Journal of Applied Electrochemistry

Smith, Carmen; Utley, James; Hammond, John

doi: 10.1007/s10800-010-0245-0pmid: N/A

The electrochemical conversion of a spruce lignosulfonate into vanillin, at nickel anodes, was explored in previously unobtainable detail. A flow reactor (FM01), in a rig that permitted considerable variation of electrolysis conditions, allowed up to 150 g to be electrolysed at up to12 A at a variety of electrode configurations. Samples taken during electrolysis gave detailed reaction profiles. The electrolyser operated at 145 °C/500 kPa/3 M NaOH and yields of vanillin were similar to those obtained industrially using chemical oxidants (about 5–7% w/w). Vanillin production was favoured by low current density and low initial concentration of lignosulfonate. Vanillin, alone, was consumed in a 2.7 F process under the above conditions. Historically, yields in chemical and electrochemical conversions of lignins into vanillin do not exceed 10%; the results herein explain this apparent limit as equilibrium between formation of vanillin, its concomitant oxidative destruction and further condensation of lignins.

Jin, Lifeng; Wang, Gengchao; Li, Xingwei; Li, Liangbin

doi: 10.1007/s10800-010-0246-zpmid: N/A

Poly(2,5-dimercapto-1,3,4-thiadiazole) (PDMcT)/sulfonated graphene conductive composite (PDMcT/SGS) was synthesized through in situ oxidative polymerization in the presence of the water-soluble sulfonated graphene sheets (SGS). Raman spectra revealed the existence of the π–π interaction between thiadiazole rings and basal planes of SGS. Scanning electron microscopy and transmission electron microscopy showed that the submicron-sized petals and nanofibers of PDMcT grew onto the surface of SGS. As evidenced by the cyclic voltammetry results, the incorporation of SGS has significantly improved the electrochemical activity and cyclability of PDMcT. The discharge capacity of PDMcT/SGS composite, measured with the charge–discharge tests, was 268 mAh g−1 at the first cycle and 124 mAh g−1 after 10 cycles.

Liu, Y.; Cheng, Y.

doi: 10.1007/s10800-010-0247-ypmid: N/A

In this study, the inhibiting effect of cerium ions (Ce3+) on corrosion of 3003 aluminum alloy (AA3003) in ethylene glycol–water solutions was investigated using a rotating cylinder electrode, simulating the hydrodynamic condition of the automotive cooling system. Electrochemical measurements and surface characterization were conducted to study the inhibiting mechanism of Ce3+ on the Al alloy corrosion. It is found that Ce3+ serves as a cathodic inhibitor, and inhibits effectively corrosion of AA3003 in the flowing ethylene glycol–water solutions. The inhibiting effect of Ce3+ is resulted from the formation and deposit of Ce oxide and/or Ce hydroxide on the electrode surface. With the immersion time, the Ce deposit layer increases its thickness to cover the second phase particles, eliminating the galvanic coupling effect between the second phase particles and Al alloy substrate.

Nath, Hilary; Wang, Xjian; Torrens, Rob; Langdon, Alan

doi: 10.1007/s10800-010-0248-xpmid: N/A

Chlorination remains a predominant method for disinfecting drinking water. Electrogeneration of chlorine has the potential to become the favoured method of chlorine production if costs can be lowered and chlorine generation efficiencies can be improved. A novel perforated electrode flow through (PEFT) cell design has been developed to address these problems. The electrodes were made from low-cost graphite sheets and stainless steel mesh and separated by a non-conducting fabric membrane. This electrode configuration allows reduction of electrode separation to 0.1 mm or less, minimizing cell resistance and increasing electrical efficiency. The new PEFT configuration generates hypochlorite from a 0.5 mol L−1 brine at a current efficiency of better than 60%. As an inline in situ device, it produces chlorine concentrations known to be sufficient to disinfect water, from chloride concentrations as low as 0.004 mol L−1 (available in most natural waters) by a single pass of the water through the cell operating at 11 V. The possibility of a portable device operated by a 12-V battery is indicated.

Mujawar, S.; Inamdar, A.; Betty, C.; Cerc Korošec, R.; Patil, P.

doi: 10.1007/s10800-010-0249-9pmid: N/A

Composite WO3–Nb2O5 thin films were deposited on the glass and fluorine-doped tin oxide (FTO)-coated glass substrates using simple and inexpensive spray pyrolysis technique. The process parameters, like nozzle-to-substrate distance, spray rate, concentration of sprayed solution, etc., were optimized to good quality films. The films were characterized for the structural, morphological, optical, and electrochromic properties. Structural and morphological characterizations of the films were carried out using scanning electron microscopy and X-ray diffraction techniques. Electrochemical properties of the Composite WO3–Nb2O5 thin films were further studied using cyclic-voltammetry, chronoamperometry, chronocoulometry, and electrochemical Impedance spectroscopy.

Köleli, Fatih; Röpke, Derya; Aydin, Rezzan; Röpke, Thorsten

doi: 10.1007/s10800-010-0250-3pmid: N/A

The ac response of polyaniline thin films on platinum electrodes was measured at different dc potentials during the N2-fixation in methanol + LiClO4 electrolyte with 0.03 mol L−1 H2SO4 for the first time. The optimum film thickness was found to be 1.5 μm, N2-pressure 50 bar and an optimum electrolysis potential of −0.12 V (NHE). The diffusion coefficients for N2 into the polymer film was found to be (5 ± 2)×10−9 cm2 s−1.

Melo, Luisa; Lima-Neto, Pedro; Correia, Adriana

doi: 10.1007/s10800-010-0251-2pmid: N/A

This study examined the influence of citrate and tartrate as complexing agents on the electrodeposition and surface morphology of Cu–Ni layers. The alloys obtained in the tartaric acid and sulphate baths were nobler than those obtained in the citric acid/citrate and citric acid/citrate/tartaric acid media. The results indicated that the complexing medium influences the nobility and the type of mass transport of the alloy formed. The morphology of the electrodeposited Cu–Ni layers changed from a rather porous appearance in the absence of the complexing agents to nodular, cracked mud and cauliflower appearances for the citric acid/sodium citrate/sodium sulphate medium, tartaric acid/sodium sulphate medium and citric acid/sodium citrate/tartaric acid/sodium sulphate medium, respectively. The chemical composition of the Cu–Ni layers revealed the preferential deposition of copper. The ultraviolet–visible spectrophotometry measurements indicated the occurrence of the d–d type transition, regardless of the complexing medium employed.

Thepkaew, Jarupuk; Therdthianwong, Supaporn; Therdthianwong, Apichai

doi: 10.1007/s10800-010-0253-0pmid: N/A

Vulcan XC-72R carbon was pretreated using acid and thermal activation methods, and the carbons obtained were used as supports for a PtSn/C catalyst synthesized by a successive reduction process. Surface characteristics of the supports, including BET surface area, pHPZC and functional group, were analyzed using physical N2 adsorption, mass titration, acid–base titration, and Fourier transform infrared (FTIR) spectrometer technique, respectively. The prepared PtSn/C catalysts were characterized by X-ray diffractometer (XRD), energy dispersive X-ray spectrometer (EDX), inductively coupled plasma–atomic emission spectrometry (ICP–AES), and transmission electron microscope (TEM) techniques, and then were examined for their behavior under ethanol oxidation as well as for their performance in a direct ethanol fuel cell (DEFC). The results showed that pretreatment by HNO3 produced various oxygenated functional groups on the support surface and increased its acidic property. The strong acidity of the acid-treated support led to an unfavorable condition for the Pt reduction reaction and resulted in low Pt content but high Pt:Sn ratio in the PtSn/C catalyst. On the other hand, thermal activation increased the base functional groups on the carbon surface, which enhanced reduction of Pt precursor, and consequently, provided a small average metal particle size of 2.2 nm. The results from cyclic voltammetry, chronoamperometry and cell performance testing confirmed that the catalytic activity for ethanol oxidation and the performance in the direct ethanol fuel cell of the heat-treated carbon-supported PtSn catalyst was superior to the fresh PtSn/C catalyst and the acid-treated carbon-supported PtSn catalyst.