Download or read book Spinel Oxides and Heteroatom doped Carbon Nano composite as Bi functional Oxygen Electrocatalyst for Rechargeable Zinc air Battery written by Moon Gyu Park and published by . This book was released on 2015 with total page 103 pages. Available in PDF, EPUB and Kindle. Book excerpt: With continued increase in energy demand for high energy-required devices such as portable electronics and electric vehicles, development of innovative energy conversion and storage systems has attracted tremendous attention. Even though lithium-ion battery technology is currently the most developed energy storage technology and employed for multiple applications, their insufficient energy density and critical problem in intrinsic chemistry limit their further development for fulfilling the ultimate requirements. As an attractive alternative technology, metal-air battery has recently captured the spotlight as promising sustainable energy conversion and storage technology. Metal-air batteries with the open architecture provide many attractive characteristics containing environmental benignity, high power and energy densities. In addition, with a wide range of selection in different metals determines different energy capacity and efficiency. Among a various types of metal-air batteries, zinc-air battery system has especially been considered as the most mature technology due to its abundance, low cost, ease handling, and safe operation as well as high energy efficiency. However, some technological challenges of zinc-air batteries such as insufficient cycling durability, low charge/discharge activity and efficiency, and poor rate capability still must be addressed for future commercialization. These main challenges interrupting the development of electrically rechargeable zinc-air batteries are primarily due to very sluggish oxygen reduction and evolution reactions generated during discharge and charge processes on air electrode. The slow oxygen reactions create large overpotentials during both discharge and charge processes, which significantly decrease energy efficiency of zinc-air battery. Accordingly, the use of electrocatalysts in air electrode has been highly required to facilitate the reactions and even propel the zinc-air batteries to practical energy applications. Therefore, it is considerably necessary to develop highly active and durable bi-functional electrocatalysts toward both ORR and OER for the sake of successful commercialization of electrically rechargeable zinc-air batteries. In this point of view, design and synthesis of advanced oxygen electrocatalysts at low cost has been favorably considered. Despite extensive efforts made, however, developing air electrode catalysts with the high activity and the long durability at low cost remain a huge challenge because mostly precious metal-based catalysts such as platinum (Pt) and iridium (Ir) show greatly high activities toward ORR and OER, respectively. However, the use of the materials as electrocatalysts for zinc-air battery is highly challengeable in that they are extremely scarce, expensive, and unstable during the oxygen reactions. Therefore, it is significantly important to develop proper materials which are inexpensive, abundant, and stable during the oxygen reactions, where they are called “non-precious catalysts” primarily composed of transition metals or metal oxides, nano-carbons, and their hybrids. The strong objectives make us focus on the design of a class of novel composite architecture for high-performance electrochemical energy storage, electrically rechargeable zinc-air battery. In this work, the strategy is based on a fast solvation-induced assembly that directly exploits strong hydrophobicity of both cobalt oxide nanocrystals (Co3O4 NCs) and Nitrogen-doped carbon nanotubes (N-CNTs). A two-phase method is exploited to prepare the nearly mono-dispersed, highly crystalline, nano-sized cobalt oxide. The reaction of the two-phase system happens at the interface between the oil (nonpolar) and water (polar) phases and the interface is an exclusive site for both nucleation and growth. N-CNTs were synthesized by a single step chemical vapor deposition technique using either ferrocene as a catalyst and etylenediamine as a carbon source. Simply at first, cobalt oxide NCs and N-CNTs are dispersed in nonpolar solvent (e.g., toluene). Upon addition of polar solvent (e.g., methanol), solvation forces induce the hydrophobic cobalt oxide NCs to assemble around the hydrophobic CNTs, which leads to the formation of cobalt oxide NCs-decorated on the N-CNTs. As an electrochemical catalyst for air electrode, Co3O4 nanoparticle is a material with little ORR activity by itself. However, when it is decorated on Nitrogen-doped carbon nanotubes, their hybrid shows unexpected, surprisingly high performance in ORR that is further enhanced by nitrogen doping of N-CNTs. The Co3O4 NC/N-CNT hybrid exhibits comparable ORR catalytic activity but superior stability to a commercial carbon-supported Pt catalyst in alkaline solutions, thus leading to a novel bi-functional catalyst for ORR. The same hybrid is also highly active for OER, making it a high-performance non-precious metal-based bi-functional catalyst for both ORR and OER. The unusual catalytic activity arises from synergetic coupling effects between Co3O4 and N-CNTs. The full cell electrochemical catalytic activity is evaluated by preparing air electrodes of rechargeable zinc-air batteries utilizing ambient air to emphasize practicality. The galvanodynamic charge and discharge behaviors are superior to Pt/Carbon and N-CNT counterparts particularly at high applied current densities. Electrochemical impedance spectroscopy reveals that Co3O4 NC/N-CNT hybrid electrode results in significantly less internal, solid-electrolyte interface, and charge transfer resistances which lead to highly efficient electrochemical reactions. Superior rechargeability has also been confirmed where virtually no voltage drops are observed over 200 pulse cycles. The practicality of Co3O4 NC/N-CNT hybrid is highlighted by demonstrating comparable discharge voltages and greatly outperforming charge voltages with excellent electrochemical stability than commercial Pt/Carbon catalyst.

Download or read book Nanostructured Spinel Oxides as Bi functional Electrocatalysts for Rechargeable Metal air Batteries written by Dong Un Lee and published by . This book was released on 2017 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to continuously increasing energy demands, particularly with the emergence of electric vehicles (EV), smart energy grids, and portable electronics, advanced energy conversion and storage systems such as fuel-cells and metal-air batteries have drawn tremendous research and industrial attention. Even though the lithium-ion battery technology is the most developed and widely distributed energy device for a wide range of applications, some researchers view its energy density insufficient for fulfilling the ultimate requirements of highly energy intensive applications such as EVs. Recently, zinc-air batteries have re-gained research attention since the initial development in the 1970s due to their remarkably highly energy density and the potential to be electrically rechargeable. However, some technological hurdles such as low charge/discharge energy efficiency, and insufficient cycle stability have hampered commercialization and introduction of rechargeable zinc-air batteries to the market. The mentioned hurdles are currently the main challenges of rechargeable zinc-air battery developed, and they stem from the fact that the reaction kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are intrinsically very sluggish. The two are the main electrochemical reactions that govern the charge and discharge processes of a rechargeable metal-air battery at the air electrode, and these oxygen reactions must be facilitated by active electrocatalysts in order to progress them at practically viable and stable rates. Currently, the best known catalysts for ORR and OER are carbon supported platinum (Pt/C) and iridium (Ir/C), respectively. However, the use of these precious metal based catalysts for large scale applications like EVs and energy storage systems is prohibitively expensive. Additionally, the durability of these catalysts have been reported to be insufficient for long-term usage under normal device operating conditions. Perhaps most importantly, the precious metal based catalysts are strongly active towards only one of the two oxygen reactions required for rechargeable applications. For example, Pt/C is a strong ORR active catalyst, while Ir/C is a strong OER active catalyst. Recently in the literature, a simple physical mixture of these two catalysts have been used to render bi-functionality, but this method is very rudimentary and still requires two separate syntheses for each catalyst. This suggests that future bi-functionally active catalysts must not only be non-precious (inexpensive), but also a single active material capable of catalyzing both ORR and OER over the same active surface. Having said above, non-precious catalyst research, specifically for bi-functional ORR and OER electrocatalyses, has increased dramatically beginning in the 90's with a very popular and positive belief in the energy community that rechargeable lithium-air batteries could potentially replace lithium-ion batteries. This wave of interest has also picked up research in rechargeable zinc-air batteries since the electrochemical oxygen reactions that take place at the air electrodes are fundamentally very similar. Additionally, the use of zinc metal as the anode, which is one of Earth's most abundant elements, and the water-based (aqueous) solutions as the electrolyte (as opposed to organic ones) made the rechargeable zinc-air battery development very attractive and seemingly easy to scale-up. Moreover, primary (non-rechargeable) zinc-air batteries have already been commercialized and are available in the market as hearing aid batteries, leading many researchers to believe that a simple tuning of the current technology would lead to a successful secondary (rechargeable) zinc-air battery development. However, there are a set of technical difficulties specific to rechargeable zinc-air batteries that have slowed the development for the past few decades. Therefore, the work presented in this thesis aims to address the challenges of rechargeable zinc-air batteries particularly from the active bi-functional electrocatalyst standpoint to make them as commercially viable as possible.

Download or read book Transition Metal Oxides Anchored Onto Heteroatom Doped Carbon Nanotubes as Efficient Bifunctional Catalysts for Rechargeable Zinc air Batteries written by Alexandra McDougall and published by . This book was released on 2021 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is well known that renewable energy, e.g., wind and solar power, are intermittent energy sources. This means that energy storage devices are needed to store the energy for when it is needed. Currently Li-ion batteries are used as these energy storage devices, not only for alternative energy plants but in vehicles and electronics. There are several drawbacks with using Li-ion batteries, such as low safety, harmful Li mining practices, and high material costs. Rechargeable zinc-air batteries (ZABs) have gained a lot of traction recently due to their low cost, high safety, low environmental impact, and high theoretical energy density. However, a major obstacle is the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the air electrode, which have hindered practical applications of ZABs. Precious metal catalysts have been applied to help mitigate the slow reaction kinetics; however, these are expensive and complicate manufacturing practices since two different precious metals are needed to achieve a bifunctional catalyst. Therefore, a low-cost bifunctional catalyst is needed to improve the slow reaction kinetics at the air electrode. This work focuses on further investigating a previously developed impregnation technique for air electrode preparation using an array of transition metal (Zn, Ni, Mn, and Co) oxide combinations. Various electrochemical and microstructural characterization techniques, e.g., linear sweep voltammetry, electrochemical impedance spectroscopy, electron microscopy, and energy dispersive X-ray spectroscopy, are used to examine each sample. The first study involved fabricating several catalysts by decorating nitrogen doped carbon nanotubes (N-CNTs) with either tri-metallic (Ni-Mn-Co) or tetra-metallic (Zn-Ni-Mn-Co) oxides, through a simple impregnation method into carbon-based, gas diffusion layers (GDL). Metal oxide compositions were selected based on previous results, preliminary electrochemical testing, and statistical design of experiments (DOE). Microstructural characterization was done using electron microscopy and X-ray photoelectron spectroscopy (XPS), and determined that the oxides fabricated were spinel oxides. Samples were electrochemically tested and the best candidates were subjected to full cell testing and bifunctional cycling for 200 charge/discharge cycles at 10 mA/cm2. The overall bifunctional efficiency, after cycling, of the best NiMnCoOx/N-CNT and ZnNiMnCoOx/N-CNT catalysts was 53.3% and 56.4%, respectively; both outperformed Pt-Ru/C in both overall bifunctional efficiency (38%) and cycling stability. The maximum power density of one of the tetra-metallic oxides exceeded that of Pt-Ru/C (110 mW/cm2) at 134 mW/cm2. The addition of Zn with Ni-Mn-Co oxide particles showed improved cycling stability and overall bifunctional efficiency. The second study investigated the effect of co-doping of carbon nanotubes with nitrogen and sulfur (N,S-CNTs), combined with tri-metallic and tetra-metallic oxides, on the ORR and OER reaction kinetics at the air electrode. The best tri-metallic (Ni-Mn-Co) oxide and tetra-metallic (Zn-Ni-Mn-Co) oxide from the first study were used in this investigation. Microstructural characterization analysis revealed that the Co and Mn valences increased for the Ni-Mn-Co and Zn-Ni-Mn-Co oxides, respectively. Electrochemical testing revealed that the Ni-Mn-Co oxide was comparable to the Pt-Ru/C catalyst with a power density of ~95 mW/cm2 and Zn-Ni-Mn-Co oxide was comparable to the Pt-Ru/C catalyst with an efficiency of 56.0% at 20 mA/cm2. The addition of sulfur to the N-CNTs positively impacted the Ni-Mn-Co oxide, leading to a round trip bifunctional cycling efficiency of 55.1% for 200 charge-discharge cycles at 10 mA/cm2. The impact of sulfur did not have a positive impact on the Zn-Ni-Mn-Co oxide; the LSV results were significantly worse than the equivalent oxide on N-CNTs and the full cell testing was comparable to the N-CNT oxide. Both tri-metallic and tetra-metallic oxides outperformed Pt-Ru/C during bifunctional cycling.

Download or read book Electrospinning of Nanofibers for Battery Applications written by Shengjie Peng and published by Springer Nature. This book was released on 2020-07-10 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprehensively discusses the basic principles and working mechanism of all kind of batteries towards clean energy storage devices. In addition, it focuses on the synthesis of various electrode materials with 1D architecture via electrospinning technique. This book will give a clear idea about recent synthetic strategy towards nanofibers and nanocomposites for alkali-ion storage applications. The reader could understand the formation mechanism of nanofibers and their potential application in the future energy storage system.

Download or read book Electrochemical Energy written by Pei Kang Shen and published by CRC Press. This book was released on 2018-10-08 with total page 1051 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrochemical Energy: Advanced Materials and Technologies covers the development of advanced materials and technologies for electrochemical energy conversion and storage. The book was created by participants of the International Conference on Electrochemical Materials and Technologies for Clean Sustainable Energy (ICES-2013) held in Guangzhou, China, and incorporates select papers presented at the conference. More than 300 attendees from across the globe participated in ICES-2013 and gave presentations in six major themes: Fuel cells and hydrogen energy Lithium batteries and advanced secondary batteries Green energy for a clean environment Photo-Electrocatalysis Supercapacitors Electrochemical clean energy applications and markets Comprised of eight sections, this book includes 25 chapters featuring highlights from the conference and covering every facet of synthesis, characterization, and performance evaluation of the advanced materials for electrochemical energy. It thoroughly describes electrochemical energy conversion and storage technologies such as batteries, fuel cells, supercapacitors, hydrogen generation, and their associated materials. The book contains a number of topics that include electrochemical processes, materials, components, assembly and manufacturing, and degradation mechanisms. It also addresses challenges related to cost and performance, provides varying perspectives, and emphasizes existing and emerging solutions. The result of a conference encouraging enhanced research collaboration among members of the electrochemical energy community, Electrochemical Energy: Advanced Materials and Technologies is dedicated to the development of advanced materials and technologies for electrochemical energy conversion and storage and details the technologies, current achievements, and future directions in the field.

Download or read book Perovskite Oxide Combined With Nitrogen Doped Carbon Nanotubes As Bifunctional Catalyst for Rechargeable Zinc Air Batteries written by Vugar Ismayilov and published by . This book was released on 2014 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zinc air batteries are among the most promising energy storage devices due to their high energy density, low cost and environmental friendliness. The low mass and cost of zinc air batteries is a result of traditional active materials replacement with a thin gas diffusion layer which allows the battery to use the oxygen directly from the air. Despite the environmental and electronic advantages offered by this system, challenges related to drying the electrolyte and catalyst, determining a high activity bifictional catalyst, and ensuring durability of the gas diffusion layer need to be optimized during the fabrication of rechargeable zinc-air batteries. To date, platinum on carbon (Pt/C) provides the best electrochemical catalytic activity in acidic and alkaline electrolytes. However, the difficult acquisition and high cost of this catalyst mandates investigation into a new composition or synthesis of a bifunctional catalyst. A number of non-precious metal catalyst have been introduced for zinc-air batteries. Nevertheless, their catalytic activities and durability are still too low for commercial rechargeable zinc-air batteries. Thus, it is very important to synthesize a highly active bifunctional catalyst with good durability for long term charge and discharge use. In this study, it is proposed that a manganese-based perovskite oxide nanoparticle combined with nitrogen doped carbon nanotubes willshow promising electrochemical activity with remarkable cycle stability as a bifunctional catalyst for zinc-air batteries. In the first part of this work, nano-sized LaMnO3 and LaMn0.9Co0.1O3 were prepared to research the effectiveness of Co doping into LaMnO3 and its effect on electrochemical catalytic activities. To prepare LaMnO3 and LaMn0.9Co0.1O3, a hydrothermal reaction method was applied to synthesize nanoparticles which can increase the activity of perovskite type oxides. The result shows that while perovskite oxides replacing 10 wt. % of Mn doped with Co metal did not iv change its crystalline structure, the oxygen evolution reaction (OER) performance was increased by 600%. In the second part, a core-corona structured bifunctional catalyst (CCBC) was synthesized by combining LaMn0.9Co0.1O3 nanoparticles with nitrogen doped carbon nanotubes (NCNT). NCNT was chosen because of its large surface area and high catalytic activity for ORR. SEM and TEM analysis show that metal oxide nanoparticles were surrounded with nanotubes. Based on the electrochemical performances, ORR and OER activity is attributed to NCNT and the metal oxide core, respectively, complementing the activities of each other. Furthermore, its unique morphology introduces synergetic activity especially for OER. Electrochemical test results show that the onset potential was enhanced from -0.2 V (in LaMnO3 and LaMn0.9Co0.1O3) to -0.09 V (in CCBC) and the half wave potential was improved from -0.38 V to -0.19 V. In the third part, a single cell zinc-air battery test was performed using CCBC as the bifunctional catalyst for the air electrode. These results were compared with battery performance against a high-performance and expensive Pt/C based air catalyst. The results show that the battery containing catalytic CCBC consumes less energy during charge/discharge. The single cell long-term durability performance was compared, further proving that CCBC provides a more suitable catalyst for zinc-air battery than Pt/C.

Download or read book Nano electrocatalyst for Oxygen Reduction Reaction written by Omar Solorza Feria and published by CRC Press. This book was released on 2024-06-21 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: Global warming switches our reliance from fossil fuels to green, sustainable renewable energy sources. Because of its promising nature, high-efficiency nano-electrocatalysts have sparked interest in renewable energy. Hydrogen fuel cell/polymer electrolyte membrane (PEM) vehicles are the most environmentally conscious electromobility vehicles, with a high energy density and quick refuelling technology, prompting the auto industry to launch a variety of PEM fuel cell vehicles around the world. Oxygen reduction reaction (ORR) primary research interests include fuel cells and metal-air batteries. The sluggish kinetic reaction of ORR, which is responsible for the rate-limiting reaction at the PEM fuel cell cathodic system, further decreases energy efficiency. Optimising ORR for market expansion with cost-effective and efficient nano-electrocatalysts, on the other hand, remains a challenge. The book covers fundamental ORR reaction kinetics theories, tools, and techniques. It also explains the nano electrocatalysts for ORR made of noble, non-noble, and nanocarbon materials. Finally, the book explores the applications of PEM fuel cells and metal-air batteries.

Download or read book Metal Oxide Based Nanostructured Electrocatalysts for Fuel Cells Electrolyzers and Metal Air Batteries written by Teko Napporn and published by Elsevier. This book was released on 2021-01-30 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Design and Engineering of Hierarchically Porous Transition Metal based Electrocatalysts for Rechargeable Zn air Batteries written by Moon Gyu Park and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the critical cathodic and anodic reactions, respectively, in electrically rechargeable Zn-air battery. With a variety of advantages including relatively high energy density (1218 Wh kg-1), the abundance of zinc in the earth, and secure handling and safe operation, electrically rechargeable (secondary) Zn-air battery technology has been regarded as highly promising energy applications in consumer electronics, electric vehicles, and smart grid storage. Zn-air batteries consist of not only zinc anode, polymer separator, and an alkaline electrolyte that are typical battery components, but also air-breathing cathode that makes Zn-"air" battery unique technology. Unlike other general battery systems such as lithium-ion batteries, there is no active material stored in cathode, but gaseous oxygen molecules in the air are used as the fuel for energy-generating reaction in the air cathode of Zn-air technology. The reactions occurring during battery discharge and charge are ORR and OER, respectively, which are mostly dominating the overall energy efficiency of the Zn-air battery system due to their intrinsically sluggish kinetics. The high energy barrier attributed to conversions between oxygen molecules diffused from the air and hydroxide ions in the electrolyte at the thin layer of the electrode leads to low charge/discharge energy efficiency and insufficient cycle stability hindering the commercialization of rechargeable Zn-air batteries to the market. Therefore, it is necessarily required to facilitate the slow kinetics of oxygen electrocatalytic reactions by using bifunctionally active and durable oxygen electrocatalyst materials to progress the reactions at practically viable and stable rates. With the use of bifunctional oxygen catalysts, kinetics of ORR and OER can be improved, leading to enhancement of Zn-air battery performances such as higher operating voltage and longer battery cycling life. The current best-known catalysts for ORR and OER are noble metals, including platinum (Pt) and iridium (Ir), respectively. However, high cost and scarcity of the precious metal-based catalysts hinder their employment in large scale energy applications. Furthermore, the electrochemical stability of these materials is well known to be very insufficient for long term usage even under typical device operating conditions. Therefore, the development of non-precious transition metal-based electrocatalysts has significantly been a momentous research field. Along with this movement, the facile synthesis and inexpensive preparation of highly active and durable electrocatalysts will take the top priority for the fulfillment of practically available rechargeable Zn-air battery technology in a variety of energy applications from portable electronics to electric vehicles and smart grid storage systems. In this work, novel design strategies of bifunctionally active and durable electrocatalysts possessing robust three-dimensional framework with hierarchical porosity are presented. A porous structure with a large surface area is essential to improve the oxygen electrocatalysis since the oxygen reactions take place at the surface of materials, where active sites reside, and thereby the large surface indicating plenty of catalytically active sites enhances kinetics of the reactions. Additionally, the porous architecture facilitates diffusion of oxygen gas molecules during the oxygen electrocatalysis, leading to enhanced mass transport of reactants and reduced overpotentials for ORR and OER polarizations, eventually resulting in improved activities. In addition to the improvement of activities, electrochemical stability is an essential fundamental property for the rational design of electrocatalysts. Thus, the 3D porous structure must have robust framework which can endure the highly oxidative environment in OER potential range. Therefore, the work presented in this thesis is aiming for the design and engineering of hierarchically porous transition metal-based electrocatalysts involving high porosity as well as electrocatalytically robust frameworks to improve the oxygen electrocatalytic activities and durability and thereby put the rechargeable Zn-air battery technology at a commercially viable level. In the first study, a facile polymer template-derived method has been used to synthesize three-dimensionally ordered meso/macro-porous (3DOM) spinel cobalt oxide as a bifunctional oxygen electrocatalyst. Physicochemical characterizations have revealed the morphology of the designed electrocatalyst to be a hierarchically meso/macro-porous metal oxide framework. As investigated by electrochemical characterizations, 3DOM Co3O4 shows far enhanced ORR and OER activities with improved kinetics compared to the bulk material. The enhancement is majorly attributed to the five times higher specific surface area and significantly greater pore volume, leading to the increased number of catalytic active sites and facilitated diffusion of oxygen molecules into and out of the structure, respectively. Moreover, the robust frameworks of 3DOM Co3O4 helps to withstand harsh cycling environments by exhibiting significantly small performance reduction and retaining the original morphology. The improved oxygen electrocatalytic activity and durability have been well demonstrated in the rechargeable Zn-air battery system. 3DOM Co3O4 presents remarkably enhanced rechargeability over 200 cycles while retaining quite comparable operating voltage gap in comparison with the precious benchmark catalyst. In the second study, palladium (Pd) nanoparticle is deposited on the surface of 3DOM Co3O4 via a simple chemical reduction process. The morphological advantages of the 3DOM framework, as confirmed in the previous study, are expected to facilitate diffusion of oxygen molecules into and out of the structure leading to the decreased overpotentials during ORR and OER. However, using metal oxides as electrocatalysts restricts fast electron transfer leading to limited activity for oxygen catalysis due to their intrinsically low electrical conductivity. Therefore, Pd nanoparticles are introduced into 3DOM Co3O4 by expecting synergy from the combination of the morphological advantage of 3DOM architecture and the significant thermodynamic stability as well as the excellent ORR activity of palladium metal. Electrochemical characterizations have revealed that the combination demonstrates synergistically improved bifunctional electrocatalytic activity and durability. Moreover, computational simulation via density-functional-theory (DFT) verifies Pd@Co3O4(3DOM) is superior in two ways; (i) Activity-wise: the d-band center of Pd deposited on 3DOM Co3O4 was found to decrease significantly, resulting in increased electron abundance at the Fermi level, which in turn enhanced the overall electrical conductivity; (ii) Durability-wise: synergistic hybrid of Pd and 3DOM Co3O4 resulted in a significantly improved corrosion resistance, due to the much higher carbon oxidation potential and bulk-like dissolution potential of Pd nanoparticles on 3DOM Co3O4. The remarkable electrochemical activities and stabilities of Pd@3DOM-Co3O4 obtained from the half-cell testing resulted in excellent rechargeability of a prototype Zn-air battery, demonstrating the synergistic introduction of Pd into 3DOM Co3O4. In the last study, a type of metal-organic-framework (MOF) is selected as a template to synthesize MOF-based electrocatalyst possessing robust framework with multi-level porosity. Typically, MOF materials consist of metal centers linked by functional organic ligands, which gives them unique material characteristics such as high porosity and surface area, morphological and compositional flexibility, and high crystallinity. Especially, transition metal-based Prussian blue analogue (PBA) nanocubes with a chemical formula MxII[MyIII(CN)6]z▪H2O, where MII and MIII are divalent and trivalent transition metal cations, respectively, are employed as the MOF precursors due to a several material advantages such as simple precipitation synthesis, various possible compositions, and robust structure with high porosity

Download or read book Design of Efficient Cobalt based Bi functional Catalysts for Zinc air Batteries written by Guihua Liu and published by . This book was released on 2019 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to its high theoretical specific energy and low-cost, rechargeable zinc-air batteries have attracted tremendous attention as a promising next-generation energy conversion system. However, there are some challenges that need to overcome before its practical application. One of the key issues is the slow reaction kinetics in the air cathode of the batteries towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This would cause insufficient charge/discharge efficiency and poor cycle stability of the batteries. Therefore, the development of efficient ORR-OER bi-functional electrocatalysts with high catalytic activity and durability is essential for the development of rechargeable zinc-air batteries. In this work, a series of catalyst design strategies have been explored to improve the activity and durability of cobalt-based bi-functional catalysts especially under the oxidative condition of OER reaction. The latter would cause catalyst oxidation and aggregation, and therefore deteriorate the cycling performance of the bi-functional catalysts in zinc-air batteries. In the first study, a surface engineering approach was adopted to prepare efficient bi-functional catalyst consists of mildly oxidized, N-doped Co9S8 catalyst supported on N-doped reduce graphite oxide (O-N-Co9S8@N-RGO). The surface decorated electrocatalyst shows excellent activity for both ORR and OER, and maintains good stability over 900 charge-discharge cycles at 10 mA cm-2 in zinc-air battery. Interestedly, it was found that O-N-Co9S8 nanoparticles responsible for the OER reaction were completely converted into Co3O4 after OER reaction, indicating Co3O4 is the actual active phase for OER. On the basis of this observation, we propose and demonstrate that oxides in-situ generated cobalt oxides during OER reaction are more active than the directly calcined oxides. This work advances fundamental insight and the design of metal chalcogenides-based bi-functional "catalysts". On the recognition of the high catalytic activity of surface-engineered Co9S8 material, a three-dimensionally ordered mesoporous (3DOM) structured surface-engineered Co9S8 catalyst was developed to explore the benefits of the 3DOM structural design for its catalytic performance. Different from the N-RGO supported O-N-Co9S8, the 3DOM-Co9S8 catalyst is self-supported, which contains only an inner carbon layer within its mesoporous structure. Due to the 3D interconnected architecture and large surface area, the air electrode delivers excellent cell performance and cycling durability. However, the partial structure crush of N-Co9S8 after long-time OER testing was observed, demonstrating that the highly oxidative operating condition of rechargeable zinc-air batteries could cause significant structural integrity issues of porous chalcogenide electrocatalysts. Thus, in the last study, a new strategy focusing on the oxidation-resistive catalyst support design using oxygen vacancy (OV)-rich, low-bandgap semiconductor was proposed. The OVs promote the electrical conductivity of the semiconductor support, and at the same time offer a strong metal-support interaction (SMSI). The SMSI enables the catalysts with small metal size, high catalytic activity, and high stability. This strategy is demonstrated by successfully synthesizing ultrafine Co metal decorated 3DOM titanium oxynitride (3DOM-Co@TiOxNy). The catalyst not only exhibits good ORR-OER activities, but also shows excellent cycling stability in alkaline conditions, e.g. less than 1% energy efficiency loss over 900 charge-discharge cycles at 20 mA cm-2. Theoretical calculation confirmed that the high stability of this catalyst is attributed to the strong SMSI between Co and 3DOM-TiOxNy. This study will provide an alternative strategy for the design of efficient and durable non-precious electrocatalysts using OV-rich semiconductors as support materials. In summary, a series of catalyst design strategies for efficient and durable bi-functional ORR-OER catalyst were developed in this work. It was found that NH3 treatment is an effective surface-engineering approach to develop highly active ORR-OER catalysts. The in-situ transformation or oxidation of Co9S8 into Co3O4 observed in post-OER analysis advanced our understanding of the chemical, structural transformation and real catalytic phase for OER "catalyst". Moreover, the results show that the 3DOM design of self-supported Co9S8 catalyst could also benefits the catalytic performance by facilitating the mass and electronic transportation within the 3DOM framework. Finally, based on our up-to-date understanding of the OV in semiconductor physics and heterogeneous catalysis, a novel bi-functional catalyst support design strategy was proposed and demonstrated using OV-rich TiOxNy semiconductor. Excellent cycling stability and activity performance of such semiconductor supported cobalt catalyst in rechargeable zinc-air batteries is achieved.

Download or read book Energy Storage and Conversion Devices written by Anurag Gaur and published by CRC Press. This book was released on 2021-10-28 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a state-of-the-art overview of the research and development in designing electrode and electrolyte materials for Li-ion batteries and supercapacitors. Further, green energy production via the water splitting approach by the hydroelectric cell is also explored. Features include: • Provides details on the latest trends in design and optimization of electrode and electrolyte materials with key focus on enhancement of energy storage and conversion device performance • Focuses on existing nanostructured electrodes and polymer electrolytes for device fabrication, as well as new promising research routes toward the development of new materials for improving device performance • Features a dedicated chapter that explores electricity generation by dissociating water through hydroelectric cells, which are a nontoxic and green source of energy production • Describes challenges and offers a vision for next-generation devices This book is beneficial for advanced students and professionals working in energy storage across the disciplines of physics, materials science, chemistry, and chemical engineering. It is also a valuable reference for manufacturers of electrode/electrolyte materials for energy storage devices and hydroelectric cells.

Download or read book Novel Non Precious Metal Electrocatalysts for Oxygen Electrode Reactions written by Hui Yang and published by MDPI. This book was released on 2019-11-01 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research on alternative energy harvesting technologies, conversion and storage systems with high efficiency, cost-effective and environmentally friendly systems, such as fuel cells, rechargeable metal-air batteries, unitized regenerative cells, and water electrolyzers has been stimulated by the global demand on energy. The conversion between oxygen and water plays a key step in the development of oxygen electrodes: oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), processes activated mostly by precious metals, like platinum. Their scarcity, their prohibitive cost, and declining activity greatly hamper large-scale applications. This issue reports on novel non-precious metal electrocatalysts based on the innovative design in chemical compositions, structure, and morphology, and supports for the oxygen reaction.

Download or read book Advanced Materials for Clean Energy written by Qiang Xu and published by CRC Press. This book was released on 2015-04-06 with total page 623 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research for clean energy is booming, driven by the rapid depletion of fossil fuels and growing environmental concerns as well as the increasing growth of mobile electronic devices. Consequently, various research fields have focused on the development of high-performance materials for alternative energy technologies.Advanced Materials for Clean Ene

Download or read book Zinc air Battery R and D Research and Development of Bifunctional Oxygen Electrode written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies were conducted of the bifunctional oxygen electrode. The development of a rechargeable metal-oxygen (air) cell has been hampered to a great extent by the lack of a stable and cost effective oxygen electrode capable of use during both charge and discharge. The first type of bifunctional electrode consists of two distinct catalytifc layers. The oxygen reduction catalyst layer containing a supported gold catalyst is in contact with a hydrophilic nickel layer in which evolution of oxygen takes place. Loadings of gold from 0.5 to 1.0 mg/cm2 were investigated; carbon, graphite, metal, and spinel oxides were evaluated as substrates. The second part of the research effort was centered on developing a reversible oxygen electrode containing only one catalytic layer for both reduction and evolution of oxygen. The work was directed specifically to the study of perovskite type of oxides with the composition AA1BO3 where A is an element of the lanthanide series, A1 is an alkaline earth metal and B, a first row transition element. Initial polarization data obtained in unscrubbed air gave a value of approximately 200 millivolts vs Hg/HgO reference electrode at a current density of 50 ma/cm2. Electrodes were made both by roll-bonding and by pelletizing techniques and tested for polarization and cycle life. This study also indicates the optimum process conditions for the manufacture of oxides and fabrication of electrodes.

Download or read book Metal Oxide Nanocomposites written by B. Raneesh and published by John Wiley & Sons. This book was released on 2021-02-17 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal Oxide Nanocomposites: Synthesis and Applications summarizes many of the recent research accomplishments in the area of metal oxide-based nanocomposites. This book focussing on the following topics: Nanocomposites preparation and characterization of metal oxide nanocomposites; synthesis of core/shell metal oxide nanocomposites; multilayer thin films; sequential assembly of nanocomposite materials; semiconducting polymer metal oxide nanocomposites; graphene-based metal and metal oxide nanocomposites; carbon nanotube–metal–oxide nanocomposites; silicon mixed oxide nanocomposites; gas semiconducting sensors based on metal oxide nanocomposites; metal ]organic framework nanocomposite for hydrogen production and nanocomposites application towards photovoltaic and photocatalytic.

Download or read book Non precious Cathode Electrocatalytic Materials for Zinc air Battery written by Baejung Kim and published by . This book was released on 2013 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past decade, rechargeable batteries attracted the attention from the researchers in search for renewable and sustainable energy sources. Up to date, lithium-ion battery is the most commercialized and has been supplying power to electronic devices and hybrid and electric vehicles. Lithium-ion battery, however, does not satisfy the expectations of ever-increasing energy and power density, which of their limits owes to its intercalation chemistry and the safety.1-2 Therefore, metal-air battery drew much attention as an alternative for its high energy density and a simple cell configuration.1 There are several different types of metal-air batteries that convey different viable reaction mechanisms depending on the anode metals; such as Li, Al, Ca, Cd, and Zn. Redox reactions take place in a metal-air cell regardless of the anode metal; oxidation reaction at the anode and reduction reaction at the air electrode. Between the two reaction, the oxygen reduction reaction (ORR) at the air electrode is the relatively the limiting factor within the overall cell reactions. The sluggish ORR kinetics greatly affects the performance of the battery system in terms of power output, efficiency, and durability. Therefore, researchers have put tremendous efforts in developing highly efficient metal air batteries and fuel cells, especially for high capacity applications such as electric vehicles. Currently, the catalyst with platinum nanoparticles supported on carbon material (Pt-C) is considered to exhibit the best ORR activities. Despite of the admirable electrocatalytic performance, Pt-C suffers from its lack of practicality in commercialization due to their prohibitively high cost and scarcity as of being a precious metal. Thus, there is increasing demand for replacing Pt with more abundant metals due economic feasibility and sustainability of this noble metal.3-5 Two different attitudes are taken for solution. The first approach is by optimizing the platinum loading in the formulation, or the alternatively the platinum can be replaced with non-precious materials. The purpose of this work is to discover and synthesize alternative catalysts for metal-air battery applications through optimized method without addition of precious metals. Different non-precious metals are investigated as the replacement of the precious metal including transition metal alloys, transition metal or mixed metal oxides, and chalcogenides. These types of metals, alone, still exhibits unsatisfying, yet worse, kinetics in comparison to the precious metals. Nitrogen-doped carbon material is a recently well studied carbon based material that exhibits great potential towards the cathodic reaction.6 Nitrogen-doped carbon materials are found to exhibit higher catalytic activity compared to the mentioned types of metals for its improved conductivity. Benefits of the carbon based materials are in its abundance and minimal environmental footprints. However, the degradation of these materials has demonstrated loss of catalytic activity through destruction of active sites containing the transition metal centre, ultimately causing infeasible stability. To compensate for these drawbacks and other limits of the nitrogen-doped carbon based catalysts, nitrogen-doped carbon nanotubes (NCNT) are also investigated in the series of study. The first investigation focuses on a development of a simple method to thermally synthesize a non-precious metal based nitrogen-doped graphene (NG) electrocatalyst using exfoliated graphene (Ex-G) and urea with varying amounts of iron (Fe) precursor. The morphology and structural features of the synthesized electrocatalyst (Fe-NG) were characterized by SEM and TEM, revealing the existence of graphitic nanoshells that potentially contribute to the ORR activity by providing a higher degree of edge plane exposure. The surface elemental composition of the catalyst was analyzed through XPS, which showed high content of a total N species (~8 at.%) indicative of the effective N-doping, present mostly in the form of pyridinic nitrogen groups. The oxygen reduction reaction (ORR) performance of the catalyst was evaluated by rotating disk electrode voltammetry in alkaline electrolyte and in a zinc-air battery cell. Fe-NG demonstrated high onset and half-wave potentials of -0.023 V (vs. SCE) and -0.110 V (vs. SCE), respectively. This excellent ORR activity is translated into practical zinc-air battery performance capabilities approaching that of commercial platinum based catalyst. Another approach was made in the carbon materials to further improve the cost of the electrode. Popular carbon allotropes, CNT and graphene, are combined as a composite (GC) and heteroatoms, nitrogen and sulfur, are introduced in order to improve the charge distribution of the graphitic network. Dopants were doped through two step processes; nitrogen dopant was introduced into the graphitic framework followed by the sulfur dopant. The coexistence of the two heteroatoms as dopants demonstrated outstanding ORR performance to those of reported as metal free catalysts. Furthermore, effects of temperature were investigated through comparing ORR performances of the catalysts synthesized in two different temperatures (500 ??? and 900 ???) during the N-doping process (consistent temperature was used for S-doping). Through XPS analysis of the surface chemistry of catalysts produced with high temperature during the N-doping step showed absence of N-species after the subsequent S-doping process (GC-NHS). Thus, the synergetic effects of the two heteroatoms were not revealed during the half-cell testing. Meanwhile, the two heteroatoms were verified in the catalyst synthesized though using low temperature during the N-doping process followed by the S-doping step (GC-NLS). Consequently, ORR activity of the resulting material demonstrated promising onset and half-wave potentials of -0.117 V (vs. SCE) and -0.193 V (vs. SCE). In combination of these investigations, this document introduces thorough study of novel materials and their performance in its application as ORR catalyst in metal air batteries. Moreover, this report provides detailed fundamental insights of carbon allotropes, and their properties as potential elecrocatalysts and essential concepts in electrochemistry that lies behind zinc-air batteries. The outstanding performances of carbon based electrocatalyst are reviewed and used as the guides for further direction in the development of metal-air batteries as a promising sustainable energy resource in the future.

Download or read book Carbon Nanotubes and Graphene written by Kazuyoshi Tanaka and published by Newnes. This book was released on 2014-07-10 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon Nanotubes and Graphene is a timely second edition of the original Science and Technology of Carbon Nanotubes. Updated to include expanded coverage of the preparation, purification, structural characterization, and common application areas of single- and multi-walled CNT structures, this work compares, contrasts, and, where appropriate, unitizes CNT to graphene. This much expanded second edition reference supports knowledge discovery, production of impactful carbon research, encourages transition between research fields, and aids the formation of emergent applications. New chapters encompass recent developments in the theoretical treatments of electronic and vibrational structures, and magnetic, optical, and electrical solid-state properties, providing a vital base to research. Current and potential applications of both materials, including the prospect for large-scale synthesis of graphene, biological structures, and flexible electronics, are also critically discussed. Updated discussion of properties, structure, and morphology of biological and flexible electronic applications aids fundamental knowledge discovery Innovative parallel focus on nanotubes and graphene enables you to learn from the successes and failures of, respectively, mature and emergent partner research disciplines High-quality figures and tables on physical and mathematical applications expertly summarize key information – essential if you need quick, critically relevant data