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About this book

This book focuses on nanocarbons (carbon nanotubes, graphene, nanoporous carbon, and carbon black) and related materials for energy conversion, including fuel cells (predominately proton exchange membrane fuel cells [PEMFC]), Li-ion batteries, and supercapacitors. Written by a group of internationally recognized researchers, it offers an in-depth review of the structure, properties, and functions of nanocarbons, and summarizes recent advances in the design, fabrication and characterization of nanocarbon-based catalysts for energy applications. As such, it is an invaluable resource for graduate students, academics and industrial scientists interested in the areas of nanocarbons, energy materials for fuel cells, batteries and supercapacitors as well as materials design, and supramolecular science.

Table of Contents

Frontmatter

Chapter 1. Carbon Nanotube-Based Fuel Cell Catalysts-Comparison with Carbon Black

Toward the next-generation fuel cell systems, the development of a novel electrocatalyst for the polymer electrolyte fuel cell (PEFC) is crucial to overcome the drawbacks of the present electrocatalyst. As a conductive supporting material for the catalyst, carbon nanotubes (CNTs) have emerged as a promising candidate because they have many remarkable electronic properties. In this chapter, we summarize unique properties of polymer (polybenzimidazole)-coated CNT-based catalysts for high-temperature (HT) PEFC and discuss their potential as a new electrocatalyst for the HT-PEFC in comparison with the conventional ones. We focus on the very high durability of the CNT-based catalysts under high temperature and non-humidified operation as well as conventional low temperature and high humidified operation.
Naotoshi Nakashima, Tsuyohiko Fujigaya

Chapter 2. Carbon Nanotube-Based Direct Methanol Fuel Cell Catalysts

The development of a durable and methanol-tolerant electrocatalyst with a high oxidation reduction reaction (ORR) activity is still a significant and important challenge. In this chapter, we focus on the use of carbon nanotubes and mesoporous carbon as well as carbon black for comparison as a carbon support for direct methanol fuel cells (DMFCs) since they are electrochemically stable. Here such stable nanocarbons are wrapped by polymer (polybenzimidazole) , and the wrapped nanocarbons/Pt catalysts exhibited high methanol tolerance , high CO-tolerance in methanol oxidation reaction, suggesting that the catalysts are important for an anode material for use in DMFCs.
Naotoshi Nakashima

Chapter 3. High-Temperature Polymer Electrolyte Membrane Fuel Cells

An introduction to high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC) is given. The rationale behind the increased temperature is outlined in terms of tolerance to carbon monoxide, less critical water management, cooling issues, and quality of waste heat. Additionally, elevated temperature might imply a shorter route to platinum-free oxygen reduction catalysts. The means for making operation possible at temperatures between 100 and 200 °C is to dope a thermally stable polymer, typically polybenzimidazole, with proton conductive phosphoric acid. Fuel cells based on this membrane system show remarkable stability when operated at 160 °C. The different materials and cell components used are reviewed with comparison to conventional low-temperature polymer fuel cells and phosphoric acid fuel cells all along. The role of nanostructured carbon materials is mostly in relation to composite membranes and catalysts. For the membranes, carbon nanotubes and graphene have been applied as structural fillers to improve mechanical properties. For catalysts, carbon black, carbon nanotubes, and graphene have been used as catalyst support for the catalytic platinum nanoparticles. Moreover, the main trend within development of alternatives to platinum as oxygen reduction catalyst is iron–nitrogen–carbon structures. These materials and their possible application in HT-PEMFC are discussed.
Jens Oluf Jensen, David Aili, Yang Hu, Lars N. Cleemann, Qingfeng Li

Chapter 4. The Role of Carbon Blacks as Catalyst Supports and Structural Elements in Polymer Electrolyte Fuel Cells

In polymer electrolyte fuel cells (PEFCs) based on proton exchange membranes (PEM), carbon blacks have been used as supports for platinum and its alloys since the 1970s.
Masahiro Watanabe, Donald A. Tryk

Chapter 5. Understanding the Stability of Nanoscale Catalysts in PEM Fuel Cells by Identical Location TEM

Proton Exchange Membrane Fuel Cells (PEMFCs) are promising energy conversion devices due to their high energy density, low operating temperature, high efficiency, and ultimate cleanness—no carbon dioxide emission. Yet, a critical factor which significantly influences the performance of PEMFC is the stability of platinum group metal catalysts, which consists of Pt or Pt-alloy nanoparticles (2–5 nm in diameter) supported on the surface of carbon particles (40–100 nm in diameter) during fuel cell cycling. In fact, the Pt or Pt-alloy catalysts typically dissolve and/or grow in size with the number of cycles. In order to reveal the degradation mechanisms of these nanocatalysts , we have developed an experimental setup which replicates on a TEM grid the effect of voltage cycling on the cathode of an MEA. Using this approach, it is possible to track the behavior of a single nanoparticle at different stages of voltage cycling at the nano/atomic scale. Through these direct observations, we demonstrated that due to carbon corrosion the defects appear at the carbon/nanoparticle interface, which in turn result in particle migration and consequently coalescence. We also revealed the mass transfer mechanisms during the coalescence of nanoparticles. In addition, we revisited the commonly held view on the mechanism of particle dissolution and deposition. Thus, during the later stages of cycling, when the concentration of dissoluble Pt reaches a critical amount, single atoms and atomic clusters appear on the carbon support, which consequently move toward other particles and re-deposit on their surface. Furthermore, we investigated the atomic surface evolution of Pt-Ni nanoparticles under the effect of voltage through advanced spectroscopy technique such as EDS.
Somaye Rasouli, Paulo J. Ferreira

Chapter 6. Synthesis of Nanoporous Carbon and Their Application to Fuel Cell and Capacitor

In Sect. 6.1, syntheses of nanoporous carbons are summarized. Especially control of pore size distributions , which is necessary to enhance the electrode functions of fuel cells, capacitors, and so on, is introduced. In Sect. 6.2, applications of the nanoporous carbon to a polymer electrolyte fuel cell (PEFC) as well as direct methanol fuel cell (DMFC) are summarized; here, the nanocarbon was wrapped by polybenzimidazole , and then Pt-nanoparticles were deposited on it. Such obtained catalysts showed a very high PEFC durability and acted a high CO tolerant, high methanol oxidation reaction, durable, and efficient DMFC catalyst under high methanol concentration (4 M, 8 M). In Sect. 6.3, applications of the nanoporous carbon to electric double-layer (EDL) capacitors were summarized. Mesoporous and macroporous carbons showed surface area-dependent capacity properties. Specific microporous carbons with worm-like shape and appropriate pore size showed unusually high EDL capacities due to desolvation of electrolyte ions in the nanospace. Hierarchical porous structure with the micropores and mesopores was effective to yield high gravimetric EDL capacities.
Koki Urita, Isamu Moriguchi, Naotoshi Nakashima

Chapter 7. Theoretical Approach for Nanocarbon-Based Energy Catalyst Design

Decoration of carbon nanotubes with nanoparticles and covalent modification is a useful tool to introduce new catalytic, electrochemical, optical function or fine-tune existing ones. Unfortunately, it is difficult to predict, let alone design, these new properties due to the complicated underlying physics and chemistry. With the rapid development of computational tools in the recent years, it is more and more possible to perform high-quality simulation of chemically realistic models of modified carbon nanotubes. First, in this chapter, we review calculations on exciton trapping and luminescence of single-wall carbon nanotubes. Then, we discuss how the curved wall of carbon nanotubes can stabilize metal nanoparticles, which can be used as catalysts.
Gergely Juhasz, Aleksandar Staykov

Chapter 8. Doped and Decorated Carbon Foams for Energy Applications

Here, we summarize progress over the past 9 years in the development of a new class of template -free carbon foam derived from the foaming and pyrolysis of sodium alkoxides, and their use in energy-related applications. Carbon foams offer a unique platform for applications in catalysis, energy storage , gas adsorption and sensing . They can have large surface area, a variety of pore sizes, and high electrical conductivity. In addition, they can be decorated with a wide variety of different nanoparticles tailored to suit the application, or doped with various heteroatoms to modify the nature of the carbon itself. The carbon foams described here are synthesized from cheap sodium alkoxide or alcohol-based feedstocks and do not require sacrificial templating to achieve the porous structure. Instead, these carbon foams are formed by foaming during decomposition of the alkoxide precursors . Despite the extremely simple method of production and the low cost of the product, the material properties are impressive. For example, surface areas in the region of 2500 m2/g can be routinely achieved, with atomically thin carbon walls. Carbon foams produced in this manner have been applied as hydrogen storage materials, electrochemical sensors, materials for spintronics , electrodes for lithium-ion batteries , oxygen reduction reaction electrocatalysts, carbon dioxide conversion electrocatalysts and superhydrophobic materials . In this chapter, the development of carbon foams , nanoparticle decorated carbon foams, and heteroatom-doped carbon foams for these applications will be reviewed. Future prospects for this material will also be speculated upon.
Stephen M. Lyth

Chapter 9. Hydrogen-Evolving CNT-Photocatalysts for Effective Use of Solar Energy

H2-evolving photocatalysts based on semiconducting single-walled carbon nanotubes (s-SWCNTs) were fabricated via a physical modification of s-SWCNTs using poly(amidoamine) dendrimer having C60 or an oligomethylene core. These CNT-photocatalysts possess the coaxial nanowire structure and show H2-evolving activity under visible and even NIR illumination since s-SWCNTs act as light absorbers, although H2 evolution reaction (HER) from water triggered by the photoexcitation of s-SWCNTs is quite rare. A coaxial s-SWCNT/C60 heterojunction was found to be quite useful for the construction of CNT-photocatalysts due to the efficient generation of mobile carriers, such as holes and electrons, via the exciton dissociation in SWCNT. Owing to the combination flexibility between the core-SWCNT and the shell material of CNT-photocatalysts , various types of CNT-photocatalysts can be synthesized in order to control the efficiency and the active wavelengths of photocatalytic HER. For example, by introducing a TiOx shell into the CNT-photocatalyst, apparent quantum yield (AQY) of HER reached 47% under 450-nm light illumination. SWCNT/fullerodendron nanocomposite having (8,3)tube at the core exhibited efficient H2 evolution , of which AQY was 7.3% under 1000-nm light illumination. It is notable that the CNT-photocatalysts are potentially useful to construct a Z-scheme photocatalytic system for the overall water splitting .
Yutaka Takaguchi, Tomoyuki Tajima, Hideaki Miyake

Chapter 10. Carbon-Based Electrodes and Catalysts for the Electroreduction of Carbon Dioxide (CO2) to Value-Added Chemicals

The electroreduction of carbon dioxide (CO2) to value-added carbon chemical feedstocks could be a sustainable approach for reducing and/or recycling excess CO2 emissions . However, key challenges remain in the development of low-cost catalysts and electrode materials that can enable the active, selective, and stable electroreduction of CO2 to a target product. This chapter highlights some of the recent advances in the development of carbon-based catalysts and electrodes for the electroreduction of CO2, advances that can in principle enable the development of low cost and tunable systems. Also, presented is a summary of the fundamental thermodynamics of CO2 electroreduction, commonly used performance metrics, as well as the overall status of the field.
Sumit Verma, Uzoma O. Nwabara, Paul J. A. Kenis

Chapter 11. Recent Progress in Non-precious Metal Fuel Cell Catalysts

Polymer electrolyte fuel cells (PEFCs) have received a great deal of attention for their utility in applications such as transportation, portable devices, and combined heat and power systems due to their energy efficiency and scalability. The cost and scarcity of platinum is a major obstacle to the globalization of PEFCs; therefore, it is necessary to develop non-precious metal (NPM) cathode catalysts. This chapter provides an overview of the recent progress on the research and development of NPM oxygen reduction reaction (ORR) catalysts for PEFCs. The first half describes carbon-based Fe/N/C and N/C cathode catalysts, which are prepared by pyrolyzing Fe, N, and C-containing precursors. Nanocarbon with Fe and N-based active sites, which are synthesized in the pyrolysis of polyimide nanoparticles, are of particular interest. The second half of the chapter describes the research on cathode catalysts prepared by combining group 4 and 5 oxides with nanocarbons. In this catalyst design, the nanocarbon plays an important role in increasing the electrical conductivity of the catalyst layers while the oxide contributes to the ORR.
Yuta Nabae, Akimitsu Ishihara

Chapter 12. Carbon Nanotube-Based Non-Pt Fuel Cell Catalysts

Carbon nanotubes are important support materials for electrocatalysts in fuel cells. In this chapter, non-Pt catalysts supported on carbon nanotubes for oxygen reduction reaction or bifunctional oxygen electrodes are summarized. According to the kinds of catalysts and the pretreatments of the carbon nanotubes, the catalysts are divided into five categories: M-N4 catalysts supported on pristine carbon nanotubes, M-N4 catalysts supported on functionalized carbon nanotubes, transition metal oxides and phosphides supported on oxidized carbon nanotubes , transition metal oxides and phosphides supported on polymer-functionalized carbon nanotubes, and N-doped carbon nanotubes . The corresponding preparation methods, microstructures, and electrocatalytic activities are summarized.
Jun Yang, Naotoshi Nakashima

Chapter 13. Polymer Electrolyte Membranes: Design for Fuel Cells in Acidic Media

Polymer electrolyte membranes with acidic functions are useful for a wide variety of applications. In particular, fuel cells have attracted considerable attention due to their high energy conversion efficiency and low pollution level. In this chapter, design strategies for proton conductive polymer electrolyte membranes aiming at next-generation fuel cells are described. In the first session, effect of sulfonic acid containing aromatic groups onto the membranes is discussed. A simplest possible structure, the sulfo-1,4-phenylene unit, as the hydrophilic component contributes to high proton conductivity as well as mechanical stability. The membrane exhibits excellent fuel cell performance comparable to that with state-of-the-art Nafion membranes. In the second session, a new copolymer composed of perfluoroalkyl and sulfophenylene groups is discussed for improving the interfacial mass transport (water and protons) with the catalyst layers. The partially fluorinated membrane with well-controlled, small-scale, phase-separated morphology derives high cathode (oxygen reduction reaction) performance.
Kenji Miyatake

Chapter 14. Development of Polymer Electrolyte Membranes for Solid Alkaline Fuel Cells

Solid-state alkaline fuel cells (SAFCs) , which use anion-exchange membranes (AEMs) , offer several advantages over prevailing proton exchange membrane fuel cells (PEMFCs), namely higher reaction kinetics for fuel oxidation and a less corrosive environment that allows for the application of a variety of cheap metals and carbon-alloy catalysts. This promising technology has the potential to overcome many problems linked with PEMFC via the construction of low-cost, high-energy density conversion devices. In addition, a vast range of liquid fuel types are available to be used by the catalyst design incorporated in this technology. Unfortunately, the development of high-performance membranes remains a key issue for real-world application of these types of systems. Currently, AEMs encounter the following two major challenges:
  • The ion conductivity of the current membrane is low. Most highly conductive membranes are highly water-absorbable, and thus do not have considerable dimensional stability.
  • Relatively low chemical stability of both the backbone and anion-exchange groups in the membrane.
Alkaline stability of AEM is significantly important for the long-term operation of any device using this technology. As such, issues surrounding the mechanisms by which degradation occurs, its material design, and the technology associated with this degradation problem often present themselves as major hurdles in the advancement of AEMs. This entry reviews recent developments in the field aimed at overcoming these problems.
Shoji Miyanishi, Takeo Yamaguchi

Chapter 15. Carbon Nanotube-Based Enzymatic Biofuel Cells

Enzymatic biofuel cells (BFCs) are bioelectric devices that utilize oxidoreductase enzymes to catalyze the conversion of chemical energy into electric energy. Here, it is reviewed that the carbon nanotube (CNT) is a key material to improve the performance of enzyme electrodes and BFCs. Thanks to the high specific surface area of the nanostructured CNT-based electrodes, the electrons involved in the bio-electrocatalytic processes can be efficiently transferred from or to an external circuit. These high-performance enzyme electrodes were applied to the insertion-type and the patch-type BEF devices. The insertion BFC device generates electricity directly from biofluids like fruits juice and animal bloods, and serves as a self-powered biosensor for sugar in biofluids. The patch-type medical devices drive the iontophoretic flow through the skin to accelerate drug dosing and wound healing.
Matsuhiko Nishizawa

Chapter 16. Improved Synthesis of Graphene-Like Materials and Their Application

Basic research on graphene is maturing, and now the application of graphene has been actively studied. For use in industrial products, it is indispensable to supply a sufficient amount of graphene; however, mass production of high-quality and defectless graphene is potentially difficult. Recent trends focus on graphene-like materials , which are prepared by chemical and electrochemical techniques. In this section, synthesis methods of graphene-like materials which have potentials for mass production are disclosed.
Yuta Nishina

Chapter 17. Alcoholic Compounds as an Efficient Energy Carrier

We introduce a power circulation system using redox reactions of glycolic acid (GC) , a monovalent alcoholic compound, and oxalic acid (OX) , a divalent carboxylic acid for the efficient circulation of renewable electricity. Electric power is efficiently accumulated in GC via four-electron reduction of OX on TiO2 electrodes. Mapping for phases of TiO2 using electron energy-loss spectroscopy revealed that anatase-type TiO2 particles exhibit superior catalytic activities, i.e. highly selective electroreduction of OX to produce GC, compared to rutile-type ones. GC was successfully produced on porous TiO2 spheres purely composed of the anatase phase under mild conditions in the potential region of −0.5 to −0.7 V versus the RHE at 50 °C with high efficiency and selectivity (70–95% Faradaic efficiency and >98% selectivity). Direct transformation of solar energy into chemical energy in GC was also achieved using a photo-assisted electrochemical cell employing oxide semiconductor photoelectrodes as the anode for water oxidation and TiO2 cathode for OX reduction. A liquid flow-type electrolyzer that continuously produces GC from OX was constructed by employing a polymer electrolyte electrolyzer, named a polymer electrolyte alcohol electrosynthesis cell (PEAEC) . Porous anatase TiO2 directly grown on Ti mesh (TiO2/Ti-M) was newly fabricated as the cathode electrode having favourable substrate diffusivity. A membrane electrode assembly composed of the TiO2/Ti-M, Nafion and an IrO2 supported on a gas-diffusion carbon electrode (IrO2/C) was applied to the PEAEC. The PEAEC achieves a maximum energy conversion efficiency of 49.6% or a continuous 99.8% conversion of 1 M OX, which is an almost saturated aqueous solution at room temperature. Electronic power generation via electro-oxidation of GC was demonstrated. The catalytic activity test on various metal materials revealed that Rh, Pd, Ir and Pt have preferable features as a catalyst for GC electro-oxidation, and Pt exhibits the highest catalytic activity. A carbon-supported Pt catalyst (Pt/C) in alkaline conditions, especially in LiOH aq., showed higher activity, durability and product selectivity for electro-oxidation of GC rather than those in acidic media. These efforts will contribute to efficient utilization of renewable electricity.
Takashi Fukushima, Sho Kitano, Masaaki Sadakiyo, Miho Yamauchi

Chapter 18. Nanocarbons in Li-Ion Batteries

The ever-increasing demand for advanced power sources with higher energy density and various form factors strongly pushes us to search for new battery materials and structures beyond current state-of-the-art Li-ion batteries (LIBs). Recent progress in nanoscience and nanotechnology suggests opportunities to develop novel electrode materials and architectures for next-generation Li-ion batteries. Among numerous nanomaterials reported to date, nanocarbons have garnered considerable attention as a promising battery element to enrich electrode chemistry and materials. Of various nanocarbons, carbon nanotube and graphene exhibit outstanding electrical and mechanical properties, large surface area, and unique structural characteristics, which thus bring significant improvements in electrochemical performance and flexibility/design diversity of lithium-based power sources. Here, we describe current status and challenges of nanocarbons in LIBs, with a particular focus on their potential application to anode materials, conductive agents, current collectors, and structure-directing substances for electrodes.
Seok-Kyu Cho, JongTae Yoo, Sang-Young Lee

Chapter 19. Nanocarbons and Their Composite Materials as Electrocatalyst for Metal–Air Battery and Water Splitting

We discuss multiple advantages of nanocarbon and their composite materials in metal–air batteries and alkaline water electrolyzer due to their unique properties and structural integrity. In energy devices, the nanocarbon-based electrocatalysts play a significant role to decide the cell efficiency and their stability. As compared with nanocarbon, the nanocarbon composites with the transition metal, metal oxide, and/or metal chalcogenides /pnictides provide additional electrocatalytic active sites to enhance the cell performance. Overall, we have discussed the recent progress on various nanocarbon composites design, tuning of their unique properties, and pros and cons in advanced metal–air batteries and water electrolyzer.
Suyeon Hyun, Arumugam Sivanantham, Sangaraju Shanmugam

Chapter 20. Applications of Carbon Nanotubes in Solar Cells

Carbon nanotubes (CNTs) have attracted the interest of numerous researchers in materials sciences and engineering because of their superior electronic and optoelectronic properties. Extensive progress has been realized through the use of CNTs, especially single-walled carbon nanotubes (SWCNTs), in optoelectronics and energy harvesting devices, including solar cells, light-emitting diodes, touch panels, and transistors. Here, we review the novel applications of CNTs in solar cells. The use of CNTs as additives, light absorbers, carrier transporters, and transparent electrodes in solar cells has been reported over the past decade. CNTs are applicable to various solar cell technologies, including CNTs/Si heterojunction , organic–inorganic perovskite, dye-sensitized, and organic photovoltaic solar cells. This review surveys recent progress in the application of CNTs to photovoltaics.
Feijiu Wang, Kazunari Matsuda

Chapter 21. Photon Energy Up-conversion in Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs) are quasi-one-dimensional nanostructures in which graphene is rolled up in a cylindrical shape. Recently, it has been discovered that SWNTs with defect-induced localized states exhibit an interesting and potentially useful anti-Stokes light-emission phenomenon called up-conversion photoluminescence (UCPL) in the near-infrared wavelength range; SWNTs can efficiently emit the luminescence of a wavelength shorter than the wavelength of the excitation light. Furthermore, recent studies have revealed that the UCPL of SWNTs is enabled by the absorption of ambient thermal energy as the source of the photon energy up-conversion . The discovery of efficient UCPL of SWNTs may lead to new applications, such as UCPL imaging of blood vessels and organs in the deep inside of a living animal’s body with negligible autofluorescence using low-cost near-infrared wavelength excitation light source and conventional silicon-based detectors.
Yuhei Miyauchi

Chapter 22. Carbon Nanotube-Based Thermoelectric Devices

Thermoelectric (TE) conversion is one of the key technologies to realize a sustainable society since large quantities of energy [1, 2] have been wasted as heat [3]; therefore recovery of heat into electricity via TE technology is quite attractive.
Tsuyohiko Fujigaya

Backmatter

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