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Herein, we report the utilization of nitrogen and sulfur dual heteroatoms co-doped activated carbon (NSAC) by hydrothermal method for electrochemical supercapacitors. Various NSACs were made by using a fixed amount of activated carbon and changing the amounts of thioacetamide. From NSAC electrodes, the coin cell configuration was fabricated and the overall electrochemical conduct was evaluated by using cyclic voltammetry, galvanostatic charge-discharge, cycle life, and electrochemical impedance methodologies. The outcomes manifest that co-doping sulfur and nitrogen into the AC improves the electrochemical performance. In comparison to pure activated carbon, the optimized NSAC produced a higher specific capacitance value of 417 F g−1 at 0.7 A g−1 and also demonstrated outstanding charge-discharge cycling stability at 7 mA (5 A g−1), maintaining 76% of its opening capacitance after 60,000 cycles in the CR2032 device configuration. The impedance studies phase angle value of 85° has added evidence of the NSAC’s good capacitor performance. Thus, we believe this work is suitable for practical applications for energy storage devices. Graphical abstract

Structural, morphological and electrical properties of the CNS/PANI composite have been studied as a function of composition of CNS. Morphological analysis by FESEM and TEM indicates an enhanced interaction between PANI and CNS as the CNS increases forming larger aggregated interconnected matrix network of CNS having hetero-structured molecular phases of sp2 and sp3. Raman spectroscopy reveals the presence of large tensile strain on the G and D bands of the CNS/PANI composite. Increase in the CNS percentage is seen to relax this large amount of strain. Electrochemical analysis of these composite structures as an active electrode gives a highest specific capacitance of 1470 Fg−1 for CNS/PANI composite with 75% of CNS with high cyclic stability.

Herein we have demonstrated facile synthesis approach to grow K+ and Na+ ions preinserted MnO2 (KxMnO2 and NaxMnO2) nanostructured thin films with the help of successive ionic layer adsorption and ...

Herein, by using chemical methods such as successive ionic layer adsorption and reaction (SILAR) and spin coating we have demonstrated a novel strategy for the synthesis of ternary hybrid to study photoelectrochemical (PEC) performance. To the best of our knowledge, for the first time we have represented a case study of achieving optimum SILAR cycles for Ag nanoparticles decoration on ZnO nanorods and a discussion was made on a role of multi-walled carbon nanotube (MWCNT) as a top layer over Ag–ZnO nanostructures for better PEC performance. Firstly, Ag nanoparticles loading over SILAR grown ZnO nanorods was varied for different SILAR cycles to optimize better photocurrent. This Ag–ZnO hybrid showed higher photocurrent density of 0.45 mA/cm2 at 1 V bias (vs SCE) and photoconversion efficiency (PCE) of 0.21% (0.45 V vs SCE). Thereafter, MWCNTs were garnished by using spin coating as a top layer on Ag–ZnO hybrid leading to the formation of ternary hybrid of MWCNT–Ag–ZnO for further enhancement of PEC activity. We believe that top layer of MWCNT plays a vital role of electron and hole transfer and bridges Ag decorated ZnO nanorods together leading to well-connected conducting pathways for efficient charge collection and transport. The appropriate band bending of MWCNT–Ag–ZnO hybrid leads to the formation of active interface helping out in charge separation leading to excellent photocurrent density of 0.56 mA/cm2 at 1 V bias (vs SCE) and photoconversion efficiency of 0.26% (0.45 V vs SCE). Enhanced light harvesting, higher donor density, appropriate band bending, lowest charge transfer radius of C–Ag–ZnO hybrid signifies that efficient charge transfer and restriction to charge recombination leading to the enhanced PEC performance.

Morphological forms of ZnO nanostructures play a vital role in deciding properties such as high internal surface area, efficient light scattering and harvesting, lowest charge transfer resistance, etc. which are important for photoelectrochemical (PEC) performance. Herein successful deposition of well oriented ZnO nanorods thin films over fluorine doped tin oxide (FTO) coated glass substrate is achieved by using simple, soft solution and scalable method known as successive ionic layer adsorption and reaction (SILAR). For the first time a compact ZnO layer over large area is deposited in one step synthesis approach, without any assistance of seed layer, by using hydrazine hydrate as a source of hydroxyl ions. The plausible growth mechanism of the morphological variation (alignment and orientation) happening with increasing SILAR cycles and its consequence on PEC performance are discussed in detail. All ZnO thin films show wurtzite crystal structure, however variations in their texture coefficients were found with SILAR cycles, which turns out to be a major aspect for PEC application. Anodic shift was observed in flat band potential values with increment in number of SILAR cycles. The ZnO thin films deposited for 120 cycles showed preferential orientation along (0002) plane and showed better PEC performance with photocurrent of 0.19 mA/cm2 (1 V) and maximum photo conversion efficiency of 0.084% at 0.45 V. On the other hand, film deposited for 60 (photocurrent of 0.11 mA/cm2 (1 V); efficiency of 0.055%) and 180 cycles (photocurrent of 0.15 mA/cm2 (1 V); efficiency of 0.063%) demonstrated inferior PEC performance.

Manganese oxide is an interesting material for electrochemical properties. It is well known that Mn

Sunlight harvesting for energy generation and environmental remediation is an evolving research area which potentially opens a propitious avenue and beneficial to tackle energy and the environment issues. Conversion of sunlight into hydrogen or electricity through photoelectrochemical (PEC) cell is one of the most auspicious approaches for a feasible energy supply in which extensive development of photoelectrode is the key. Last few years witnessed the outstanding PEC performance flourished due to incorporating complexity in ZnO nanostructures and decorating them by metal nanoparticles. This chapter gives an overview of the current state of metal nanoparticles decorated ZnO nanostructures for PEC application. We discuss worthwhile role of ZnO and its key properties such as crystal structure, morphologies, and band potential beneficial from PEC viewpoint. A brief discussion on the basics of localized surface plasmon resonance (LSPR) shown by plasmonic metal nanoparticles followed by its capability towards increment in the PEC performance is displayed. Hybrids of metal nanoparticles decorated on ZnO have been utilized as photoelectrodes because of amazing features like enhanced visible light harvesting due to LSPR, higher conductivity, quicker charge transfer rate, increased photogenerated charge carrier separation, supporting band bending mechanism leading to long stability and high efficiency of PEC cell. All such features are explored in a systematic manner. A comparative section is dedicated to doped and decorated photoelectrodes for PEC studies. Rather being descriptive or thoroughgoing, this chapter talks about representative examples of novel and recent ideas to amplify PEC performance. Finally, conclusion point outs current challenges and gives an outlook.

Nickel nanoparticles were grown on graphite by using a comparatively simpler and cost effective method, namely successive ionic layer adsorption and reaction. Size and morphology of the nickel nanoparticles were observed using field emission scanning electron microscopy. X-ray diffraction, X-ray photoelectron spectroscopy and energy dispersive spectroscopy studies confirmed the presence of nickel. Electrocatalytic activity and stability of the grown nickel nanoparticles were investigated by recording cyclic voltammograms and chronoamperometry. Variations in growth parameters, such as reduction time, nickel chloride concentration and number of growth cycles affect the activity of the grown nickel nanoparticles. The grown nickel nanoparticles exhibited electrocatalytic activity towards ethanol electrooxidation reaction. The phase change as a result of mass change that occurred during the redox reactions and ethanol electrooxidation was studied using an electrochemical quartz crystal microbalance. The successive ionic layer adsorption and reaction method promises to be a viable option for growth of nickel nanoparticles for electrocatalytic applications.

“Superstructures” are basically three dimensional (3D) nano/microstructures which arise at the expense of one dimensional (1D) and two dimensional (2D) nanostructures with controlled morphology and orientation. As compared to 1D and 2D nanostructures ZnO superstructures are superior because they possess good crystallinity, integrated stacked arrays with periodic arrangement, high surface area, and good conductivity. Over the past few decades specific focus has been given on the synthesis of ZnO superstructures in view of their astonishing physicochemical properties and promising applications in numerous fields. ZnO superstructures show exceptional performance for hydrogen production via photoelectrochemical (PEC) water splitting because of their certain advantageous properties such as high internal surface area, enhanced scattering with improved light harvesting, reduced recombination rate, low charge transfer resistance, better crystallinity, channelled conducting pathways, etc. These properties are majorly dependent on the various morphologies of ZnO superstructures. Recently different synthesis strategies have been developed to obtain a variety of morphologies of ZnO superstructures. In view of the search for renewable energy sources in the form of hydrogen, produced through water splitting using PEC cell, it is crucial to study different recent approaches of synthesizing ZnO superstructures and understand their role in enhancing PEC performance. Herein, we recap the principles governing hierarchy, complexity, orientation and crystallinity of ZnO superstructures. In general, they are distinguished by considering their geometrical shapes and common names used in the literature and discussion is done on the strategies acquired for their synthesis. This review summarizes the reasons behind the exceptional performance of ZnO superstructures and discusses those in detail. In the field of ZnO superstructures synthesis and their applicability for hydrogen production through PEC this review will not only help in basic understanding, but also ignite innovative ideas.

Manganese oxide is an interesting material for electrochemical properties. It is well known that Mn3O4 (spinel) can be electrochemically converted to MnO2 (birnessite) via the electrochemical route during cyclic voltammetry (CV) cycling in aqueous Na2SO4 solution. Herein, the novel way is represented for the growth of highly adherent and compact Mn3O4 thin films by using successive ionic layer adsorption and reaction (SILAR) method. As grown Mn3O4 thin films are converted into MnO2 after chemical treatment by hydrochloric acid (HCl) via a disproportionate reaction. Mn3O4 thin films are converted into MnO2 by both chemical and electrochemical paths. During chemical conversion, at acidic pH, the crystal water insertion (H3O+) in Mn3O4 crystal provides the necessary driving force to transform it into MnO2 crystal. During electrochemical transformation, the specific capacitance was found to increase from 72 (1st CV cycle) to 393 F/g (1600th CV cycle). On the other hand, the specific capacitance was increased from 72 to 258 F/g through chemical transformation. Electrochemical and chemical conversion leads to ~5.5 and ~3.5 fold, respectively, improved supercapacitive performance than pristine Mn3O4 thin films. Both chemical and electrochemical conversion routes are extremely useful to recycle battery waste for supercapacitor applications.

We report the production parameters of single-stage, ecologically fabricated, flexible Carbon-Nano-Spheres (CNS) supercells. These supercells can deliver a total energy, ED, of 100.0 W h kg−1 and power density, PD, of 50.0 W kg−1@38.4 V and 20 mA for a payload of 15 g (5.0 × 2.5 cm2). According to the material analysis, CNS consists of a spherically (40.0 to 50.0 nm) coagulated, interconnected, 3D network of hetero-structured sp2/sp3 carbon with a low crystalline length, La, of ∼3.0 nm and containing a native O-moiety (12.0 at%). They have an appreciably high specific surface area, SA, of ∼790.0 m2 g−1 and an average pore size of ∼3.42 nm combined with multi-channel pore size distribution. Upon integration in electrodes, CNS provided excellent electrochemical performance without any material modification. CNS showed a nearly rectangular cyclic voltammetry (CV) response in 1 M HCl for both two- and three-electrode systems, yielding superior specific capacitances, CSP, of ∼1080.0 and 570.0 F g−1, respectively (@10 mV s−1). They maintained a high cyclic stability of ∼86.0% (@20 000 cycles), with no material degradation according to post-investigations at a molecular level. The electrode showed hybrid battery/electric double layer capacitor (EDLC) behavior, as revealed by Ragone studies. In Nyquist studies, a shift in the Knee frequency with cycling indicated mitigation of the charge transfer process. In Bode studies, the ionic phase shift decreased insignificantly from ∼80 ° to ∼77 ° after 1000 cycles. The performance characteristics of CNS from laboratory scale measurements to supercell-level device development are discussed.

Novel hierarchical nanostructures have huge potential in different applications. Herein, we report a facile way of engineering different morphologies of zinc oxide (ZnO) thin films by using successive ionic layer adsorption and reaction (SILAR) method. By changing the degree of supersaturation, significant variation in the crystal orientation and the morphology were obtained for ZnO thin films. X-ray diffraction (XRD) study revealed wurtzite crystal structure of zinc oxide nanostructures, which was further supported by Raman spectra. Surface morphology unveils nanostructures such as nanoflakes, nanoflowers, and branched nanorods. To our best knowledge, this is the first report on branched nanorod nanostructures by SILAR method. Nucleation and crystal growth are driven by the amount of Zn(OH)42– species in the solution through which new structures can be obtained. Photoluminescence spectra revealed ultraviolet and visible emission (green and yellow) from all of the morphologies. Wettability test shows hydr...

Polythiophene incorporated carbon materials have sought huge attention due to various improved electrochemical properties including enhanced electrical conductivity. Our work includes the synthesis of polythiophene (PTP)-multi-wallcarbon nanotubes (MWCNTs) via in-situ polymerization method. The homogeneous distribution of MWCNT in PTP was confirmed by Field Emission Scanning Electron Microscope (FESEM). Examination of the specimen using X-Ray diffraction (XRD), Fourier Transform-Infrared (FTIR) and Raman spectroscopy confirmed the composite formation. Other electrochemical characterizations like electrochemical impendence spectroscopy (EIS) and cyclic voltammetry (CV)of the PTP-MWCNT composite affirmed that incorporation of MWCNT improves the electrochemical properties of neat PTP including a significant increase in the capacitance. Hence making PTP-MWCNT isa better material for supercapacitor application than neat PTP.

We report deposition of zinc sulfide nanoflakes on glass substrates by modified chemical method. The modified chemical method involves adsorption of zinc–thiourea complex on the substrate and its dissociation in presence of hydroxide ions to release sulfur ions from thiourea which react with zinc ions present in the complex to form zinc sulfide nanoflakes at room temperature. Influence of zinc salt and thiourea concentrations ratios on the morphology of the films was investigated by scanning electron microscope (SEM). The ratio of zinc and thiourea in the zinc–thiourea complex significantly affect the size of the zinc sulfide nanoflakes, especially width and density of the nanoflakes. The X-ray diffraction analysis exhibits polycrystalline nature of the zinc sulfide nanoflakes with hexagonal phase.