Download or read book Studies of Photocatalytic Processes at Nanoporous TiO2 Film Electrodes by Photoelectrochemical Techniques and Development of a Novel Methodology for Rapid Determination of Chemical Oxygen Demand written by Dianlu Jiang and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: In this work, a series of simple, rapid and effective photoelectrochemical methodologies have been developed and successfully applied to the study of kinetic and thermodynamic characteristics of photocatalytic oxidation processes at TiO2 nanoparticulate films. As an application of the systematic studies of photocatalytic processes by photoelectrochemical techniques, a rapid, direct, absolute, environmental-friendly and accurate COD analysis method was successfully developed. In this work, the TiO2 nanoparticles colloid was prepared by the sol-gel method. The TiO2 nanoparticles were immobilized onto ITO conducting glass slides by dip-coating method. Thermal treatment was carried out to obtain nanoporous TiO2 films of different structures. At low calcination temperature (below 600 degrees C), nanoporous TiO2 films of pure anatase phase were prepared. At high calcination temperature (above 600 degrees C), nanoporous TiO2 films of mixed anatase and rutile phases were obtained. At these film electrodes, the work was carried out. By employing steady state photocurrent method and choosing phthalic acid as the model compound, the photocatalytic activity of the TiO2 nanoporous films calcined at various temperatures and for different lengths of time was evaluated. It was found that the films with mixed anatase and rutile phases calcined at high temperature exhibited high photocatalytic activity. Based on semiconductor band theory, a model was proposed, which explained well this finding. By employing linear sweep voltammetry (under illumination) and choosing glucose (an effective photohole scavenger) as a model compound, the characteristics of the photocatalytic processes at nanoparticulate semiconductor electrodes were investigated. Characteristics of the nanoporous semiconductor electrodes markedly different from bulk semiconductor electrodes were observed. That is, within a large range of electrode potentials above the flat band potential the electrodes behaved as a pure resistance instead of exhibiting variable resistance expected for bulk semiconductor electrodes. The magnitude of the resistance was dependent on the properties of the electrodes and the maximum photocatalytic oxidation rate at TiO2 surface determined by the light intensity and substrate concentration. A model was proposed, which explained well the special characteristics of particulate semiconductor electrodes (nanoporous semiconductor electrodes). This is the first clear description of the overall photocatalytic process at nanoparticulate semiconductor electrodes. The investigation set a theoretical foundation for employing photoelectrochemical techniques to study photocatalytic processes. By using the transient technique (illumination step method analogous to potential step method in conventional electrochemistry), the adsorption of a number of strong adsorbates on both low temperature and high temperature calcined TiO2 nanoporous films was investigated. Similar adsorption characteristics for different adsorbates on different films were observed. In all the cases, three different surface bound complexes were identified, which was attributed to the heterogeneity of TiO2 surface. The photocatalytic degradation kinetics of the pre-adsorbed organic compounds of different chemical nature was also studied by processing the photocurrent-time profiles. Two different photocatalytic processes, exhibiting different rate characteristics, were observed. This was, again, attributed to the heterogeneity of the TiO2 surface corresponding to heterogeneous adsorption characteristics. The catalytic first order rate constants of both fast and slow processes were obtained for different organic compounds. It was found that for different adsorbates of different chemical nature the magnitudes of rate constant for the slow kinetic process were very similar, while the magnitudes of rate constant for the fast process were significantly affected by the photohole demand characteristics of different adsorbates. Photohole demand distribution that depends on the size and structure of the adsorbed molecules was believed to be responsible for the difference. By employing steady state photocurrent method, the photocatalytic degradation kinetic characteristics of both strong adsorbates and weak adsorbates of different chemical structures were compared at pure anatase TiO2 nanoporous TiO2 films as well as at anatase/rutile mixed phase TiO2 nanoporous film electrodes. At the former electrodes for all the different organic compounds studied, the photocatalytic reaction rate increased linearly with concentration at low concentrations. Under such conditions, it was demonstrated that the overall photocatalytic process was controlled by diffusion and was independent of the chemical nature of organic compounds. However, the linear concentration range and the maximum photocatalytic reaction rate at high concentrations were significantly dependent on the chemical nature of the substrates. This was explained by the difference in the interaction of different organic compounds with TiO2 surface, the difference in their photohole demand distributions at the TiO2 surface and the difference in their nature of intermediates formed during their photocatalytic mineralization. In contrast, at the latter electrodes for the photocatalytic oxidation of different organic compounds the linear ranges (diffusion control concentration range) and the maximum reaction rates at high concentration were much larger than at the former electrodes and much less dependent on the chemical nature of the organic compounds. The spatial separation of photoelectrons and photoholes (due to the coexistence of rutile phase and anatase phase) and the increase in the lifetime of photoelectrons and photoholes are responsible for the excellent photocatalytic activity of the electrodes. By employing the thin-layer photoelectrochemical technique (analogous to the thin-layer exhaustive electrolytic technique), the photocatalytic oxidation of different organic compounds at the mixed phase TiO2 nanoporous electrodes were investigated in a thin layer photoelectrochemical cell. It was found that the charge derived from exhaustive oxidation agreed well with theoretical charge expected for the mineralisation of a specific organic compound. This finding was true for all the compounds investigated and was also true for mixtures of different organic compounds. The photocatalytic degradation kinetics of different organic compounds of different chemical identities in the thin layer cell was also investigated by the photoelectrochemical method. Two kinetic processes of different decay time constants were identified, which were attributed to the degradation of preadsorbed compounds and the degradation of compounds in solution. For the degradation of compounds in solution, a change in the overall control step from substrate diffusion to heterogeneous surface reaction was observed. For different organic compounds, the variation of the rate constant was determined by the photohole demand rather than by the chemical identities of substrates. The kinetics of the fast kinetic process, on the other hand, was greatly affected by the adsorption properties of the substrates. For the strong adsorbates, the rate was much larger than for weak adsorbates. However, the rate constant of the process was independent of the chemical identities of the substrates and the variation of the constant was also determined by the photohole demand. Based on the principles of exhaustive photoelectrocatalytic degradation of organic matter in a thin layer cell, a novel, rapid, direct, environmental-friendly and absolute COD analysis method was developed. The method was tested on synthetic samples as well as real wastewater samples from a variety of industries. For synthetic samples with given compositions the COD values measured by my method agree very well with theoretical COD value. For real samples and synthetic samples the COD values measured by my method correlated very well with those measured by standard dichromate COD analysis method.

Download or read book Nanoscale Sensors written by Shibin Li and published by Springer Science & Business Media. This book was released on 2014-01-07 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a comprehensive introduction to nanoscale materials for sensor applications, with a focus on connecting the fundamental laws of physics and the chemistry of materials with device design. Nanoscale sensors can be used for a wide variety of applications, including the detection of gases, optical signals, and mechanical strain, and can meet the need to detect and quantify the presence of gaseous pollutants or other dangerous substances in the environment. Gas sensors have found various applications in our daily lives and in industry. Semiconductive oxides, including SnO2, ZnO, Fe2O3, and In2O3, are promising candidates for gas sensor applications. Carbon nanomaterials are becoming increasingly available as “off-the-shelf” components, and this makes nanotechnology more exciting and approachable than ever before. Nano-wire based field- effect transistor biosensors have also received much attention in recent years as a way to achieve ultra-sensitive and label-free sensing of molecules of biological interest. A diverse array of semiconductor-based nanostructures has been synthesized for use as a photoelectrochemical sensor or biosensor in the detection of low concentrations of analytes. A novel acoustic sensor for structural health monitoring (SHM) that utilizes lead zirconate titanate (PZT) nano- active fiber composites (NAFCs) is described as well.

Download or read book Development of New Characterization Methods to Study the Photocatalysis Processes at Nanoparticulate TiO2 Film Electrodes written by Victor Wolthers de Lorena Pires and published by . This book was released on 2005 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Photo Electrochemical Studies of Nanoporous TiO2 and Ce doped TiO2 Film Electrodes Prepared by the Sol gel Method written by Sutasinee Kityakarn and published by . This book was released on 2009 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modern Electrochemical Methods in Nano Surface and Corrosion Science written by Mahmood Aliofkhazraei and published by BoD – Books on Demand. This book was released on 2014-06-11 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: The basics and principles of new electrochemical methods and also their usage for fabrication and analysis of different nanostructures were discussed in this book. These methods consist of electrochemical methods in nanoscale (e.g. electrochemical atomic force microscopy and electrochemical scanning tunneling microscopy) and also electrochemical methods for fabrication of nanomaterials.

Download or read book Titanium Dioxide Photocatalysis written by Vladimiro Dal Santo and published by MDPI. This book was released on 2019-05-27 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although the seminal work of Fujishima et al. dates back to 1971, TiO2 still remains the most diffused and studied semiconductor, employed in photo-oxidation processes for cleantech (i.e., polluted water and air treatment), in solar fuel production (mainly hydrogen production by water photo splitting), and in Carbon Capture and Utilization (CCU) processes by CO2 photoreduction. The eleven articles, among them three reviews, in this book cover recent results and research trends of various aspects of titanium dioxide photocatalysis, with the chief aim of improving the final efficiency of TiO2-based materials. Strategies include doping, metal co-catalyst deposition, and the realization of composites with plasmonic materials, other semiconductors, and graphene. Photocatalysts with high efficiency and selectivity can be also obtained by controlling the precise crystal shape (and homogeneous size) and the organization in superstructures from ultrathin films to hierarchical nanostructures. Finally, the theoretical modeling of TiO2 nanoparticles is discussed and highlighted. The range of topics addressed in this book will stimulate the reader’s interest as well as provide a valuable source of information for researchers in academia and industry.

Download or read book Green Photocatalytic Semiconductors written by Seema Garg and published by Springer Nature. This book was released on 2021-09-20 with total page 855 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprises a detailed overview on the role of photocatalysts for environmental remediation, hydrogen production and carbon dioxide reduction. Effective ways to enhance the photocatalytic activity of the material via doping, hybrid material, laser light and nanocomposites have been discussed in this book. The book also further elaborates the role of metal nanoparticles, rare earth doping, sensitizers, surface oxygen vacancy, interface engineering and band gap engineering for enhancing the photocatalytic activity. An approach to recover the photocatalytic material via immobilization is also presented. This book brings to light much of the recent research in the development of such semiconductor photocatalytic systems. The book will thus be of relevance to researchers in the field of: material science, environmental science & technology, photocatalytic applications, newer methods of energy generation & conversion and industrial applications.

Download or read book Development of a Novel TiO2 polymeric Photocatalyst for Water Purification Both Under UV and Solar Illuminations written by Debjani Mukherjee and published by . This book was released on 2011 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprising about 70% of the Earth's surface, water is undoubtedly the most precious natural resource. According to the W.H.O, around 3.5 million people are dying every year from different water related diseases. Different kinds of dyes and pharmaceutical products have been detected in drinking water, all over the world. These organic compounds being non removable by traditional water purification processes, made advanced oxidation processes come into existence. Among all kind of advanced oxidation processes, photocatalytic oxidation is the most promising one. The photocatalytic process is based on aqueous phase hydroxyl radical chemistry and couples low energy UV light with semiconductors acting as photocatalyst. The slurry form of TiO2 though being efficient has several disadvantages (particularly, post treatment expensive separation steps) which brings the immobilization of the catalysts on surfaces into existence. In this study, a TiO2-polymeric film photocatalyst was synthesized by reaction of gelatin, polyvinyl alcohol and polyvinyl pyrrolidone. TiO2 Degussa P25 powder was embedded into the polymeric matrix. The characterization of the film by OM, SEM, FTIR, revealed the topography of the catalyst films. Optimization of photocatalysts functionality was carried out by varying the cross linking methods and conducting several photodegradation reactions both under UV and solar light. Aspirin and methyl orange were chosen as model compounds, as traces of these compounds were detected in the drinking water of South-Western Ontario. The freeze-dried film photocatalyst was observed to degrade organic compounds efficiently, under both UV and solar illuminations. Degradation of high concentrated organic pollutants, was observed to follow Langmuir-Hinshelwood kinetics while at low concentration, first-order kinetics was observed. The effects of initial concentration, flow rate, pH, light intensity, photocatalyst loading, and thickness of the film on the degradation rates were studied. Mechanism of degradation of aspirin was studied from LC/MS analysis. The TOC analysis was carried out to analyse the organic carbon content of the intermediates formed during the course of degradation. Finally, photocatalytic degradation reaction was carried out in a continuous flow reactor under LED lights. film photocatalyst holds the potential of being an efficient and economical form of future photocatalyst for water purification.

Download or read book Semiconductor Electrochemistry written by Rüdiger Memming and published by John Wiley & Sons. This book was released on 2015-06-22 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt: Providing both an introduction and an up-to-date survey of the entire field, this text captivates the reader with its clear style and inspiring, yet solid presentation. The significantly expanded second edition of this milestone work is supplemented by a completely new chapter on the hot topic of nanoparticles and includes the latest insights into the deposition of dye layers on semiconductor electrodes. In his monograph, the acknowledged expert Professor Memming primarily addresses physical and electrochemists, but materials scientists, physicists, and engineers dealing with semiconductor technology and its applications will also benefit greatly from the contents.

Download or read book Photoelectrocatalysis written by Leonardo Palmisano and published by Elsevier. This book was released on 2022-10-21 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photoelectrocatalysis: Fundamentals and Applications presents an in-depth review of the topic for students and researchersworking on photoelectrocatalysis-related subjects from pure chemistry to materials and environmental chemistry inorder to propose applications and new perspectives. The main advantage of a photoelectrocatalytic process is the mildexperimental conditions under which the reactions are carried out, which are often possible at atmospheric pressure androom temperature using cheap and nontoxic solvents (e.g., water), oxidants (e.g., O2 from the air), catalytic materials (e.g.,TiO2 on Ti layer), and the potential exploitation of solar light. This book presents the fundamentals and the applications of photoelectrocatalysis, such as hydrogen production fromwater splitting, the remediation of harmful compounds, and CO2 reduction. Photoelectrocatalytic reactors and lightsources, in addition to kinetic aspects, are presented along with an exploration of the relationship between photocatalysisand electrocatalysis. In addition, photocorrosion issues and the application of selective photoelectrocatalytic organictransformations, which is now a growing field of research, are also reported. Finally, the advantages/disadvantages andfuture perspectives of photoelectrocatalysis are highlighted through the possibility of working at a pilot/industrial scale inenvironmentally friendly conditions. Presents the fundamentals of photoelectrocatalysis Outlines photoelectrocatalytic green chemistry Reviews photoelectrocatalytic remediation of harmful compounds, hydrogen production, and CO2 reduction Includes photocorrosion, photoelectrocatalytic reactors, and modeling along with kinetic aspects

Download or read book Photoelectrochemical Water Splitting written by Zhebo Chen and published by Springer Science & Business Media. This book was released on 2013-08-28 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book outlines many of the techniques involved in materials development and characterization for photoelectrochemical (PEC) – for example, proper metrics for describing material performance, how to assemble testing cells and prepare materials for assessment of their properties, and how to perform the experimental measurements needed to achieve reliable results towards better scientific understanding. For each technique, proper procedure, benefits, limitations, and data interpretation are discussed. Consolidating this information in a short, accessible, and easy to read reference guide will allow researchers to more rapidly immerse themselves into PEC research and also better compare their results against those of other researchers to better advance materials development. This book serves as a “how-to” guide for researchers engaged in or interested in engaging in the field of photoelectrochemical (PEC) water splitting. PEC water splitting is a rapidly growing field of research in which the goal is to develop materials which can absorb the energy from sunlight to drive electrochemical hydrogen production from the splitting of water. The substantial complexity in the scientific understanding and experimental protocols needed to sufficiently pursue accurate and reliable materials development means that a large need exists to consolidate and standardize the most common methods utilized by researchers in this field.

Download or read book Studies of Model Photocatalysts written by Krishna Kumar Barakoti and published by . This book was released on 2016 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation covers photocatalytic and stochastic photoelectrochemical studies of colloidal semiconducting nanomaterials. Photocatalytic properties of colloidal titanium dioxide nanoparticles (TiO2 NPs) and stochastic interaction of colloidal dye sensitized nanoparticles (DSNPs) with Pt ultramicroelectrode are studied. These nanostructured materials are potentially useful substances in solar energy based photovoltaics and water-splitting devices. In this dissertation, we present the photoelectrochemical study of bare TiO2 nanoparticles, sensitized nanoparticles and cadmium selenide (CdSe) materials, suspended in methanol as a model system. Methanol oxidation reaction is studied as a model reaction of photocatalysis that provides a comprehensive view of the process. Mechanistic and kinetic details of the process and their relationship with colloidal properties are described based on our findings. To accomplish this, we adapted analytical methods for quantitative analysis of formaldehyde, formic acid and carbon dioxide present in neat methanol. Our observations reveal formaldehyde is the predominant reaction product in controlled conditions that minimize the content of oxygen and water. Methanol oxidation to formaldehyde is consistent with two-electron oxidation mechanism. The photoelectrochemical study of dye sensitized TiO2 NPs shows stochastic interaction between DSNPs, suspended in methanol with a Pt ultramicroelectrode. In the dark, the current steps observed are anodic, consistent with the oxidation of dye "N719" at the Pt electrode surface. Under illumination, cathodic steps are observed as a dominant step response and are assigned to the reduction of the oxidized form of dye that is generated after electrons are injected into the TiO2 NPs. We also present preliminary results for stochastic photoelectrochemical study of quantum dots, CdSe and CdSe/ZnS materials.

Download or read book TiO2 Photocatalysis written by Akira Fujishima and published by . This book was released on 1999 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development of Nanostructured Titanium Dioxide Electrodes for Energy Storage and Environmental Applications written by Joshua van der Zalm and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanoporous TiO2 electrodes were fabricated by a three-step anodization process that yielded a uniformly structured and reproducible morphology, which increased the available surface area for electrochemical and photoelectrochemical activities. Enhancement of the electrochemical and photoelectrochemical performance of the prepared TiO2 electrodes was achieved via a reduction treatment at -5mA cm-2 for 10min. The capacitance of the electrode displayed a 25-fold increase following the reduction with an average capacitance of 3.20mF cm-2, which was determined through a variety of electrochemical techniques. The TiO2 electrodes exhibited 83% capacitance retention after 5000 charge/discharge cycles. The photoelectrochemical investigation revealed a six-fold increase in the photocurrent of the reduced over the unreduced electrodes. Removal of the pollutant atrazine was achieved by a photoelectrocatalytic process using a UV light source and an applied potential of 1.5V at the reduced TiO2 electrode. LC-MS and UV-Vis monitoring of the solution revealed that 96.1% of the target pollutant was removed.

Download or read book Heterogeneous Photocatalysis Using Inorganic Semiconductor Solids written by Umar Ibrahim Gaya and published by Springer Science & Business Media. This book was released on 2013-11-08 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book underscores the essential principles of photocatalysis and provides an update on its scientific foundations, research advances, and current opinions, and interpretations. It consists of an introduction to the concepts that form the backbone of photocatalysis, from the principles of solid-state chemistry and physics to the role of reactive oxidizing species. Having recognised the organic link with chemical kinetics, part of the book describes kinetic concepts as they apply to photocatalysis. The dependence of rate on the reaction conditions and parameters is detailed, the retrospective and prospective aspects of the mechanism of photocatalysis are highlighted, and the adsorption models, photocatalytic rate expressions, and kinetic disguises are examined. This book also discusses the structure, property, and activity relationship of prototypical semiconductor photocatalysts and reviews how to extend their spectral absorption to the visible region to enable the effective use of visible solar spectrum. Lastly, it presents strategies for deriving substantially improved photoactivity from semiconductor materials to support the latest applications and potential trends.

Download or read book Chemistry Companion written by Richard John and published by . This book was released on 2011 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Photocatalytic Semiconductors written by Aracely Hernández-Ramírez and published by Springer. This book was released on 2014-11-17 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: This critical volume examines the different methods used for the synthesis of a great number of photocatalysts, including TiO2, ZnO and other modified semiconductors, as well as characterization techniques used for determining the optical, structural and morphological properties of the semiconducting materials. Additionally, the authors discuss photoelectrochemical methods for determining the light activity of the photocatalytic semiconductors by means of measurement of properties such as band gap energy, flat band potential and kinetics of hole and electron transfer. Photocatalytic Semiconductors: Synthesis, Characterization and Environmental Applications provide an overview of the semiconductor materials from first- to third-generation photocatalysts and their applications in wastewater treatment and water disinfection. The book further presents economic and toxicological aspects in the production and application of photocatalytic materials.