Search results for "Anodizing"
showing 10 items of 116 documents
Ultraplāni anodēta alumīnija oksīda pārklājumi un to pielietojumi
2014
1 ANOTĀCIJA Ultraplāni anodēta alumīnija oksīda pārklājumi un to pielietojumi. Raimonds Popļausks, zinātniskais vadītājs Dr. ķīm. Donāts Erts. Promocijas darbs veltīts aktuālām problēmām par ultraplāna anodētā alumīnija oksīda pārklājumu iegūšanu uz dažādām virsmām un to pielietojumiem. Darbā izstrādātas metodikas atkārtojamu liela laukuma (virs 1 cm2) ultraplānu anodētā alumīnija oksīda masku ar variējamiem poru diametriem, starpporu attālumiem un biezumiem iegūšanai un pārnešanai uz dažādām virsmām, kā arī nanodaļiņu masīvu sensoru pielietojumiem iegūšanu caur šīm maskām. Izstrādāta metode ultraplānu anodētā alumīnija oksīda masku iegūšanai lai iegūtu nanodaļiņu masīvus ar diametru zem 20…
Customized WO3 nanoplatelets as visible-light photoelectrocatalyst for the degradation of a recalcitrant model organic compound (methyl orange)
2018
[EN] WO3 nanoplatelets have been synthesized by electrochemical anodization in acidic electrolytes containing two different complexing agents: fluorides and hydrogen peroxide. The influence of the morphology and size of these nanoplatelets on their photoelectrocatalytic performance has been studied following the degradation of a model organic recalcitrant compound, such as methyl orange (MO). The effect of several supporting electrolytes on this photodegradation process has also been checked. The best MO decoloration was observed for nanoplatelets fabricated in the presence of low H2O2 concentrations, whose distribution and small size made them expose a very high surface area to the problem…
Elimination of pesticide atrazine by photoelectrocatalysis using a photoanode based on WO3 nanosheets
2018
[EN] The photoelectrocatalytic (PEC) degradation of a persistent and toxic herbicide, atrazine, has been investigated by using a novel and high-performance WO3 nanostructure in the form of nanosheets/nanorods as photoanode. The nanostructure has been synthesized by anodization in acidic media in the presence of a very small amount (0.05 M) of H2O2, and its morphology, as well as its electrochemical and photoelectrochemical properties have been characterized. Atrazine was completely degraded after similar to 180 min of reaction following pseudo-first order kinetics, and 2-hydroxyatrazine was identified as the main intermediate species. Moreover, the s-triazine ring in cyanuric acid (the fina…
Influence of annealing conditions on the photoelectrocatalytic performance of WO3 nanostructures
2020
[EN] Nanostructured WO3 photoanodes have been synthesized by electrochemical anodization under controlled hydrodynamic conditions in acidic media in the presence of 0.05 M H2O2. Subsequently, samples have been subjected to a thermal treatment (annealing) at different temperatures (400 degrees C, 500 degrees C and 600 degrees C) and under different gaseous atmospheres (air, N-2, Ar). The influence of these annealing conditions on the morphology, crystallinity, photoelectrochemical behavior and dopant chemistry of the different photoanodes has been investigated through Electronic Microscopy, Raman Spectroscopy, Photoelectrochemical Impedance Spectroscopy and Mott-Schottky analysis. In general…
Synthesis of WO3 nanorods through anodization in the presence of citric acid: Formation mechanism, properties and photoelectrocatalytic performance
2021
[EN] In this study, WO3 nanomds have been fabricated by simple anodization in the presence of different amounts of citric acid and at different anodization times. A comprehensive morphological, structural, electrochemical and photoelectrochemical characterization of different samples has been carried out. Moreover, a formation mechanism for WO3 nanorods has been proposed. Finally, these nanostructures have been proven to be excellent visible-light photoelectrocatalysts to remove persistent organic pollutants present in wastewaters, such as fenamiphos. Almost the 80% of this molecule was eliminated from the test solution after 180 min of irradiation, indicating the great potential of these W…
Formation of ZnO nanowires by anodization under hydrodynamic conditions for photoelectrochemical water splitting
2020
[EN] The present work studies the influence of hydrodynamic conditions (from 0 to 5000 rpm) during Zn anodization process on the morphology, structure and photoelectrocatalytic behavior of ZnO nanostructures. For this purpose, analysis with Confocal Laser-Raman Spectroscopy, Field Emission Scanning Electron Microscope (FE-SEM) and photoelectrochemical water splitting tests were performed. This investigation reveals that hydrodynamic conditions during anodization promoted the formation of ordered ZnO nanowires along the surface that greatly enhance its stability and increases the photocurrent density response for water splitting in a 159% at the 5000 rpm electrode rotation speed.
Controlled hydrodynamic conditions on the formation of iron oxide nanostructures synthesized by electrochemical anodization: Effect of the electrode …
2017
[EN] Iron oxide nanostructures are of particular interest because they can be used as photocatalysts in water splitting due to their advantageous properties. Electrochemical anodization is one of the best techniques to synthesize nanostructures directly on the metal substrate (direct back contact). In the present study, a novel methodology consisting of the anodization of iron under hydrodynamic conditions is carried out in order to obtain mainly hematite (alpha-Fe2O3) nanostructures to be used as photocatalysts for photoelectrochemical water splitting applications. Different rotation speeds were studied with the aim of evaluating the obtained nanostructures and determining the most attract…
Iron oxide nanostructures for photoelectrochemical applications: Effect of applied potential during Fe anodization
2019
[EN] In photoelectrochemistry, a suitable photoanode leading to high efficiencies in photocatalytic processes is a research challenge. Iron oxide nanostructures are promising materials to be used as photoanodes. In this work, different potentials during iron anodization were applied to study the properties of the synthesized nanostructures. Results revealed that nanostructures anodized at 50V presented well-defined nanotubular structures with open-tube tops, and they achieved values of photocurrent density of 0.11 mA cm(-2) at 0 rpm and 0.14 mA cm(-2) at 1000 rpm (measured at 0.50 V-Ag/Agcl), corresponding to the oxygen evolution reaction from water, i.e. 2H(2)O+4h(+)-> 4H(+)+O-2, demonstra…
Improvement in photocatalytic activity of stable WO3 nanoplatelet globular clusters arranged in a tree-like fashion: Influence of rotation velocity d…
2016
This study investigates the influence of controlled hydrodynamic conditions during anodization of tungsten (W) on the morphological, electrochemical and photocatalytic properties of a novel WO3 nanostructure: globular clusters of nanoplatelets associated in a tree-like fashion. For this purpose different techniques such as Field-Emission Scanning Electronic Microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS) measurements, Mott-Schottky (M-S) analysis and photoelectrochemical water splitting tests have been carried out. Photoanodes obtained at 375 rpm showed the best photoresponse, much higher than that of conventional WO3 nanoplatelets, which can be ascribed to a noteworthy in…
Photo-Activity Research of Nano-Structured TiO2Layers
2011
Titania with anatase structure is investigated due to its photo-active properties that can be used in the water photocatalysis applications and in the organic photovoltaic devices. In this work the anodization conditions are described to obtain stable thin film TiO2 layers formed from vertically oriented nanotubes with approximate height 358 nm, inner tube diameter 48 nm and wall thickness 20 nm, but centre to centre distance 100 nm. Annealed at 500 o C TiO2 layer mostly consists from oxide with anatase structure, though XRD spectroscopy shows rutile impurities as well. Obtained nanotube layers are sensitive mostly to UV light.