Faculty Publications
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Item Electrodeposition and electro-catalytic study of nanocrystalline Ni-Fe alloy(Elsevier Ltd, 2014) Ullal, Y.; Hegde, A.C.This paper presents the electrodeposition protocol for development of a stable, inexpensive and efficient electrode material for water splitting reaction. Nanocrystalline Ni-Fe alloy coatings were deposited on copper electrode from acidic bath, at different cathode current densities (c.d). Coatings were tested for their electro-catalytic behaviours, namely for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 6 M KOH by cyclic voltammetry and chrono-potentiometry techniques. Experimental results demonstrated that these coatings can be used as potential material for water electrolysis. The corrosion stability of these coatings has also been tested in their working conditions (6 M KOH) by DC polarization method. The deposition conditions of Ni-Fe alloy were optimized for peak performance for both electro-catalytic reactions and corrosion stability. Ni-Fe alloy coatings deposited towards low and high c.d limits were found to be the better materials for OER and HER, respectively from same electrolytic solution. Further, Ni-Fe coating deposited at 6.0 Ad m-2 was found to be the most corrosion resistant. The structure-property relationship of electrodeposited coatings has been discussed by exploring PXRD, EDX and FESEM study. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Item Novel Co-Ni-graphene composite electrodes for hydrogen production(Royal Society of Chemistry, 2015) Subramanya, B.; Ullal, Y.; Shenoy, S.U.; Bhat, D.; Hegde, A.C.Active, stable and cost-effective electrocatalysts are key to water splitting for hydrogen production through electrolysis. Herein, we report the facile preparation of highly porous Co-Ni-graphene (Co-Ni-G) composite electrodes by electrodeposition for electrocatalytic applications. The incorporation of graphene into the Co-Ni matrix enhances the catalyst's activity for the hydrogen evolution reaction (HER) in an alkaline solution. The best coating exhibits a maximum current density of -850 mA cm-2 at -1.6 V, which is approximately 4 times better than that of the binary Co-Ni alloy indicating higher activity for hydrogen production. The addition of graphene to an electrolyte bath results in a porous encapsulated bundle of alloy nano-particles within the graphene network which effectively increases the electrochemically active surface area. As indicated by XPS analysis results, on addition of graphene the Co(0) and Ni(0) content in the deposit increases and as a result both cobalt/cobalt oxide and nickel/nickel oxide sites are evenly distributed on the Co-Ni-G electrode surface which is responsible for increased HER activity. The Tafel slope analysis showed that the HER follows a Volmer-Tafel mechanism. The structure-property relationship of the Co-Ni-G composite coating has been discussed by interpreting field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis results. © The Royal Society of Chemistry 2015.Item Morphological and structural characterisation of sol-gel electrospun Co3O4 nanofibres and their electro-catalytic behaviour(Royal Society of Chemistry, 2015) George, G.; Elias, L.; Hegde, A.C.; Anandhan, S.Evolution of hydrogen and oxygen are a crucial part of many renewable energy systems. The replacement of the essential and expensive components in such systems can reduce the capital cost and improve the effectiveness of those systems. In this study, Co3O4 nanofibres were fabricated from sol-gel assisted electrospun poly(styrene-co-acrylonitrile)/cobalt acetate tetrahydrate precursor composite fibres. The morphological and compositional features of the Co3O4 nanofibres obtained after calcination of the precursor nanofibers were studied using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results of X-ray diffraction study and Raman spectroscopy revealed that the average grain size of the fibres increased with the calcination temperature. Clear evidence of defects in the fibres was observed in ultraviolet-visible-near infrared and energy dispersive spectroscopic measurements. The electrocatalytic behaviour of Co3O4 nanofibres obtained at different calcination temperatures was studied using them for the water splitting reaction in an alkaline medium. The maximum efficiency in the hydrogen evolution reaction was achieved using the Co3O4 nanofibres obtained at the lowest calcination temperature, which had the highest surface area and the smallest grain size. © The Royal Society of Chemistry 2015.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.Item Electrolytic Synthesis of Ni-W-MWCNT Composite Coating for Alkaline Hydrogen Evolution Reaction(Springer New York LLC barbara.b.bertram@gsk.com, 2018) Elias, L.; Hegde, A.C.Nickel–tungsten multi-walled carbon nanotube (Ni-W-MWCNT) composite films were fabricated by an electrodeposition technique, and their electrocatalytic activity toward hydrogen evolution reaction (HER) was studied. Ni-W-MWCNT composite films with a homogeneous dispersion of MWCNTs were deposited from an optimal Ni-W plating bath containing functionalized MWCNTs, under galvanostatic condition. The presence of functionalized MWCNT was found to enhance the induced codeposition of the reluctant metal W and resulted in a W-rich composite coating with improved properties. The electrocatalytic behaviors of Ni-W-MWCNT composite coating toward HER were studied by cyclic voltammetry (CV) and chronopotentiometry techniques in 1.0 M KOH medium. Further, Tafel polarization and electrochemical impedance spectroscopy (EIS) studies were carried out to establish the kinetics of HER on the alloy and composite electrodes. The experimental results revealed that the addition of MWCNTs (having a diameter of around 10-15 nm) into the alloy plating bath has a significant effect on the electrocatalytic behavior of Ni-W alloy deposit. The Ni-W-MWCNT composite coating was found to show better HER activity than the conventional Ni-W alloy coating. The enhanced electrocatalytic activity of Ni-W-MWCNT composite coating is attributed to the MWCNT intersticed in the deposit matrix, evidenced by surface morphology, composition and phase structure of the coating through SEM, EDS and XRD analyses, respectively. © 2018, ASM International.Item Effect of TiO2 nanoparticles on hydrogen evolution reaction activity of Ni coatings(University of Science and Technology Beijing, 2018) Kullaiah, R.; Elias, L.; Hegde, A.C.The electrocatalytic activity of electrodeposited Ni and Ni–TiO2 coatings with regard to the alkaline hydrogen evolution reaction (HER) was investigated. The Ni coatings were electrodeposited from an acid chloride bath at different current densities, and their HER activities were examined in a 1.0-mol·L-1 KOH medium. The variations in the HER activity of the Ni coatings with changes in surface morphology and composition were examined via the electrochemical dissolution and incorporation of nanoparticles. Electrochemical analysis methods were used to monitor the HER activity of the test electrodes; this activity was confirmed via the quantification of gases that evolved during the analysis. The obtained results demonstrated that the Ni–TiO2 nanocomposite test electrode exhibited maximum activity toward the alkaline HER. The surface appearance, composition, and the phase structure of all developed coatings were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), respectively. The improvement in the electrocatalytic activity of Ni–TiO2 nanocomposite coating toward HER was attributed to the variation in surface morphology and increased number of active sites. © 2018, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature.Item Polymorph nickel titanate nanofibers as bifunctional electrocatalysts towards hydrogen and oxygen evolution reactions(Royal Society of Chemistry, 2019) Kumar, B.; Tarafder, K.; Shetty, A.R.; Hegde, A.C.; Gudla, V.C.; Ambat, R.; Kalpathy, S.K.; Anandhan, S.Producing pure H2 and O2 to sustain the renewable energy sources with minimal environmental damage is a key objective of photo/electrochemical water-splitting research. Metallic Ni-based electrocatalysts are expensive and eco-hazardous. This has rendered the replacement or reduction of Ni content in Ni-based electrocatalysts a decisive criterion in the development of bifunctional electrocatalytic materials. In the current study, spinel/ilmenite composite nickel titanate (NTO) nanofibers were synthesised using sol-gel assisted electrospinning followed by pyrolysis at different soaking temperatures (viz., 773, 973, and 1173 K). The presence of a defective spinel NTO phase (SNTO) distributed uniformly along the nanofibers was confirmed by X-ray photoelectron and Raman spectroscopy. The electron micrographs revealed the morphological change of NTO nanofibers from a mosaic to bamboo structure with an increase in pyrolysis soaking temperature. The electrocatalytic activity of NTO nanofibers obtained at different pyrolysis soaking temperatures for alkaline water-splitting was studied. The highly defective SNTO manifests properties similar to metallic Ni and favours H2 evolution through the hydrogen evolution reaction (HER) by adsorbing more H+ ions on active sites. In contrast, the ilmenite NTO favours O2 discharge. These results are explained based on the morphology of the NTO nanofibers. The mosaic structure which has higher porosity and greater SNTO content shows excellent HER performance. In contrast, the large bamboo structured NTO nanofibers which have lesser porosity and SNTO content cage the bigger (OH)ads ions at their catalytic sites to facilitate OER performance. 2019 © The Royal Society of Chemistry.