ABSTRACT

Carbon nanostructures have been gaining considerable interest over the last three decades after the discovery of fullerenes in 1985 showed the possibility of stable curvatures of carbon forms [1]. Elongated forms of fullerenes in the shape of carbon nanotubes (CNTs) and nanocones have become the focus of intense research over the last two decades [2]. The last few years have seen a resurgence of interest in the flat carbon nanostructure called graphene [3]. All the above-mentioned carbon nanostructures exhibit very unique and superior mechanical, electrical, thermal, optical, and chemical properties, resulting in diverse applications ranging from nanoelectronics and nanocomposites, to nanomedicine. The large surface areas and porosities of these carbon nanostructures also helped their applications in energy production, storage, and transmission [4–7]. In recent years, one-dimensional (1D) nanostructure field emitters (e.g., nanowires) have attracted great interest due to their potential application as field emission (FE) flat-panel displays [8,9]. The incorporation of defects in CNTs has been shown to enhance the surface areas of the CNTs, and subsequently increase the electric double-layer capacitance (EDLC). The ion irradiation of CNTs generates fundamental as well as technological interest since it has the potential to introduce a wide range of defects in a controlled manner for tailoring the material properties [10]. We have investigated the influence of Ga+ ion irradiation on the EDLC of multiwalled carbon nanotubes (MWCNTs). Cyclic voltammetry (CV) was employed to analyze the capacitive performance of MWCNTs before and after irradiation at varying cumulative ion doses. Also, CNTs in layered transition metal oxides are very attractive materials for high-energy-density supercapacitor applications. These materials overcome the drawbacks of conventional supercapacitors, but their commercial realization has been hindered by the high cost and poor electrical conductivity, which results in low power density, a narrow operation voltage window, and sluggish faradaic redox kinetics [11–15]. The randomly entangled mesoporous network of CNTs provides the electrical conducting pathways that allow easy diffusion of ions to the active surface area of nanosized metal oxides, which facilitates 94the faradaic processes across the interface. We found that our MoO3–MWCNT nanocomposites-based electrochemical supercapacitor in terms of energy storage mechanism is operated in dual modes: (i) pseudocapacitance mode due to MoO3 and (ii) EDLC mode due to MWCNTs. The results showed that the presence of MWCNTs in the nanocomposites improved the electronic conductivity, homogeneous electrochemical accessibility, and high ionic conductivity by avoiding an agglomerative binder, which makes them a promising material for the fabrication of electrochemical energy storage devices Recently, a few researchers have reported the electron field emission property of graphene film and few-layer graphene prepared by different techniques [16–20]. Chemically exfoliated single-layer graphene by an electrophoretic deposition technique, screen-printed graphene, and vertically oriented graphene grown by plasma-enhanced chemical vapor deposition (PECVD) techniques have been used to investigate its field emission properties. Palnitkar et al. used boron and nitrogen doping of graphene (produced by an arc discharge method) to tailor the turn-on field [20]. We explored the effect of morphological disorder on the field emission property of graphene synthesized by a thermal chemical vapor deposition technique (TCVD).