scholarly journals APPLICATION OF PLASMA-ELECTROLYTE COATINGS ON TITANIUM WITH REFRACTORY METALS FOR DETOXIFICATION OF ENVIRONMENTS FROM POLLUTING SUBSTANCES

2021 ◽  
pp. 96-102
Author(s):  
Mykola Sakhnenko ◽  
Serhii Indykov ◽  
Hanna Karakurkchi
Keyword(s):  
Photocatalytic Activity ◽  
Low Cost ◽  
Autonomous Systems ◽  
Quantitative Composition ◽  
High Catalytic Activity ◽  
Catalytic Layer ◽  
Oxide Systems ◽  
Metal Compounds ◽  
Anthropogenic Pollutants ◽  
Plasma Electrolyte

Based on the review of the peculiarities of the photocatalytic processes, the peculiarities of the catalytic action of oxide systems based on titanium dioxide are determined. It is shown that TiO2 is one of the most chemically and thermally stable and non-toxic inorganic oxides of semiconductors, whose photocatalytic activity is manifested by irradiation with ultraviolet part of the spectrum (λ 320–400 nm) and allows the oxidation of a significant amount of toxic agents to water and carbon dioxide. The essence of the photocatalytic process of oxidation of toxicants under the action of UV radiation on the TiO2 surface is considered. The proposed technology of photocatalytic detoxification of contaminants is economically available, environmentally friendly and allows its widespread use, in particular for autonomous systems, including dual purpose. It is established that the main requirements for materials for photocatalysis are their chemical and biological inertness, photocatalytic stability and activity, low cost. It is shown that the most rational technological form of the photocatalyst is the application (synthesis) of the catalytic layer on structured metal substrates, in particular titanium alloys. It is proved that these catalytic oxide systems can be effectively formed by the method of plasma-electrolyte oxidation in aqueous electrolytes with the addition of dopant metal compounds that increase the photocatalytic activity of the obtained heterooxide systems. It is proposed to use tungsten oxides of variable valence as the target additive. The kinetic regularities of the process of plasma-electrolytic oxidation of titanium VT1-0 in a diphosphate-borate electrolyte with the addition of tungstates have been studied. It is shown that in an electrolyte of this type at a current density of 1.0 A/dm2 in the galvanostatic mode for 30 min a uniform coating of TiO2·WxOy with a tubular torus-like structure and tungsten content of 2.5–7.5 wt.% is formed. The predicted quantitative composition of the heteroxide layer in combination with the surface morphology creates the preconditions for high catalytic activity of the synthesized coating for detoxification of media from anthropogenic pollutants.

scholarly journals Photocatalytic activity of oxide systems based on doped d-elements of titanium alloys

2021 ◽  
pp. 97-102
Author(s):  
Mykola Sakhnenko ◽  
Iryna Stepanova ◽  
Svitlana Zyubanova ◽  
Anatoly Djenyuk ◽  
Sergey Indykov
Keyword(s):  
Photocatalytic Activity ◽  
Surface Morphology ◽  
Metal Oxide ◽  
Decomposition Reaction ◽  
Titanium Monoxide ◽  
Tio2 Films ◽  
Oxide Systems ◽  
Plasma Electrolyte ◽  
Plasma Electrolyte Oxidation ◽  
Electrolyte Oxidation

CO-, W-, MO- and Zn-containing hetero-oxide nanostructured coatings on titanium and its alloys formed by plasma-electrolyte oxidation in galvanostatic mode from alkaline electrolytes were investigated. The morphology of the surface of the formed coatings was studied by scanning microscopy on the Zeiss Evo 40XVP microscope. The phase composition of the obtained coatings was determined on the X-ray diffractometer Drone-2. Photocatalytic activity of ZnO-WO3/TiO2 films, ZnO-MOO3/TIO2, ZnO-Co3O4/TiO2, CoO-WO3/TiO2 tested in a model reaction of decomposition of an aqueous solution of azobye with a concentration of 12,2·10-5 mol/L (MО) at UV irradiation. It is shown that with plasma-electrolyte oxidation of titanium and its alloys in alkaline diphosphate electrolytes in the mode of «drop-down power» forming heterostructural composites with micro-globular surface morphology. The possibility of controlling the phase and elemental composition of oxide layers, as well as the topography of the surface by changing the composition of the electrolyte and the content of individual components, as well as the modes of formation is confirmed. Heteroxide coatings formed in PEO modes differ in composition and surface morphology, but all exhibit photocatalytic properties of varying degrees of activity. The study of the photocatalytic activity of the obtained coatings in the azo dye decomposition reaction by means of UV testing allowed to rank the heteroxide systems according to the specified parameter. Thus, the degree of decomposition of MF on ZnO-WO3/TiO2 films in 50 minutes was 23 %. Metal oxide systems ZnO-Co3O4/TiO2 had similar characteristics of the degree of decomposition – 21 %. The incorporation of CoO and WO3 oxides into the coating composition reduced the catalytic activity of the system to 19 %. The unstable mode of formation of ZnO-MoO3/TiO2 oxides and the low speed of the process have affected the quality of the catalytic coating activity, reduced the degree of decomposition of MO to values of titanium monoxide Ti/TiO2 without dopants. Comparison of quantitative characteristics of the properties of the obtained coatings allowed to determine the effects of dopants, incorporated into metal oxide systems, on their photocatalytic activity.

scholarly journals Vanadium doped CaTiO3 cuboids: Role of vanadium in improving the photocatalytic activity

2021 ◽  
Author(s):  
Harsha Bantawal ◽  
Sandhya U. Shenoy ◽  
Denthaje Krishna Bhat
Keyword(s):  
Photocatalytic Activity ◽  
Water Splitting ◽  
Dye Degradation ◽  
Low Cost ◽  
Physicochemical Stability ◽  
Photocatalytic Dye Degradation

CaTiO3 has attracted enormous interest in the field of photocatalytic dye degradation and water splitting owing to its low cost, excellent physicochemical stability and structural tunability. Herein, we have developed...

P-doped CdS integrated with multiphasic MoSe2 nanosheets accomplishing prominent photocatalytic activity for hydrogen evolution

2021 ◽  
Author(s):  
Xuanxuan Yang ◽  
Hong Yang ◽  
Tiantian Zhang ◽  
Yongbing Lou ◽  
Jinxi Chen
Keyword(s):  
Photocatalytic Activity ◽  
Transition Metal ◽  
Hydrogen Evolution ◽  
Low Cost ◽  
Cds Nanorods

Rational modulation of low-cost and versatile Cd-based photocatalysts coupled with transition metal diselenides is favorable to reinforcing the performance of hydrogen evolution. Herein, the P-doped CdS nanorods (denoted as PCS)...

scholarly journals Fabrication of TiO2/Fe2O3/CdS systems: effects of Fe2O3 and CdS content on superior photocatalytic activity

RSC Advances ◽  
2021 ◽  
Vol 11 (17) ◽  
pp. 10300-10308
Author(s):  
Hui Feng ◽  
Siqi Feng ◽  
Niu Tang ◽  
Songbai Zhang ◽  
Xiangyang Zhang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Photocatalytic Activity ◽  
Organic Pollutants ◽  
High Performance ◽  
Low Cost

New idea for the low cost synthesis of high performance photocatalysts for the photodegradation of organic pollutants in aqueous solution.

scholarly journals High catalytic activity for formaldehyde oxidation of an interconnected network structure composed of δ-MnO2 nanosheets and γ-MnOOH nanowires

2020 ◽  
Vol 8 (4) ◽  
pp. 429-439
Author(s):  
Ying Tao ◽  
Rong Li ◽  
Ai-Bin Huang ◽  
Yi-Ning Ma ◽  
Shi-Dong Ji ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Network Structure ◽  
Manganese Oxides ◽  
Active Oxygen Species ◽  
Low Cost ◽  
High Dispersion ◽  
Hydroxyl Groups ◽  
High Catalytic Activity ◽  
Interconnected Network ◽  
Surface Hydroxyl

AbstractAmong the transition metal oxide catalysts, manganese oxides have great potential for formaldehyde (HCHO) oxidation at ambient temperature because of their high activity, nontoxicity, low cost, and polybasic morphologies. In this work, a MnO2-based catalyst (M-MnO2) with an interconnected network structure was successfully synthesized by a one-step hydrothermal method. The M-MnO2 catalyst was composed of the main catalytic agent, δ-MnO2 nanosheets, dispersed in a nonactive framework material of γ-MnOOH nanowires. The catalytic activity of M-MnO2 for HCHO oxidation at room temperature was much higher than that of the pure δ-MnO2 nanosheets. This is attributed to the special interconnected network structure. The special interconnected network structure has high dispersion and specific surface area, which can provide more surface active oxygen species and higher surface hydroxyl groups to realize rapid decomposition of HCHO.

scholarly journals Combined first-principles calculations and experimental study on the photocatalytic mechanism of natural dolomite

RSC Advances ◽  
2021 ◽  
Vol 11 (39) ◽  
pp. 24416-24423
Author(s):  
Xiaomin Hou ◽  
Qi Cheng ◽  
Jianrong Wang ◽  
Qingfeng Wu ◽  
Weibin Zhang
Keyword(s):  
Experimental Study ◽  
Photocatalytic Activity ◽  
First Principles ◽  
Low Cost ◽  
Isomorphous Substitution ◽  
First Principles Calculations ◽  
Photocatalytic Mechanism

Natural dolomite exhibits notable photocatalytic activity due to the isomorphous substitution of Fe2+ for Mg2+ in the lattice, implying that it can be used as a low-cost photocatalyst.

Structure, morphology features and photocatalytic properties of α-Ag2WO4 nanocrystals-modified Palygorskite clay

2021 ◽  
Vol 02 ◽  
Author(s):  
Amanda Carolina Soares Jucá ◽  
Francisco Henrique Pereira Lopes ◽  
Herbert Vieira Silva-Júnior ◽  
Lara Kelly Ribeiro Silva ◽  
Elson Longo ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Rhodamine B ◽  
Dye Degradation ◽  
Degradation Kinetics ◽  
Low Cost ◽  
Catalytic Efficiency ◽  
Photocatalytic Properties ◽  
Impregnation Method ◽  
Heat Treated ◽  
Modified Palygorskite

Aims: In the present study, we investigate the photocatalytic properties of α-Ag2WO4 nanocrystals-modified Palygorskite (PAL) clay synthesized by the impregnation method. The PAL clay was chemically purified and heat-treated (500 ºC for 2 h), which served as an excellent supporting matrix for loading α-Ag2WO4(α-AWO) nanocrystals. Background: Water contamination is one of the most serious problems affecting human health, ecosystem survival, and the economic growth of societies. Industrial effluents, such as textile dyes, when not treated and improperly discharged into water resources are considered the main cause of water pollution. Thus the scientific community has been developing effective remediation technologies based on advanced oxidative processes to reduce the harmful effects of these organic pollutants. Objective: Improve the photocatalytic activity of PAL clay with α-AWO nanocrystals to degradation of Rhodamine B (RhB) dye. Methods: We purify and heat-treated the PAL clay, synthesize nanocrystals ofα-AWO nanocrystals and modify PAL clay with 30% α-AWO nanocrystals by the impregnation method. The modified PAL clay was able to improve RhB dye degradation. The materials were characterized by XRD, RAMAN,FE-SEM, FT-IR, XRF, etc. The samples were used as photocatalysts under UV-C lamps for the degradation of RhB dye in order to analyze its catalytic performances. Results: ThePAL clay modified with 30% α-AWO nanocrystals showed a catalytic efficiency of 79%, and degradation kinetics about 16 times higher when compared to PAL-500 only purified and heat-treated at 500 ºC. In this way, this PAL-modified is an alternative as a low-cost photocatalyst for the degradation of RhB dye. Conclusion: Ultraviolet-Visiblespectra revealed that our materials have opticalband gap energies controlled by indirect and direct electronic transitions and suitable to be activated under ultraviolet illumination. The adequate amount (30 wt.%) of α-Ag2WO4 nanocrystals added to PAL brought significant improvement of photocatalytic activity for the degradation of rhodamine B. Finally, a photocatalytic mechanism was proposed in detail.

Synthesis of YFeO3-δ and LaFeO3-δ Perovskites with High Catalytic Activity in Carbon Oxidation Reactions

2021 ◽  
Vol 316 ◽  
pp. 105-109
Author(s):  
Evgeny A. Kirichenko ◽  
Pavel G. Chigrin ◽  
Anton A. Gnidenko
Keyword(s):  
Oxidation Mechanism ◽  
Soot Oxidation ◽  
Complex Oxide ◽  
Maximum Temperature ◽  
High Catalytic Activity ◽  
Carbon Oxidation ◽  
Oxidation Reactions ◽  
Oxide Systems ◽  
Reduction Of Metal Oxides ◽  
Catalytic Reaction Mechanism

YFeO3-δ (δ = 0.26) and LaFeO3-δ (δ = 0.5) perovskites with a high specific surface and oxygen non-stoichiometry was firstly synthesized by pyrolysis of polymer-salt compositions. It was shown that the catalytic oxidation of carbon in the presence of these complex oxide systems proceeds in the range of 400 - 700 °С, with a maximum temperature at 556 °С for YFeO3-δ; and 380 - 620 °С ,with a maximum temperature at 501 °С for LaFeO3-δ, in one-stage mode for both. By means of thermal analysis and diffractometry, it was shown that there is no contribution to the soot oxidation mechanism by cyclic perovskite surface transformations, due to the reduction of metal oxides by the soot and their subsequent reoxidation. It has been established that the basis of the catalytic reaction mechanism for both perovskites is the presence of oxygen vacancies on the surface of complex oxides.

scholarly journals Enhanced Photocatalytic Activity of Semiconductor Nanocomposites Doped with Ag Nanoclusters Under UV and Visible Light

Catalysts ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 31 ◽  
Author(s):  
Jorge González-Rodríguez ◽  
Lucía Fernández ◽  
Yanina B. Bava ◽  
David Buceta ◽  
Carlos Vázquez-Vázquez ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Inductively Coupled Plasma ◽  
Emerging Contaminants ◽  
Low Cost ◽  
Optical Emission ◽  
Silver Nanoclusters ◽  
Emission Spectrometry ◽  
Wide Range ◽  
Semiconductor Nanocomposites

Emerging contaminants (ECs) represent a wide range of compounds, whose complete elimination from wastewaters by conventional methods is not always guaranteed, posing human and environmental risks. Advanced oxidation processes (AOPs), based on the generation of highly oxidizing species, lead to the degradation of these ECs. In this context, TiO2 and ZnO are the most widely used inorganic photocatalysts, mainly due to their low cost and wide availability. The addition of small amounts of nanoclusters may imply enhanced light absorption and an attenuation effect on the recombination rate of electron/hole pairs, resulting in improved photocatalytic activity. In this work, we propose the use of silver nanoclusters deposited on ZnO nanoparticles (ZnO–Ag), with a view to evaluating their catalytic activity under both ultraviolet A (UVA) and visible light, in order to reduce energetic requirements in prospective applications on a larger scale. The catalysts were produced and then characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and inductively coupled plasma-optical emission spectrometry (ICP-OES). As proof of concept of the capacity of photocatalysts doped with nanoclusters, experiments were carried out to remove the azo dye Orange II (OII). The results demonstrated the high photocatalytic efficiency achieved thanks to the incorporation of nanoclusters, especially evident in the experiments performed under white light.

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