Preparation of Au, Pt, Pd and Ag Doped TiO2 Nanofibers and their Photocatalytic Properties under LED Illumination

2018 ◽  
Vol 762 ◽  
pp. 283-287 ◽  
Author(s):  
Reinis Drunka ◽  
Jānis Grabis ◽  
Aija Krūmiņa

In the present work formation of active TiO2 nanofibers in microwave-assisted synthesis and their modification with Au, Pt, Pd and Ag nanoparticles were studied. Anatase nanopowder and 10M KOH solution were used as raw materials. Microwave-assisted synthesis permitted to obtain TiO2 nanofibers and nanowires with a diameter of 10nm and a specific surface area 158.5m2/g. Chemical deposition method were used to modify TiO2 nanofibers with precious metal nanoparticles. After modification, specific surface area decreased and were in range 73.1 – 74.7m2/g. Photocatalytic activity was determined by degradation of the methylene blue (MB) solution under visible light irradiation. High intensity LED lamp was used as light source. The obtained samples showed higher photocatalytic activity with respect to pure TiO2 nanofibers. The doped TiO2 nanofibers were appropriate for degradation of harmful organic compounds as well as for hydrogen production by water splitting.

2016 ◽  
Vol 51 (21) ◽  
pp. 9822-9829 ◽  
Author(s):  
Mieke Meire ◽  
Sammy W. Verbruggen ◽  
Silvia Lenaerts ◽  
Petra Lommens ◽  
Pascal Van Der Voort ◽  
...  

2021 ◽  
Vol 43 (2) ◽  
pp. 124-124
Author(s):  
Min keng He Min keng He ◽  
Jin Zhang Jin Zhang ◽  
Fang yan Chen Fang yan Chen ◽  
Ke keShu Ke keShu ◽  
Yu bin Tang Yu bin Tang

K-doped g-C3N4/SiO2composite (SiO2/K-CN) was synthesized by a facile thermal polymerization with potassium chloride, melamine and nano-silica as raw materials. The as-prepared SiO2/K-CN was characterized by various measures. The photocatalytic activity of SiO2/K-CN was tested via the photocatalytic degradation of tetracycline under visible-light irradiation. The results showed that the specific surface area of SiO2/K-CN catalyst was 28.16m2/g, which is larger than that of pristine K-doped g-C3N4. Both K-doping and silica-combination can reduce the recombination rate of photo-generated electrons-holes pairs and broaden the region of visible light-harvesting. Compared with the pristine K-doped g-C3N4 and composite SiO2/g-C3N4, SiO2/K-CN exhibits distinctly higher photocatalytic activity for degradation of tetracycline. The enhanced photocatalytic performance of SiO2/K-CN is attributed to the increased specific surface area and the synergistic effect of K-doping and silica-combination in both accelerating separation of charged carries and improving visible light-absorption. During photocatalytic degradation of tetracycline, superoxide radicals play the most important role, followed by holes.SiO2/K-CN complex has excellent stability and shows promising application in photocatalytic degradation of organic contaminants in water.


2019 ◽  
Vol 800 ◽  
pp. 132-137
Author(s):  
Reinis Drunka ◽  
Jānis Grabis ◽  
Aija Krumina

Microwave-assisted hydrothermal synthesis of TiO2 nanofibers under various temperature and pressure conditions were done in this research. High quality TiO2 nanofiber coatings where obtained when temperature was in range 240 – 245 °C and pressure was 27.3 – 29.1 bar. Obtained TiO2 nanofiber coatings are with a specific surface area of ​​151.5 to 158.9 m2· g-1 before calcination. Comparing with nanopowder photocatalysts nanofiber coatings photocatalysts can be much easier removed from solution after the photocatalysis process. Such coatings with relative large specific surface area are with higher potential application in industry.


Author(s):  
Т.В. САВЕНКОВА ◽  
М.А. ТАЛЕЙСНИК ◽  
Н.А. ЩЕРБАКОВА ◽  
С.Ю. МИСТЕНЕВА ◽  
И.И. МИЗИНЧИКОВА

Описаны и теоретически обоснованы разработанные технологические приемы производства мучных кондитерских изделий при сохранении влаги на всех стадиях производства. В рамках исследования решали следующие задачи: увеличение удельной поверхности частиц дисперсной фазы эмульсии за счет моделирования рецептурного состава; дезагрегирование муки, повышение равномерности распределения дисперсионной среды (эмульсии) с образованием оболочек вокруг максимально возможного количества частиц муки различных фракций. Объектом для моделирования рецептурного состава было сахарное печенье. Установлено, что замена рецептурных компонентов с повышенной влажностью на сырье с высоким содержанием сухих веществ позволяет высвободить влагу и использовать новые виды сырья с повышенными нативными свойствами. Предложенные приемы подготовки сырьевых компонентов: снижение вязкости солодового экстракта, используемого для снижения количества сахара-песка, осмотическое набухание яичного порошка, пластикация жира со стабилизацией его структуры лецитином, инверсия сахарозы в условиях совмещения гидродинамического и акустического кавитационных воздействий при получении инвертного сиропа – обеспечивают благоприятные условия получения эмульсии с повышенной удельной поверхностью. Отличительной особенностью предлагаемой технологии является получение эмульсии в две стадии: приготовление суспензии без жира и собственно получение эмульсии. Раздельная подача сахара в два приема: 40–60% его рецептурного количества вносится на стадии приготовления суспензии, оставшаяся часть – при приготовлении эмульсии – и кавитационная обработка суспензии при температуре 36–38°С и частоте колебаний волновода 24 кГц позволяют повысить частичную концентрацию частиц сахара в 8–12 раз. При приготовлении эмульсии пластицированный жир и лецитин предварительно смешивают с оставшейся частью сахара-песка, а затем с суспензией. Дезагрегированную путем аэрации муку и эмульсию одновременно и параллельно подают в месильную машину для достижения их заданного соотношения до начала процесса тестообразования. Разработанный комплекс технологических приемов позволил создать технологический поток производства сахарного печенья с улучшенными показателями качества – намокаемостью до 230% (по классической технологии 180–200%), сниженной на 20% плотностью, повышенными пористостью и рассыпчатостью и сохраняющего до 92% влажности, что на 18% выше, чем в изделиях, полученных по классической технологии. The developed technological techniques for the production of flour confectionery products while maintaining moisture at all stages of production are described and theoretically justified. The following tasks were solved in the framework of the study: increasing the specific surface area of the particles of the dispersed phase of the emulsion by modeling the recipe composition; disaggregating flour, increasing the uniformity of the distribution of the dispersion medium (emulsion) with the formation of shells around the maximum possible number of flour particles of various fractions. The object for modeling the formulation composition was sugar cookies. It is established that the replacement of prescription components with high humidity with raw materials with a high content of dry substances allows you to release moisture and use new types of raw materials with increased native properties. The proposed methods of preparation of raw materials: reducing the viscosity of malt extract used to reduce the amount of granulated sugar, osmotic swelling of egg powder, fat plasticization with the stabilization of its structure with lecithin, sucrose inversion under conditions of combining hydrodynamic and acoustic cavitation effects in the production of invert syrup – provide favorable conditions for obtaining an emulsion with an increased specific surface area. The production of an emulsion in two stages is a distinctive feature of the proposed technology: the preparation of a suspension without fat and the actual production of the emulsion. Separate supply of sugar in two steps: 40–60% of its prescription amount is introduced at the stage of preparation of the suspension, the remaining part – during the preparation of the emulsion – and cavitation treatment of the suspension at a temperature of 36–38°С and the waveguide oscillation frequency of 24 kHz, it is possible to increase the partial concentration of sugar particles by 8–12 times. When preparing the emulsion, the plasticized fat and lecithin are pre-mixed with the remaining part of the granulated sugar, and then with the suspension. The aeration-disaggregated flour and emulsion are fed simultaneously and in parallel to the kneading machine to achieve their desired ratio before the dough-forming process begins. The developed complex of technological techniques allowed to create a technological flow for the production of sugar cookies with improved quality indicators – wetting up to 230% (according to the classical technology 180–200%), reduced density by 20%, increased porosity and friability, and preserving up to 92% humidity, which is 18% higher than in products obtained by the classical technology.


Author(s):  
Hieр Nguyen Tien

The kinetics of metallic cobalt nanopowder synthesizing by hydrogen reduction from Co(OH)2 nanopowder under isothermal conditions were studied. Co(OH)2 nanopowder was prepared in advance by chemical deposition from aqueous solutions of Co(NO3)2 cobalt nitrate (10 wt.%) and NaOH alkali (10 wt.%) at room temperature, pH = 9 under continuous stirring. The hydrogen reduction of Co(OH)2 nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 270 to 310 °C. The crystal structure and composition of powders was studied by X-ray phase analysis. The specific surface area of samples was measured using the BET method by low-temperature nitrogen adsorption. The average particle size of powders was determined by the measured specific surface area. Particles size characteristics and morphology were investigated by transmission and scanning electron microscopes. Kinetic parameters of Co(OH)2 hydrogen reduction under isothermal conditions were calculated using the Gray–Weddington model and Arrhenius equation. It was found that the rate constant of reduction at t = 310 °C is approximately 1.93 times higher than at 270 °C, so the process accelerates by 1.58 times for 40 min of reduction. The activation energy of cobalt nanopowder synthesizing from Co(OH)2 by hydrogen reduction is ~40 kJ/mol, which indicates a mixed reaction mode. It was shown that cobalt nanoparticles obtained by the hydrogen reduction of its hydroxide at 280 °C are aggregates of equiaxed particles up to 100 nm in size where individual particles are connected to several neighboring particles by contact isthmuses.


2016 ◽  
Vol 18 (2) ◽  
pp. 141 ◽  
Author(s):  
A.A. Atchabarova ◽  
R.R. Tokpayev ◽  
A.T. Kabulov ◽  
S.V. Nechipurenko ◽  
R.A. Nurmanova ◽  
...  

<p>Electrode materials were prepared from activated carbonizates of walnut shell, apricot pits and shungite rock from “Bakyrchik” deposit, East Kazakhstan. Physicochemical characteristics of the obtained samples were studied by the Brunauer-Emett-Taylor method, scanning electron microscopy, Raman spectroscopy and other methods. Electrochemical properties of the obtained materials were studied by the method of cyclic voltammetry. It was found that the samples have an amorphous structure. Samples based on plant raw materials after hydrothermal carbonization at 240 °С during 24 h, have more homogeneous and developed surface. Specific surface area of carbon containing materials based on apricot pits is 1300 m<sup>2</sup>/g, for those on the based on mineral raw material, it is 153 m<sup>2</sup>/g. It was shown that materials after hydrothermal carbonization can be used for catalytic purposes and electrodes after thermal carbonization for analytical and electrocatalytic purposes. Electrode obtained by HTC have electrocatalytic activity. CSC 240 has high background current (slope i/Е is 43 mА V<sup>–1</sup> cm<sup>–2</sup>), low potential of the hydrogen electroreduction (more positive by ~ 0.5 V than samples based on plant raw materials). The reaction of DA determination is more pronounced on the electrodes obtained by HTC 240 °C, 24 h, due to the nature, carbon structure and high specific surface area of obtained samples.</p>


2017 ◽  
Vol 10 (03) ◽  
pp. 1750028 ◽  
Author(s):  
Yan Zhu ◽  
Xiaoxia Yan ◽  
Yuanxin Ge ◽  
Shumin Wang ◽  
Dongmei Deng ◽  
...  

A facile approach was developed to synthesize novel Roe-like TiO2 hollow nanospheres via a template-assisted self-assembly process. These TiO2 nanospheres possessing mesoporous cavity manifest significantly improved photocatalytic activity owing to the synergistic effects of increased charge separation, more efficient use of the light and specific surface area.


2014 ◽  
Vol 604 ◽  
pp. 93-101
Author(s):  
Maris Kodols ◽  
Sabine Didrihsone ◽  
Janis Grabis

The influence of glycine, glycerine, ethylene glycol and citric acid fuel and their ratio to NO3- on formation and dispersity of Bi2WO6 nanoparticles prepared by combustion synthesis has been studied. The pure crystalline Bi2WO6 with specific surface area 24,8 m2/g and crystallite size of 28 nm was obtained by using glycerine as fuel at its ratio to NO3- of 0,67. The photocatalytic activity of the prepared Bi2WO6 in degradation of methylene blue depended on its specific surface area of samples and solution pH.


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