Metal air battery has captured the spotlight recently as a promising class of sustainable energy storage for the future energy systems. Metal air batteries offer many attractive features such as high energy density, environmental benignity, as well as ease of fuel storage and handling. In addition, wide range of selection towards different metals exists where different energy capacity can be achieved via careful selection of different metals. The most energy dense systems of metal-air battery include lithium-air, aluminum-air and zinc-air. Despite the choice of metal electrode, oxygen reduction (ORR) occurs on the air electrode and oxidation occurs on the metal electrode. The oxidation of metal electrode is a relatively facile reaction compared to the ORR on the air electrode, making latter the limiting factor of the battery system. The sluggish ORR kinetics greatly affects the power output, efficiency, and lifetime of the metal air battery. One solution to this problem is the use of active, affordable and stable catalyst to promote the rate of ORR. Currently, platinum nanoparticles supported on conductive carbon (Pt/C) are the best catalyst for ORR. However, the prohibitively high cost and scarcity of platinum raise critical issues regarding the economic feasibility and sustainability of platinum-based catalysts. Cost reduction via the use of novel technologies can be achieved by two approaches. The first approach is to reduce platinum loading in the catalyst formulation. Alternatively platinum can be completely eliminated from the catalyst composition. The aim of this work is to identify and synthesize alternative catalysts for ORR toward metal air battery applications without the use of platinum or other precious metals (i.e., palladium, silver and gold). Non-precious metal catalysts (NPMC) have received immense international attentions owing to the enormous efforts in pursuit of novel battery and fuel cell technologies. Different types of NPMC such as transition metal alloys, transition metal or mixed metal oxides, chalcogenides have been investigated as potential contenders to precious metal catalysts. However, the performance and stability of these catalysts are still inferior in comparison. Nitrogen-doped carbon materials (NCM) are an emerging class of catalyst exhibiting great potential towards ORR catalysis. In comparison to the metal oxides, MCM show improved electrical conductivity. Furthermore, NCM exhibit higher activity compared to chalcogenides and transition metal alloys. Additional benefits of NCM include the abundance of carbon source and environmental benignity. Typical NCM catalyst is composed of pyrolyzed transition metal macrocycles supported by high surface area carbon. These materials have demonstrated excellent activity and stability. However, the degradation of these catalysts often involves the destruction of active sites containing the transition metal centre. To further improve the durability and mass transport of NCM catalyst, a novel class of ORR catalyst based on nitrogen-doped carbon nanotubes (NCNT) is investigated in a series of studies. The initial investigation focuses on the synthesis of highly active NCNT using different carbon-nitrogen precursors. This study investigated the effect of using cyclic hydrocarbon (pyridine) and aliphatic hydrocarbon (ethylenediamine) towards the formation and activity of NCNT. The innate structure of the cyclic hydrocarbon promotes the formation of NCNT to provide higher product yield; however, the aliphatic hydrocarbon promotes the formation of surface defects where the nitrogen atoms can be incorporated to form active sites for ORR. As a result, a significant increase in the ORR activity of 180 mV in half-wave potential is achieved when EDA was used as carbon-nitrogen precursor. In addition, three times higher limiting current density was observed for the NCNT synthesized from ethylenediamine. Based on the conclusion where highly active NCNT was produced from aliphatic hydrocarbon, similar carbon-nitrogen precursors with varying carbon to nitrogen ratio in the molecular structure (ethylenediamine, 1, 3-diaminopropane, 1, 4-diaminobutane) were adapted for the synthesis of NCNT. The investigation led to the conclusion that higher nitrogen to carbon ratio in the molecular structure of the precursors benefits the formation of active NCNT for ORR catalysis. The origin of such phenomena can be correlated with the higher relative nitrogen content of the resultant NCNT synthesized from aliphatic carbon precursor that provided greater nitrogen to carbon ratio. As the final nitrogen content increased in the molecular structure, the half-wave potential of the resultant NCNT towards ORR catalysis was increased by 120 mV. The significant improvement hints the critical role of nitrogen content towards ORR catalysis.

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.

Metal-air batteries (MABs) have attracted attention because of their high specific energy, low cost, and safety features. This book discusses science and technology including material selection, synthesis, characterization, and their applications in MABs. It comprehensively describes various composite bifunctional electrocatalysts, corrosion/oxidation of carbon-containing air cathode catalysts, and how improvements can be achieved in the catalytic activities of oxygen reduction reaction and oxygen evolution reaction and their durability/stability. This book also analyzes, compares, and discusses composite bifunctional electrocatalysts in the applications of MABs, matching the fast information of commercial MABs in requirements. Aimed at researchers and industry professionals, this comprehensive work provides readers with an appreciation for what bifunctional composite electrocatalysts are capable of, how this field has grown in the past decades, and how bifunctional composite electrocatalysts can significantly improve the performance of MABs. It also offers suggestions for future research directions to overcome technical challenges and further facilitate research and development in this important area.

Offering comprehensive coverage of this hot topic, this two-volume handbook and ready reference treats a wide range of important aspects, from synthesis and catalytic properties of carbon materials to their applications as metal-free catalysts in various important reactions and industrial processes. Following a look at recent advances in the development of carbon materials as carbon-based metal-free catalysts, subsequent sections deal with a mechanistic understanding for the molecular design of efficient carbon-based metal-free catalysts, with a special emphasis on heteroatom-doped carbon nanotubes, graphene, and graphite. Examples of important catalytic processes covered include clean energy conversion and storage, environmental protection, and synthetic chemistry. With contributions from world-leading scientists, this is an indispensable source of information for academic and industrial researchers in catalysis, green chemistry, electrochemistry, materials science, nanotechnology, energy technology, and chemical engineering, as well as graduates and scientists entering the field.

Offering comprehensive coverage of this hot topic, this two-volume handbook and ready reference treats a wide range of important aspects, from synthesis and catalytic properties of carbon materials to their applications as metal-free catalysts in various important reactions and industrial processes. Following a look at recent advances in the development of carbon materials as carbon-based metal-free catalysts, subsequent sections deal with a mechanistic understanding for the molecular design of efficient carbon-based metal-free catalysts, with a special emphasis on heteroatom-doped carbon nanotubes, graphene, and graphite. Examples of important catalytic processes covered include clean energy conversion and storage, environmental protection, and synthetic chemistry. With contributions from world-leading scientists, this is an indispensable source of information for academic and industrial researchers in catalysis, green chemistry, electrochemistry, materials science, nanotechnology, energy technology, and chemical engineering, as well as graduates and scientists entering the field.

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.

This book is a printed edition of the Special Issue "Electrocatalysis in Fuel Cells" that was published in Catalysts

Metal-Air Batteries: Principles, Progress, and Perspectives covers the entire spectrum of metal-air batteries, their working principles, recent advancement, and future perspectives. Leading international researchers address materials design, electrochemistry, and architectural aspects. The fundamentals of metal-air materials for cathode and anode, their synthetic approaches, chemistries to modify their properties to provide high energy and power densities, along with long life and stable electrochemical characteristics are detailed. Key Features: Covers materials, chemistry, and technologies for metal-air batteries Reviews state-of-the-art progress and challenges in metal-air batteries Provides fundamentals of the electrochemical behavior of various metal-air batteries Offers insight into tuning the properties of materials to make them suitable for metal-air batteries Provides new direction and a better understanding to scientists, researchers, and students working in diverse fields This is a unique offering and a valuable resource for a wide range of readers including those in academia and industries worldwide.

Carbon-Based Metal Free Catalysts: Preparation, Structural and Morphological Property and Application covers the different aspects of carbon-based metal free catalysts, including the fabrication of catalysts from natural sources and carbon allotropes, their manufacturing and design, characterization techniques, and applications. Special features in the book include illustrations and tables which summarize up-to-date information on research carried out on manufacturing, design, characterization and applications of metal free catalysts. This book assembles the information and knowledge on metal free catalysts and emphasizes the concept of green technology in the field of manufacturing and design. It is an ideal reference source for lecturers, students, researchers and industrialists working in the field of new catalyst development, especially polymer composites and is a valuable reference book handbook for teaching, learning, and research. - Describes the design on metal-free catalysts - Includes manufacturing technique of carbon-based metal free catalysts - Lists applications of carbon-based metal free catalysts - Discusses the characterization of carbon-based metal free catalysts

In this second volume in the first book series on nanocarbons for advanced applications the highly renowned series and volume editor has put together a top author team of internationally acclaimed experts on carbon materials. Divided into three major parts, this reference provides a current overview of the design, synthesis, and characterization of nanocarbons, such as carbon nanotubes, fullerenes, graphenes, and porous carbons for energy conversion applications. It covers such varied topics as electrocatalysts for oxygen reduction reactions in the different types of fuel cells, metal-air batteries and electrode materials for photovoltaic devices, as well as photocatalysts, electrocatalysts and photoelectrocatalysts for water splitting. Throughout, the authors highlight the unique aspects of nanocarbon materials in these fields, with a particular focus on the physico-chemical properties which lead to enhanced device performances.