Development of metal phosphate incorporated polyaniline electrodes for supercapattery / Fatin Saiha Omar

As the demand for green and sustainable energy increases, the advantages of high power density, instantaneous charge and discharge capabilities as well as long life span have made supercapacitor as one of the important device for energy storage and power supply management. Nevertheless, one of the main issues is their low energy density which has limit the employment of supercapacitors in broader applications. To address this issue, developing electrode materials that are efficient, cost-effective, tunable and have high surface area is an appealing alternative to boost the performance of supercapacitor (i.e. capable to store high charge and yet undergo minimal decayed during prolong life cycle). Herein, this work is reported on the synthesis of electrode materials and their relationships with supercapacitor performance. In this study, different nanostructures and morphologies of nickel phosphate Ni3(PO4)2 have been prepared by sonochemical method followed by calcination (with different calcination temperatures). The crystallinity, purity, morphology and surface area of Ni3(PO4)2 were authenticated by X-ray diffraction (XRD), fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) analysis. The electrochemical performances such as specific capacity, rate capability and electrical conductivity of the synthesized materials were studied through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. It was observed that the amorphous structure of Ni3(PO4)2 renders in high specific capacity (539 C/g at the current density of 1 A/g)) mainly because of its highly porous structure that augmented the electroactive sites for redox reaction. Nevertheless, it exhibited low rate capability due to its poor electrical conductivity which motivated the incorporation of Ni3(PO4)2 with silver (Ag) ions to form binary composite of nickel phosphate-silver phosphate nanocomposite (Ni3(PO4)2-Ag3PO4). Ni3(PO4)2-Ag3PO4 was prepared by fixing the amount of Ag precursor with various mass of Ni3(PO4)2. Crystalline structure of Ag3PO4 nanoparticles were found to be intimately decorated on the surface of Ni3(PO4)2 and had significantly improved the rate capability of the host Ni3(PO4)2 from 29 to 78 % of capacity retention. Unfortunately at low current rate, the specific capacity achieved by Ni3(PO4)2-Ag3PO4 was lower than that of Ni3(PO4)2 with the specific capacity of 478 C/g at 1 A/g. Ni3(PO4)2-Ag3PO4 was further blended with polyaniline (PANI) (synthesized by chemical oxidative polymerization of aniline monomer) without any binder to form tertiary composite of polyaniline-nickel phosphate-silver phosphate (PANI-Ni3(PO4)2-Ag3PO4). The specific capacity shown by PANI-Ni3(PO4)2-Ag3PO4 was increased to 677 C/g at 1 A/g with the rate capability of 76 % capacity retention. Overall, the improved performance displayed by PANI-Ni3(PO4)2-Ag3PO4 electrode is attributed to (i) the utilization of the surface area from each material for the effective redox reaction, (ii) the presence of Ag3PO4 nanoparticles which increased the electrical conductivity and (iii) tubular shape of conductive PANI that support Ni3(PO4)2-Ag3PO4, providing the interconnected paths for quick electron transfer rate and preventing closely packed of Ni3(PO4)2-Ag3PO4 particles. For real application, PANI-Ni3(PO4)2-Ag3PO4 was fabricated into hybrid supercapacitor (PANI-Ni3(PO4)2-Ag3PO4//activated carbon) and obtained energy density of 38.9 Wh/kg at 400 W/kg with 88 % capacity retention after 5000 cycles

Microwave synthesis of ZnO/rGO nanocomposites for enhanced degradation of dye / Fatin Saiha binti Omar

Zinc oxide/reduced graphene oxide (ZnO/rGO) nanocomposites were successfully synthesized in the presence of diethylenetriamine (DETA) via a facile microwave assisted method. The x-ray diffraction (XRD) patterns of the ZnO/rGO nanocomposites reveal that obtained nanocomposite materials containing ZnO in hexagonal phase with wurtzite structure. The high-resolution transmission electron microscopy (HRTEM) images indicates that the prepared nanocomposites having ZnO nanorods, with an average length:diameter ratio of 10 and which is found to be deposited onto the rGO sheets. Under the irradiation of sunlight, the ZnO/rGO nanocomposites showed two-fold improved photocatalytic performance than that of unmodified ZnO towards the photodegradation of methylene blue. This may due to the high adsorbtivity of ZnO/rGO nanocomposite and synergistic effect raised between smaller ZnO nanorods and rGO matrix led to the improved photocatalytic activity. Further, the ZnO/rGO nanocomposites showed six-fold enhanced photocurrent response than that of bare ZnO nanorods. The excellent photocatalytic performance of the newly prepared ZnO/rGO nanocomposites could be a potential candidate for the photocatalysis and photoelectrochemical applications

Microwave Synthesis of Zinc Oxide/Reduced Graphene Oxide Hybrid for Adsorption-Photocatalysis Application

This work reports on synthesis of zinc oxide/reduced graphene oxide (ZnO/rGO) nanocomposites in the presence of diethylenetriamine (DETA) via a facile microwave method. The X-ray diffraction (XRD) patterns of the nanocomposites correspond to the ZnO hexagonal phase wurtzite structure. The high-resolution transmission electron microscopy (HRTEM) images revealed that the ZnO nanorods, with an average length : diameter ratio of 10, were successfully deposited on the rGO sheets. Under the irradiation of sunlight, the nanocomposites showed enhanced adsorption-photocatalysis by more than twofold and photocurrent response by sixfold compared to the ZnO. The excellent photoactivity performance of the nanocomposites is contributed by smaller ZnO nanorod and the presence of rGO that acts as a photosensitizer by transferring electrons to the conduction band of ZnO within the nanocomposite during sunlight illumination

Solid terpolymer electrolyte based on poly(vinyl butyral-co -vinyl alcohol-co -vinyl acetate) incorporated with lithium salt and tetraglyme for EDLCs

Solid terpolymer electrolytes (STEs) consist of different ratios of poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVBVA) and bis(trifluoromethane) sulfonamide lithium salt (LiTFSi) were prepared and the ionic conductivity of the prepared STEs was evaluated. The optimized STE (denoted as STE 20) was further doped with various amount of tetraglyme (10, 20, and 30 wt % and denoted as G10, G20, and G30, respectively). G20 enhanced the ionic conductivity from 6.22 (for STE 20) to 21.9 µS cm−1. This enhancement is due to the presence of abundant oxygen-containing functional group in tetraglyme that provides more charge carrier mobility in the polymer matrix. The structure and complexation of the materials are authenticated via X-ray diffraction and Fourier transform infrared spectroscopy analysis. The performance of electric double layer capacitors based on activated carbon (AC) fabricated with STE 20 (AC/STE 20/AC) and G20 (AC/G 20/AC) were studied via cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. AC/G 20/AC achieved the maximum specific capacitance of 10.20 F/g [which is higher than AC/STE 20/AC (9.30 F/g)] with 75% of specific capacitance retention after 1500 cycles

Enhanced efficiency in dye-sensitized solar cell based on zinc oxide-modified poly(ethylene oxide) gel electrolyte

Gel polymer electrolytes (GPEs) are more preferable than liquid electrolyte for dye-sensitized solar cells (DSSCs) due to several advantages. However, GPEs have poor ionic conductivity which renders the low efficiency of DSSCs. GPE systems based on poly(ethylene oxide) (PEO) as host polymer, sodium iodide (NaI) salt, and various amount of zinc oxide (ZnO) (1, 3, 5, and 7 wt%) were prepared and optimized. The highest ionic conductivity obtained for these systems was 7.05 × 10−3 S cm−1 for the GPE at 5 wt% of ZnO. The formation of structural features and complexes of the materials have been confirmed by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Under the illumination of AM 1.5 (100 mW cm−2), the fabricated DSSCs (with an arrangement of FTO glass/TiO2/N719dye/electrolyte/Pt/FTO glass) achieved the maximum power conversion efficiency of 6.94%, with a maximum short-circuit current density (JSC) of 18.75 mA cm−2, open-circuit voltage (VOC) of 0.666 mV, and fill factor (FF) of 55.6%

Optimization of poly(vinyl alcohol-co-ethylene)-based gel polymer electrolyte containing nickel phosphate nanoparticles for dye-sensitized solar cell application

For the first time, metal phosphate, particularly nickel phosphate, Ni3(PO4)2 nanoparticle has been incorporated into gel polymer electrolyte (GPE) for the application in dye-sensitized solar cells (DSSCs). Poly(vinyl alcohol-co-ethylene), PVA-co-PE copolymer and sodium iodide, NaI have been employed as the host polymer and dopant salt, respectively. X-ray diffraction (XRD) studies revealed that the degree of crystallinity of the overall GPE reaches the minimum at 4 wt.% of Ni3(PO4)2 nanoparticles. The amorphous domains have boosted the mobility of the charge carriers and successfully increased the ionic conductivity from 2.27 mS cm−1 to 3.75 mS cm−1. Temperature dependence studies affirmed that the GPEs obey Arrhenius behavior in which ion hopping mechanism is dominant. This explanation was further corroborated by the results obtained from electrical modulus studies. The addition of Ni3(PO4)2 also increases both the dielectric constant and dielectric loss dramatically. Fourier transform infrared studies proved the complexation of different components found in the polymer electrolyte. Besides, the Ni3(PO4)2 nanoparticles also smoothen the morphologies of the GPE which was originally porous and rough. The efficiency of the fabricated DSSCs also nearly doubled from 3.3% to 5.8% with the incorporation of Ni3(PO4)2 nanoparticles

Polyacrylonitrile–poly(1‐vinyl pyrrolidone‐co‐vinyl acetate) blend based gel polymer electrolytes incorporated with sodium iodide salt for dye‐sensitized solar cell applications

New gel polymer electrolytes (GPEs) were prepared via the blending of a polyacrylonitrile polymer and a poly(1-vinyl pyrrolidone-co-vinyl acetate) copolymer. The sodium iodide (NaI) salt concentration was varied for each GPE sample. From ionic conductivity (σ) studies, we observed that the sample with a 40 wt % NaI salt content (N40) showed the highest σ of 3.54 × 10 −3 ± 0.05 S/cm at room temperature, and all of the GPE samples obeyed Arrhenius behavior. The dielectric properties of the GPE samples were also analyzed to study the electrical polarization of the materials. The developed GPE samples were also characterized with X-ray diffraction and Fourier transform infrared spectroscopy. We also then used the developed GPE samples for the fabrication of dye-sensitized solar cells by sandwiching them between a photoanode and Pt counter electrode for photovoltaic studies. The highest photovoltaic performance was achieved by N40, with an efficiency of 3.04%. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47810. © 2019 Wiley Periodicals, Inc

Solid-phase diffusion controlled growth of nickel silicide nanowires for supercapacitor electrode

This work reports on the influence of nickel (Ni) thickness on the growth of nickel silicide nanowires (NiSi NWs) using a solid-phase diffusion controlled growth treatment. The NiSi NWs were grown on two different substrates (i.e. crystal silicon (c-Si) and Ni foil) which were coated with Ni film with different thicknesses; 110 ± 5 and 220 ± 5 nm. FESEM images revealed that the shape, the size and the density of NiSi on both substrates were strongly dependent on the thickness of Ni film. These NWs exhibited morphology of straight NWs with diameter and length of between 16 to 23 nm and 2.9 to 3.9 µm, respectively. The NWs showed a single-crystalline Ni 3 Si 2 phase with a preferred orientation in the (1 0 0) plane. XRD diffractogram proved that the formation of Ni-rich NiSi NWs is strongly dependent on the Ni film's thickness rather than on the types of substrates. NiSi NF220 demonstrated the highest specific capacity with a maximum value of 313.3 C/g. This is attributed from the high density of NWs which endows more redox reaction and the high conductivity of Ni foil substrate that facilitated the high charge transfer kinetics. The fabricated NiSi NWs//activated carbon-based asymmetric supercapacitor exhibited the maximum energy density of 13.37 W h/kg at 200 W/kg and good cyclic stability with 79% capacity retention after 3000 cycles

Performance studies of ZnO and multi walled carbon nanotubes-based counter electrodes with gel polymer electrolyte for dye-sensitized solar cell

Counter electrode (CE) is one of the major component which determine the energy conversion efficiency of the dye-sensitized solar cells (DSSCs). Here in, five types of CEs using two different materials were fabricated. Three types are zinc oxide (ZnO) based while other two are multi-walled carbon nanotubes based CEs. The thickness and resistance per cm2 of each CE were measured. The gel polymer electrolyte based on polyacrylonitrile polymer, sodium iodide salt, 1-Hexyl-3-methyl-imidazolium iodide ionic liquid was also prepared. The conductivity studies revealed that the highest ionic conductivity of gel polymer electrolyte was 6.72 mS cm−1 upon incorporation of 100 wt% 1-Hexyl-3-methyl-imidazolium iodide ionic liquid. This gel polymer electrolyte was sandwiched between commercial TiO2 photo-anode and different types of CE to fabricate the DSSCs. The J-V characteristic curves of the DSSCs were obtained and the DSSC characterization parameters were determined. The efficiencies achieved using ZnO and MWCNT-based CEs were ranging from 0.46% to 7.07%. The results demonstrate that ZnO and multi-walled carbon nanotubes are good candidates of CEs for DSSC application