Faculty Publications
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Item A comparative study on the electrocatalytic activity of electrodeposited Ni-W and Ni-P alloy coatings(Elsevier Ltd, 2018) Elias, L.; Hegde, A.Bright Ni-W and Ni-P alloy coatings were synthesized through direct electrolysis from an aqueous alkaline citrate bath. The effect of alloying elements, W and P, on the electrocatalytic activity of Ni was studied, based on their induced codeposition behavior and related to the composition, structure and surface morphology of the developed coatings. The electrocatalytic activity of the alloy coatings towards hydrogen evolution reaction (HER) was studied using electrochemical techniques such as cyclic voltammetry (CV) and chronopotentiometry (CP), in 1. M KOH medium. A comparison of the electrocatalytic efficiencies of these Ni-based alloys was made in consideration with its physical and electrochemical characteristics. The obtained results showed that the alloying of Ni with W gives superior properties towards HER, attributed by its better hydrogen adsorption energy than in Ni-P alloy. The surface appearance, chemical composition and phase structure of the coatings were studied using SEM, EDS and XRD analyses, respectively. © 2018 Elsevier Ltd. All rights reserved.Item Solar exfoliated graphene and its application in supercapacitors and electrochemical H2O2 sensing(Elsevier Ltd, 2015) Moolayadukkam, M.; Huang, N.M.; Nagaraja, H.S.In the present study, graphene nanosheets are synthesized using sunlight irradiation focussed onto graphite oxide. The morphological characteristics of graphene are examined using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Raman spectroscopy and X-ray diffraction (XRD) are used for the structural characterization of the sample. The electrochemical performance is evaluated using cyclic voltammetry (CV), charge-discharge characteristics and impedance spectroscopy. A high specific capacitance value of 223 F g-1 is obtained using cyclic voltammetry. The electrochemical detection of H2O2, a common biological species using solar graphene is demonstrated. The impedance spectroscopy and CV are used to study the electrocatalytic activity of the material. High sensitivity of 64.79 ?A mM-1 cm-2 is reported. © 2015 Elsevier Ltd. All rights reserved.Item Multi-wall carbon nanotube-NiO nanoparticle composite as enzyme-free electrochemical glucose sensor(Elsevier, 2015) Prasad, R.; Badekai Ramachandra, B.R.We report a simple, solvent-free method to decorate multi-walled carbon nanotubes (MWCNTs) with nickel oxide nanoparticles (NiO-NPs). The as prepared NiO-MWCNT composite were characterised by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The enzyme-free modified carbon paste electrode (CPE) was fabricated using as-synthesised composite material and investigated for glucose sensing. The 10% NiO-MWCNTs composites sensor showed excellent electro-catalytic activity towards direct glucose oxidation. The sensitivity of this sensor is found to be 1696 ?A mM-1 cm-2 and 122.1 ?A mM-1 cm-2 and the limit of detection (LOD) was found to be 11.04 nM and 31 ?M for the linear response over glucose concentration ranging from 1-200 ?M to 0.5-9.0 mM, respectively. Furthermore, the 10% NiO-MWCNTs sensor also showed excellent anti-interference ability, high stability and good reproducibility. Hence, due to simple method of material preparation, easy sensor fabrication and excellent electro catalytic activity towards glucose oxidation, the 10% NiO-MWCNT/CPE is a potential material for the development of enzyme-free sensor for reliable glucose determination. © 2015 Elsevier B.V. All rights reserved.Item Electrolytic Synthesis and Characterization of Electrocatalytic Ni-W Alloy(Springer New York LLC barbara.b.bertram@gsk.com, 2015) Elias, L.; Scott, K.; Hegde, A.Inspired by the more positive (about 0.38 V nobler) discharge potential of hydrogen on Ni-W alloy compared to that on both Ni and W, a Ni-W alloy has been developed electrolytically as an efficient electrode material for water electrolysis. The deposition conditions, for peak performance of the electrodeposits for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH medium have been optimized. Electrocatalytic activity of the coatings, deposited at different current densities (c.d.’s) for water splitting reactions of HER and OER was tested by cyclic voltammetry and chronopotentiometry. It was found that Ni-W alloys deposited, at 4.0 A/dm2 (having about 12.49 wt.% W) and 1.0 A/dm2 (having about 0.95 wt.% W) are good electrode materials as cathode (for HER) and anode (for OER), respectively. A dependency of the electrocatalytic activity for HER and OER with relative amount of Ni and W, in the deposit was found. The variation of electrocatalytic activity with W content showed the existence of a synergism between high-catalytic property of W (due to low hydrogen overvoltage) and Ni (having increased adsorption of OH? ions), for hydrogen (as cathode) and oxygen (as anode) evolution, respectively. Electrocatalytic activities of the coatings, developed at different c.d.’s were explained in the light of their phase structure, surface morphology, and chemical composition, confirmed by XRD, FESEM, and EDX analysis. The effect of c.d. on thickness, hardness, composition, HER, and OER was analyzed, and results were discussed with possible mechanisms. © 2015, ASM International.Item Modification of Ni-P alloy coatings for better hydrogen production by electrochemical dissolution and TiO2 nanoparticles(Royal Society of Chemistry, 2016) Elias, L.; Hegde, A.This work reports the modification of Ni-P alloy coatings for better hydrogen production by electrochemical dissolution and TiO2 nanoparticle incorporation. The first part is devoted to optimization of a new citrate bath for the development of an efficient electroactive Ni-P electrode material by electrodeposition, using glycerol as an additive. The Ni-P alloys developed at 4.0 A dm-2 and 2.0 A dm-2 were found to be good for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively as demonstrated by cyclic voltammetry (CV) and chronopotentiometry (CP) methods. The Ni-P alloy showing good catalytic activity for HER is found to be less active for OER and vice versa. The unique electrocatalytic property of the coatings was attributed to its structure, morphology and composition, confirmed by XRD, SEM and EDS analyses. In the second part, the electrocatalytic activity of Ni-P alloy coatings for HER has been improved further by anodic dissolution and TiO2 nanoparticle incorporation. Drastic improvement in the electrocatalytic activity for HER was found in both anodically treated and Ni-P-TiO2 composite coatings, compared to as-coated Ni-P alloys. The highest electrocatalytic character of the Ni-P-TiO2 composite coating was attributed to a greater number of electroactive centres, affected by TiO2 nanoparticle incorporation, and experimental results are discussed. © The Royal Society of Chemistry 2016.Item Magnetoelectrodeposition of Ni-W alloy coatings for enhanced hydrogen evolution reaction(Royal Society of Chemistry, 2016) Elias, L.; Cao, P.; Hegde, A.The electrocatalytic efficiency of electrodeposited (ED) Ni-W alloy coatings for the hydrogen evolution reaction (HER) has been improved drastically through magnetoelectrodeposition (MED) approach. Ni-W alloy coatings have been developed under different conditions of magnetic field intensity 'B' (applied perpendicular in the range of 0.1-0.4 T), and their electrocatalytic activity for the HER has been tested using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques in 1.0 M KOH solution. A drastic improvement in the electrocatalytic behavior of the MED coating, represented as (Ni-W)B=0.2 T was found as compared to its conventional Ni-W alloy coatings. Improved performance of the MED coatings was explained on the basis of differences in the process of electrocrystallization affected due to the applied magnetic field, supported by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. A magnetic field has been used advantageously for the first time to increase the W content of the alloy. Increased activity of the MED coatings was attributed to the increased W content in the alloy, characterized by the unique (220) reflection, explained by the magnetohydrodynamic (MHD) effect due to Lorentz force. © 2016 The Royal Society of Chemistry.Item Synthesis and characterization of Ni-P-Ag composite coating as efficient electrocatalyst for alkaline hydrogen evolution reaction(Elsevier Ltd, 2016) Elias, L.; Hegde, A.C.The effect of addition of silver nanoparticle sol (SNS) into Ni-P plating bath was studied in terms of the variation in electrocatalytic behavior of the developed coatings in 1.0 M KOH. Ni-P-Ag composite coating was achieved through direct electrolysis by adding a known quantity of the conventionally prepared SNS into Ni-P bath. Ni-P-Ag coatings electrodeposited galvanostatically on copper under different conditions of the bath was used as electrode material for alkaline hydrogen evolution reaction (HER). The optimal concentration of the SNS required for maximum electrocatalytic activity towards HER was obtained by adding different volumes of SNS (from 0 to 50 mL L?1) into the bath. The HER efficiency of the test electrodes in 1.0 M KOH medium was examined using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. The kinetics of HER on the alloy and composite electrodes were established through Tafel polarization and electrochemical impedance spectroscopy (EIS) analyses. Energy dispersive spectroscopy (EDS) was used to confirm the incorporation of Ag nanoparticles into the Ni-P alloy matrix. The microstructure and morphology of the alloy and composite coatings were analyzed by Scanning Electron Microscopy (SEM). A significant improvement in the electrocatalytic property of nano-Ag derived composite coatings was found, and was attributed to the enhanced electroactive sites of Ag particles. Deposition conditions to maximize the electrocatalytic activity of Ni-P-Ag nanocomposite coatings in relation to traditional Ni-P alloy coatings was arrived, and results are discussed. © 2016Item Electrodeposition of Sn-Ni Alloy Coatings for Water-Splitting Application from Alkaline Medium(Springer Boston, 2017) Shetty, S.; Hegde, A.C.In this work, Sn-Ni alloy coatings were developed onto the surface of copper from a newly formulated electrolytic bath by a simple and cost-effective electrodeposition technique using gelatin as an additive. The electrocatalytic behavior of coatings deposited at different current densities (c.d.’s) for water-splitting applications, in terms of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), has been researched. The experimental results showed that the electrocatalytic activity of Sn-Ni coatings has a close relationship with its composition, surface morphology, and phase structure depending on the c.d. used, supported by scanning electron microscopy (SEM-EDX) and X-ray diffraction (XRD) analyses. Cyclic voltammetry and chronopotentiometry techniques have demonstrated that Sn-Ni alloy deposited at 4.0 A dm?2 (having 37.6 wt pct Ni) and 1.0 A dm?2 (having 19.6 wt pct Ni) exhibit, respectively, the highest electrocatalytic behavior for HER and OER in 1.0-M KOH solution. Sn-Ni alloy coatings were found to be stable under working conditions of electrolysis, confirmed by electrochemical corrosion tests. High electrocatalytic activity of Sn-Ni alloy coatings for both HER and OER is specific to their composition, surface morphology, and active surface area. © 2016, The Minerals, Metals & Materials Society and ASM International.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 Synthesis of effective electrocatalyst for water splitting application from simple Cu-Ni bath(Allerton Press Incorporation journals@allertonpress.com, 2017) Elias, L.; Banjan, R.U.; Hegde, A.C.Electrocatalytically active Cu-Ni alloy coatings have been developed from a simple electrolyte having only Cu+2 and Ni+2 ions, without the use of any additive. Electrocatalytic character of the coatings was tested for their hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH medium, alongside with their corrosion behaviours. Cyclic voltammetry and chronopotentio-metry study revealed that the deposition current density has a prominent role on the alkaline water splitting behaviour of the coatings, depending on their phase structure, composition and surface morphology. It was found that the c.d. has an inverse dependence on HER and OER. The Cu-Ni alloy coatings developed, respectively at 3.0 and 4.0 A dm–2, were found to be the best coatings for HER and OER, depending on the surface morphology. The electrocatalytic activity of Cu-Ni alloy coating for HER, deposited at 3.0 A dm–2 (optimal), was further improved through electrochemical dissolution of the as-deposited coating. The increase in the electrocatalytic activity for HER has been attributed to the enhancement in the exposed surface area of Ni active sites due to the leaching of Cu from the alloy matrices, evidenced by the energy-dispersive X-ray spectroscopy and scanning electron microscopy. The dependencies of HER and OER on to the surface of Cu-Ni alloy coatings were analysed in terms of deposition c.d. of the coatings, and the results are discussed. © 2017, Allerton Press, Inc.