B.C. Tripathy

Electrolytic manganese dioxide (EMD): a perspective on worldwide production, reserves and its role in electrochemistry

Electrolytic manganese dioxide (EMD) is the critical component of the cathode material in modern alkaline, lithium, and sodium batteries including electrochemical capacitors and hydrogen production. In terms of environmental and cost considerations, EMD is likely to remain the preferred energy material for the future generation, as it has been in recent decades. Diminishing fossil fuels and increasing oil prices have created the need to derive energy from sustainable sources. The energy storage device from alternative and inexpensive sources, such as low grade manganese ores, has a niche in the renewable energy and portable electronics market. Despite vast manganese sources along with the current activity in producing modified EMD materials from secondary sources, to a surprise, India mostly imports EMD to meet its demand. Keeping this in view, a comprehensive review has been prepared on the synthesis, physical and electrochemical characterization of EMD produced from synthetic solutions and secondary sources. This review summarizes the available EMD sources in the world including Indian deposits and the recent investigations of fundamental advances in understanding the electrochemical mechanism involved in aqueous rechargeable batteries and electrochemical capacitors, thus leading to an improved energy storage performance, which is essential for their long term use in storing renewable energy supply.

Effect of antimony(III) on the electrocrystallisation of zinc from sulphate solutions containing SLS

A detailed investigation has been carried out to determine the effect of antimony(III) on the electrocrystallisation of zinc from sulphate solutions containing sodium lauryl sulphate (SLS). The results indicated that addition of Sb(III) at trace level to the electrolysis bath without sodium lauryl sulphate decreased the current efficiency (CE) and deteriorated the quality of the zinc electrodeposits. However, its addition to the bath containing sodium lauryl sulphate increased the current efficiency and also improved the surface morphology of the zinc electrodeposits. There was no trace of antimony found in any of the deposits. Cathodic polarisation curves were traced and analysed to determine the kinetic parameters, exchange current density, Tafel slopes and transfer coefficients so as to elucidate the nature of the electrode reactions. Presence of Sb(III) alone in the electrolyte depolarised the cathode and SLS alone polarised it; however, presence of both gave a balanced condition suitable for zinc electrowinning.

Electrodeposition of manganese dioxide: effect of quaternary amines

The effect of quaternary ammonium salts (tetraethyl ammonium bromide, tetrapropyl ammonium bromide, and tetrabutyl ammonium bromide) on the structural, morphological, and electrochemical characteristics of electrolytic manganese dioxide (EMD) obtained from acidic aqueous sulfate solution has been investigated. Physical characterization of the EMD was achieved by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, and Fourier transform infrared spectroscopy. The charge–discharge profile of the materials was determined to evaluate their potential for alkaline battery applications. The presence of these quaternary ammonium salts as organic additives in the solution increased the current efficiency while decreasing energy consumption during electrochemical deposition of manganese dioxide (MnO2). All the additives influenced the discharge characteristics of the EMD samples significantly, producing a cathode material with increased cumulative discharge capacity relative to EMD prepared in the absence of additives. This is attributed to the ability of the additives to affect the particle size and morphology, and therefore electrochemical activity, of electrodeposited materials; the effects in the case of the additives investigated in this work were positive, producing a material with potential application to battery technology.

Electrodeposition of cobalt from aqueous sulphate solutions in the presence of tetra ethyl ammonium bromide

Abstract The effect of tetra ethyl ammonium bromide (TEAB) as an additive on the structural, morphological characteristics of the cobalt metal produced from aqueous sulphate solutions was investigated. The concentration of TEAB was varied in a range of 1–50 mg/L to evaluate its effect on current efficiency, energy consumption and quality of electrodeposited cobalt metal. Smooth and bright deposits of cobalt were obtained at low concentration of TEAB (10 mg/L) maintaining a current efficiency of 99.6%, with a low energy consumption of 2.38 kW·h/kg. X-ray diffraction studies reveal that (100) plane is the most preferred plane of crystal growth during cobalt electrodeposition. Scanning electron micrographs indicate that smooth and uniform deposit of cobalt is obtained at 10 mg/L beyond which the deposit quality deteriorates. Cyclic voltammetric studies indicate that the presence of TEAB in the electrolytic bath polarizes the cathode and decreases the cathodic current considerably. XPS results confirm the electrodeposition of high pure cobalt with no sign of chemical bonding with TEAB as evident from the FTIR spectra.

Role of hydrazine and hydrogen peroxide in aluminium hydroxide precipitation from sodium aluminate solution

Aluminium hydroxide precipitation from synthetic sodium aluminate solution was studied in the presence of hydrazine or hydrogen peroxide. The addition of low concentration of hydrazine is found to be effective, while higher amount of hydrogen peroxide is required to generate similar effect. XRD data confirm the product phase to be gibbsitic by nature. The scanning electron micrographs (SEM) show that agglomerated products form in the presence of hydrazine while fine discrete particles are produced with hydrogen peroxide. The probable mechanism of precipitation in the presence of hydrazine and hydrogen peroxide is also discussed.

An evaluation of cadmium sorption potential of waste aluminium dross

Abstract The removal of Cd(II) from aqueous solution onto aluminium dross surface was investigated. The influence of pH, contact time, initial metal ion concentration and temperature on the effectiveness of the removal process was studied. The variation of adsorption efficiency with pH indicates that the aluminium dross has residual negative charge on the surface. At low pH, H+ ion gets adsorbed preferentially than Cd(II) ion but at higher pH, Cd(II) ion gets adsorbed in larger numbers. It has been further observed that the adsorption efficiency increases with temperature indicating an increase in kinetic energy of the solute ions or decrease in boundary layer resistance to mass transfer. Kinetic study indicated that in the present work the adsorption process follows mainly pseudo-first-order rate model. The low activation energy (18.3 kJ mol−1) reveals that the process is spontaneous and physical in nature. The value of is negative which further decreases with temperature indicating spontaneity of the ad...

Synthesis and characterization of fibrous nickel hydroxide obtained from spent nickel catalyst

The recovery of nickel from spent nickel catalyst for the preparation of nickel hydroxide was studied. Nickel was extracted from the spent catalyst by acid leaching with 1 mol/L sulfuric acid at 90 C. Purified nickel solution was used in the preparation of nickel hydroxide. Three different methods, namely urea hydrolysis, conventional, and hydrothermal methods, of precipitation using NaOH were employed to get various nickel hydroxides samples named as Ni(OH) 2-U, Ni(OH)2-C, and Ni(OH)2-H, respectively. Hydrothermal treatment induced better crystallinity in the Ni(OH)2 compared with conventional method. Both Ni(OH)2-C and Ni(OH) 2-H samples have mixed phases of β-Ni(OH)2 and α*-Ni(OH)2·0.75H2O phases, whereas Ni(OH)2-U has only α*-Ni(OH) 2·0.75H2O. TEM image of Ni(OH)2-U sample shows rod-like Ni(OH)2 structures. Among all, Ni(OH)2-U shows the best electrochemical activity.

Electrodeposition of γ-MnO 2 from Manganese Nodule Leach Liquor: Surface Modification and Electrochemical Applications

The electrolytic manganese dioxide (EMD) production through electrodeposition from manganese nodules by reduction leaching in H2SO4 medium using sucrose as reductant followed by purification through 2-stage precipitation methods is described. The purified leach liquor was the starting solution for electrodeposition. Influence of in situ addition of a cationic surfactant Cetyltri-methylammonium bromide (CTAB) (0–500 mg dm−3) on the surface morphology and electrochemical properties of the EMD was examined. The XRD patterns of the deposited material were indexed to the γ-MnO2 phase. FESEM results demonstrated that in the presence of CTAB uniform nano-fibrous type grains were formed. Higher concentration of CTAB in the electrolytic bath however, drastically decreased the current efficiency (CE) and increased the energy consumption (EC) during electrodeposition. Under the optimum CTAB concentration of 100 mg dm−3 the obtained CE and EC values were 87.64% and 1.70 kWh/Kg respectively.

Effect of Tween 80 on electrochemical deposition of cobalt from sulphate solutions

Cobalt is an essential engineering metal among the less abundant metals found in the earth crust with wide range of applications. However due to the scarcity of resources, it is required to produce the metal in a cost effective manner to meet the supply demands. Cobalt is produced by electrodeposition from chloride or sulphate media, the latter being a widely used method. The use of additives in the electrolytic bath during electrodeposition from sulphate solutions can not only solve issues related to current efficiencies, but also result in production of uniform, smooth and bright deposits of the metal. The present work investigates the effect of Tween 80 a non-ionic additive, on the electrodeposition of cobalt. The concentration of the additive Tween 80 was varied over a range of 1–50 mg/L to evaluate the changes in current efficiency, specific energy consumption and quality of electrodeposited cobalt metal. The results indicated that, apart from increasing the current efficiency, the additive produced bright cobalt deposits. A maximum current efficiency of 98.1% was achieved with 20 mg/L Tween 80 in the electrolytic bath. X-ray diffraction studies have revealed that <100> direction is the most preferred orientation of crystal growth during cobalt electrodeposition. However it is shifted to <110> at higher concentrations (50 mg/L) of the additive. Scanning electron micrographs indicate that smooth, compact and uniform deposits of cobalt are obtained at 20 mg/L beyond which there is deterioration in the quality of deposits. Cyclic voltammetric studies indicated polarization of the cathode in the presence of Tween 80. This behaviour was also reflected in the decrease of the rate of electron transfer as evident from exchange current density (i0) values.

Erratum to: Electrodeposition of manganese dioxide: effect of quaternary amines

The effect of quaternary ammonium salts (tetraethyl ammonium bromide, tetrapropyl ammonium bromide, and tetrabutyl ammonium bromide) on the structural, morphological, and electrochemical characteristics of electrolytic manganese dioxide (EMD) obtained from acidic aqueous sulfate solution has been investigated. Physical characterization of the EMD was achieved by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, and Fourier transform infrared spectroscopy. The charge–discharge profile of the materials was determined to evaluate their potential for alkaline battery applications. The presence of these quaternary ammonium salts as organic additives in the solution increased the current efficiency while decreasing energy consumption during electrochemical deposition of manganese dioxide (MnO2). All the additives influenced the discharge characteristics of the EMD samples significantly, producing a cathode material with increased cumulative discharge capacity relative to EMD prepared in the absence of additives. This is attributed to the ability of the additives to affect the particle size and morphology, and therefore electrochemical activity, of electrodeposited materials; the effects in the case of the additives investigated in this work were positive, producing a material with potential application to battery technology.