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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 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 Electrodeposition of laminar coatings of Ni-W alloy and their corrosion behaviour(Elsevier, 2015) Elias, L.; Hegde, A.The attractiveness of electroplating for the synthesis of advanced materials is linked to large selection of plating conditions coupled with different mass transfer processes towards the cathode, and this allows the tailoring of different properties of many electrodeposited coatings. This theme has been exploited effectively in the development of a new class of coatings; called composition modulated multilayered (CMM), or in short laminar coatings. The work embodied in this paper is to demonstrate how the corrosion resistance of monolayer Ni-W alloys can be increased to many fold of its magnitude by multilayer deposition. Ni-W coatings have been deposited on mild steel (MS) in a laminar multilayer pattern from a citrate bath using single bath technique (SBT). Electrodeposits having alternate layers of alloys, having different compositions were developed by modulating the direct current (DC). CMM coating configurations have been optimized from a newly developed bath, in terms of current pulse height and thickness of each layer to maximize its corrosion protection ability, in relation to its monolayer coating, developed from same bath for same time. The process and product of the Ni-W coatings have been characterized using different instrumental methods, such as cyclic voltammetry (CV), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) study. The better corrosion resistance behaviour of CMM Ni-W coatings has been analysed in the light of increased surface areas of the coatings due to layering, and results are discussed. © 2015 Elsevier B.V.Item Development of nanolaminated multilayer Ni-P alloy coatings for better corrosion protection(Royal Society of Chemistry, 2016) Elias, L.; Bhat, K.U.; Hegde, A.Nanolaminated multilayer Nickel-Phosphorous (Ni-P) alloy coatings were developed on mild steel from a citrate bath using glycerol as an additive. Multilayer Ni-P alloy coatings having nanolaminated layers of alloys of alternatively different compositions have been developed using pulsed direct current (DC) by cyclic modulation of the cathode current density. The composition and number (hence thickness) of the layers were tailored by periodic modulation of the current density (c.d.) and time using a programmable power source. The deposition conditions were optimized for both the composition and thickness of the individual layers for the best performance of the coatings against corrosion. Electrochemical corrosion study, evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) demonstrated that the multilayer Ni-P alloy coating with 300 nanolaminated layers, represented as (Ni-P)1.0/4.0/300 showed several fold better corrosion resistance compared to its monolayer counterpart (deposited using regular DC) from the same electrolytic bath. Drastic improvement in the corrosion protection efficacy of the nanolaminated multilayer Ni-P alloy coatings were attributed to an increase in number of interfaces, separating layers of alloys having different morphologies, compositions and phase structures, which was supported by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses, respectively. The corrosion rates of the multilayer Ni-P alloy coatings were decreased with increasing number of layers, only up to an optimal level and then increased. The increase in corrosion rates at a higher degree of layering were attributed to the diffusion of layers, due to the very short deposition time of each layer. © The Royal Society of Chemistry 2016.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 Effect of magnetic field on corrosion protection efficacy of Ni-W alloy coatings(Elsevier Ltd, 2017) Elias, L.; Hegde, A.C.High corrosion resistant Ni-W alloy coatings were developed using magnetoelectrodeposition (MED) approach for the protection of mild steel substrates. The conditions for the development of more corrosion resistant MED Ni-W alloy coatings were optimized by inducing a magnetic field (B) during deposition, in terms of intensity and direction. The applied magnetic field was used as a tool to alter the crystallinity, composition and thereby the corrosion resistance of the coatings. It was demonstrated that the corrosion resistance of Ni-W alloy coatings can be improved to many folds of its magnitude by MED approach. Significant increase in corrosion resistance exhibited by MED coatings (under both parallel and perpendicular magnetic field, B) is attributed to the increased W content of the alloy affected by an increase in limiting current density (iL). The high corrosion resistance of the MED Ni-W alloy coatings was explained in the light of magnetohydrodynamic (MHD) effect, responsible for the increased W content, brought about by the enhanced mass transport. The inherent limitations of the bath like low iL and induced type of codeposition which impedes the development of W rich alloy coatings has been successfully resolved by MED method. Drastic improvement in corrosion resistance is ascribed to the basic difference in the process of electrocrystallization and phases formed during MED, confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) study. The results are discussed with greater insight into binary alloy deposition and mass transfer process at cathode/electrolyte interface. © 2017 Elsevier B.V.Item Multilayered Zn-Ni alloy coatings for better corrosion protection of mild steel(Elsevier B.V., 2017) Rashmi, S.; Elias, L.; Hegde, A.C.A simple aqueous electrolyte for the deposition of anti-corrosive Zn-Ni alloy coatings was optimized using conventional Hull cell method. The corrosion protection value of the electrodeposited coatings at a current density (c.d.) range of 2.0–5.0 A dm?2 has been testified in 5 wt% NaCl solution, as representative corrosion medium. The electrochemical behavior of the coatings towards corrosion was related to its surface topography, elemental composition and phase structure using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses, respectively. Among the monolithic coatings developed at different c.d.’s, the coating obtained at 3.0 A dm?2 was found to be the best with least corrosion current (icorr) value. Further, the corrosion protection efficacy of the monolayer coatings were improved to many folds through multilayer coating approach, by modulating the cyclic cathode current densities (CCCD's). The composition modulated multilayer (CMM) Zn-Ni alloy coating with 60 layers, developed from the combination of CCCD's 3.0 and 5.0 A dm?2 was found to be the best with 3 fold enhancement in corrosion protection efficiency. The formation of multilayer coatings was confirmed using cross-sectional SEM, and the experimental results are discussed with tables and figures. © 2016 Karabuk UniversityItem Effect of including the carbon nanotube and graphene oxide on the electrocatalytic behavior of the Ni-W alloy for the hydrogen evolution reaction(Royal Society of Chemistry, 2017) Elias, L.; Hegde, A.C.The present work reports the electrocatalytic activities of the composite coatings of Ni-W developed using the carbon nanotube (CNT) and graphene oxide (GO). Ni-W-CNT and Ni-W-GO coatings were developed by exploiting the advantages of the composite electrodeposition technique. The effect of CNT and GO on the induced codeposition behavior of the reluctant metal W and the relationship with their electrocatalytic efficiency was studied. The electrocatalytic alkaline water splitting efficiency for the hydrogen evolution reaction (HER) of each of the electrode materials was tested by using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Furthermore, the practical utility of each of the electrode materials was evaluated by measuring the amount of H2 gas evolved. The variation in electrocatalytic activity with composition, structure, and morphology of the coatings was examined systematically using XRD, SEM, and EDS analyses. The Ni-W-CNT and Ni-W-GO composite coatings yielded much better electrocatalytic activities for the HER than did the as-coated Ni-W alloy. The obtained results showed Ni-W-CNT composite coating as the best electrode material for alkaline HER, attributed by both increased W content and number of electroactive centres. Moreover, the number of electroactive centres was found to be affected by the homogeneous distribution of CNT in the alloy matrix. © 2017 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.