Download or read book Electrocatalytic Water Oxidation by Manganese Oxides Ways to Influence the Catalyst Activity and Stability written by Jens Melder and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metal Oxide based Nano structured Catalyst Materials for Water Oxidation written by Monika Fekete and published by . This book was released on 2014 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogen has the potential to revolutionalise the transportation fuels market towards a greener future. (Photo)electrocatalytic water splitting into oxygen and hydrogen, at present, is one of the most promising technologies that could render large-scale hydrogen production commercially viable. One of the main challenges that has hampered the widespread use of water electrolysis techniques is the large overpotential involved in the water oxidation (anode) reaction, that accompanies the hydrogen evolution (cathode reaction). Therefore, the development of efficient catalyst materials for water oxidation is of crucial importance.Nano-materials have been found to exhibit unique, improved properties over bulk materials when used as either water oxidation or reduction catalysts. This finding mirrors those in many other applications in different fields of science.This thesis investigates the effect of nanostructuring on two prominent catalyst materials, ZnO and MnOx. The fabrication of nanostructured electrodes was explored first by a well-established electrodeposition method, then screen printing was introduced as a novel deposition method for water splitting catalysts. The results indicate that, besides intrinsic material properties and electrode geometry, the method of deposition has a significant effect on catalytic activity. Screen-printing was found to be a particularly effective and versatile method for the preparation of highly active, uniform catalyst films. A series of electrodeposited zinc oxide photoanodes were prepared first. ZnO, a wide-bandgap semiconductor, had previously been found to be a highly active water oxidizing photoanode when illuminated by UV light. With an aim to optimize the performance of electrodeposited ZnO photoanodes, a series of ZnO nanorod arrays was prepared with a variation in the seeding layer deposition. The effect of the inclusion of small amounts of Al in the ZnO films was also tested with a view to improve charge transfer from the semiconductor/liquid junction to the conducting glass substrate. The seeding layer was found to greatly affect film morphology and, consequently, catalytic performance. The inclusion of Al had little effect on catalytic activity. A preliminary investigation of the effects of the electrolyte pH showed a strong influence on catalytic activity and stability. This finding led to the further exploration of these effects on a reproducible model nano-ZnO catalyst, with a focus on addressing photodecomposition of the electrode.Photoanodes, using commercial ZnO nanoparticles, were prepared via a screen-printing process. The catalyst films were highly uniform, which allowed a systematic assessment of the effects of the electrolyte pH on photocorrosion of ZnO in aqueous electrolytes. The pH range, where ZnO is least susceptible to photodecomposition, was proposed to lie between pH 9 - 12.5 based on thermodynamic considerations. The hypothesis was tested by long-term controlled potential electrolysis and was, in most aspects, verified. Using a pH 10.5 borate buffer, 75% of the initial activity was preserved after 12 hours, representing a more than ten-fold improvement over standard testing conditions. High photocatalytic activity by the screen-printed ZnO films was observed, especially at little or no applied potential. At pH 10.5, a light current of 0.6 mA/cm2 was measured under zero-bias conditions, which is one of the highest currents reported recently under similar conditions.The promising results observed when using screen-printed ZnO electrodes led to the adaptation of the screen-printing method to the preparation of other water oxidizing catalysts. Initially, a series of nano-structured Mn-Ce composite oxides was tested, as these materials had been previously shown to exhibit high activity in the oxidative breakdown of organic pollutants in wastewaters, mainly alcohols. The screening of a series of these composites, differing mainly in their Mn:Ce ratios, showed that, unlike in wastewater treatment, the presence of Ce was detrimental to catalytic activity. However, the pure MnOx catalyst showed promising activity as a ``dark" electrocatalyst in water oxidation. The nano-MnOx catalyst film was characterized by electron microscopy, X-ray diffraction and electrochemical testing methods. The manganese oxide phase was identified as beta-MnO2 with one or two other phases being present in small concentrations. The nano-MnO2 film exhibited much higher catalytic activity than a beta-MnO2 commercial reference sample, especially in alkaline media. At pH 13.6, the onset of oxidation current was below 300 mV overpotential, and current density reached 10 mA/cm2 at 500 mV overpotential. The catalytic activity, verified by oxygen evolution measurements, matched that of the most active manganese oxide catalysts reported to date. Additionally, the ease, versatility and high throughput capability of the screen-printing technique could potentially contribute to rendering this process attractive for commercial up-scaling in the future.
Download or read book Developing Enhanced Mixed Metal Oxide Catalysts for Electrocatalytic Water Oxidation Using Insights from X ray Absorption Spectroscopy written by Linsey C. Seitz and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Efficient and economic conversion of renewable energy sources is critical for development of technologies that can shift global energy dependence away from fossil fuels. Increased global energy consumption along with heightened awareness of environmental, health, and political issues with fossil fuels are driving the need for alternative technologies. Wind and sun provide more than enough energy to meet the growing energy demand, provided that challenges with intermittency, scale, and cost-effectiveness can be overcome. These obstacles can be mitigated through development of highly active catalysts using abundant and inexpensive materials to convert solar and wind energy into fuels and chemicals. One promising method of converting solar energy into fuel is by splitting water to produce hydrogen and oxygen. This can be achieved using a monolithic photoelectrochemical (PEC) water splitting device which combines photon-absorbing semiconductors with catalysts that drive the respective reactions or a photovoltaic/electrolyzer system which separates these two components. The first part of this thesis presents a model to quantify loss mechanisms in PEC water splitting based on the current state of materials research and calculate maximum solar-to-hydrogen (STH) conversion efficiencies. Results of this model indicate that a major limitation to the efficiency of solar-driven electrochemical water splitting is the oxygen evolution reaction (OER) which requires significant overpotential beyond the thermodynamic redox potential to proceed. The remainder of this dissertation focuses on understanding the interaction between metals in mixed metal oxide catalysts for the OER using electrochemical and advanced spectroscopic techniques towards the development of highly active and stable catalysts. Mixed metal oxide catalysts provide a robust platform for tuning binding energies of OER reaction intermediates to the catalyst surface, thereby affecting activity, through controlled material composition and geometry. We investigate two distinct mixed metal oxide catalyst systems using X-ray absorption spectroscopy (XAS) to probe local geometric and electronic structure and correlate the results with changes in activity. XAS is a synchrotron based technique which provides elemental-specific information by exciting electronic transitions from core to valence orbitals at various elemental edges. XAS studies at the Co K and L edges for a cobalt titanium oxide (CoTiOx) catalyst system identify stabilization effects on the Co oxidation state and overall structure from varying amounts of Ti precursor used during material synthesis. XAS before and after catalyst exposure to OER conditions indicate that catalysts with the least long range order become most oxidized and exhibit the highest activities. Similarly, in situ XAS at the Mn K and Au LIII edges reveal that there is a charge transfer at interfacial sites between manganese oxide (MnOx) and gold (Au) under OER conditions which coincides with significantly increased OER activity compared to MnOx without Au. Our results indicate that Au facilitates stabilization of more oxidized phases of Mn at lower overpotentials, thereby allowing for earlier onset of OER and higher activity. Lastly, we present an investigation of a novel mixed metal oxide catalyst, strontium iridium oxide (SrIrO3) which has the highest reported activity for any known OER catalyst. While it depends on use of Ir, a precious metal, its remarkably high activity compared to rutile IrO2 reduces the Ir loading necessary to achieve similar current densities. In summary, this dissertation explores a broad spectrum of catalysts for the oxygen evolution reaction and uses advanced material characterization methods to draw correlations between the structure, oxidation state, and catalytic activity for these materials. This work provides fundamental insight towards improving efficiency of electrochemical water oxidation processes for the conversion of renewable energy sources to fuels and chemicals.
Download or read book Manganese Oxides as Electrocatalysts in Water Oxidation Synthesis Characterization and Their Activity in the Oxygen Evolution Reaction written by Justus Heese-Gärtlein and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Comprehensive Coordination Chemistry II written by J. A. McCleverty and published by Newnes. This book was released on 2003-12-03 with total page 11845 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive Coordination Chemistry II (CCC II) is the sequel to what has become a classic in the field, Comprehensive Coordination Chemistry, published in 1987. CCC II builds on the first and surveys new developments authoritatively in over 200 newly comissioned chapters, with an emphasis on current trends in biology, materials science and other areas of contemporary scientific interest.
Download or read book Manganese Oxides as Electrocatalyst for the Water oxidation Reaction written by Seung Young Lee and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Comprehensive Treatise of Electrochemistry written by John Bockris and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is now time for a comprehensive treatise to look at the whole field of electrochemistry. The present treatise was conceived in 1974, and the earliest invitations to authors for contributions were made in 1975. The completion of the early volumes has been delayed by various factors. There has been no attempt to make each article emphasize the most recent situation at the expense of an overall statement of the modern view. This treatise is not a collection of articles from Recent Advances in Electrochemistry or Modern Aspects of Electrochemistry. It is an attempt at making a mature statement about the present position in the vast area of what is best looked at as a new interdisciplinary field. Texas A & M University J. O'M. Bockris University of Ottawa B. E. Conway Case Western Reserve University Ernest Yeager & M University Texas A Ralph E. White Preface to Volume 2 This volume brings together some dozen processes well known to the electro chemist and treats them according to their various degrees of importance. The production of hydrogen is one of the more important processes, particularly with respect to the prospects of a hydrogen economy. No one would doubt, however, that the most commercially important electrochemical processes at the present time are the production of aluminum and of chlorine. Each of these processes has a separate chapter devoted to it.
Download or read book Alkaline Electrochemical Water Oxidation by NiFe based Metal Oxide Catalysts written by and published by . This book was released on 2015 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: The oxygen evolution reaction (OER) is the ideal anodic reaction for a photoelectrochemical cell that converts solar energy into chemical fuels; however it is currently limited by catalyst efficiency and cost. In order to overcome these limitations, much effort has been devoted to the discovery of more efficient earth-abundant metal oxide electrocatalysts, particularly mixed-metals oxides, as well as understanding their mechanisms. This thesis addresses both of these challenges. An O2-sensitive fluorescence-based screening assay was developed and arrays of ternary oxide electrocatalysts were examined. Analysis of the intensity of the resulting fluorescence signal allowed for the identification of compositions with high activity. Compositions exhibiting the highest activities were validated through Tafel analyses, and good qualitative agreement was observed between screening results and electrochemical measurements. While Fe is known to improve the activity of Ni oxide catalysts, the incorporation of a third metal into Ni-Fe binary oxides was often observed to further enhance OER activity, with Ni-Fe-Al amorphous oxide showing the highest activity during our initial screening. The previously observed instability led to the investigation of a well-defined NiFeAlO4 inverse spinel oxide as a water oxidation electrocatalyst, where structural analyses confirmed the substitution of Al for Fe lattice sites. A comparison of electrochemical activity against compositionally and structurally relevant oxides, including the known OER catalysts NiO, NiFe 9:1, and NiFe2O4 established NiFeAlO4 as a superior electrocatalyst with no Al leaching, and cyclic voltammograms of the oxides indicated that the electron-withdrawing M+3 ions in the inverse spinels make Ni+2 sites more difficult to oxidize. Furthermore, it was observed that neither of the bimetallic spinel oxides (NiFe2O4 & NiAl2O4) outperformed NiFeAlO4, suggesting a unique synergistic effect between all three metal sites that influences the OER rate determining step. In addition to catalyst discovery, we also pursued mechanistic studies to better understand the dramatic activity enhancement that results when Fe is added to various Ni oxide electrocatalysts. Operando Mössbaurer spectroscopic studies of a 3:1 Ni:Fe layered oxide and anhydrous Fe oxide electrocatalyst was performed. Catalyst materials were prepared by a hydrothermal precipitation method that enabled growth of the oxide catalysts directly on a carbon paper electrode, thereby enhancing charge transport and mechanical stability needed for the operando studies. Fe+4 species are evident in the NiFe-oxide catalyst during steady-state water oxidation, accounting for up to 21% of the total Fe in the catalyst. No Fe+4 is detected under any conditions in the Fe-oxide catalyst. The lifetime of the observed Fe+4 species suggests they do not participate directly in water oxidation; however, their presence has important implications for the promoting effect of Fe in NiFe-oxide electrocatalysts.
Download or read book Spectroelectrochemistry written by Wolfgang Kaim and published by Royal Society of Chemistry. This book was released on 2008 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: A practical guidebook illustrating the applications of spectroelectrochemistry to the understanding of redox reactions through identification of their intermediaries and products.
Download or read book Alkaline Electrochemical Water Oxidation by NiFe based Metal Oxide Catalysts written by Jamie Yung-Chieh Chen and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The oxygen evolution reaction (OER) is the ideal anodic reaction for a photoelectrochemical cell that converts solar energy into chemical fuels; however it is currently limited by catalyst efficiency and cost. In order to overcome these limitations, much effort has been devoted to the discovery of more efficient earth-abundant metal oxide electrocatalysts, particularly mixed-metals oxides, as well as understanding their mechanisms. This thesis addresses both of these challenges. An O2-sensitive fluorescence-based screening assay was developed and arrays of ternary oxide electrocatalysts were examined. Analysis of the intensity of the resulting fluorescence signal allowed for the identification of compositions with high activity. Compositions exhibiting the highest activities were validated through Tafel analyses, and good qualitative agreement was observed between screening results and electrochemical measurements. While Fe is known to improve the activity of Ni oxide catalysts, the incorporation of a third metal into Ni-Fe binary oxides was often observed to further enhance OER activity, with Ni-Fe-Al amorphous oxide showing the highest activity during our initial screening. The previously observed instability led to the investigation of a well-defined NiFeAlO4 inverse spinel oxide as a water oxidation electrocatalyst, where structural analyses confirmed the substitution of Al for Fe lattice sites. A comparison of electrochemical activity against compositionally and structurally relevant oxides, including the known OER catalysts NiO, NiFe 9:1, and NiFe2O4 established NiFeAlO4 as a superior electrocatalyst with no Al leaching, and cyclic voltammograms of the oxides indicated that the electron-withdrawing M+3 ions in the inverse spinels make Ni+2 sites more difficult to oxidize. Furthermore, it was observed that neither of the bimetallic spinel oxides (NiFe2O4 & NiAl2O4) outperformed NiFeAlO4, suggesting a unique synergistic effect between all three metal sites that influences the OER rate determining step. In addition to catalyst discovery, we also pursued mechanistic studies to better understand the dramatic activity enhancement that results when Fe is added to various Ni oxide electrocatalysts. Operando Mössbaurer spectroscopic studies of a 3:1 Ni:Fe layered oxide and anhydrous Fe oxide electrocatalyst was performed. Catalyst materials were prepared by a hydrothermal precipitation method that enabled growth of the oxide catalysts directly on a carbon paper electrode, thereby enhancing charge transport and mechanical stability needed for the operando studies. Fe+4 species are evident in the NiFe-oxide catalyst during steady-state water oxidation, accounting for up to 21% of the total Fe in the catalyst. No Fe+4 is detected under any conditions in the Fe-oxide catalyst. The lifetime of the observed Fe+4 species suggests they do not participate directly in water oxidation; however, their presence has important implications for the promoting effect of Fe in NiFe-oxide electrocatalysts.
Download or read book Oxide Surfaces written by and published by Elsevier. This book was released on 2001-05-21 with total page 677 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book is a multi-author survey (in 15 chapters) of the current state of knowledge and recent developments in our understanding of oxide surfaces. The author list includes most of the acknowledged world experts in this field. The material covered includes fundamental theory and experimental studies of the geometrical, vibrational and electronic structure of such surfaces, but with a special emphasis on the chemical properties and associated reactivity. The main focus is on metal oxides but coverage extends from 'simple' rocksalt materials such as MgO through to complex transition metal oxides with different valencies.
Download or read book Nonstoichiometric Oxides written by O.T. Soerensen and published by Elsevier. This book was released on 2012-12-02 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nonstoichiometric Oxides discusses the thermodynamic and structural studies of nonstoichiometric oxides. This eight-chapter text also covers the defect-defect interactions in these compounds. The introductory chapters describe the thermodynamic properties of nonstoichiometric oxides in terms of defect complexes using the classical thermodynamic principles and from a statistical thermodynamics point of view. These chapters also include statistical thermodynamic models that indicate the ordered nonstoichiometric phase range in these oxides. The subsequent chapters examine the transport properties, such as diffusion and electrical conductivity. Diffusion theories and experimental diffusion coefficients for several systems, as well as the electrical properties of the highly defective ionic and mixed oxide conductor, are specifically tackled in these chapters. The concluding chapters present the pertinent results obtained in nonstoichiometric oxide structural studies using high-resolution electron microscopy and X-ray and neutron diffraction. Inorganic chemists and inorganic chemistry teachers and students will greatly appreciate this book.
Download or read book Testing Novel Water Oxidation Catalysts for Solar Fuels Production written by Carminna Ottone and published by Springer. This book was released on 2019-05-06 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers comprehensive information on the main techniques for measuring water-oxidation-catalyst (WOC) performance, with a particular focus on the combined use of sacrificial oxidants and dyes within closed-batch reactors. It provides an overview of the latest advances in the synthesis of more efficient WOCs, followed by an analysis of the requirements for sustainable energy production. Readers will find a detailed description of the reaction mechanism used in catalyst assessment systems, which reveals the benefits and limitations of the most common sacrificial oxidant/dye pair. Experimental techniques including electrochemical methods for characterizing novel and non-photoactive WOCs are also described. Throughout the book, various manganese oxides are used as examples of the techniques reviewed or proposed systems. Cost considerations and technological perspectives of the scale-up of solar-driven hydrogen production are also addressed. Lastly, the book presents lessons learned from the implementation of a large-scale real-world device.
Download or read book Manganese Oxide Materials for Electrocatalytic Water Oxidation written by Robert W. Arndt and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Water oxidation Electrocatalysis by Manganese Oxides Syntheses Electrode Preparations Electrolytes and Two Fundamental Questions written by Jens Melder and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Electrochemical Oxygen Reduction written by Pei Kang Shen and published by Springer Nature. This book was released on 2021-01-16 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses systematically the theoretical research and the applications of electrochemical oxygen reduction. Oxygen reduction reaction is a common issue in electrochemistry, but is also an important process involved in the field of energy, cryogenic fuel cells, metal–air cells, oxygen sensors and hydrogen peroxide preparation. This book is divided into 6 chapters; it starts with a description of dynamic mechanisms, followed by a detailed introduction on the related experimental methods and related catalyst preparation technology. By providing the basic methods and testing techniques, and by demonstrating their applications, it helps readers gain a better understanding of oxygen reduction reactions, making it a valuable resource for the industrialization of scientific research achievements. Accordingly, the book appeals to a broad readership, particularly graduate students, those working at universities and research organizations, and industrial researchers.
Download or read book Standard Potentials in Aqueous Solution written by AllenJ. Bard and published by Routledge. This book was released on 2017-11-22 with total page 854 pages. Available in PDF, EPUB and Kindle. Book excerpt: The best available collection of thermodynamic data!The first-of-its-kind in over thirty years, this up-to-date book presents the current knowledgeon Standard Potentials in Aqueous Solution.Written by leading international experts and initiated by the IUPAC Commissions onElectrochemistry and Electroanalytical Chemistry, this remarkable work begins with athorough review of basic concepts and methods for determining standard electrodepotentials. Building upon this solid foundation, this convenient source proceeds to discussthe various redox couples for every known element.The chapters of this practical, time-saving guide are organized in order of the groups ofelements on the periodic table, for easy reference to vital material . AND each chapteralso contains the fundamental chemistry of elements ... numerous equations of chemicalreactions .. . easy-to-read tables of thermodynamic data . . . and useful oxidation-statediagrams.Standard Potentials in Aqueous Solution is an ideal, handy reference for analytical andphysical chemists, electrochemists, electroanalytical chemists, chemical engineers, biochemists,inorganic and organic chemists, and spectroscopists needing information onreactions and thermodynamic data in inorganic chemistry . And it is a valuable supplementarytext for undergraduate- and graduate-level chemistry students.
