Metal Tungstate Based Nanocomposites for Environmental Applications: Photocatalysis Mini-Review

2020 ◽  
Vol 18 (12) ◽  
pp. 853-860
Author(s):  
Mohamed Jaffer Sadiq Mohamed
Keyword(s):  
Photogenerated Electron ◽  
Surface Region ◽  
Electron Hole ◽  
Light Reaction ◽  
Natural Toxins ◽  
Metal Tungstate ◽  
Treatment Measures ◽  
Reaction Capacity ◽  
Photocatalytic Applications ◽  
Hole Recombination

Photocatalysis is viewed as perhaps the best-progressed treatment measures in eliminating numerous dangerous natural toxins from wastewater. It enjoys numerous benefits, however some downsides are: (i) Fast photogenerated electron–hole recombination productivity, (ii) they restricted noticeable light reaction capacity, (iii) low specific surface region, and (iv) the expense of reagents utilization. To improve the economy of the process, it is likewise needed to expand the catalyst’s effectiveness. Consequently, there is an extraordinary requirement for the improvement of elite catalysts. This mini-review survey addresses the basics and uses of photocatalytic materials on metal tungstate-based nanocomposites. The mini-review shows how metal tungstate-based nanocom-posites can help take care of ecological issues. This mini-review also expected survey gives outlines, synthesis, characterizations, and exploration discoveries in the field of metal tungstate-based nanocomposites for photocatalytic applications in the future examination.

scholarly journals Advanced Photocatalytic Materials

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 821 ◽  
Author(s):  
Vlassis Likodimos
Keyword(s):  
Rational Design ◽  
Photogenerated Electron ◽  
Photoelectrochemical Cells ◽  
Original Research ◽  
Fuel Production ◽  
Electron Hole ◽  
Volatile Organic ◽  
Photocatalytic Applications ◽  
Hole Recombination ◽  
Photocatalytic Materials

Semiconductor photocatalysts have attracted a great amount of multidiscipline research due to their distinctive potential for solar-to-chemical-energy conversion applications, ranging from water and air purification to hydrogen and chemical fuel production. This unique diversity of photoinduced applications has spurred major research efforts on the rational design and development of photocatalytic materials with tailored structural, morphological, and optoelectronic properties in order to promote solar light harvesting and alleviate photogenerated electron-hole recombination and the concomitant low quantum efficiency. This book presents a collection of original research articles on advanced photocatalytic materials synthesized by novel fabrication approaches and/or appropriate modifications that improve their performance for target photocatalytic applications such as water (cyanobacterial toxins, antibiotics, phenols, and dyes) and air (NOx and volatile organic compounds) pollutant degradation, hydrogen evolution, and hydrogen peroxide production by photoelectrochemical cells.

Tuning the electronic and structural properties of WO3 nanocrystals by varying transition metal tungstate precursors

RSC Advances ◽  
2014 ◽  
Vol 4 (107) ◽  
pp. 62423-62429 ◽  
Author(s):  
Sara Rahimnejad ◽  
Jing Hui He ◽  
Wei Chen ◽  
Kai Wu ◽  
Guo Qin Xu
Keyword(s):  
Methylene Blue ◽  
Transition Metal ◽  
Oxygen Vacancy ◽  
Band Gap ◽  
Azo Dye ◽  
Electron Hole ◽  
Recombination Time ◽  
Metal Tungstate ◽  
Electronic And Structural Properties ◽  
Hole Recombination

WO3 nanoplates derived from NiWO4 were found to have the highest concentration of oxygen vacancy, narrowest band gap, longest electron–hole recombination time, and in turn the highest rate of photodegradation of azo dye methylene blue.

scholarly journals Photoactive Tungsten-Oxide Nanomaterials for Water-Splitting

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1871
Author(s):  
Yerkin Shabdan ◽  
Aiymkul Markhabayeva ◽  
Nurlan Bakranov ◽  
Nurxat Nuraje
Keyword(s):  
Tungsten Oxide ◽  
Water Splitting ◽  
Diffusion Length ◽  
Photogenerated Electron ◽  
Photoelectrochemical Cell ◽  
High Electron ◽  
Applied Bias ◽  
Electron Hole ◽  
Research Directions ◽  
Photocatalytic Applications

This review focuses on tungsten oxide (WO3) and its nanocomposites as photoactive nanomaterials for photoelectrochemical cell (PEC) applications since it possesses exceptional properties such as photostability, high electron mobility (~12 cm2 V−1 s−1) and a long hole-diffusion length (~150 nm). Although WO3 has demonstrated oxygen-evolution capability in PEC, further increase of its PEC efficiency is limited by high recombination rate of photogenerated electron/hole carriers and slow charge transfer at the liquid–solid interface. To further increase the PEC efficiency of the WO3 photocatalyst, designing WO3 nanocomposites via surface–interface engineering and doping would be a great strategy to enhance the PEC performance via improving charge separation. This review starts with the basic principle of water-splitting and physical chemistry properties of WO3, that extends to various strategies to produce binary/ternary nanocomposites for PEC, particulate photocatalysts, Z-schemes and tandem-cell applications. The effect of PEC crystalline structure and nanomorphologies on efficiency are included. For both binary and ternary WO3 nanocomposite systems, the PEC performance under different conditions—including synthesis approaches, various electrolytes, morphologies and applied bias—are summarized. At the end of the review, a conclusion and outlook section concluded the WO3 photocatalyst-based system with an overview of WO3 and their nanocomposites for photocatalytic applications and provided the readers with potential research directions.

Synthesis of TiO2-Reduced Graphene Oxide Nanocomposites Offering Highly Enhanced Photocatalytic Activity

2019 ◽  
Vol 19 (11) ◽  
pp. 7089-7096 ◽  
Author(s):  
Wufa Li ◽  
Xiaohong Yang ◽  
Haitao Fu ◽  
Xizhong An ◽  
Haiyang Zhao
Keyword(s):  
Photocatalytic Activity ◽  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Environmental Remediation ◽  
Hydrothermal Reaction ◽  
Photogenerated Electron ◽  
Electron Hole ◽  
Reduced Graphene ◽  
Vis Spectroscopy ◽  
Hole Recombination

Photogenerated electron–hole recombination significantly restricts the catalytic efficiency of titanium dioxide (TiO2). Various approaches have been developed to overcome this problem, yet it remains challenging. Recently, graphene modification of TiO2 has been considered as an effective alternative to prevent electron–hole recombination and consequently enhance the photocatalytic performance of TiO2. This study reports an efficient but simple hydrothermal method utilizing titanium (IV) butoxide (TBT) and graphene oxide (GO) to prepare TiO2-reduced graphene oxide (RGO) nanocomposites under mild reaction conditions. This method possesses several advantageous features, including no requirement of high temperature for TiO2 crystallization and a one-step hydrothermal reaction for mild reduction of GO without a reducing agent, which consequently makes the production of TiO2-RGO nanocomposites possible in a green and an efficient synthetic route. Moreover, the as-synthesized nanocomposites were characterized by numerous advanced techniques (SEM, TEM, BET, XRD, XPS, and UV-vis spectroscopy). In particular, the photocatalytic activities of the synthesized TiO2-RGO nanocomposites were evaluated by degrading the organic molecules (methylene blue, MB), and it was found that the photocatalytic activity of TiO2-RGO nanocomposites is ~4.5 times higher compared to that of pure TiO2. These findings would be useful for designing reduced graphene oxide-metal oxide hybrids with desirable functionalities in various applications for energy storage devices and environmental remediation.

Formation Mechanism and Recombination-Enhanced Dissociation of a Hydrogen-Carbon Complex in Silicon

1992 ◽  
Vol 262 ◽  
Author(s):  
Yoichi Kamiura ◽  
Fumio Hashimoto ◽  
Minoru Yoneta
Keyword(s):  
Formation Mechanism ◽  
Chemical Etching ◽  
Surface Region ◽  
Electronic Energy ◽  
Hydrogen Atoms ◽  
Electron Hole ◽  
Near Surface ◽  
Depth Profiles ◽  
Schottky Structure ◽  
Hole Recombination

ABSTRACTWc have found that chemical etching induced an electron trap E3 (0.15) into n-typc Si. We attribute this trap to a hydrogen-carbon complex on the basis of available experimental data. By measuring DLTS depth profiles of the E3 trap, we propose a model of the formation mechanism of the hydrogen-carbon complex as follows. Hydrogen atoms arc adsorbed on the Si surface to terminate Si dangling bonds during chemical etching, and after the etching some unstably adsorbed ones diffuse into the near-surface region of silicon and are trapped by carbon to form the complex. The E3 trap is stable up to 100δC in the dark but is annihilated by the illumination of band gap light around 250K only outside the depletion layer of the Schottky structure. This provides unambiguous experimental evidence for the recombination-enhanced dissociation, in which the electronic energy released by the electron-hole recombination at the E3 level is converted into local kinetic energy of hydrogen to be released from carbon.

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 Preparation, Characterization, and Photocatalytic Applications of MWCNTs/TiO2Composite

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Ahmed M. Kamil ◽  
Falah H. Hussein ◽  
Ahmed F. Halbus ◽  
Detlef W. Bahnemann
Keyword(s):  
Photocatalytic Activity ◽  
Diffuse Reflectance ◽  
Diffuse Reflectance Spectroscopy ◽  
Multiwall Carbon Nanotubes ◽  
Photogenerated Electron ◽  
Drying Process ◽  
Electron Hole ◽  
Activity Performance ◽  
Photocatalytic Applications ◽  
Multiwall Carbon

The multiwall carbon nanotubes (MWCNTs)/titanium dioxide (P25) composite in different ratios was prepared using simple evaporation and drying process. The composite was characterized by Raman spectroscopy, X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy, and scanning electron microscopy (SEM). The photocatalytic activity of this composite was investigated using degradation of the Bismarck brown R dye (BBR). An optimal MWCNTs/TiO2ratio of 0.5% (w/w) was found to achieve the maximum rate of BBR degradation. It was observed that the composite exhibits enhanced photocatalytic activity compared with TiO2. The enhancement in photocatalytic activity performance of the MWCNTs/P25 composite is explained in terms of recombination of photogenerated electron-hole pairs. In addition, MWCNTs act as a dispersing support to control the morphology of TiO2particles in the MWCNTs/TiO2composite.

scholarly journals Ternary Composite of Co-Doped CdSe@electrospun Carbon Nanofibers: A Novel Reusable Visible Light-Driven Photocatalyst with Enhanced Performance

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 348 ◽  
Author(s):  
Gopal Panthi ◽  
Oh Hoon Kwon ◽  
Yun-Su Kuk ◽  
Kapil Raj Gyawali ◽  
Yong Wan Park ◽  
...  
Keyword(s):  
Carbon Nanofibers ◽  
Photocatalytic Performance ◽  
Electrospun Nanofibers ◽  
Electron Hole ◽  
Ternary Composite ◽  
Photogenerated Electrons ◽  
Visible Light Driven ◽  
Photocatalytic Applications ◽  
Hole Recombination

In this work, flexible ternary composites of cobalt-doped cadmium selenide/electrospun carbon nanofibers (Co-CdSe@ECNFs) for photocatalytic applications were fabricated successfully via electrospinning, followed by carbonization. For the fabrication of the proposed photocatalysts, Co-CdSe nanoparticles were grown in situ on the surface of ECNFs during the carbonization of precursor electrospun nanofibers obtained by dispersing Se powder in the electrospinning solution of polyacrylonitrile/N,N-Dimethylformamide (PAN/DMF) containing Cd2+ and Co2+. The photocatalytic performance of synthesized samples is investigated in the photodegradation of methylene blue (MB) and rhodamine B (RhB) dyes. Experimental results revealed the superior photocatalytic efficiency of Co-CdSe@ECNFs over undoped samples (CdSe@ECNFs) due to the doping effect of cobalt, which is able to capture the photogenerated electrons to prevent electron–hole recombination, thereby improving photocatalytic performance. Moreover, ECNFs could play an important role in enhancing electron transfer and optical absorption of the photocatalyst. This type of fabrication strategy may be a new avenue for the synthesis of other ECNF-based ternary composites.

Effects of hydrothermal temperature on the morphology and photoelectrocatalytic performance of TiO2-based nanomaterials photoelectrode

2015 ◽  
Vol 08 (04) ◽  
pp. 1550034 ◽  
Author(s):  
Dong Li ◽  
Xiujuan Yu ◽  
Xiuwen Cheng
Keyword(s):  
Three Dimensional ◽  
Photogenerated Electron ◽  
Comparative Investigation ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Photoelectrochemical Performance ◽  
Electron Hole ◽  
Hydrothermal Temperature ◽  
Dimensional Network ◽  
Hole Recombination

TiO 2-based nanomaterials (BNMs) photoelectrode was successfully synthesized via a facile and controllable hydrothermal procedure. The as-prepared TiO 2-BNMs photoelectrode was characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The resulting TiO 2-BNMs samples assembled by different morphologies were obtained through changing hydrothermal temperature that were: (i) One-dimensional (relative to nanosheets) nanobelts at 140°C, (ii) two-dimensional nanosheets at 160–180°C and (iii) three-dimensional network nanowires at 200–220°C. Structural investigation of the obtained nanomaterials revealed that the content of anatase increased as increasing the apparent dimensionality of the materials. The photoelectrochemical performance of TiO 2-BNMs photoelectrode was elucidated by comparative investigation on the electron transport and electron–hole (e-/h+) recombination in TiO 2-BNMs sample with typically morphology. The photoelectrochemical performance of the TiO 2-BNMs sample was obviously dependent on the morphology. Compared to the nanobelts and the network nanowires structure, the two-dimensional nanosheets displayed the more effective photogenerated electron transfer and reduced electron–hole recombination rate. Moreover, two-dimensional nanosheets had significantly enhanced photoelectrocatalytic efficiency for degradation of methyl orange (MO).

scholarly journals Paving the Way for A Sustainable and Efficient SiO2/TiO2 Photocatalytic Composite

Environments ◽  
2019 ◽  
Vol 6 (8) ◽  
pp. 87 ◽  
Author(s):  
Mattia Pierpaoli ◽  
Xu Zheng ◽  
Vladimir Bondarenko ◽  
Gabriele Fava ◽  
Maria Letizia Ruello
Keyword(s):  
Large Scale ◽  
Photogenerated Electron ◽  
Adsorbed Water ◽  
Hydroxyl Groups ◽  
Scale Production ◽  
Electron Hole ◽  
Macroscopic Structure ◽  
Large Scale Production ◽  
Hole Recombination ◽  
Secondary Materials

Although photocatalysis is an extraordinary and tremendously explored topic, there is a need to find new ways to encourage the production of composite materials that are economical, efficient and with limited environmental impact. Nanocatalysts may benefit from appropriate support material for many reasons. In this study, TiO2 was deposited on SiO2, so that the silica not only provides the macroscopic structure on which the TiO2 is formed, but it positively affects the photocatalytic activity as well. This is because of the greater specific surface area which favors the adsorption of pollutants near the photocatalyst, the higher amount of surface-adsorbed water and hydroxyl groups and the inhibition of the photogenerated electron-hole recombination. The choice of preparing the Ti-precursor starting from titanium shavings and to directly deposit TiO2 on micrometric-sized silica by a simple hydrothermal method highlights the process sustainability. The results showed that it is possible to produce a photocatalytic composite from secondary materials, exhibiting excellent photocatalytic properties, comparable to the pristine one, and opening the possibility for large-scale production.

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