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Unlike the flat Cu sheet, we employed Cu foam to explore the specific porous effect on the expanding specific area. We found that the foam structure is superior to the sheet feature in the specific location from the morphology investigation. In the practical measurement of surface area, we found that the adsorbate could aptly agglomerate, resulting in a consequential block in the transport path. The specific location of the Cu foam was underestimated because the channels of the deep foam layer were blocked by the agglomerated adsorbate. To explore the protonation process of the electro-reduction, we adopted the carbonate electrolyte as the control group in contrast to the experimental group, the bicarbonate electrolyte. In the carbonate electrolyte, the primary intermediate was shown to be CO molecules, as verified using XPS spectra. In the bicarbonate electrolyte, the intermediate CO disappeared; instead, it was hydrogenated as a hydrocarbon intermediate, CHO*. The bicarbonate ion was also found to suppress electrocatalysis in the deep structure of the Cu foam because its high-molecular-weight intermediates accumulated in the diffusion paths. Furthermore, we found a promotion of the oxidation valence on the electrode from Cu2O to CuO, when the electrode structure transformed from sheet to foam. Cyclic voltammograms demonstrate a succession of electro-reduction consequences: at low reduction potential, hydrogen liberated by the decomposition of water; at elevated reduction potential, formic acid and CO produced; and at high reduction potential, CH4 and C2H4 were formed from −1.4 V to −1.8 V. [ABSTRACT FROM AUTHOR]

Electrodes of ruthenium oxide modified nickel were prepared by a thermal decomposition method. The stoichiometry of the modifier, RuO x , was quantitatively determined to be a meta-stable phase, RuO 5 . The electrodes were employed to sense ascorbic acid in alkaline solution with a high sensitivity, 296 μAcm −2 mM −1 , and good selectivity for eight kinds of disturbing reagents. We found that the ascorbic acid was oxidized irreversibly in solution. To match with the variation of the morphology, the sensitivity reached a maximum when the RuO x segregated with a nano-crystalline feature. We find that the substrate oxidized as the deposited RuO x grew thicker. The feature of the deposited RuO x changed from nano-particles to small islands resulting from the wetting effect of the substrate oxide, NiO; meanwhile the sensitivity decreased dramatically. The endurance of the RuO x /Ni electrode also showed a good performance after 38 days of successive test. [ABSTRACT FROM AUTHOR]

Abstract: An amperometric sensor that measured ascorbic acid by the oxidation of the ascorbic acid on a Ni–Pt electrode was fabricated. The Ni component of the Ni–Pt alloy played a crucial role as a modifier that developed an erinaceous surface, which enlarged the sensing area and increased the sensitivity of the electrode. The Pt82Ni18 electrode exhibited the best sensitivity of 333μAcm−2 mM−1 for ascorbic acid sensing. This electrode was further tested for reproducibility of the sensitivity, endurance, and interference; it exhibited excellent performance compared with electrodes reported in the literature. [Copyright &y& Elsevier]

A telemetric system was designed and constructed to sense pH and ethanol variation in aqueous solutions. The measured signals were transferred by software digitally and transmitted wirelessly by the telemeter, personal digital assistant (PDA), through the General Packet Radio Service (GPRS) protocol. The pH sensing electrode was designed to measure a chemical potential induced by a proton concentration gradient on the electrode’s surface which exhibits internal Donnon diffusion behavior, and a linear relationship between the electrical potential and pH was found. The result shows that the wireless sensing system allowed not only long-term usage and long-distance transmission but also with high accuracy (e.g. S.D. less than ±2%). The telemetric system can also be modified to measure ethanol concentration in aqueous solution amperometrically. It was found that the sensitivity of that ex situ measurements matched those of in field measurements with negligible deviation, less than 4%. [Copyright &y& Elsevier]

Ionic liquids containing lithium methylsulfonyl group were prepared from the precursors poly(propylene glycol)-block-(ethylene glycol)-block-(propylene glycol)-bis(2-aminopropyl ether) with different molecular weight. These liquids revealed excellent electrical conductivity in the temperature range -25 to 85 °C. Also, they exhibited a high boiling temperature and hence a low vapor pressure in ambient condition. Additionally, they showed a high fluidity with their viscosities being comparative with that of water. To determine the sensitivity of an ethanol sensor by using these ionic liquids, these liquids were subjected into a sequential electrochemical tests with nickel electrodes which performed a high sensitivity for the ethanol sensor. It was found that only the derivative with low molecular weight could detect ethanol. Furthermore, a linear relationship between the response current and the concentration of ethanol was constructed. The detection limit was found to be 0.13% (v/v) and its response time was 336 s. [Copyright &y& Elsevier]

A laminated Pd-Cu alloy/C/Nafion multilayer was prepared to sense O2 atmosphere in a metal-air structure. As a matrix, palladium was doped with various amounts of copper to conduct a preliminary test with optimum response, and four compositions, Pd, Pd8Cu2, Pd6Cu4, and Pd5Cu5, were selected as the candidate electrodes. It was found that the Pd6Cu4/C electrode showed higher sensitivity for all the electrodes. According to the phase identification of X-ray diffraction and X-ray photoelectron spectroscopy tests, the high sensitivity was attributed to the doped Cu, which was merged into the Pd matrix to repel the Pd out of the matrix as a Pd-skin layer on the surface. In the Pd-Cu alloy, the Cu site served as a template reaction site to break the O-O bond and reduce the interaction force of adsorbated oxygen on the Pd site. During the oxygen reduction reaction, not only did the decomposition of O2 molecules occur on the electrode, but the electrode itself proceeded with a phase transformation to high valance of oxide, PdO3. The sensing potential for O2 sensing was determined by polarization curves in which the flat region resulting from a diffusion-control was adopted. Chronoamperometric measurements were employed to construct calibration curves for the selected electrodes. A successive response was measured to test the endurance, which showed appreciable sensitivity decay. We also tested the selectivity by introducing a series of disturbance gases, CO, SO2, and NO2, in which the Pd6Cu4 electrode prevailed over the other electrodes. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, binary Pt–Ru/Nafion working electrodes for amperometric sensing of hydrogen were characterized and evaluated. Pt was alloyed with Ru on Nafion membranes by the Takenaka–Torikai method (T–T method). By controlling the amount of Ru in the alloys, the morphologies of the films varied from coarse particles to fine granules, some of which were fine enough to merge into the substrate. The response currents of all electrodes were proportional to hydrogen concentrations ranging from 100 to 1000ppm. The sensitivity of the Pt–Ru/Nafion electrodes was inversely proportional to the amount of Ru in the electrodes. However, both response and recovery times as well as sensitivity of the Pt80Ru20/Nafion electrode were improved while increasing the operational temperature. Binary electrodes that possessed a bi-functional mechanism for hydrogen oxidation were found to mitigate the impact of CO poisoning effectively only at low applied potential of 0.2V (vs. Ag/AgCl). Moreover, the Pt80Ru20/Nafion electrode entailed fast response and recovery times (90% response and recovery times) within 40s. [Copyright &y& Elsevier]