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Nanostructured Anodic Metal Oxides

Nanostructured Anodic Metal Oxides Book
Author : Grzegorz D Sulka
Publisher : Micro and Nano Technologies
Release : 2020-03
ISBN : 0128167068
Language : En, Es, Fr & De

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Book Description :

Nanostructured Anodic Metal Oxides: Synthesis and Applications reviews the current status of fabrication strategies that have been successfully developed to generate nanoporous, nanotubular and nanofibrous anodic oxides on a range of metals. The most recent achievements and innovative strategies for the synthesis of nanoporous aluminum oxide and nanotubular titanium oxide are discussed. However, a special emphasis is placed on the possibility of fabrication of nanostructured oxide layers with different morphologies on other metals, including aluminum titanium, tantalum, tin, zinc, zirconium and copper. In addition, emerging biomedical applications of synthesized materials are discussed in detail. During the past decade, great progress has been made both in the preparation and characterization of various nanomaterials and their functional applications. The anodization of metals has proven to be reliable for the synthesis of nanoporous, nanotubular and nanofibrous metal oxides to produce a desired diameter, density, aspect ratio (length to diameter) of pores/tubes, and internal pore/tube structure.

Nanostructured Anodic Metal Oxides

Nanostructured Anodic Metal Oxides Book
Author : Grzegorz D. Sulka
Publisher : Elsevier
Release : 2020-03-27
ISBN : 0128168773
Language : En, Es, Fr & De

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Book Description :

Nanostructured Anodic Metal Oxides: Synthesis and Applications reviews the current status of fabrication strategies that have been successfully developed to generate nanoporous, nanotubular and nanofibrous anodic oxides on a range of metals. The most recent achievements and innovative strategies for the synthesis of nanoporous aluminum oxide and nanotubular titanium oxide are discussed. However, a special emphasis is placed on the possibility of fabrication of nanostructured oxide layers with different morphologies on other metals, including aluminum titanium, tantalum, tin, zinc, zirconium and copper. In addition, emerging biomedical applications of synthesized materials are discussed in detail. During the past decade, great progress has been made both in the preparation and characterization of various nanomaterials and their functional applications. The anodization of metals has proven to be reliable for the synthesis of nanoporous, nanotubular and nanofibrous metal oxides to produce a desired diameter, density, aspect ratio (length to diameter) of pores/tubes, and internal pore/tube structure. Provides an in-depth overview of anodization techniques for a range of metals Explores the emerging applications of anodic metal oxides Explains mechanisms of formation valve metal oxides via anodization

Porous Anodic Aluminum Oxide Scaffolds Formation Mechanisms and Applications

Porous Anodic Aluminum Oxide Scaffolds   Formation Mechanisms and Applications Book
Author : Jihun Oh
Publisher : Unknown
Release : 2010
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

Nanoporous anodic aluminium oxide (AAO) can be created with pores that self-assemble into ordered configurations. Nanostructured metal oxides have proven to be very useful as scaffolds for growth of nanowires and nanotubes with tunable diameters and with tight diameter distributions. For 50 years, field-assisted dissolution of the oxide has been cited as the mechanism that leads to pore formation in alumina, and by analogy, porous anodic TiO2 and other functional metal oxides. We show that field-assisted dissolution models are consistent with the observed dependence of the Al2O3 dissolution rate on the electric field, as well as the existence of a critical field for pore initiation. However, we further show that the well-known ordered porous structure, which has a significantly different length scale, does not result from a field-induced instability, but is instead the result of a strain-induced instability with forced plastic deformation and flow of the oxide during further anodization. We demonstrate that these pore generation mechanisms can be controlled independently, even when they co-exist, by controlling the electric field across the oxide as well as the anodization conditions. We also show that mechanical confinement results in a dendritic pore structure. Through interpretation of these results we develop a generalized mechanism for ordered pore formation in AAO in analogy with cellular solidification. In addition, we report on abnormal behavior in anodic oxidation of Al in mechanically confined structures for formation of horizontal nanoporous anodic alumina oxide, H-AAO. Instead of smooth pore walls, periodic dendrite inner pore structures form, the growth rate is suppressed to 5 % of its value during bulk anodization under the same conditions, and a steady-state is never reached. These anomalies associated with formation of H-AAO originate from suppressed volume expansion and plastic flow of Al2O3 confined by the SiO2 hard mask. By determining new anodization conditions leading to zero volume expansion, dendritic H-AAO can be avoided and kinetic retardation can be minimized. A new method for perforation of the AAO barrier layer has been developed, based on anodization of Al/W bilayer films on substrates. When Al/W bilayer films are anodized and pores approach the Al/W interface, tungsten oxide forms and penetrates the alumina barrier oxide, in part, due to enhanced plasticity of the alumina layer. By selectively etching the tungsten oxide, the barrier oxide can be removed and the base of the pores opened, without etching of the AAO. Finally, we further refined the selective barrier perforation process using the W interlayer to develop a methodology for fabrication of through-pore AAO scaffolds on any conducting substrate (AS) by anodizing an Al/W/AS tri-layer. Structural and kinetic study of the WO3 extrusion revealed that the anodization of W consumes a fixed thickness of the W layer in acidic electrolytes under specific anodization conditions. Based on this study, the optimum thickness of the W interlayer in the Al/W/Au tri-layer was measured for various anodization conditions. Through-pore AAOs were fabricated on Au layers with exposure of the surface at the base of the pores, using the optimum W thickness without a violent O2 evolution reaction and without changing the pore diameters. With scaffolds made using this methodology, vertically-aligned free-standing Au and Pt nanowires with diameters ranging from about 12 nm to about 120 nm were grown by electrodeposition on a gold substrate.

1 Dimensional Metal Oxide Nanostructures

1 Dimensional Metal Oxide Nanostructures Book
Author : Zainovia Lockman
Publisher : CRC Press
Release : 2018-12-07
ISBN : 1351266713
Language : En, Es, Fr & De

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Book Description :

1-D metal oxide nanostructures, especially those with semiconducting properties, have attracted much attention in recent years due to their potential and emerging applications, specifically in environment purification and energy devices. For these applications, there have been many efforts to grow 1-D nanostructures in the form of nanotubes, nanorods, and nanowires using processes that conserve energy, are cost effective, and can be scaled up for large-scale production. 1-Dimensional Metal Oxide Nanostructures gathers under one title the most recent development of oxide nanomaterials, especially those fabricated via oxidation process in the nanoscale field. Thermal and anodic oxidation processes are reviewed with an aim to offer an in-depth understanding of mechanisms of 1-D nanostructure formation, their characteristics, and limitations. Other more common methods are also discussed, including sol-gel, hydrothermal, and other templated methods. Important applications of 1-D nanostructures are then presented, focusing on oxides like zinc oxide, titanium oxide, zirconium oxide, copper oxide, and iron oxide. A chapter on carbon nanotubes hybrid with these oxides is also included as well as one on silicon oxide nanowires formation by local anodic oxidation process. Aimed at researchers, academics, and engineers working across the fields of nanotechnology, materials science, chemistry, physics, semiconductors, and environmental and biomedical engineering, this essential reference enables readers to grasp the main concepts of nanomaterials in 1-D: formation technique, characteristics, and uses. It also encourages practical innovations in nanotechnology, especially in curbing pressing global issues related to energy, environment, and security.

Anodic Nanostructures for Solar Cell Applications

Anodic Nanostructures for Solar Cell Applications Book
Author : Jia Lin
Publisher : Unknown
Release : 2016
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

As a versatile, straightforward, and cost-effective strategy for the synthesis of self-organized nanomaterials, electrochemical anodization is nowadays frequently used to synthesize anodic metal oxide nanostructures for various solar cell applications. This chapter mainly discusses the synthesis of various anodic TiO2 nanostructures on foils and as membranes or powders, and their potential use as the photoanode materials based on foils, transparent conductive oxide substrates, and flexible substrates in dye-sensitized solar cell applications, acting as dye-loading frames, light-harvesting enhancement assembly, and electron transport medium. Through the control and modulation of the electrical and chemical parameters of electrochemical anodization process, such as applied voltages, currents, bath temperatures, electrolyte composition, or post-treatments, anodic nanostructures with controllable structures and geometries and unique optical, electronic, and photoelectric properties in solar cell applications can be obtained. Compared with other types of nanostructures, there are several major advantages for anodic nanostructures to be used in solar cells. They are (1) optimized solar cell configuration to achieve efficient light utilization; (2) easy fabrication of large size nanostructures to enhance light scattering; (3) precise modulation of the electrochemical processes to realize periodic nanostructured geometry with excellent optical properties; (4) unidirectional electron transport pathways with suppressed charge recombination; and (5) large surface areas by modification of nanostructures. Due to the simple fabrication processes and unique properties, the anodic nanostructures will have a fascinating future to boost the solar cell performances.

Multifunctional Nanostructured Metal Oxides for Energy Harvesting and Storage Devices

Multifunctional Nanostructured Metal Oxides for Energy Harvesting and Storage Devices Book
Author : Vijay B. Pawade,Paresh H. Salame,Bharat Apparao Bhanvase
Publisher : CRC Press
Release : 2020-05-21
ISBN : 1000073203
Language : En, Es, Fr & De

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Book Description :

Metal oxide nanoparticles exhibit potential applications in energy and environmental fields, such as solar cells, fuel cells, hydrogen energy, and energy storage devices. This book covers all points from synthesis, properties, and applications of transition metal oxide nanoparticle materials in energy storage and conversion devices. Aimed at graduate-level students and researchers associated with the energy and environment sector, this book addresses the application of nontoxic and environmentally friendly metal oxide materials for a clean environment and deals with synthesis properties and application metal oxides materials for energy conversion, energy storage, and hydrogen generation.

Nanostructured Metal Oxide Electrode Materials for Water Purification

Nanostructured Metal Oxide Electrode Materials for Water Purification Book
Author : Onoyivwe Monday Ama,Suprakas Sinha Ray
Publisher : Springer Nature
Release : 2020-04-07
ISBN : 3030433463
Language : En, Es, Fr & De

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Book Description :

This book reports on the development of nanostructured metal-oxide-based electrode materials for use in water purification. The removal of organic pollutants and heavy metals from wastewater is a growing environmental and societal priority. This book thus focuses primarily on new techniques to modify the nanostructural properties of various solvent-electrolyte combinations to address these issues. Water treatment is becoming more and more challenging due to the ever increasing complexity of the pollutants present, requiring alternative and complementary approaches toward the removal of toxic chemicals, heavy metals and micro-organisms, to name a few. This contributed volume cuts across the fields of electrochemistry, water science, materials science, and nanotechnology, while presenting up-to-date experimental results on the properties and synthesis of metal-oxide electrode materials, as well as their application to areas such as biosensing and photochemical removal of organic wastewater pollutants. Featuring an introductory chapter on electrochemical cells, this book is well positioned to acquaint interdisciplinary researchers to the field, while providing topical coverage of the latest techniques and methodology. It is ideal for students and research professionals in water science, materials science, and chemical and civil engineering.

Semiconductors Metal Oxides and Composites Metallization and Electrodeposition of Thin Films and Nanostructures

Semiconductors  Metal Oxides  and Composites  Metallization and Electrodeposition of Thin Films and Nanostructures Book
Author : G. Oskam
Publisher : The Electrochemical Society
Release : 2010-02
ISBN : 156677800X
Language : En, Es, Fr & De

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Book Description :

This symposium provided a forum for current work on the electrodeposition and characterization of functional coatings and nanostructures. Central issues include the control of size and architecture and the ample choices and demands of substrate and deposited materials. The focus materials of this symposium were semiconductors, oxides and composites with e.g. ceramic nanoparticles or nanotubes.

Fabrication of Metal Oxide Nanostructures by Anodization Processes for Biosensor Drug Delivery and Supercapacitor Applications

Fabrication of Metal Oxide Nanostructures by Anodization Processes for Biosensor  Drug Delivery and Supercapacitor Applications Book
Author : Po-Chun Chen
Publisher : Unknown
Release : 2015
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

This dissertation proposed to initiate the research into the fabrication of metal/oxide nanostructures by anodization process for biosensor, drug delivery and supercapacitor applications by producing different nanostructures which lead to the potential for various applications. This study focuses on the establishment of the knowledge and techniques necessary to perform metal/oxide nanostructures on biological and energy applications. This study will investigate: (1) the sensor and drug delivery applications of micro/nano structures; (2) novel processes to innovate anodic aluminum oxide nanotube template; (3) the supercapacitor applications of anodic titanium oxide. First, the extremely high surface area AAO coated microneedle and microneedle array can be developed as sensor and drug delivery devices. Due to the large surface area of the AAO, the film can absorb indicators to make it sensitive to testing targets. pH detection was demonstrated to show the sensing capability of the microneedle. Then, the microneedles were further built as an array by combining micromachining technique. The microneedle array provides a 3-D structure that possesses several hundred times more surface area and capacity than a traditional nanochannel template. Second, the nanoengineering process was conducted to innovate anodic aluminum oxide nanotube template. Guided anodization assisted by nanoimprint process formed AAO arrays that can be formed on controlled locations. More importantly, it shows the periodically ordered AAO array with different sizes of nanopores. With the improved AAO template, melting injection, electro/electroless deposition and sol-gel deposition were conducted to fabricate Ni nanowires/ TiO2 nanotubes, Ni/BaTiO3 core-shell nanotubes, and UHMWPE nanotubes. Third, various Ti-based alloys were anodized to form ordered nanotubes for supercapacitor application. Ti alloy oxide contains some porous layers which are not presented on TiO2 nanotube film. Thus, Ti alloys anodized oxide nanotubes have better supercapacitor behaviors than the conventional TiO2 nanotubes. However, a high surface area nanoporous Ti/TiO2 structure, which was fabricated by selective etching process, can accumulate large quantity of electrons and energy for supercapacitor needs. Additionally, nanoporous metals obtained by dealloying hold a unique combination of a highly conductive network and a bicontinuous open. The characteristics formed through dealloying also present a nice charge/discharge behavior and a good capacitance performance. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152487

Electrochemical Synthesis of Nanostructured Materials and Related Anodic Behaviors

Electrochemical Synthesis of Nanostructured Materials and Related Anodic Behaviors Book
Author : Mingliang Wang
Publisher : Unknown
Release : 2011
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

[Truncated abstract] This work studies the formation mechanisms of anodized materials and their related electrochemical anodic behaviors. Electrochemical anodization is a versatile method to create various materials with intricate nanostructured morphologies. These materials have potentials for various functional applications in chemical and biomedical sensing, photocatalysis, energy conversion in batteries and supercapacitors. The study is focused on three main aspects: experimental synthesis of anodized materials, theoretical analysis of formation mechanisms of anodized materials and fabrication metallic nanowires using anodized porous alumina. The following summarizes the highlights of the study. Firstly, different anodized structures are synthesized experimentally, including nano-channeled anodized alumina, nanoporous anodized tin oxide and anodized SnC2O4 particles. The related electrochemical behaviors of the metals during anodization are quantified and explained. Anodization current oscillations: The phenomenon of spontaneous periodical current oscillation during electrochemical anodization of tin in alkaline electrolytes is observed. Such phenomenon has been reported in the literature. Attempts have been made to explain this phenomenon on the basis of oxide film lift-off and electrolyte diffusion. This study demonstrates that the current oscillation is caused by oxygen generation and release on the tin anode, causing periodic redistribution of ion concentration in the electrolyte. The analysis also enables determination of the contributions of the two anodic reactions of tin oxidation and oxygen generation to the total anodic current. Secondly, a unified theory for the formation of surface structures of metals induced by anodization is proposed. The theory is based on thermodynamic and electrochemical principles. It is able to explain the main experimental observations of all three types of anodic structures, including solid compact oxide films, porous oxides and porous metal surface layers...

Transition Metal Oxides MxOy M

Transition Metal Oxides  MxOy  M Book
Author : Junzhe Dong
Publisher : Unknown
Release : 2019
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

n the past few decades, transition metal oxides (TMO) show various unique properties and wide applications due to their electronic configuration and multiple possible structures. Among different TMO, titanium dioxide (TiO2), tungsten trioxide(WO3), and zinc oxide (ZnO) are most commonly oxides used as catalyst, sensors and electric devices due to their unique physical and chemical properties. Electrochemical anodization is a facile and cost-effective way to produce 1D self-assembly metal oxides,which integrates the advantage of larger surface area, short diffusion path, low quantum confinement, high charge transfer efficiency and tunable electronic structures. Post-annealing is a possible way to rearrange the disordered atomic arrangement of the anodic oxides and tune their electronic structure. In addition, the decoration of the anodic oxides with metal nanoparticles is another efficient way to modify the as-synthesized anodic oxides, which helps supress the recombination of the photogenerated charge carriers and prolong their life time. The as-prepared and modified anodic metal oxides exhibit various applications, including the photocatalyst, electrochemical catalyst and SERS substrates.The pre-treatment of the Ti substrate and electrolyte were conducted before formal anodization. Their influence on the morphology and mechanical properties of the anodic TiO2 were discussed. The results indicated that the regular TiO2 NTs with the hierarchical shape was produced on the patterned Ti substrate prepared by two-step anodization. Although the regularity of TiO2 NTs improved a lot with the increase of aging time, the pore size decreased as well as the surface homogeneity. The nanohardness and reduced modulus showed the obvious increase with the aging time and highest adhesion between TiO2 and Ti substrate was achieved by anodizing in the 25 h aging electrolyte. Anodic TiO2 initially has an amorphous structure and crystallizes into anatase after thermal annealing. High resolution transmission electron microscopy and in situ synchrotron X-ray diffraction were employed to study the dynamic phase transformation process and the effect of annealing parameters on the atomic structure. At temperatures above 330°C the crystallization process began immediately and ceased within ~500 s. The material was not fully crystallized (crystallinity only ~70 wt.%), even when the annealing time was prolonged to 7000 s at an elevated temperature. The incomplete crystallization could be ascribed to the effect of grain boundaries, oxygen vacancies, and fluorine ions. Besides the phase structure change of anodic TiO2 after annealing, the electric resistivity and wettability of the TiO2 were found to have a close relationship with the post heat treatment. The as-synthesized and annealed TiO2 were used as the electroplating substrate for fabrication Ni-TiO2 nanocomposite. The results reveal that the deposited Ni grows inside the nanotube on annealed TiO2 substrate, while it only forms a compact layer on the top of as-anodized. The resultant Ni-TiO2 nanocomposite on annealed TiO2 substrates also exhibited better oxygen evolution performance than on amorphous substrates in terms of low overpotential at a current density of 10 mA/cm2 and small Tafel slope. The modification of TiO2 can also be achieved by a novel technique that combines magnetron sputtering and thermal dewetting. The obtained Cu-TiO2 nanocomposite catalyst exhibited 4-fold increase in the photodegradation rate of methylene blue aqueous solution under solar light irradiation than anatase TiO2 prepared with sameanodization conditions. The enhanced photocatalytic activity was attributed to thesynergistic effect of Schottky barrier and surface plasmon resonance.Similar to anodic TiO2, regular self-organized nanoporous WO3 was prepared through anodization in the electrolyte containing ethylene glycol, ammonium fluoride and DI water, which was subsequently used as a template for deposition of Ag nanoparticles by magnetron sputtering and thermal dewetting. The synthesized Ag-WO3 nanocomosites showed large SERS enhancement factor of ~2.1× 107 and a low detection limit of ~1× 10-6 M Rhodamine B. The visible light responding behaviour of WO3, synergistic interaction between Ag nanoparticles and the WO3 substrate, and the plasmonic behaviour of Ag collectively contribute to the enhanced Raman scattering. Although TiO2 nanotube and WO3 nanoporous structure can be successfully prepared in the ethylene glycol electrolyte containing the NH4F, it did not work for anodic ZnO. A new type of self-assembled Zinc oxide (ZnO) nanostructure has been prepared by electrochemical anodization of Zinc foil in NaOH aqueous electrolyte. The experimental results indicate that the primary factor affecting anodic nanostructure is the applied voltage, while anodization time and electrolyte concentration also play significant roles in tailoring nanorod morphology.

Metal Oxide Based Nanostructured Electrocatalysts for Fuel Cells Electrolyzers and Metal Air Batteries

Metal Oxide Based Nanostructured Electrocatalysts for Fuel Cells  Electrolyzers  and Metal Air Batteries Book
Author : Teko Napporn,Yaovi Holade
Publisher : Elsevier
Release : 2021-02-12
ISBN : 0128184973
Language : En, Es, Fr & De

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Book Description :

Metal Oxide-Based Nanostructured Electrocatalysts for Fuel Cells, Electrolyzers, and Metal-Air Batteries is a comprehensive book summarizing the recent overview of these new materials developed to date. The book is motivated by research that focuses on the reduction of noble metal content in catalysts to reduce the cost associated to the entire system. Metal oxides gained significant interest in heterogeneous catalysis for basic research and industrial deployment. Metal Oxide-Based Nanostructured Electrocatalysts for Fuel Cells, Electrolyzers, and Metal-Air Batteries puts these opportunities and challenges into a broad context, discusses the recent researches and technological advances, and finally provides several pathways and guidelines that could inspire the development of ground-breaking electrochemical devices for energy production or storage. Its primary focus is how materials development is an important approach to produce electricity for key applications such as automotive and industrial. The book is appropriate for those working in academia and R&D in the disciplines of materials science, chemistry, electrochemistry, and engineering. Includes key aspects of materials design to improve the performance of electrode materials for energy conversion and storage device applications Reviews emerging metal oxide materials for hydrogen production, hydrogen oxidation, oxygen reduction and oxygen evolution Discusses metal oxide electrocatalysts for water-splitting, metal-air batteries, electrolyzer, and fuel cell applications

Journal of the Electrochemical Society

Journal of the Electrochemical Society Book
Author : Anonim
Publisher : Unknown
Release : 2009
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

Download Journal of the Electrochemical Society book written by , available in PDF, EPUB, and Kindle, or read full book online anywhere and anytime. Compatible with any devices.

Functional Metal Oxide Nanostructures

Functional Metal Oxide Nanostructures Book
Author : Junqiao Wu,Jinbo Cao,Wei-Qiang Han,Anderson Janotti,Ho-Cheol Kim
Publisher : Springer Science & Business Media
Release : 2011-09-22
ISBN : 9781441999313
Language : En, Es, Fr & De

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Book Description :

Metal oxides and particularly their nanostructures have emerged as animportant class of materials with a rich spectrum of properties and greatpotential for device applications. In this book, contributions from leadingexperts emphasize basic physical properties, synthesis and processing, and thelatest applications in such areas as energy, catalysis and data storage. Functional Metal Oxide Nanostructuresis an essential reference for any materials scientist or engineer with aninterest in metal oxides, and particularly in recent progress in defectphysics, strain effects, solution-based synthesis, ionic conduction, and theirapplications.

On Delveloping Novel Energy related Nanostructured Matericals by Atomic Layer Depositon

On Delveloping Novel Energy related Nanostructured Matericals by Atomic Layer Depositon Book
Author : Xiangbo Meng
Publisher : Unknown
Release : 2011
ISBN : 0987650XXX
Language : En, Es, Fr & De

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This thesis presents the fabrication of a series of novel nanostructured materials using atomic layer deposition (ALD). In contrast to traditional methods including chemical vapor deposition (CVD), physical vapor deposition (PVD), and solution-based processes, ALD benefits the synthesis processes of nanostructures with many unrivalled advantages such as atomic-scale control, low temperature, excellent uniformity and conformality. Depending on the employed precursors, substrates, and temperatures, the ALD processes exhibited different characteristics. In particular, ALD has capabilities in fine-tuning compositions and structural phases. In return, the synthesis and the resultant nanostructured materials show many novelties This thesis covers ALD processes of four different metal oxides including iron oxide, tin oxide, titanium oxide, and lithium titanium oxide. Four different substrates were used in the aforementioned ALD processes, i.e., undoped carbon nanotubes (CNTs), nitrogen doped CNTs (N-CNTs), porous templates of anodic aluminum oxide (AAO), and graphene nanosheets (GNS). In practice, owing to their distinguished properties and structural characters, the substrates contributed to various novel nanostructures including nanotubes, coaxial core-shell nanotubes, and three-dimensional (3D) architectures. In addition, the surface chemistry of the substrates and their interactions with ALD precursors also were considered. The ALD process of iron oxide (ALD-Fe2O3) was the first one studied and it was fulfilled on both undoped CNTs and N-CNTs by using ferrocene and oxygen as precursors. It was found that N-CNTs are better than undoped CNTs for the ALD-Fe2O3, for they provide reactive sites directly due to their inherent properties. In contrast, undoped CNTs need pretreatment via covalent acid oxidation or non-covalent modification to create reactive sites before the ALD-Fe2O3 could proceed on their surface. This work resulted in different CNT-Fe2O3 core-shell structures with controlled growth of crystalline -Fe2O3 Another metal oxide, tin dioxide (SnO2) was performed using tin chloride (SnCl4) and water as ALD precursors. It was synthesized into different nanostructures based on NCNTs, AAO, and GNS. The work on N-CNTs disclosed that the ALD-SnO2 is favored by doped nitrogen atoms but the effects of different nitrogen-doping configurations vary with growth temperatures. In comparison, the ALD-SnO2 on AAO and GNS mainly relies on hydroxyl groups. A common finding from the studies is that growth temperatures influence the resultant SnO2, leading to amorphous, crystalline phase, or the mixtures of the aforementioned two. In addition, the cyclic nature of ALD contributes to controlled growth of SnO2. Based on the results from the ALD-SnO2 on AAO, it was concluded that the ALD-SnO2 experience three different growth modes with temperature, i.e., layer-by-layer, layer-by-particle, and evolutionary particles. The layers are in amorphous phase while the particles are in crystalline rutile phase. The aforementioned understandings on ALD-SnO2 led to pure SnO2 nanotubes based on AAO, CNT-SnO2 core-shell coaxial nanotubes, and GNS-based SnO2 3D architectures with controlled growth and structural phases. The third metal oxide, titanium dioxide (TiO2) was deposited using titanium isopropoxide (TTIP) and water as ALD precursors. It was found that the ALD-TiO2 is tunable from amorphous to crystalline anatase phase with temperature while the resultant deposition is controllable from nanoparticles to nanofilms as well. Based on different substrate, i.e., AAO, acid-pretreated CNTs, and GNS, TiO2 was fabricated with different nanostructures including nanotubes, core-shell coaxial nanotubes, and 3D architectures. In particular, the resultant nanostructures are distinguished with controlled phases and morphologies of TiO2. Different from the above binary metal oxides, the last metal oxide, lithium titanium oxide (Li4Ti5O12, LTO) is a ternary compound. The route for ALD-LTO is based on combining and tuning two sub-ALD systems. One sub-ALD system is for TiO2 using TTIP and water, and another sub-ALD system is for lithium-containing films using lithium tert-butoxide (LTB) and water as precursors. It was revealed that, through suitably matching the ratios of the two sub-ALD systems and annealing the resultant films, LTO is successfully synthesized on N-CNTs. However, this pioneering work shows a bit rutile TiO2 with LTO, and thus further effort is needed in future work.

Nanostructure of Transition Metal and Metal Oxide for Electrocatalysis

Nanostructure of Transition Metal and Metal Oxide for Electrocatalysis Book
Author : Yanjuan Gu
Publisher : Open Dissertation Press
Release : 2017-01-27
ISBN : 9781361427170
Language : En, Es, Fr & De

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Book Description :

This dissertation, "Nanostructure of Transition Metal and Metal Oxide for Electrocatalysis" by Yanjuan, Gu, 谷艳娟, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled NANOSTRUCTURE OF TRANSITION METAL AND METAL OXIDE FOR ELECTROCATALYSIS Submitted by Gu Yan Juan for the degree of Doctor of Philosophy at The University of Hong Kong in August 2006 Pd, Pt, and Ru nanoparticles that were uniformly dispersed on multi-walled carbon nanotubes (MWNTs) were synthesized by vacuum pyrolysis using metal acetylacetonate as metal precursor, and the nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X- ray diffraction (XRD). The size and distribution of the nanoparticles were strongly affected by the reaction time, temperature, and the initial mass ratio of the metal precursors to MWNTs. The higher temperature, the smaller Pd nanoparticles were formed at the range of 250 to 500 C. The average size of the Pd nanoparticles increased with the increase in mass ratio of the metal precursors to MWNTs. The particle size of Pt and Ru showed little change with the change in mass ratio. Pt and Ru nanoparticles had the mean diameters of 3.00.6 and 2.50.4 nm when the mass ratio of Pt(acac) and Ru(acac) to 2 3 MWNTs was both 2:1 at 500 C. The electrocatalytic activity of Pt/MWNTs and PtRu/MWNTs was investigated at room temperature by cyclic voltammetry and chronoamperometry. All of the electrochemical results showed that the PtRu/MWNTs catalyst exhibit high activity for methanol oxidation that resulted from the high surface area of carbon nanotubes and the platinum/ruthenium nanoparticles. Compared with Pt/MWNTs, the onset potential is much lower and the ratio of forward anodic peak current to reverse anodic peak current is much higher for methanol oxidation. Pt Ru /MWNTs displayed the best electrocatalytic 45 55 activities among all carbon nanotubes supported Pt and PtRu catalysts. Hyperbranched RuO nanostructures can be formed through the oxidation of Ru nanoparticles at relatively low temperatures in air, which is a very simple and low cost method. The morphology of the RuO nanostructure is closely associated with the dispersivity of the Ru nanoparticles on the MWNTs. Cu, Pt and Pd nanoparticles are very effective catalysts in the formation of RuO hyperbranched nanostructures. The electrochemical studies of these nanorods demonstrated that they display characteristic properties of RuO (110) surface. The successful attachment of Pt nanoparticles to RuO surface through a simple, two-step chemically controlled procedure is reported. The effect of the single crystal structure of RuO nanorods on the electrocatalytic activity of Pt nanoparticles was investigated, showing that the presence of the RuO nanorods greatly increases the electrochemical activity of electrodes toward methanol oxidation, not only increasing the current density but also shifting the onset potential of methanol electrooxidation to over 200 mV lower than that on the Pt nanoparticle electrode. The results described here also demonstrate the ability of metal oxide nanorods to serve as a conductive support for fuel cell applications. DOI: 10.5353/th_b3777439 Subjects: Electrocatalysis Transition metals Nanoparticles Nanostructured materials Methanol - Oxidation

Metal Oxide Based Nanostructured Electrocatalysts for Fuel Cells Electrolyzers and Metal Air Batteries

Metal Oxide Based Nanostructured Electrocatalysts for Fuel Cells  Electrolyzers  and Metal Air Batteries Book
Author : Teko Napporn,Yaovi Holade
Publisher : Elsevier
Release : 2021-02-19
ISBN : 0128184965
Language : En, Es, Fr & De

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Book Description :

Metal Oxide-Based Nanostructured Electrocatalysts for Fuel Cells, Electrolyzers, and Metal-Air Batteries is a comprehensive book summarizing the recent overview of these new materials developed to date. The book is motivated by research that focuses on the reduction of noble metal content in catalysts to reduce the cost associated to the entire system. Metal oxides gained significant interest in heterogeneous catalysis for basic research and industrial deployment. Metal Oxide-Based Nanostructured Electrocatalysts for Fuel Cells, Electrolyzers, and Metal-Air Batteries puts these opportunities and challenges into a broad context, discusses the recent researches and technological advances, and finally provides several pathways and guidelines that could inspire the development of ground-breaking electrochemical devices for energy production or storage. Its primary focus is how materials development is an important approach to produce electricity for key applications such as automotive and industrial. The book is appropriate for those working in academia and R&D in the disciplines of materials science, chemistry, electrochemistry, and engineering. Includes key aspects of materials design to improve the performance of electrode materials for energy conversion and storage device applications Reviews emerging metal oxide materials for hydrogen production, hydrogen oxidation, oxygen reduction and oxygen evolution Discusses metal oxide electrocatalysts for water-splitting, metal-air batteries, electrolyzer, and fuel cell applications

Metal Oxide Nanostructures

Metal Oxide Nanostructures Book
Author : Daniela Nunes,Ana Pimentel,Lidia Santos,Pedro Barquinha,Luis Pereira,Elvira Fortunato,Rodrigo Martins
Publisher : Elsevier
Release : 2018-11-01
ISBN : 012811505X
Language : En, Es, Fr & De

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Book Description :

Metal Oxide Nanostructures: Synthesis, Properties and Applications covers the theoretical and experimental aspects related to design, synthesis, fabrication, processing, structural, morphological, optical and electronic properties on the topic. In addition, it reviews surface functionalization and hybrid materials, focusing on the advantages of these oxide nanostructures. The book concludes with the current and future prospective applications of these materials. Users will find a complete overview of all the important topics related to oxide nanostructures, from the physics of the materials, to its application. Delves into hybrid structured metal oxides and their promising use in the next generation of electronic devices Includes fundamental chapters on synthesis design and the properties of metal oxide nanostructures Provides an in-depth overview of novel applications, including chromogenics, electronics and energy

Aluminum Anodic Oxide AAO as a Template for Formation of Metal Nanostructures

Aluminum Anodic Oxide AAO as a Template for Formation of Metal Nanostructures Book
Author : Piotr Tomassi
Publisher : Unknown
Release : 2015
ISBN : 0987650XXX
Language : En, Es, Fr & De

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Book Description :

The aim of the chapter is to describe the applications of AAO as a template in metal nanostructures formation and to present the experimental results obtained by authors in this field. The basic mechanism of the process of anodic oxidation of aluminum was described. The influence of oxidation parameters on the AAO structure was discussed. The processes of electrochemical metal deposition in AAO were described. The main present as well as future applications of metal nanostructures formed were listed.

Nanostructured Metal Oxide Enabled Silicon Based Solar Fuel Cell

Nanostructured Metal Oxide Enabled Silicon Based Solar Fuel Cell Book
Author : Ke Sun
Publisher : Unknown
Release : 2013
ISBN : 9781303198151
Language : En, Es, Fr & De

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Book Description :

Intrinsic drawbacks of Si, a well adapted material in photovoltaics, including the high valence band position compared to the proton reduction level, the unfavorable self-oxidation level compared to the one of water oxidation, and indirect energy band, prevent Si as a good candidate for applications in photoelectrochemical water splitting, despite its small band gap which matches the solar irradiance spectrum. Strategies need to be developed to overcome these problems. This dissertation presents a study of metal oxides integrated Si photoelectrode for solar driven water splitting. Different metal oxides including zinc oxide, titanium dioxide, indium tin oxide, and nickel oxide are coated on polished and nanotextured p-type and n-type Si from various methods. This heterogeneous uniform coating effectively replaces the problematic water Si interface which can be corrosive and oxidative to Si. The Schottky junction formed either using an n-type coating (ZnO and TiO2) on p-type Si or a p-type coating (NiO) on n-type Si is able to effectively separate the photo-generated charges in Si. In addition, nanotextured Si is able to dramatically improve light absorption and provide enlarged surface chemical reaction sites. In this case, integration of metal oxides in the form of nanoscale structures on the nanostructured Si, a so-called branched nanowire structure or a "nanotree" array, is able to enhance the light absorption and reduce the radius of curvature to ease the gas evolution. Earth abundant transition metal, primarily Ni, was used to catalyze the water reduction and oxidation reaction. Solution-casted NiO from a cost-effective approach provides higher activity compared to the one prepared from gas phase sputtering. Surfactant and thermal treatment effect are studied to achieve an optimized catalytic activity. This catalyst is then successfully demonstrated on a surface inverted n-Si photoanode protected with a novel semitransparent conducting oxide. Considerable contributions have been made through this dissertation study. Suggestions on future improvements are provided.