the major growing threats in the wastewaters. In the current study, TiO2 thin film photocatalysts were designed by nanocrystal engineering and fabricated for degradation of the acetaminophen (ACE) in a photocatalytic reaction under UV light irradiation in batch and continuous systems. The photocatalyst was prepared by sputtering and then engineered by thermal treatment (annealing at 300°C (T300) and 650°C (T650)). The annealing effects on the crystallinity and photocatalytic activity of the TiO2 film were completely studied; it was found that annealing at higher temperatures increases the surface roughness and grain size which are favorable for photocatalytic activity due to the reduction in the recombination rate of photo-generated electron-hole pairs. For the continuous system, a flat plate reactor (FPR) was designed and manufactured. The photocatalytic performance was decreased with the increase of flow rate because the higher flow rate caused to form the thicker film of the liquid in the reactor and reduced the UV light received by photocatalyst. The reusability and durability of the samples after 6 h of photocatalytic reaction showed promising performance for the T650 sample (annealed samples in higher temperatures).