Faculty Publications
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Item Activated carbon-polyethylenedioxythiophene composite electrodes for symmetrical supercapacitors(2008) Muthu, M.S.; Bhat, D.K.A symmetrical (p/p) supercapacitor has been fabricated by making use of activated carbon (AC)-poly-ethylenedioxythiophene (PEDPT)-composite electrodes for the first time. The composite electrodes have been prepared via electrochemical deposition of ?-napthalenesulphonate doped PEDPT onto AC electrodes. The characteristics of the electrodes and the fabricated supercapacitor have been investigated using cyclic voltammetry (CV) and AC impedance spectroscopy. The electrodes show a maximum specific capacitance of 158 Fg-1 at a scan rate of 10 mV s_1. This indicates that the in situ electro-polymerization of ethylenedioxythiophene (EDPT) onto AC could improve the performance of carbon electrodes for use in supercapacitors. © 2007 Wiley Periodicals, Inc.Item Novel eco-friendly synthesis of graphene directly from graphite using 2,2,6,6-tetramethylpiperidine 1-oxyl and study of its electrochemical properties(Elsevier B.V., 2015) Subramanya, B.; Bhat, D.K.Herein we report a simple, low cost, highly efficient and environment friendly one-pot method for the high throughput synthesis of graphene directly from graphite using 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and H2O2 under microwave irradiation. The formation mechanism of graphene nanosheets (GNS) as investigated by Raman spectroscopy and electron microscopy techniques reveal surface defect generation, intercalation and exfoliation as the main steps. The rapid and local Joule heating of graphite by microwave radiation results in simultaneous deoxygenation and exfoliation forming GNS. The as-synthesized GNS are a few layer thick with a high surface area of 937.6 m2 g-1 and a high C/O ratio of 9.2. These results open the perspective of replacing toxic oxidizing and reducing agents by environment friendly chemicals of similar efficacy, thus facilitating the large-scale production of GNS by a greener method. Furthermore, GNS exhibits good electrochemical performance with a large specific capacitance (197 F g-1), excellent rate capability and a long cycle life (1000 cycles) in neat 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) electrolyte. It also has a high energy density of 76.03 W h kg-1 while simultaneously possessing a high power density of 1.12 kW kg-1. © 2014 Elsevier B.V.Item Novel Fe-Ni-Graphene composite electrode for hydrogen production(Elsevier Ltd, 2015) Badrayyana, S.; Bhat, D.K.; Shenoy, U.S.; Ullal, Y.; Hegde, A.We have developed a novel, efficient and economical composite electrode for hydrogen production. The electrode has been formed by embedding graphene in the Fe-Ni matrix via room temperature electrodeposition. The obtained active coatings have been tested for their efficiency and performance as electrode surfaces for hydrogen evolution reaction (HER) in 6 M KOH by cyclic voltammetry and chronopotentiometry techniques. The coating obtained at 60 mA cm-2 exhibited approximately 3 times higher activity for hydrogen production than that of binary Fe-Ni alloy. Addition of graphene to electrolyte bath resulted in porous 3D projections of nano-sized spheres of Fe-Ni on the surface of graphene, which effectively increased the electrochemically active surface area. XPS analysis results showed the equal distribution of both Ni metal and NiO active sites on the composite. The addition of graphene favoured the deposition of metallic nickel, which accelerated the rate determining proton discharge reaction. All these factors remarkably enhanced the HER activity of Fe-Ni-Graphene (Fe-Ni-G) composite electrode. The Tafel slope analysis showed that the HER follows Volmer-Tafel mechanism. The structure-property relationship of Fe-Ni-G coating has been discussed by interpreting field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis results. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Item Electrodeposition and characterization of Ni-Mo alloy as an electrocatalyst for alkaline water electrolysis(Elsevier B.V., 2017) Shetty, S.; Mohamed, M.; Bhat, D.K.; Hegde, A.C.This work details the efficiency of Ni-Mo alloy as an electrode for water splitting application through electrodeposition method. Nano-crystalline Ni-Mo alloy coatings were deposited in the current density (c.d.) range of 1.0–4.0 A dm? 2 on a copper substrate, and were investigated for their deposit characters, and their electrocatalytic behaviours in 1.0 M KOH solution. The electrocatalytic behaviour of the coatings, in terms of their hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), were evaluated by electrochemical methods, like cyclic voltammetry (CV) and chronopotentiometry (CP). Experimental results revealed that Ni-Mo alloy electrodeposited at 1.0 A dm? 2 (38.3 wt% Mo) and 4.0 A dm? 2 (33.2 wt% Mo) shows the highest electrocatalytic tendency for HER and OER, respectively. The corrosion behaviour of Ni-Mo alloy coated at 4.0 A dm? 2 is found to be the most corrosion resistant in the same alkaline medium, compared to other coatings. The highest electrocatalytic activity of Ni-Mo alloy deposit for both HER and OER, depending on deposition c.d. was attributed to their composition (in terms of Ni and Mo content), structure and surface morphology; supported by EDXA, XRD, SEM and AFM analyses. The experimental study demonstrated that Ni-Mo alloy coatings follow Volmer-Tafel type of mechanism for HER, testified by Tafel slope analyses. © 2017 Elsevier B.V.Item RGO/ZnWO4/Fe3O4 nanocomposite as an efficient electrocatalyst for oxygen reduction reaction(Elsevier B.V., 2017) Mohamed, M.; Mutyala, S.; Mathiyarasu, J.; Bhat, D.K.Development of low cost, environmental friendly and noble metal free catalyst materials with excellent performance is essential for commercialization. In fact, this is the need of the day too. Herein, we report a facile microwave irradiation method for the synthesis of novel RGO/ZnWO4/Fe3O4 cathode catalysts for the oxygen reduction reaction (ORR) in alkaline medium. The structural and morphological features of synthesized materials are fully examined using transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM). The chemical composition and elemental analysis of the catalyst is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy techniques. Efficiency of RGO/ZnWO4/Fe3O4 catalyst material for oxygen reduction reaction (ORR) in 0.1 M KOH is reported. The activity of catalyst is determined by linear sweep voltammogram (LSV) and rotating disk electrode (RDE) measurements in O2 saturated 0.1 M KOH electrolyte. RGO/ZnWO4/Fe3O4 catalyst exhibits higher ORR activity than RGO, ZnWO4, RGO/ZnWO4 and its electrocatalytic performance is comparable to Pt/C material and is superior to it in stability and methanol tolerance. Further, it is determined that process follows a direct four electron reaction pathway. These combined results strongly signpost that RGO/ZnWO4/Fe3O4 composite can function as an economic noble metal free ORR cathode catalyst for energy applications. © 2017 Elsevier B.V.Item A porous graphene-NiFe2O4nanocomposite with high electrochemical performance and high cycling stability for energy storage applications(Royal Society of Chemistry orders@rsc.org, 2020) Sethi, M.; Shenoy, U.S.; Bhat, D.K.It is well agreed that supercapacitors form an important class of energy storage devices catering to a variety of needs. However, designing the same using eco-friendly and earth abundant materials with high performance is still the dire need of the day. Here, we report a facile solvothermal synthesis of a porous graphene-NiFe2O4 (PGNF) nanocomposite. Thorough elemental, diffraction, microscopic and spectroscopic studies confirmed the formation of the PGNF composite, in which the NF nanoparticles are covered over the PG surface. The obtained 10 PGNF composite showed a surface area of 107 m2 g-1, with large pore volume which is favorable for charge storage properties. When utilizing the material as an electrode for a supercapacitor in a 2 M KOH aqueous electrolyte, the electrode displayed an impressive specific capacitance value of 1465.0 F g-1 at a scan rate of 5 mV s-1 along with a high capacitance retention of 94% after 10?000 discharge cycles. The fabricated symmetrical supercapacitor device exhibited an energy density of 4.0 W h kg-1 and a power density of 3600.0 W kg-1 at a high applied current density of 14 A g-1. The superior electrochemical performance is attributed to the synergetic effect of the composite components which not only provided enough electroactive channels for the smooth passage of electrolyte ions but also maintained the hybrid structure intact in the ongoing electrochemical process. The obtained results underpin the promising utility of this material for future electrochemical energy storage devices. © The Royal Society of Chemistry.Item Exploring the potential of CoAl2O4 nanoflakes in supercapacitor applications(Elsevier B.V., 2025) Ramesh, T.P.; Shenoy, U.S.; Bhat, D.K.Spinel structured nanoparticles with binary and ternary metal oxide combinations have recently been identified as a viable material for use in supercapacitors. Two mixed-valence metal cations provide easy electron transport between various metal cations. High-performance CoAl2O4 spinel nanoflakes were synthesized using a mixed-solvent solvothermal method, followed by calcination. First principles calculations revealed high density of states near the Fermi level indicating its potential for supercapacitor applications. These nanostructured materials were then experimentally explored as promising electrode candidates for supercapacitor applications, using a 2 M KOH aqueous electrolyte. The results were impressive: the material demonstrated a high specific capacitance of 851.9 F/g at a current density of 1 A/g and the fabricated supercapacitor exhibited a power density of 14940.0 W/kg at a current density of 12 A/g. Even under more demanding conditions, the electrode maintained strong durability, in terms of cyclic stability along with high energy and power density values making it a strong contender for next-generation energy storage devices. © 2025 Elsevier B.V.