Mahmood-ul-Hassan

Bio: Mahmood-ul-Hassan is an academic researcher from University of the Punjab. The author has contributed to research in topics: Graphene & Supercapacitor. The author has an hindex of 7, co-authored 12 publications receiving 193 citations.

Effect of Graphene Oxide Thin Film on Growth and Electrochemical Performance of Hierarchical Zinc Sulfide Nanoweb for Supercapacitor Applications

Abstract: Surface morphological induced electrical conductivity and specific surface area of a material play a significant role to facilitate electrochemical behavior for supercapacitors applications. Therefore, the synthesis step for controlling such parameters becomes very imperative and challenging. Herein, ZnS nanoweb is deposited directly on Ni foam having pre-deposited graphene oxide thin layer developed via hydrothermal method. The structure and surface morphology of modified ZnS is observed using, respectively, XRD and SEM. The electrical conductivity determined for graphene oxide supported ZnS nanoweb, using four probes method, is 100.15 Scm -1 , while the specific surface area is 104.42 m 2 g -1 by BET measurements. Pseudocapacitive behavior is monitored by cyclic voltammetry, and the excellent specific capacity of 3052 Fg -1 has been found at the scan rate 2 mVs -1 , while it is 2400.30 Fg -1 according the galvanostatic charge-discharge profile at (current density) 3 mAcm -2 , which significantly higher than those measured for bare GO or ZnS layers. The energy and power densities of GO supported ZnS nanoweb, determined using three electrode systems, are 120 WhKg -1 at 3 mAcm -2 and 4407.73 Wkg -1 , respectively. The symmetric 10.1002/celc.201800633 A cc ep te d M an us cr ip t ChemElectroChem This article is protected by copyright. All rights reserved. 3 behavior using two electrode systems show an energy density 20.29 WhKg -1 at 2 mAcm -2 . Hence, both symmetric and asymmetric measurements suggest that GO supported ZnS nanoweb can be applied as the suitable electrode for supercapacitors.

Significantly improved electrochemical characteristics of nickel sulfide nanoplates using graphene oxide thin film for supercapacitor applications

Abstract: Tremendous efforts have been devoted for designing the excellent electrochemical electrode structures, exhibiting good electrochemical characteristics for supercapacitor applications. Herein, nickel sulfide nanoplates on graphene oxide thin film (GO NSNPs) were fabricated on nickel foam using hydrothermal method. The structural, morphological, electrical and electrochemical study was carried out using the X-ray diffractometer, scanning electron microscope, four probe electrical set up and electrochemical work station. GO NSNPs showed oxidation and reduction peaks in cyclic voltammetry curves and recommended the pseudocapacitive nature. The specific capacitance and specific energy was found as 1745.50 Fg−1 and 87.30 WhKg−1 at 5 mAcm−2, respectively, through galvanostatic charge and discharge profile using three electrodes system. While, the measured specific energy from two electrodes symmetric measurements was 15.72 WhKg−1 at 1 mAcm−2. Hence, GO NSNPs electrodes were suggested as suitable for high performance asymmetric and symmetric supercapacitor applications.

Preparation of different heteroatom doped graphene oxide based electrodes by electrochemical method and their supercapacitor applications

Abstract: In this study, one-step preparation method of different heteroatom (-S, -N, -Cl) doped graphene oxide electrodes were achieved as electrode materials for the purpose of high-capacity supercapacitors Microscopic, spectroscopic, and electrochemical methods were used to characterize the prepared electrodes Formation of -ClO2, -ClO3, -SOx (x:2, 3) and -NO2 groups on the graphene oxide-based electrodes were determined by X-ray photoelectron spectroscopy analysis Detail reaction mechanisms were suggested for the formation of these groups on the electrode surface for the first time in the literature Different surface properties of graphene oxide structures in the electrodes were investigated by scanning electron microscopy and atomic force microscopy Electrochemical behaviors of the prepared electrodes were characterized by cyclic voltammetry and electrochemical impedance spectroscopy Sulphur, nitrogen, and chlorine doped graphene oxide electrodes were used as electrode materials for supercapacitor applications Since different heteroatom doped graphene oxide-based electrodes showed different capacitive behavior Areal capacitances of -S, -N and -Cl doped graphene oxide electrodes were determined as 2064 mFcm−2, 5332 mFcm−2 and 1098 mFcm−2, respectively with 10 mAcm−2

Facile synthesis of ternary graphene nanocomposites with doped metal oxide and conductive polymers as electrode materials for high performance supercapacitors.

Abstract: Supercapacitors (SCs) due to their high energy density, fast charge storage and energy transfer, long charge discharge curves and low costs are very attractive for designing new generation of energy storage devices. In this work we present a simple and scalable synthetic approach to engineer ternary composite as electrode material based on combination of graphene with doped metal oxides (iron oxide) and conductive polymer (polypyrrole) with aims to achieve supercapacitors with very high gravimetric and areal capacitances. In the first step a binary composite with graphene mixed with doped iron oxide (rGO/MeFe2O4) (Me = Mn, Ni) was synthesized using new single step process with NaOH acting as a coprecipitation and GO reducing agent. This rGO/MnFe2O4 composite electrode showed gravimetric capacitance of 147 Fg−1 and areal capacitance of 232 mFcm−2 at scan rate of 5 mVs−1. In the final step a conductive polypyrrole was included to prepare a ternary composite graphene/metal doped iron oxide/polypyrrole (rGO/MnFe2O4/Ppy) electrode. Ternary composite electrode showed significantly improved gravimetric capacitance and areal capacitance of 232 Fg−1 and 395 mFcm−2 respectively indicating synergistic impact of Ppy additives. The method is promising to fabricate advanced electrode materials for high performing supercapacitors combining graphene, doped iron oxide and conductive polymers.

Structural, optical, and magnetic study of Ni-doped TiO 2 nanoparticles synthesized by sol-gel method

Abstract: In this research, the effects of transition metal (Ni) doping to metal-oxide nanoparticles (TiO2) were studied. Various weight ratios (5, 10, 15, and 20%) of Ni-to-TiO2 nanoparticles were synthesized using the sol–gel technique. These doped nanoparticles were prepared using titanium butoxide and nickel nitrate as precursors and methanol as a solvent. The effects of Ni doping to TiO2 were examined using a variety of characterization techniques, X-ray diffraction (XRD), Fourier-transform-infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, field-emission scanning electron microscopy (FESEM), and vibrating sample magnetometer (VSM). The XRD reveals that the Ni-doped TiO2 crystallizes in a tetragonal structure with anatase phase. The particle size and lattice strain were calculated by Williamson–Hall equation. The presence of strong chemical bonding and functional groups at the interface of TiO2 nanoparticles was confirmed by FTIR. The optical properties of undoped and doped samples were recorded by UV–Vis spectroscopy. The saturation magnetization (Ms) was found higher for undoped as compared to doped samples. The surface morphology and the element structure of the Ni-doped TiO2 nanoparticles were examined by FESEM.