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![SE micrographs of electrodeposited cobalt metal at different concentration of additives (TPAB) (a) Blank, (b) 10 mg/L, (c) 20 mg/L, (d) 50 mg/L [Co] in electrolyte = 60 g/L, pH of solution = 4, electrolysis time = 3 h, current density = 200 A/m 2 , temperature = 333 K (60 °C).](profile/Bankim-Tripathy-3/publication/273351322/figure/fig6/AS:593897222848519@1518607540661/SE-micrographs-of-electrodeposited-cobalt-metal-at-different-concentration-of-additives.png)
SE micrographs of electrodeposited cobalt metal at different concentration of additives (TPAB) (a) Blank, (b) 10 mg/L, (c) 20 mg/L, (d) 50 mg/L [Co] in electrolyte = 60 g/L, pH of solution = 4, electrolysis time = 3 h, current density = 200 A/m 2 , temperature = 333 K (60 °C).
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In the current study, the effect of an organic additive tetra propyl ammonium bromide (TPAB) on the structural, morphological characteristics of the cobalt metal produced from aqueous sulfate solutions has been investigated. The concentration of TPAB was varied over a range of 1 to 50 mg/L to evaluate its effect on current efficiency, energy consum...
Citations
... In Figure 3a, the as-prepared catalyst was mostly present in Co 3 O 4 , where the peaks were assigned to a pure Co 3 O 4 phase. [38][39][40] The crystallite structure of the spent catalyst changed significantly with new diffraction peaks observed at 41, 47, and 76°2θ, corresponding to metallic Co (100), (101), (110), respectively, [41,42] while the peak at 44°2θ indicated the dominant Co 3 O 4 (404) phase. This confirms the change in the oxidation state of Co from higher one (Co 3 O 4 ) to lower one CoO x during the catalytic reaction under the reducing condition of RWGS and the applied polarization. ...
In this study, Copper‐modified Co3O4 (Cu/Co3O4) catalysts were investigated for the reverse water gas shift (RWGS) reaction at 200–400 °C under different CO2 : H2 ratios. It was found that the electrocatalytic performance of Co3O4 was improved by loading 4 weight percent (wt.%) Cu nanoparticles (average size: 13 nm), which could be then used as an electrode in electrochemical promotion of catalysis (EPOC) studies. Under the applied voltages of +2 V and −1 V, the catalytic rates were suppressed and increased by about 40 % and 14 %, respectively. This was due to the changes in the active oxidation states of Cu and Co caused by O²⁻ migration under polarization, as confirmed by XPS, XRD, and cyclic voltammetry (CV). The study also revealed that the exchange current density (i0) was counter‐correlated with the open‐circuit catalytic rate (r0) and could serve as an informative tool for predicting the catalytic rate, which was demonstrated for the first time in the instance of RWGS reaction.
... Mechanical, tribological, corrosion and magnetic properties of electrodeposits are strongly affected by microstructure and morphology of the coatings, which themselves are a function of bath composition and deposition conditions [2,7−9]. Direct current is widely used for depositing metal coatings due to its simplicity [2,13]. However, application of the alternative pulse electrodeposition technique has increased recently due to its ability in producing nanocrystalline deposits with adjusting the pulse parameters [2,14]. ...
Nanocrystalline cobalt coatings were produced from cobalt sulfate based electrolytes by using pulse current electrodeposition technique. The effects of bath composition and electrodeposition condition on current efficiency, morphology, structure and hardness of the coatings were investigated and the optimum deposition condition was determined. It was found that increment of cobalt sulfate concentration and sodium dodecyl sulfate (SDS) concentration in the bath had a negligible effect on microhardness of the coatings, while they were effective on electrodeposition current efficiency. Adding saccharin to electrodeposition bath decreased crystallite size of hexagonal close-packed (hcp) cobalt films and increased their microhardness without significant effect on current efficiency. Smoother and less defective coatings were also obtained from baths containing SDS and saccharin. The results revealed that both the current efficiency and microhardness were changed by variation of peak current density and duty cycle. Besides change of smooth morphology of the coatings to needle-shaped one, crystallite sizes and preferred orientation also varied with increasing the current density and duty cycle.
The structural stability of DNA origami nanostructures in various chemical environments is an important factor in numerous applications, ranging from biomedicine and biophysics to analytical chemistry and materials synthesis. In this work, the stability of six different 2D and 3D DNA origami nanostructures is assessed in the presence of three different chaotropic salts, i.e., guanidinium sulfate (Gdm2SO4), guanidinium chloride (GdmCl), and tetrapropylammonium chloride (TPACl), which are widely employed denaturants. Using atomic force microscopy (AFM) to quantify nanostructural integrity, Gdm2SO4 is found to be the weakest and TPACl the strongest DNA origami denaturant, respectively. Despite different mechanisms of actions of the selected salts, DNA origami stability in each environment is observed to depend on DNA origami superstructure. This is especially pronounced for 3D DNA origami nanostructures, where mechanically more flexible designs show higher stability in both GdmCl and TPACl than more rigid ones. This is particularly remarkable as this general dependence has previously been observed under Mg2+-free conditions and may provide the possibility to optimize DNA origami design toward maximum stability in diverse chemical environments. Finally, it is demonstrated that melting temperature measurements may overestimate the stability of certain DNA origami nanostructures in certain chemical environments, so that such investigations should always be complemented by microscopic assessments of nanostructure integrity.
The voltammetric responses of novel porous Co3O4 spinel materials supported on MOF-derived carbons (MOFDC) have been described. The electrocatalysts were prepared using microwave-assisted hydrothermal methods, obtaining both Rich- and Starved-Co3O4 MOF-derived carbons (i.e., R-Co3O4@MOFDC and S-Co3O4@MOFDC). The physicochemical properties of the porous electrode materials were thoroughly characterized via XRD, SEM, BET, EDX and XPS. The R-Co3O4@MOFDC shows low specific surface area and small pore volume, while the S-Co3O4@MOFDC is characterized with high specific surface area and large pore volume, about four times larger than the former. Using dopamine as a model analyte, the study shows the voltammetric response towards the detection of dopamine detection to be strongly dependent on the diffusive and adsorptive/capacitive modes: R-Co3O4@MOFDC exhibits high diffusive mode with enhanced dopamine detection, while S-Co3O4@MOFDC exhibits high adsorptive mode and relatively poor dopamine detection. The overall voltammetric response is interpreted in terms of fast semi-infinite planar diffusion of dopamine towards the electrode surface and the inhibition of the thin layer diffusion process due to the depletion of the electrolyte trapped within pores (leading to disadvantageous adsorption). At higher concentrations (DA > 3 mM) the adsorption behaviour at these porous electrode follows the Langmuir adsorption isotherm with adsorption equilibrium constant (β) of (1.96 ± 0.16) × 10⁵ and (2.53 ± 0.20) × 10⁵ M⁻¹ for R-Co3O4@MOFDC and S-Co3O4@MOFDC, respectively. This study opens doors for rational design and development of transition metal-based MOFDC for the detection of biomolecules.
To develop cobalt coating for use in diamond tools, cobalt electrodeposition was conducted in Watts-type baths. The effects of tetrabutylammonium bromide and 2-butyne-1,4-diol on the surface morphology, crystallographic structure, surface roughness and microhardness of thick cobalt deposits were investigated in the presence of saccharin. The addition of tetrabutylammonium bromide had a modest effect on the morphology, crystallographic structure and microhardness of cobalt deposits, while it reduced the surface roughness noticeably. On the other hand, the addition of 2-butyne-1,4-diol favored the formation of a much smoother deposit, but unexpectedly, it dramatically decreased the microhardness as a result of increased grain size, accompanied by the changes both in the morphology from fine-grained structure to lenticular structure and in the crystal structure from (0002) preferred orientation to (101¯0) preferred orientation. With the addition of a mixture of saccharin, tetrabutylammonium bromide and 2-butyne-1,4-diol, a harder and smoother thick cobalt deposit was obtained. To understand the role of these additives, linear sweep voltammetry and transmission electron microscopy were also used to investigate the reduction behavior of Co ions and the microstructure of cobalt deposits, respectively, which were compared with the morphological, structural and mechanical properties of cobalt deposits. Possible mechanisms for the alteration in the properties of cobalt deposits were discussed.
Cobalt electrodeposition was carried out in Watts type bath to investigate the effects of sodium saccharin and tetramethylammonium bromide on the crystal structure, morphology, surface roughness and microhardness of thick cobalt deposits. The addition of sodium saccharin changed the crystal orientation from mixed hcp (101¯0) and (112¯0) planes to mixed hcp (101¯0), (0002) and (101¯1) planes; deposit morphology was correspondingly changed from curved dihedral structure to fine grained structure; it also favored the formation of deposits of small grain size and high microhardness, yet led to a much rougher surface. Tetramethylammonium bromide had minor effects on the crystal structure, morphology and microhardness of Co deposits; however, combined with sodium saccharin, it decreased both the density and height of hillock shaped surface structure resulted from the addition of saccharin and favored the formation of smoother deposit. These changes could be associated with the behaviors of the two additives in cobalt deposition process.
The electrodeposition of manganese metal from aqueous solutions is problematic due to its high electroreduction potential demanding unique process challenges. In the present work, electrolytic manganese metals (EMMs) of high quality are deposited from sulphate solutions in the presence of quaternary amines: tetra ethyl ammonium bromide (TEABr), tetra propyl ammonium bromide and tetra butyl ammonium bromide. The concentrations of these additives were varied over a relatively broad range to evaluate their effect on current efficiency (CE), specific energy consumption, polarisation behaviour of the cathode and deposit morphology of the electrodeposited manganese metal. A maximum CE of more than 68% was achieved in the presence of 100 mg.L⁻¹ TEABr in the electrolytic bath at a current density of 500 A.m⁻². X-ray diffraction studies revealed that (330, 411) planes were the most preferred planes of crystal growth during manganese electrodeposition resembling alpha-manganese regardless of the type of quaternary amines used. A smooth and compact deposit was obtained with TEABr that was also supported by the scanning electron micrographs showing uniform deposit morphologies. The presence of these quaternary amines in the electrolyte causes polarisation of the cathode during electrodeposition. The degree of polarisation increases with an increase in the bulkiness of the alkyl group on the quaternary nitrogen atom of the additive. The quaternary amine TEABr was found to be the most suitable additive for producing the desired quality of EMM with better current yield.
