scholarly journals A Review on Recent Progression of Modifications on Titania Morphology and its Photocatalytic Performance

2020 ◽  
Vol 67 (2) ◽  
pp. 361-374
Author(s):  
Nur Farhana Jaafar ◽  
Nur Farhana Jaafar ◽  
Melati Khairuddean ◽  
Norazzizi Nordin
Keyword(s):  
Recent Progress ◽  
Photocatalytic Performance ◽  
Uv Light ◽  
Synthesis Methods ◽  
Light Radiation ◽  
Reactive Site ◽  
Electron Hole ◽  
And Performance ◽  
Hole Recombination ◽  
Degradation Of Pollutants

Titanium dioxide (TiO2) has been broadly used as a photocatalyst because it has good stability and performance for degradation of pollutants. On the other hand, its efficiency as photocatalyst is limited since it can only be excited under UV-light radiation and has a rapid electron-hole recombination that occurs during the photodegradation. There are many studies focusing on adjusting the synthesis methods, addition of dopants and modifying the TiO2 structure to enhance its photocatalytic performance. Among them, synthesis of TiO2 as porous nanoparticles as one of the strategies in modifying the TiO2 structure has gained attention due to its benefits for better adsorption and accessibility of various pollutants onto the reactive site of catalyst, thus enhancing the photocatalytic performance. In this review, we recapitulated on modifications of synthesis methods for TiO2 and their effect on the structure along with the photocatalytic performance. Recent progress for TiO2 in terms of synthesis approaches, effect of dopants, modified structures, and applications are also briefly discussed in this review.

scholarly journals High photocatalytic activity of Fe2O3/TiO2 nanocomposites prepared by photodeposition for degradation of 2,4-dichlorophenoxyacetic acid

2017 ◽  
Vol 8 ◽  
pp. 915-926 ◽  
Author(s):  
Shu Chin Lee ◽  
Hendrik O Lintang ◽  
Leny Yuliati
Keyword(s):  
Photocatalytic Activity ◽  
Uv Light ◽  
Active Species ◽  
High Photocatalytic Activity ◽  
Dichlorophenoxyacetic Acid ◽  
Electron Hole ◽  
And Performance ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
Hole Recombination

Two series of Fe2O3/TiO2 samples were prepared via impregnation and photodeposition methods. The effect of preparation method on the properties and performance of Fe2O3/TiO2 for photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under UV light irradiation was examined. The Fe2O3/TiO2 nanocomposites prepared by impregnation showed lower activity than the unmodified TiO2, mainly due to lower specific surface area caused by heat treatment. On the other hand, the Fe2O3/TiO2 nanocomposites prepared by photodeposition showed higher photocatalytic activity than the unmodified TiO2. Three times higher photocatalytic activity was obtained on the best photocatalyst, Fe2O3(0.5)/TiO2. The improved activity of TiO2 after photodeposition of Fe2O3 was contributed to the formation of a heterojunction between the Fe2O3 and TiO2 nanoparticles that improved charge transfer and suppressed electron–hole recombination. A further investigation on the role of the active species on Fe2O3/TiO2 confirmed that the crucial active species were both holes and superoxide radicals. The Fe2O3(0.5)/TiO2 sample also showed good stability and reusability, suggesting its potential for water purification applications.

Synthesis and Photocatalytic Degradation Performance of g-C3N4/ CoAPO-5/rGO Ternary Composite

2018 ◽  
Vol 281 ◽  
pp. 848-853
Author(s):  
Ling Fang Qiu ◽  
Xiao Bin Qiu ◽  
Zhi Wei Zhou ◽  
Shu Wang Duo
Keyword(s):  
Visible Light ◽  
Carbon Nitride ◽  
Photocatalytic Performance ◽  
Doping Content ◽  
Electron Mediator ◽  
Electron Hole ◽  
Obvious Effect ◽  
Ternary Composite ◽  
Hole Recombination ◽  
Binary Composite

Graphitic carbon nitride is a promising photocatalyst for environmental purification, but the photocatalytic performance is limited significantly due to its narrow visible-light adsorption and high photo-reduced electron-hole recombination rate. This work developed a novel way to overcome the two defects and obtained obvious effect. CoAPO-5 was used to broaden visible-light adsorption range by conducting g-C3N4/CoAPO-5 binary composite. In further, rGO was integrated into the binary system to form novel ternary composite. rGO performs as a electron mediator, which can inhibit photo-reduced electron-hole recombination efficiently. The samples were characterized by XRD, SEM, PL, IR and DRS. The photocatalytic performances for degrading RhB (10mg/L) indicated that g-C3N4/CoAPO-5/rGO have much higher activity than g-C3N4/CoAPO-5 because of synergistic effect. When the doping content of rGO in g-C3N4/CoAPO-5 was 0.5%, the degradation efficiency was improved by 14%.

Temperature and Salinity Effects on Photocatalytic Performance of Cerium Doped Zinc Oxide

2020 ◽  
Vol 307 ◽  
pp. 223-228
Author(s):  
Wan Rafizah Wan Abdullah ◽  
Lee Chia Siang ◽  
Maishara Syazrinni Rooshde ◽  
Mohd Sabri Mohd Ghazali
Keyword(s):  
Photocatalytic Performance ◽  
Catalyst Surface ◽  
Uv Light ◽  
Operating Temperature ◽  
Chloride Ions ◽  
Photocatalytic Efficiency ◽  
Electron Hole ◽  
Doped Zno ◽  
The Stability ◽  
Uv C

Cerium (Ce) doped ZnO is a promising material for advanced photocatalysis. It is useful for inducing the treatment of many organic pollutants in water. However, the stability of its performance under varying temperature and saline condition has never been not fully assessed. In this study, powder form photocatalyst comprising 99.0 mol% ZnO and 1 mol% CeO2 has been synthesized via modified citrate gelation technique and solid-state sintering at 1200 °C for 5 hours. The conversion of Ce doped ZnO from its precursors has been confirmed using XRD, SEM, and EDX techniques. The photocatalytic efficiency of the synthesized Ce doped ZnO under UV-C light (λ=265 nm) was determined. In the experiment, the operating temperature was varied between 25 to 40 °C, and the salinity of the treated solution was increased from 0 to 40 g/L NaCl. The findings revealed that the photocatalytic efficiency of Ce doped ZnO under UV light improved from 78.2% to 88.6% as the temperature increased from 25 to 40 °C. The performance of Ce doped ZnO decreased from 86.7% to 36.7% when the salinity increased from 0 g/L to 40 g/L. The elevation of temperature encouraged the photogeneration of electron-hole pairs on catalyst surface while the presence of chloride ions in treated medium caused scavenging of hydroxyl radicals or hole.

scholarly journals Synthesis of Titanium Dioxide Nanotubes with Different N-Containing Ligands via Hydrothermal Method

2021 ◽  
Vol 6 (2) ◽  
pp. 67-73
Author(s):  
Cheng Yee Leong ◽  
Ye Shen Lo ◽  
Pei Wen Koh ◽  
Siew Ling Lee
Keyword(s):  
Titanium Dioxide ◽  
Hydrothermal Method ◽  
Tio2 Nanotubes ◽  
Uv Light ◽  
Anatase Phase ◽  
Anatase Tio2 ◽  
Molar Ratio ◽  
Electron Hole ◽  
Tauc Plot ◽  
Hole Recombination

Titanium dioxide (TiO2) nanotubes (TNT) were successfully synthesized using different N-containing ligands via hydrothermal method. Methylamine, ethylenediamine and diethylenetriamine with different Ti/ligand molar ratios (1:1, 1:3, 1:5 and 1:8) were prepared. As-synthesized TiO2 without N-containing ligands were also prepared for comparison purpose. The X-Ray Diffraction patterns confirmed the presence of anatase phase of TiO2 in all the synthesized samples whereas the presence of sodium titanate was only detected in the samples containing N-containing ligands. The Transmission Electron Microscopy images also showed that the N-containing ligands promoted the formation of nanotubes in the anatase TiO2. Based on the Tauc Plot, the band gap energy of anatase TiO2 was shifted with the addition of methylamine, ethylenediamine and diethylenetriamine. The photoluminescence spectra also showed that with the addition of sufficient amount of N-containing ligands, the intensity of photoluminescence spectrum decreased, suggesting formation of more nanotube and reduction of electron hole recombination rate. The photocatalytic performance of all synthesized samples was determined through photodegradation of Congo red under UV light for 6 hours. The results suggested that among the synthesized materials, the sample which contained diethylenetriamine with molar ratio of 5 gave the highest photocatalytic activity of 76.71% which could be attributed to successful formation of nanotube, its higher surface rate reaction and low electron hole recombination. Diethylenetriamine showed higher efficiency in assisting the formation of TiO2 nanotubes compared to methylamine and ethylenediamine.

scholarly journals Synthesis and characterization of black TiO2/graphene composites with enhanced photocatalysis

2020 ◽  
Author(s):  
Zhaoqing Li ◽  
Zhufeng Liu ◽  
Xiao Yang ◽  
Peng Chen ◽  
Lei Yang ◽  
...  
Keyword(s):  
Visible Light ◽  
Photocatalytic Performance ◽  
Sol Gel ◽  
Photogenerated Electron ◽  
Catalytic Performance ◽  
Attractive Potential ◽  
Electron Hole ◽  
Hole Recombination

Abstract According to the composite design, a series of black TiO2/graphene composites were synthesized to improve its photocatalytic activity. TiO2 is generated in situ on the surface of graphene by a facile sol-gel method. The combination of graphene and TiO2 was beneficial for eliminating the opportunity of photogenerated electron-hole recombination due to the excellent conductivity of graphene. In the subsequent hydrogenation process, the self-doping Ti3+ was introduced accompanied by the crystallization of amorphous TiO2. The narrowed bandgap caused by self-doping Ti3+ enhanced the visible light absorption and make the composites appear black. Both of them improved the photocatalytic performance of the synthesized black TiO2/graphene composites. The band structure of the composite was analyzed by valence band XPS, revealing the reason for the high visible light catalytic performance of the composite. The results proved that the black TiO2/graphene composites synthesized show attractive potential for applications in environmental and energy issues.

scholarly journals Synthesis of Heterostructure of ZnO@MOF-46(Zn) to Improve the Photocatalytic Performance in Methylene Blue Degradation

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1379
Author(s):  
Jiraporn Buasakun ◽  
Phakinee Srilaoong ◽  
Ramida Rattanakam ◽  
Tanwawan Duangthongyou
Keyword(s):  
Methylene Blue ◽  
Band Gap ◽  
Photocatalytic Performance ◽  
Degradation Process ◽  
Band Gap Energy ◽  
Photocatalytic Efficiency ◽  
Electron Hole ◽  
Methylene Blue Degradation ◽  
Gap Energy ◽  
Hole Recombination

The heterostructure of ZnO and MOF-46(Zn) was synthesized to improve the photocatalytic performance of ZnO and prove the synergistic theory that presented the coexistence of ZnO and MOF-46(Zn), providing better efficiency than pure ZnO. The heterostructure material was synthesized by using prepared ZnO as a Zn2+ source, which was reacted with 2-aminoterephthalic acid (2-ATP) as a ligand to cover the surface of ZnO with MOF-46(Zn). The ZnO reactant materials were modified by pyrolysis of various morphologies of IRMOF-3 (Zn-MOF) prepared by using CTAB as a morphology controller. The octahedral ZnO obtained at 150 mg of CTAB shows better efficiency for photodegradation, with 85.79% within 3 h and a band gap energy of 3.11 eV. It acts as a starting material for synthesis of ZnO@MOF-46(Zn). The ZnO/MOF-46(Zn) composite was further used as a photocatalyst material in the dye (methylene blue: MB) degradation process, and the performance was compared with that of pure prepared ZnO. The results show that the photocatalytic efficiency with 61.20% in the MB degradation of the heterostructure is higher than that of pure ZnO within 60 min (90.09% within 180 min). The reason for this result may be that the coexistence of ZnO and MOF-46(Zn) can absorb a larger range of energy and reduce the possibility of the electron–hole recombination process.

scholarly journals Electrospun Active Media Based on Polyvinylidene Fluoride (PVDF)-Graphene-TiO2 Nanocomposite Materials for Methanol and Acetaldehyde Gas-Phase Abatement

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1017
Author(s):  
Carlo Boaretti ◽  
Giuseppe Vitiello ◽  
Giuseppina Luciani ◽  
Alessandra Lorenzetti ◽  
Michele Modesti ◽  
...  
Keyword(s):  
Gas Phase ◽  
Polyvinylidene Fluoride ◽  
Indoor Air Pollution ◽  
Uv Light ◽  
Band Gap Energy ◽  
Electron Hole ◽  
Volatile Organic ◽  
High Concern ◽  
Nanostructured Membranes ◽  
Hole Recombination

The abatement of organic pollutants by TiO2 photocatalysis has been established as one of the benchmark applications of advanced oxidation processes for both liquid and gas phase purification. Such solution is particularly suitable for indoor air pollution where volatile organic compounds (VOCs) represent a class of chemicals of high concern for their adverse effects on both environment and human health. However, different shortcomings still affects TiO2 photocatalytic performance in terms of weak adsorptivity and fast electron-hole recombination, limiting its applicability. As a result, different strategies have been investigated over the last years in order to promote a higher TiO2 photo-efficiency. In this study we used electrospun (PVDF) nanofibers as a support for the photo catalytic system obtained by coupling graphene based materials and TiO2 during solvothermal synthesis. The resultant nanostructured membranes have been tested for acetaldehyde and methanol degradation under UV light showing an increase in the photocatalytic activity compared to bare TiO2. Such results may be ascribed to the decrease of band-gap energy and to increased electron mobility in the photocatalytic nanocomposite.

scholarly journals Improved photocatalytic activity of anatase titanium dioxide by reduced graphene oxide

2015 ◽  
Vol 11 (3) ◽  
Author(s):  
Nor Shuhada Alim ◽  
Hendrik O. Lintang ◽  
Leny Yuliati
Keyword(s):  
Titanium Dioxide ◽  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Uv Light ◽  
Electronic Conductivity ◽  
Anatase Tio2 ◽  
Electron Hole ◽  
Reduced Graphene ◽  
Xrd Patterns ◽  
Hole Recombination

Reduced graphene oxide (rGO) has been one of the most investigated carbon based materials due to its great electronic conductivity that make it able to accept and transport electron easily. In order to study the effect of rGO, anatase titanium dioxide-reduced graphene oxide (TiO2-rGO) composite was prepared by UV-assisted photocatalytic reduction method using the anatase TiO2 as a photocatalyst and various different loadings of graphene oxide (GO). The characterizations of the prepared samples were investigated by X-ray diffractometer (XRD), Fourier transform infrared (FTIR), and fluorescence spectroscopies. The XRD patterns and FTIR spectra confirmed that all the TiO2-rGO composites samples were successfully synthesized without disrupting the structure of the anatase TiO2. Fluorescence spectroscopy revealed the role of the rGO to reduce the electron-hole recombination on the anatase TiO2. In the photocatalytic removal of phenol, all the TiO2-rGO composites showed better photocatalytic activities than the bare anatase TiO2 under UV light irradiation. The activity of the anatase TiO2 was enhanced by more than four times with the addition of the GO with the optimum amount (3 wt%). It was proposed that the good photocatalytic performance obtained on the composites were caused by the successful suppression of electron-hole recombination by the rGO on the TiO2.

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