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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]

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]

[Display omitted] • Au and Pt atoms are preferentially deposited onto (1 0 0) and (1 1 1) planes of Pd NCs. • Formed conformal Pd/Au NCs and concave Pd/Pt NCs are used for catalyzing neutral GORs. • EQCM are employed for the in-situ measnuremt of GOR kinetics. • Pd/Pt CNC with Pt(2 1 0) plane has a remarkable activity for the sequential GOR. • Pd/Au NC shows a wide linear ranage for sensing glucose in the transisent GOR. Core-shell structures can improve the performance of electrocatalysts in fuel cells and biosensors owing to the tunable electron density of the shell metal by the core metal. In this study, Au and Pt atoms are preferentially deposited onto the (1 0 0) and (1 1 1) planes of the basal and truncated surfaces of Pd nanocubes (NCs), thus forming conformal Pd/Au NCs and concave Pd/Pt NCs (Pd/Pt CNCs), respectively. Furthermore, the activities and performances of these two core–shell NCs as catalysts in the sequential and transient catalysis of the d -glucose oxidation reaction (GOR) in the phosphate-buffered solution are studied. In the sequential catalysis in situ, an electrochemical quartz crystal microbalance is used. The Pd/Pt CNC with Pt-rich corners and the (2 1 0) plane exhibits remarkable specific activity (S A1 , 7.26 × 10–8 mol·cm−2) for the amount of bonded d -glucose per electrochemical active surface area (ECSA). Simultaneously, the catalyst has a significant specific activity (S A2 , 1.2 × 10–7 mol·cm−2) for the number of moles of released electrons involved in the GOR. In the transient GOR catalysis, the Pd/Au NC catalyst with Au (1 0 0) exhibits high sensitivity (S ECSA , 6.28 μA·mM−1·cm−2) for the present of d -glucose per ECSA in the wide linear range (0.25–14 mM). Furthermore, the Pd/Au NC exhibits its potential for high recoveries (99.23–100.14 %) and low relative standard deviation (≤1.08 %) in real sample tests for serum samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ternary ZnCuNi alloys were successfully electrodeposited from Ethaline DES. • Anodic or cathodic dealloying of the deposited alloys produced porous ZnCuNi. • Porous ZnCuNi alloys were more active to nitrate reduction than as-deposited ZnCuNi. • Cathodic dealloying gives Cu-rich surface against Ni-rich one from anodic dealloying. • A self-enhancing electrode formed by in-situ cathodic dealloying was developed. Electrodeposition of zinc-rich ternary ZnCuNi alloys were potentiostatically studied from an Ethaline deep eutectic solvent (DES) (having a molar ratio of 1:2 choline chloride-ethylene glycol) containing ZnCl 2 , CuCl 2 and NiCl 2. Voltammetry was conducted to understand the cathodic deposition and anodic stripping occurred in this system as a function of potential before the deposition of the ternary alloys. Selective anodic dissolution of Zn from the as-deposited alloys in a NaOH aqueous solution produced porous structures; however, Cu was also dissolved from the alloys if the alloys are overoxidized. Alternatively, porous structures were also produced via cathodic dealloying of the Zn when the as-deposited alloy was subjected to the electroreduction of NaNO 3. When used as electrode, both kinds of porous structure showed enhanced activities towards nitrate reduction. Because the cathodic dealloying did not consume Cu, the electrodes produced by cathodic dealloying exhibited activity and stability superior to the electrodes produced by anodic dealloying. More importantly, because the dealloying process and electrode activation could be simultaneously achieved in one step during the cathodic electrolysis of nitrate, the term "self-enhancing electrode formed by in-situ cathodic dealloying" was used in this study. The XPS analysis indicated that Ni-rich surfaces of ZnCuNi electrodes were produced with the anodic dealloying in contrast to the Cu-rich surfaces produced with the cathodic dealloying. This study demonstrates a facile approach to control the electrode surface compositions in dealloying zinc alloys. Although the application of the porous electrodes prepared in this study was tested for electroreduction of nitrate, this approach can be extended to the electrocatalysis of other systems. [ABSTRACT FROM AUTHOR]

Abstract Water-insoluble PbSO 4 only slightly dissolved in an amide-type hydrophobic protic ionic liquid (IL); the protonated betaine bis((trifluoromethyl)sulfonyl)amide ([Hbet][TFSA]). However, the paste of [Hbet][TFSA]-PbSO 4 coated on screen-printed carbon electrode (SPCE) could be electrochemically converted to Pb or PbO 2 in aqueous 0.1 M KCl via constant-potential electrolysis for the former and continuous cyclic voltammetry in 0.1 M NaOH for the latter. The formation of PbO 2 , which could be converted to CoO x (containing Co 3 O 4) through galvanic displacement in a Co(NO 3) 2 aqueous solution, was verified with Raman scattering spectroscopy and X-ray photoelectron spectroscopy (XPS); the latter also verified the formation of Co 3 O 4. The CoO x -modified electrode showed activity and high stability towards the oxygen evolution reaction (OER) in alkaline solutions. The approach shown in this study can be further developed as a procedure for extracting Pb metal or preparing CoO x catalysts from wastes, such as the discarded lead-storage batteries. Graphical abstract Unlabelled Image Highlights • A protic hydrophobic amide-type ionic liquid (IL) was mixed with PbSO 4 to be a paste. • The paste can be electrochemically converted to Pb or PbO 2. • PbO 2 can be further converted to Co 3 O 4 via galvanic displacement. • The Co 3 O 4 -modified PbO 2 electrode showed activity to oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

Abstract Two electropolymerizable carbazole-functionalized viologen compounds were synthesized and characterized using NMR, ESI-MS, voltammetry, and spectroelectrochemistry. The compounds were electropolymerized onto indium tin oxide electrode and glassy carbon electrode through a radical-induced polymerization triggered by electrochemical oxidation at the carbazole moieties in electrolytes composed of room temperature ionic liquid/organic solvents or NaClO 4 /acetonitrile. It was found that the properties of the electropolymerized polymers were crucially controlled by the chemical structure of the monomer and the electrolyte compositions. The polymer films showed electrochromic behavior, and the color changed from greenish at the potential where carbazole groups were oxidized to violet or colorless at which reduction of viologen groups occurred; violet or colorless depended on which of the two reductive states of the viologen moieties was reached. The polymer films were capable of enhancing the oxidative current of uric acid and ascorbic acid, respectively, in neutral media, which might be due to the concentrating ability of the viologen moieties towards negatively charged species such as ferricyanide ([Fe(CN) 6 ]3−) and ferrocyanide ([Fe(CN) 6 ]2−). Graphical abstract Unlabelled Image Highlights • Carbazole substituted viologen was prepared as electropolymerizable monomers. • Monomers with mono- or di-carbazole groups were prepared. • Single-backbone or two-backbone conducting polymers could be formed. • Not only the monomer structures but the electrolytes control the polymer properties. • The polymers show the electrochromic and anion-adsorptive behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] • Size of polyhedral Cu nanoparticles (NPs) shrank once Cd was introduced. • Size shrink was accompanied with evident activity promotion to nitrate reduction. • Mismatch between the two metal lattices might cause the size shrink. • Rate determining step for CuNPs and CuCdNPs was probably different. • Size or synergistic (CuCd bimetal) effect needs to be further studied. Polyhedral copper nanoparticles (CuNPs) were potentiostatically electrodeposited upon stainless-steel from a hydrophobic protic amide-type ionic liquid (IL), i.e. protonated-betaine bis((trifluoromethyl)sulfonyl)amide ([Hbet][TFSA]) containing CuO as the precursor. The surface morphologies and electrocatalytic activities of the CuNPs towards nitrate reduction were significantly altered after the co-deposition of cadmium (Cd). The variation of morphology and activity was caused by the significant shrinkage of the particle size as a result of the Cd co-deposition and the synergistic effect of Cu and Cd bimetal. In the galvanostatic electrolysis of nitrate, CuNPs showed a much higher reductive overpotential in comparison with CuCdNPs. It might be caused by a kinetic hindrance for the CuNPs in the rate-determining step of nitrate reduction (i.e. formation of nitrite ion NO 2 −). CuCdNPs, however, exhibited the robust and stable activity in which the rate-determining step was determined as a two-electron transfer reaction in accordance with the Tafel slope. [ABSTRACT FROM AUTHOR]

In this study, an ionic liquid-Fe 3 O 4 nanoparticles-graphite composite electrode (IL-Fe 3 O 4 NPs-GP) with high sensitivity was fabricated using easy-to-made materials and convenient techniques. A hydrophobic ionic liquid 1-butyl-1-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)amide (IL BMP-TFSA) was used to substitute paraffin oil that is conventionally used as the organic binder for preparing carbon paste electrodes. Fe 3 O 4 NPs show pseudo-peroxidase activity toward hydrogen peroxide (H 2 O 2 ) that was electrocatalytically reduced at the electrode. This electrode shows the synergistic effect from the combination of IL and Fe 3 O 4 NPs, exhibiting a high sensitivity of 200.7 μA mM −1 cm −2 but a narrower dynamic range of 1–25 μM with a detection limit of 0.5 μM. This electrode also shows good stability and several common interferents show negligible effect on the determination of H 2 O 2 . [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]