Author: Yao Yang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Electrocatalysis has been the cornerstone for enhancing energy efficiency, minimizing environmental impacts and carbon emissions, and enabling a more sustainable way of meeting global energy needs. Elucidating the structure and reaction mechanisms of electrocatalysts at electrode-electrolyte interfaces is fundamental for advancing renewable energy technologies, including fuel cells, and water electrolyzers, among others. One of the fundamental challenges in electrocatalysis is understanding how to activate and sustain electrocatalytic activity, under operating conditions, for extended time periods, which calls for the use of in situ/operando methods. This thesis first introduces the design and understanding of electrocatalysts for alkaline fuel cells since they enable the use of non-precious metals to catalyze the sluggish oxygen reduction reaction (ORR) at the cathode. Metal oxide-based ORR electrocatalysts, synthesized by a hydrothermal method, in particular, Mn-Co spinel nanoparticles, have demonstrated over 1 W/cm2 benchmark peak power density with a Pt-based anode and a record 200 mW/cm2 with a Ni-based anode for a completely non-precious metal-containing alkaline fuel cell, in membrane electrode assembly (MEA) measurements. Analytical scanning transmission electron microscopy (STEM) has been extensively employed to resolve the heterogeneous crystal structures and chemical environments at the atomic scale. Operando X-ray absorption spectroscopy (XAS) methods revealed that the superior performance of Mn-Co spinels in low humidity, relative to Pt, originates from synergistic effects in which the Mn sites bind O2 while the Co sites activate H2O to facilitate the proton-coupled electron transfer process. Moving beyond oxides, we have developed nitride-core oxide-shell Co4N/C and Pd-based alloys as ORR electrocatalysts for high-power alkaline fuel cells. The second part of this thesis focuses on operando studies of electrochemical interfaces. In situ heating STEM and heating X-ray diffraction were used to track the dynamic order-disorder phase transition of Pt3Co intermetallic ORR catalysts during annealing and quantify the degree of ordering as a key structural factor for long-term MEA durability. This thesis then presents the efforts to tackle a grand challenge in physical chemistry : understanding and spatially resolving the electrochemical double layer (EDL) at electrolyte/nanocrystal electrode interfaces. Preliminary studies, with heavy halide anion and/or alkali cations as chemical probes, while promising, have yet to provide compelling evidences of potential-dependent changes of ionic distributions. However, the pursuit of these EDL studies led to the unexpected observation of cathodic corrosion, an enigmatic electrochemical process in which noble metal electrodes corrode under sufficiently reducing potentials. I employed operando EC-STEM to reveal that cathodic corrosion at solid-liquid-gas interfaces yields significantly higher levels of structural degradation for nanocrystals than bulk electrodes. The dynamic evolution of morphology, composition, and structural information was retrieved by analytical and 4D-STEM. Such microscopic studies can provide unprecedented insights into the structural evolution of nanoscale electrocatalysts during electrochemical reactions under highly reducing potentials, such as CO2 and N2 reduction.
Author: Nicolas Alonso-Vante
Publisher: John Wiley & Sons
ISBN: 1119460549
Category : Technology & Engineering
Languages : en
Pages : 236
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Book Description
This book addresses some essential topics in the science of energy converting devices emphasizing recent aspects of nano-derived materials in the application for the protection of the environment, storage, and energy conversion. The aim, therefore, is to provide the basic background knowledge. The electron transfer process and structure of the electric double layer and the interaction of species with surfaces and the interaction, reinforced by DFT theory for the current and incoming generation of fuel cell scientists to study the interaction of the catalytic centers with their supports. The chief focus of the chapters is on materials based on precious and non-precious centers for the hydrogen electrode, the oxygen electrode, energy storage, and in remediation applications, where the common issue is the rate-determining step in multi-electron charge transfer processes in electrocatalysis. These approaches are used in a large extent in science and technology, so that each chapter demonstrates the connection of electrochemistry, in addition to chemistry, with different areas, namely, surface science, biochemistry, chemical engineering, and chemical physics.
Author: Rui Zeng
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Electrocatalysis is the keystone to realize the transition from a fossil fuels-based energy landscape to one dominated by renewable energy sources. However, the sluggish reaction kinetics and low selectivity have severely limited their broad application. In this dissertation, I aim to advance electrocatalysis by combining atomistic insights to design high-performance electrocatalysts, and operando methods to reveal dynamic changes of electrocatalysts and reactants/products under real-time electrochemical conditions.As one of the most valuable operando techniques for electrocatalysis, differential electrochemical mass spectrometry (DEMS) was extensively employed to identify the potential dependent dynamic formation of gaseous or volatile products during the formic acid oxidation and alkene hydrogenation reactions. The successful employment of a dual-thin-layer flow cell enabled quantification of the current efficiencies of the main products and side products in the oxidation of formic acid, catalyzed by a series of Pt-Fe-Cu intermetallics. Lattice strain was proposed to account for the observed differences in current efficiencies based on a dual-pathway mechanism. DEMS was further used to evaluate alkene hydrogenation catalyzed by cobalt complexes, in which hydrogen signals were monitored as key products. The suppressed hydrogen evolution along with increased Faradaic current provided compelling evidence for alkene hydrogenation. Furthermore, the effects of electronic properties of catalysts and alkene structures on alkene hydrogenation efficiency were systematically investigated. Developing non-precious electrocatalysts for the sluggish kinetics of the oxygen reduction reaction (ORR) is regarded as one of the key bottlenecks for anion exchange membrane fuel cells (AEMFCs). I demonstrated that cobalt nitride electrocatalysts could overcome the conductivity challenge of oxide counterparts and enhance ORR performance by combining a conductive nitride core and an active oxide shell. Further, a systematic study of a family of transition metal nitrides identified cobalt nitride as the most active single metal nitride ORR electrocatalyst, which was in turn extensively evaluated by operando X-ray absorption spectroscopy during operating conditions. To unveil the underlying structure-property relationships in transition metal nitride electrocatalysts, we successfully synthesized well-defined manganese nitride nanocuboids and enriched an atomistic understanding of the interface between the surface oxide and the nitride core. A combination of theoretical calculations and microscopic study revealed that the ligand effects of the nitride core played a major role in determining the ORR performance of the surface oxide, rather than the effects of the applied tensile strain. Finally, I showed that a rigorous and systematic study of single-crystalline metal oxide/nitrides could benefit mechanistic understanding of ORR electrocatalysis for transition metal-based materials.
Author: Luis Rebollar Tercero
Publisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages : 0
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Book Description
It is well known that the hydrogen reaction rates on Pt and other electrocatalysts are fast at low pH but 1-2 orders of magnitude slower at high pH. Although the electrochemical hydrogen evolution and oxidation reactions (HER and HOR) are arguably the best-understood reactions in electrocatalysis, the anomalous effect of pH on reaction kinetics has defied simple explanation for decades. This longstanding puzzle not only limits applied catalyst design, but also exposes gaps in the fundamental understanding of electrocatalysis by showing that singular adsorption descriptors (e.g., the hydrogen binding energy) cannot describe kinetic effects across electrolytes. The goal of this work is to examine the possible sources of the strong pH dependence in hydrogen electrocatalysis. This dissertation delves in logical progression into the interfacial processes that govern this anomalous pH dependence, beginning with fundamental experimental and theoretical investigations of the chemical and physical processes occurring at the interface, and ending with the incorporation of "double-layer dopants" able to further enhance the kinetics of highly active electrocatalysts in alkaline media. In this work, we have applied electroanalytical techniques to the reversible hydrogen reaction on single crystal Pt surfaces to gain insight into the role of coadsorbed species, the potential of zero charge (Epzc), transition state barrier heights, and "double-layer dopants" in the alkaline hydrogen reaction mechanism. Combining experimental results with microkinetic modeling, we determined that adsorbed hydroxide being an active participant in the alkaline hydrogen reaction mechanism is thermodynamically unfeasible, and therefore the anomalous effect of pH on kinetics must come from changes in kinetic parameters rather than from changes in thermodynamic binding energies. Focused on interfacial water mobility as the basis for such changes in kinetic parameters, we performed kinetic isotope effect (KIE) voltammetry measurements to quantify the importance of solvent mobility on the overall hydrogen reaction kinetics. Large KIE values of up to 3.4 for HOR in KOD on Pt(111) compared to no measurable effects in DClO4 confirmed that interfacial water mobility drives the pH dependence of the reversible hydrogen reaction. With this insight, we further assessed the impact of interfacial electric field strength, as described by the electrode's Epzc, on electrochemical reaction kinetics in the context of hydrogen electrocatalysis. Previous findings from our group demonstrated the use of molecular interfacial additives such as adsorbed caffeine for enhancing the alkaline HER/HOR kinetics, possibly by disrupting the double layer structure and affecting the orientation and dynamics of water. Hence, using caffeinated Pt as a model surface, we correlated reaction kinetics to the electrode's Epzc and to the solvent mobility. The activity of composite Pt surfaces was found to correlate with the proximity of the Epzc, measured by CO displacement, to the equilibrium potential of HER/HOR, but larger KIE values measured on caffeinated Pt at high pH indicate that this is not a causal relationship and Epzc is not a mechanistic descriptor of the alkaline hydrogen reaction kinetics. The use of "double-layer dopants" such as caffeine represents a new approach for designing not just HER/HOR catalysts with increased activity but also experiments that may bring light to interfacial phenomena dictating reaction kinetics. Hence, to uncover the mechanistic origin of the observed enhancement in alkaline HER/HOR kinetics, we have performed single-crystal voltammetry measurements of Pt(111) electrodes covered with surface additives in buffered electrolytes of varying pH. The results show a decrease/increase transition in kinetics around the additive's pKa, suggesting that double-layer dopants reduce transition state barriers for HER/HOR by regulating the interfacial pH. We have also made steps towards determining the relationship between Epzc and interfacial water structure through in-situ XAS measurements on caffeinated Pt and Au electrodes. Finally, we propose paths forward for improving the mechanistic understanding of how specific interactions between the surface and species in solution affect macroscopic rates, which include combining single-crystal voltammetry, electroanalytical chemistry, in-operando spectroscopy, atomic-scale DFT calculations, and other molecular "double layer dopants".
Author: Inamuddin
Publisher: Springer Nature
ISBN: 3030271617
Category : Technology & Engineering
Languages : en
Pages : 469
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Book Description
This book explores key parameters, properties and fundamental concepts of electrocatalysis. It also discusses the engineering strategies, current applications in fuel-cells, water-splitting, metal-ion batteries, and fuel generation. This book elucidates entire category viewpoints together with industrial applications. Therefore, all the sections of this book emphasize the recent advances of different types of electrocatalysts, current challenges, and state-of-the-art studies through detailed reviews. This book is the result of commitments by numerous experts in the field from various backgrounds and expertise and appeals to industrialists, researchers, scientists and in addition understudies from various teaches.
Author: Shibin Li
Publisher: Springer Science & Business Media
ISBN: 3319027727
Category : Technology & Engineering
Languages : en
Pages : 293
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Book Description
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.
Author: Li-chyong Chen
Publisher: World Scientific
ISBN: 9811284652
Category : Science
Languages : en
Pages : 298
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Book Description
Nanomaterials have become a key component for energy-related applications. Their design principle, synthesis and applications are well discussed in various scientific and engineering books, but a gap remains in discussions regarding the application of cutting-edge X-ray techniques to these materials. This volume provides insights from the latest development of X-ray techniques to investigate nanomaterials in specific energy fields, bridging the gap between X-ray analytical scientists and material researchers.We aim to provide researchers with a tool to choose suitable X-ray techniques, carry them out with the right procedure, and analyze the data to give the best reliable results. The approach is microscopic and specific. Among the applications emphasized by the chapters in this book are x-ray techniques in heterogeneous catalysis, electrocatalysis for fuel cells, photocatalysis for water splitting and carbon dioxide reduction, organic photovoltaics, and other energy-related applications.
Author: Zhikun Wu
Publisher: Morgan & Claypool Publishers
ISBN: 1636390250
Category : Science
Languages : en
Pages : 141
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Book Description
Atomically precise metal nanocluster research has emerged as a new frontier. This book serves as an introduction to metal nanoclusters protected by ligands. The authors have summarized the synthesis principles and methods, the characterization methods and new physicochemical properties, and some potential applications. By pursuing atomic precision, such nanocluster materials provide unprecedented opportunities for establishing precise relationships between the atomic-level structures and the properties. The book should be accessible to senior undergraduate and graduate students, researchers in various fields (e.g., chemistry, physics, materials, biomedicine, and engineering), R&D scientists, and science policy makers.
Author: James Joseph Burton
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 360
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Book Description
Advanced Materials in Catalysis is a collection of materials that discusses various catalysts. The book presents the physical and chemical properties that indicate that a particular class of materials may be of catalytic interest. The text first covers bimetallic catalysts, and then proceeds to examining the catalytic properties of compounds such as graphite intercalation compounds; oxides with the scheelite structure; and synthetic layered silicates and aluminosilicate. The book also covers reduction catalysts, biological catalysts, and monolithic catalyst supports. The selection will be of g ...
Author: Zongyou Yin
Publisher: John Wiley & Sons
ISBN: 3527348921
Category : Technology & Engineering
Languages : en
Pages : 887
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Book Description
Atomic and Nano Scale Materials for Advanced Energy Conversion Discover the latest advancements in energy conversion technologies used to develop modern sustainable energy techniques In Atomic and Nano Scale Materials for Advanced Energy Conversion, expert interdisciplinary researcher Dr. Zongyou Yin delivers a comprehensive overview of nano-to-atomic scale materials science, the development of advanced electrochemical, photochemical, photoelectrochemical, and photovoltaic energy conversion strategies, and the applications for sustainable water splitting and other technologies. The book offers readers cutting-edge information of two-dimensional nano, mixed-dimensional nano, nano rare earth, clusters, and single atoms. It constructively evaluates emerging nano-to-atomic scale energy conversion technologies for academic research and development (R&D) researchers and industrial technique consultants and engineers. The author sets out a systematic analysis of recent energy-conversion science, covering topics like adaptable manufacturing of Van der Waals heterojunctions, mixed-dimensional junctions, tandem structures, and superlattices. He also discusses function-oriented engineering in polymorphic phases, photon absorption, excitons-charges conversion, non-noble plasmonics, and solid-liquid-gas interactions. Readers will also benefit from: A thorough introduction to emerging nanomaterials for energy conversion, including electrochemical, photochemical, photoelectrochemical, and photovoltaic energy conversion An exploration of clusters for energy conversion, including electrochemical, photochemical, and photoelectrochemical clusters Practical discussions of single atoms for energy conversion in electrochemical, photochemical, and photoelectrochemical energy conversion technologies A thorough analysis of future perspectives and directions in advanced energy conversion technology Perfect for materials scientists, photochemists, electrochemists, and inorganic chemists, Atomic and Nano Scale Materials for Advanced Energy Conversion is also a must-read resource for catalytic chemists interested in the intersection of advanced chemistry and physics in energy conversion technologies.
