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Water-insoluble PbSO 4 , PbO 2 , and PbO are fairly soluble in choline chloride/urea deep eutectic solvent (ChCl/urea DES) in 1:2 molar ratio. Very interestingly, solution prepared from PbO 2 exhibits the almost identical electrochemical behavior as those from PbSO 4 and PbO, indicating that Pb(II) is formed in the DES regardless of what Pb compound is introduced. The electrochemical reduction of the Pb(II) species is determined as an irreversible process, and involves the three-dimensional (3D) instantaneous nucleation with diffusion-controlled growth. From the dependence of the diffusion coefficient on temperature, the activation energy for diffusion of PbSO 4 and PbO 2 is determined to be 33.7 and 34.1 kJ mol −1 , respectively. Electrodeposition of Pb was achieved potentiostatically and galvanostatically. The surface morphology of Pb deposits significantly depends on the applied potential and current. The coulombic efficiency of Pb electrodeposition is higher than 90%. Electrodeposition of Pb from a wet DES containing a mixture of three different Pb sources is also investigated. The XRD analysis confirmed that the electrodeposits consisted of metallic Pb. [ABSTRACT FROM AUTHOR]

A nanoporous gold wire electrode (NPGWE) was prepared using a published one-step method from a 0.3 M oxalic acid at room temperature. It was found in this study that the surface morphology, including the pore size and the width of the ligaments, and thus the surface roughness of the NPGWE could be easily manipulated by controlling the solution stirring rate. The NPGWE was used for the study of electrochemical oxidation and determination of glucose in 0.1 M NaOH using cyclic voltammetry. The effect of two potential interferences chloride ion and ascorbic acid was assessed. The electrode showed a linear range of glucose concentration from 0.5 mM to 10 mM with a detection limit of 8 μM. [ABSTRACT FROM AUTHOR]

Abstract: The voltammetric behavior of cuprous ions has been studied at disk electrodes of glassy carbon and polycrystalline platinum in a new hydrophilic 1-butyl-3-methylimidazolium salicylate ionic liquid (BMI-SAL IL). Cuprous ions Cu(I) were introduced into the IL by the anodic dissolution of a Cu wire electrode or by the addition of CuCl. This air- and water-stable hydrophilic IL is very similar to dicyanamide (DCA)-based ILs because both DCA anions and salicylate (SAL) anions have very strong ligand properties; therefore, many metal salts, such as metal halides, are very soluble in this IL. However, the source of SAL anions, sodium salicylate, is considerably cheaper than sodium dicyanamide salt. The potentiostatic electrodeposition of copper onto iron substrates has also been investigated in this study. The surface morphologies of the copper deposits were significantly altered by the electrodeposition potential; granular, mirror-like, and porous copper deposits could be obtained at different negative potentials. The activity of the copper deposit-modified iron electrodes toward the electrochemical nitrate reduction in alkaline solutions was found to significantly depend on the surface morphologies. The granular and the porous surfaces showed better activities. The mirror-like surface, however, had no activity on the electrochemical nitrate reduction. [Copyright &y& Elsevier]

Abstract: In this study, the voltammetric behavior of Pd(II), Ni(II), and mixtures of Pd(II) and Ni(II) was carried out in room-temperature N-butyl-N-methylpyrrolidinium dicyanamide ionic liquid (BMP-DCA IL). Electrodeposition of PdNi bimetal was achieved by controlled-potential electrolysis at iron wire electrodes from BMP-DCA containing various molar ratios of PdCl2/NiCl2. BMP-DCA shows good solubilities to PdCl2 and NiCl2, respectively, leading to the convenience for preparing the electrodepositing baths. By tuning the molar ratios of Pd(II)/Ni(II) in the electrodepositing baths and/or the applied potentials, PdNi coatings with various atomic contents of Pd could be obtained. Among these PdNi bimetallic coatings, the PdNi coatings with atomic ratios of ∼80/20 had the highest oxidation current in methanol oxidation reaction (MOR) in 1M NaOH and exhibited the best poisoning tolerance. Powder X-ray diffraction analysis indicated that two separate metallic phases belonging to Pd and Ni existed in the PdNi coatings. The diffraction signal of Pd was very broad, indicating the tiny crystal size of Pd in the bimetal coatings. The scanning electron spectroscopic micrographs of PdNi coatings demonstrated that the Pd∼80Ni∼20 coatings had three-dimensional structures. This morphological characteristic implied that the composition and the surface morphology of the PdNi coatings equivalently contributed to the electrocatalytic activity toward MOR. The Pd∼80Ni∼20-coated iron-electrode (Fe/Pd∼80Ni∼20) was used to detect methanol and the linearity was observed in 3.53μM to 758.88μM using hydrodynamic chronoamperometry where a potential of −0.1V (vs. Ag/AgCl) was applied. [Copyright &y& Elsevier]

Abstract: Nonenzymatic electrochemical determination of ethanol and glucose was respectively achieved using PdNi- and Pd-coated electrodes prepared by electrodeposition from the novel metal-free ionic liquid (IL); N-butyl-N-methylpyrrolidinium dicyanamide (BMP-DCA). BMP-DCA provided an excellent environment and wide cathodic limit for electrodeposition of metals and alloys because many metal chlorides could dissolve in this IL where the reduction potentials of Pd(II) and Ni(II) indeed overlapped, leading to the convenience of potentiostatic codeposition. In aqueous solutions, the reduction potentials of Pd(II) and Ni(II) are considerably separated. The bimetallic PdNi coatings with atomic ratios of ∼80/20 showed the highest current for ethanol oxidation reaction (EOR). Ethanol was detected by either cyclic voltammetry (CV) or hydrodynamic amperometry (HA). Using CV, the dependence of EOR peak current on concentration was linear from 4.92 to 962μM with a detection limit of 2.26μM (σ =3), and a linearity was observed from 4.92 to 988μM using HA (detection limit 0.83μM (σ =3)). The Pd-coated electrodes prepared by electrodeposition from BMP-DCA showed electrocatalytic activity to glucose oxidation and CV, HA, and square-wave voltammetry (SWV) were employed to determine glucose. SWV showed the best sensitivity and linearity was observed from 2.86μM to 107μM, and from 2.99mM to 10.88mM with detection limits of 0.78μM and 25.9μM (σ =3), respectively. For glucose detection, the interference produced from ascorbic acid, uric acid, and acetaminophen was significantly suppressed, compared with a regular Pt disk electrode. [ABSTRACT FROM AUTHOR]

Abstract: The voltammetric behavior of N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid (BMP-TFSI) containing Cu(I), Mn(II), or mixtures of Cu(I) and Mn(II) as well as the electrodeposition of copper–manganese alloy coatings (Cu–Mn alloy coatings) was studied at 323K. The Cu(I) and Mn(II) species required to prepare these coatings were introduced into the BMP-TFSI by anodic dissolution of the relevant metallic electrodes. Electrodeposits of Cu, Mn, and Cu–Mn with various contents of Mn can be obtained by controlled-potential electrolysis. It was found that the compositions and surface morphology of the electrodeposited Cu–Mn alloy coatings depend on the deposition potentials and the concentration ratio of [Cu(I)]/[Mn(II)] in BMP-TFSI. The Cu–Mn alloy coatings obtained in this study were compact and adherent. They did not show any significant X-ray diffraction signal that could be assigned to the crystalline structures of Cu, Mn, or Cu–Mn alloys. In the aqueous solution containing 0.1M NaCl, the Cu–Mn alloy coatings demonstrated passive behavior—no continuous oxidation was observed. However, a significant oxidation current was observed at the electrodes deposited with Cu or Mn. [Copyright &y& Elsevier]

Abstract: Carbazole was electropolymerized on indium tinoxide (ITO) electrodes in two air- and water-stable room-temperature ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6) and N-butyl-N-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide (BMP-TFSI), respectively, using three potentiostatic methods (i.e., cyclic voltammetry, potentiostatic electrolysis, and potentiostatic pulse electrolysis). The polymer films obtained in both ionic liquids (ILs) adhered on the electrode surface well; however, the polycarbazole (PCz) films obtained in the more viscous BMI-PF6 exhibited a denser structure. The PCz films showed electrochromic behavior; deep green was observed in the oxidative state and pale green in the reductive state. Anions or viscosities of the ILs seem to influence the depth of color change. PCz films were also prepared under a normal atmosphere. [Copyright &y& Elsevier]

The electrochemistry of cesium was investigated at mercury electrodes in the tri-1-butylmethylammonium bis((trifluoromethyl)sulfonyl)imide (Bu3MeN+Tf2N-) room-temperature ionic liquid (RTIL) by using cyclic staircase voltammetry, rotating disk electrode voltammetry, and chronoamperometry. The reduction of cesium ions at mercury exhibits quasireversible behavior with k0 = 9.8 × 10-5cms-1 and α = 0.36. The diffusion coefficient of Cs+ in this RTIL was 1.04 × 10-8cm2s-1 at 303K. Bulk deposition/stripping experiments conducted at a rotating mercury film electrode gave an average recovery of 97% of the electrodeposited Cs. The density, absolute viscosity, and equivalent conductance of Bu3MeN+Tf2N- were measured over the range of temperatures from 298 to 353K. A polynomial equation describing the temperature dependence of the density is presented. Both the viscosity and conductance exhibited the non-Arrhenius temperature dependence typical of glass-forming liquids. The ideal glass transition temperature and the activation energies for viscosity and conductance were obtained by fitting the Vogel–Tammann–Fulcher (VTF) equation to the experimental data for these transport properties. [Copyright &y& Elsevier]

Electrodeposition of lead (Pb) is important because of the application for energy storage and Pb recovery. Water, however, is not a good solvent because many Pb compounds, such as Pb oxides used in Pb storage batteries, are insoluble. Ionic liquids (ILs), especially for deep eutectic solvents (DESs), have been used for Pb electrodeposition. However, most DESs are water-miscible. Here, a hydrophobic Brønsted acidic amide-type IL, protonated betaine bis((trifluoromethyl)sulfonyl)amide ([Hbet][TFSA]), was used to dissolve PbO and PbO 2 under an ambient air for the voltammetric study and electrodeposition. PbSO 4 was only slightly soluble but extraction of Pb metal was achieved from the PbSO 4 /[Hbet][TFSA] paste. Very smooth, uniform, and crystalline electrodeposits were obtained from the PbO and PbO 2 baths, respectively, regardless of potentiostatic or galvanostatic electrodeposition but dendritic Pb was obtained from DESs. The Pb species in the IL was carefully studied, and the different species might explain why different morphologies of Pb were obtained from this IL and DESs, respectively. This study demonstrates that a protic IL is appropriate to be used as the electrolyte for electrochemically extracting Pb from various water-insoluble Pb compounds. [ABSTRACT FROM AUTHOR]

Free sulfide anion (S 2− ) in alkaline media was determined using cathodic stripping voltammetry (CSV) and a graphene oxide-modified screen-printed carbon electrode (SPCE/GO) electrodeposited with Ag, Au, or AuAg nanoparticles (NPs). Electrodeposition was achieved using cyclic voltammetry in dilute sulfuric acid containing AgNO 3 and/or HAuCl 4 ·4H 2 O in which thiourea was essential for stabilizing Ag + . The existence of GO resulted in higher density and more uniform distribution of NPs, compared with those electrodeposited on bare SPCE. The composite electrode SPCE/GO/AgNPs showed the greatest sensitivity but poorest reproducibility. The SPCE/GO/AuNPs, in contrast, showed the best reproducibility with a linear dynamic range of S 2− from 6.25 to 400 μM and no significant interference from various inorganic anions and cations. EDTA, however, was essential to eliminate the interfering effects from metal cations. By co-depositing Au and Ag to form SPCE/GO/AuAgNPs, the sensitivity was significantly improved in contrast to SPCE/GO/AuNPs, and the reproducibility was approximately reserved. By using differential-pulse CSV (DPCSV), a linear dynamic range of 0.05∼1.5 μM was observed. A wider but two-segmented dynamic range, 0.5∼12.5 and 12.5∼312.5 μM, was obtained by using liner-scan CSV (LSCSV). SPCE/GO/AuAgNPs, however, showed a poorer resistance against metal cationic interferents, compared with SPCE/GO/AuNPs, although EDTA was used. This study reveals a facile approach of preparing sensitive modified electrodes for the determination of S 2− in alkaline aqueous media. [ABSTRACT FROM AUTHOR]

The cathodic limit of the electrochemicalwindow in the second-generationionic liquids (composed of air- and water-stable metal-free cationsand anions) is traditionally believed to be determined by the reductionof the cation. More and more exceptions, however, were found in variousionic liquids. In this study, the cathodic limit of the electrochemicalwindow in 1-butyl-1-methylpyrrolidinium salicylate ionic liquid (BMP-SALIL) was studied. It has been found that the cathodic limit of BMP-SALis determined by the reduction of SAL–anion ratherthan the reduction of BMP+cation. The cyclic voltammetricbehavior, NMR spectra, and MALDI-TOF MS spectra of BMP-SAL recordedbefore and after the IL was electrolyzed at the cathodic limit providesufficient evidence that the major reaction at the cathodic limitof BMP-SAL is the reduction of SAL–anion. The theoreticalcalculations support the experimental data, and the results indicatethat anion reduction dominated cathodic limit should be a common phenomenonin ionic liquids. [ABSTRACT FROM AUTHOR]

Abstract: The voltammetric behavior of Pt(II), Fe(II), and mixtures of Pt(II) and Fe(II) was studied in N-butyl-N-methylpyrrolidinium dicyanamide ionic liquid (BMP-DCA IL), N-butyl-N-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide ionic liquid (BMP-TFSI IL), and a mixture of BMP-DCA and BMP-TFSI, respectively. Electrodeposition of PtFe coatings was achieved by controlled-potential electrolysis on tungsten from the aforementioned ILs containing Pt(II) and Fe(II). The Pt(II) species required to prepare these PtFe coatings was introduced into the ILs by addition of PtCl2. In BMP-TFSI, an additional two equivalents of N-butyl-N-methylpyrrolidinium chloride (BMP-Cl) were essential to assist one equivalent of PtCl2 to dissolve. The Fe(II) species was introduced into the ILs by addition of FeCl2 or by anodizing an iron spiral electrode. In BMP-TFSI, additional BMP-Cl had to be added to assist FeCl2 dissolution (FeCl2:BMP-Cl=1:2 (mol:mol)). The PtFe coatings with various atomic ratios of Pt/Fe were studied for their voltammetric behavior towards the oxygen reduction reaction (ORR) in acidic solutions. This study shows that the PtFe alloy coatings with atomic ratios of ∼0.5/0.5 had the highest reductive current density for ORR, better than regular Pt or Pt-electrodeposited electrodes. [ABSTRACT FROM AUTHOR]