Polymer-Engineered Nanostructures for Advanced Energy Applications

Electrospinning is increasingly used as a simple and straightforward technique to fabricate one-dimensional fibers from both organic and inorganic materials. These one-dimensional fibers with controlled sizes possess some unique features such as large surface area to volume ratio, high porosity, and low density. Compared to other conventional materials, these features make them attractive for applications such as energy harvesting, energy storage, super-hydrophobic membranes, and sensors. This chapter provides an overview on the synthesis of inorganic fibers through polymer-mediated electrospinning. Some of the common techniques employed by many researchers, such as solgel combined with electrospinning, emulsion electrospinning, and electrospinning combined with solid–gas reaction, to fabricate metal oxide fibers are discussed. In addition, techniques to fabricate ceramic and metal oxide fibers having different morphologies and hierarchical structures are described. Recent applications of electrospun metal oxide fibers are finally highlighted with a focus on filtration, sensors, photocatalysis, and energy.

In this chapter, nanostructures templated by polymer microbead, which is usually made of polystyrene with a diameter range of 300 nm–1 µm, are reviewed. We first focus on formation of the microbead monolayer in terms of the driving force for self-assembly, the junction among the neighbouring microbeads and the uniformity of microbead monolayer. Then, we discuss applications of microbead monolayer as a template for nanostructure fabrication. Because the assembled monolayer features an ordered structure scaling up to centimetre (cm) size, microbead-templated nanostructures also show an ordered arrangement in cm size, which is attractively simple and can be achieved in common laboratories. From the microbead monolayer template, the subsequent fabrication approaches include electrochemical deposition, sputter coating deposition, plasma etching, annealing, wet etching and dry etching as well. The templating targets include metals, semiconductors, polymers, and nano-moieties such as nanobeads and nanocubes. Various types of nanostructure have been fabricated using these approaches individually or by combining them to increase the flexibility of fabrication. Controllable and ordered nanostructures have been achieved by adjusting the fabrication parameters. Finally, we review the application of nanostructures templated by the polymer microbeads, particularly as surface-enhanced Raman scattering (SERS) substrates. We demonstrate approaches for identifying the position of the hot spot and how to achieve single-molecule detection.

Putting metal into macromolecules has drawn immense attention in materials science due to the tunable features and large spectrum of potential applications of these metallopolymers. However, a precise control in metallopolymer nanostructure is always required for tailoring the final application. A variety of nanopatterning methods has been reported in recent years and can be simply classified into either bottom-up or top-down approaches. This chapter will be focused on the general strategy for the fabrication of well-defined nanostructures of metal-containing polymers by using top-down techniques with selected examples.

The synthesis of porous organic polymer materials with nanoscale range has long been an important science subject and received an increasing level of research interest owing to their essential properties merging both of the porous materials and polymers such as low skeleton density, processability, easy functionality, and diverse synthetic methods. In this chapter, several porous polymer materials including covalent organic frameworks (COFs), hypercrosslinked polymers (HCPs), conjugated microporous polymers (CMPs), polymers of intrinsic microporosity (PIMs), and macroporous polymers from high internal phase emulsions (HIPEs) will be introduced as well as their diversiform synthetic methods and potential applications including gas storage, carbon capture, separation, catalysis, sensing, energy storage and conversion.

Since colorimetric sensors can respond to environmental stimulus by the color change, they are widely concerned because of their low cost and low power consumed. A new material in colorimetric sensors called photonic crystals (PCs) was fabricated for sensing the external stimulus. PCs are composed of periodic ordered dielectrics nanostructures with photonic band gap. Different from dye, PCs can exhibit vivid structural color, which can be tailored by lattice spacing variation under the external stimulus. The PCs materials have important applications in the fields of display, sensors, anti-counterfeiting, and others. In this chapter, we will discuss strategies and mechanism for the fabrication of responsive PCs. Moreover, PCs materials demonstrate response characteristic under external stimuli, such as mechanical force, temperature, pH, ionic species, solvents, biomolecules, light, electrical or magnetic fields, and others. Challenge and perspective of this emerging area will also be discussed at the end of this chapter.

Here in this review, we describe recent advances and challenges toward the design and development of stimuli-responsive polymeric materials that are self-assembled to from nanostructured building blocks. A short introduction describing non-materials in general along with the different synthetic methodologies for making polymeric materials that are responsive toward several physical, chemical, or biochemical stimuli such as temperature, light, pH, redox reaction, ionic strength, glucose, CO₂, enzyme. A general discussion on the cause of thermoresponsivenes in polymers having either lower critical solution temperature (LCST) or upper critical solution temperature (USCT) transition is described. This followed by the detailed description of the nanostructured polymer materials, which are responsive to temperature. pH-responsive polymers are important materials in terms of their diverse range of applications, such as drug delivery, diagnostics. Thus, we describe the details of synthesis of different polymer and copolymer systems and their pH-responsive assembly into several types of nanostructures such as micelles, vesicles followed by their pH-triggered disassembly in aqueous solution. The polymeric nanomaterials responsive to light in particular has attracted much attention since light can be localized in time and space and can be applied from outside of the system. Therefore, it is indeed important to discuss the nanostructured polymer materials that are responsive to light followed by their potential applications. Polymeric nanomaterials that are responsive to other different stimuli such as redox reaction, CO₂, sugar are also described in this review. Finally, we also describe different multi-stimuli-responsive nanostructured polymer systems. The main goal of this chapter is to serve as a guideline to inspire future researchers toward the design and synthesis of stimuli-responsive materials so that novel applications and new generations of smart materials can be realized.

There is ever-increasing demand for energy worldwide. The constant use of energy particularly in portable devices and vehicles has required highly efficient and high-capacity energy storage. Materials research is at the front of addressing the society’s demand for energy storage. This chapter focuses on the fabrication and use of polymer and carbon-based nanofibers for energy storage. The widely used fabrication methods such as chemical vapour deposition, electrospinning and the recently developed methods including controlled freezing and gelation for nanofibers have been described. Upon the preparation of polymer nanofibers, carbon nanofibers can be produced by pyrolysis under inert atmosphere. We then review the applications of carbon-based nanofibers in different types of rechargeable batteries and supercapacitors. The chapter is completed with conclusion and outlook.

In recent years, tremendous research effort has been focused on novel supercapacitors because of their stable ultra-high power density, cycling life, and fast charging–discharging rate. These researches aimed at increasing the energy density of supercapacitors without sacrificing high power capability so that they reach the levels achieved in batteries and at lowering fabrication costs. For this purpose, conjugated polymers have been effectively integrated with graphene nanosheets for supercapacitor applications, which sparked great excitement in superior performance owing to their synergistic effects on charge absorption and transportation, and extraordinary characteristic of the reversible oxidation–reduction activity which enables a high energy density. In this chapter, simple pathways to tailor polymer/graphene composites architectures for improving supercapacitor performances were summarized. Further, a theoretical model has been established to quantify the influences of various factors on the supercapacitor behaviors. On this basis, challenges and perspectives in this exciting field are also discussed. These results not only provide fundamental insight into supercapacitors but also offer an important guideline for future design of advanced next-generation supercapacitors for industrial and consumer applications.

Conducting polymers/inorganic nanohybrids embrace the key to basic advances in electrical energy system, which are very important in order to meet the challenge of global warming and the finite nature of fossil fuels. This architecture has opened the possibility to combine in a single material both the attractive properties of a mechanically and thermally stable inorganic backbone and the specific chemical reactivity, dielectric, ductility, flexibility, and processability of the conducting polymer. Nanohybrids in particular offer combinations of properties as electrodes in a range of electrical energy devices. This chapter explains some recent developments in the discovery of electrodes for rechargeable batteries, fuel cells, and supercapacitors. The advantages and disadvantages of the conducting polymers/inorganic hybrid electrode design for such devices are also discussed.

Polymer-derived carbon/inorganic nanocomposites are developed as high-performed materials for electrochemical energy conversion and storage. Via the hybridization with carbon species, the enhanced conductivity, varied band structures, and promoted stability are responsible for the optimized thermodynamics and kinetics of electrochemical processes, resulting in the high capacity/activity and good durability. In this chapter, the general strategies to construct nanocomposites will be firstly introduced. And then, electrocatalytic hydrogen evolution reaction and lithium ion batteries are taken as the examples to illustrate the enhancement of inorganics by the integration with polymer-derived carbon. Their structure–activity relationship is focused in discussing the promising electrochemical performance. We seek to provide some rational design of key structures and properties for efficient electrode materials via the controlled derivation of polymer-derived carbon and their composites.

The flammable organic solvent-based electrolytes used in lithium batteries impose serious safety concerns and temperature restrictions. A switch to solid polymer electrolytes can significantly increase chemical/mechanical stability, improve safety, reduce cost, and advance manufacturability, if only issues such as low conductivity and transference, limited operating temperature range, and insufficient mechanical strength can be overcome. To this end, significant research efforts have been directed to understand the mechanism of lithium ion motion in polymer matrices and to modify the chemistry, architecture, and morphology of the poly(ethylene oxide) polymer typically used in polymer electrolytes. Furthermore, the incorporation of nanoparticles into polymer electrolytes has created new opportunities for simultaneous improvement of conductivity and of mechanical properties. The performance of such composite polymer electrolytes can be modulated by the judicious surface chemical modification of the nanoparticles and/or by the addition of organic solvents or ionic liquids. The examples highlighted here point to the importance of formulation design for the improvement of the performance characteristics of multi-component systems such as polymer electrolytes.

Ferroelectric polymers are promising functional materials for energy harvesting applications, given their low stiffness, high flexibility, toughness, ease of modification to tailor properties, processability and low density. This chapter provides detailed description of the molecular structure, polymorphs and properties of ferroelectric vinylidene fluoride (VDF)-based fluoropolymers and related nanocomposites. The nature of the ferroelectric crystalline phase plays a key role in the piezo- and pyroelectric properties of the polymer‚ various methods to increase the content of the polar ferroelectric polymorphs in the polymers are discussed, such as copolymerization, addition of nanoparticles, nanoconfinement, electrospinning, and post-treatment.

Thermoelectric generators (TEGs) are being considered as one of the most promising green technology to convert the waste energy into useful electricity. Conjugated polymers and their nanostructures possess high electrical conductivity, low thermal conductivity, and reasonable Seebeck coefficient, which can meet the requirements for high-efficiency TEGs. This chapter focuses on recent progress in the development of nanostructured polymers and polymer/inorganic nanocomposites with multi-dimensional nanostructures (0D, 1D to 2D) for thermoelectric applications. The challenges and perspectives in the emerging field of nanostructured polymers are also involved.

Polymer/inorganic nanocomposites represent a unique class of amorphous, flexible, and isotropic materials for applications in high, intermediate, and low temperature polymer electrolyte membrane fuel cells (PEMFCs). Nanocomposite polymer electrolyte membranes in PEMFCs constitute of either a polymer matrix continuous phase with dispersed inorganic proton conducting particles or a proton conducting polymer matrix continuous phase with dispersed inorganic particles. Therefore, these nanocomposites are basically composites of polymer having nanoscale building blocks of inorganic particles. These remarkable hybrid materials possess combined advantages of both the inorganic and the polymer phases, often with synergistic outcomes. In essence, materials of hybrid nature possessing nanosized interfaces between the dispersed inorganic and the continuous polymer domains present remarkable opportunities to produce unique material properties. Accordingly, significant thermal and ionic conductivities, thermal stability, flexibility, corrosion resistance, mechanical strength, dielectricity, ductility, optical density, and processability are some important and attractive attributes of these nanocomposite materials. In addition, these properties can be controlled easily by varying the composition, synthetic procedure, bonding between the polymer and the inorganic particles, and the size of the nanophases. This chapter will deal with the use of polymer/inorganic nanocomposite materials in various categories of PEMFCs, namely hydrogen, direct methanol, and microbial fuel cells. The advantages obtained upon utilizing these hybrid nanocomposite materials over that of the state-of-the-art materials will be highlighted in details. In addition, possible future directions will be provided regarding possibilities of fabricating and utilizing new and prospective hybrid materials for these applications.

Controlling the solid-state orientation of semiconducting polymers has been a challenging topic in order to achieve high mobilities in organic field-effect transistors and good power conversion efficiencies in organic photovoltaics. In this chapter, we focus on how the orientation of semiconducting polymer backbones is influenced by the chemical structures, such as backbone regularity, polymer main chain geometry, backbone coplanarity, molecular weight, heteroatoms, and side chains. A detailed analysis of the polymer thin films has been conducted by various techniques, especially including two-dimensional grazing incidence X-ray diffraction measurements, and there is now a clear correlation between the polymer orientation and electronic device performances.

Excitonic solar cells (ESCs) including dye-sensitized solar cells, quantum dot-sensitized solar cells, perovskites solar cells, and inverted organic photovoltaics are built upon metal oxide semiconductors (MOSs), which have attracted considerable attention recently and showed a promising development for the next generation solar cells. The development of nanotechnology has created various MOS nanostructures to open up new perspectives for their exploitation, significantly improving the performances of ESCs. One of the outstanding advantages is that the nanostructured mesoporous MOSs offer large specific surface area for loading a large number of active materials (dyes, quantum dots, or perovskites) so as to capture a sufficient fraction of photons as well as to facilitate efficient charge transfer. This review focuses on the recent work on the design, fabrication, and surface modification of nanostructured MOSs to improve the performance of ESCs. The key issues for the improvement of efficiency, such as enhancing light harvesting and reducing surface charge recombination, are discussed in this paper.

The direct utilization of sunlight, especially the visible light part of solar spectrum as a clean and abundant energy source to activate organic reactions is a great challenge in organic chemistry and materials science. Beside the well-developed metal-based photocatalysts such as inorganic semiconductors or transition metal complexes, pure organic photocatalytic systems have gained much attention currently. Among metal-free photocatalysts, nanostructured and highly porous conjugated polymers are of particular interest due to their flexible tunability of optical and electronic properties. In this chapter, an overview on the development of this new class of functional materials is given. Various structural design methods such as donor–acceptor combination on the molecular level, band positions modification, and p/n character variation are shown, and porosity, morphology control and their impact on the photocatalytic efficiency are also described.