Abstract: The exchange current density for the hydrogen oxidation/evolution reactions was determined in a proton exchange membrane fuel cell. Ultralow Pt-loaded electrodes (0.003 mg pt /cm 2 ) were used to obtain measurable kinetic overpotential signals (50 mV at 2 A/cm 2 ). Using a simple Butler-Volmer equation, the exchange current density and transfer coefficient were determined to lie within the range of 235-600 mA/cm 2 Pt and 0.5-1, respectively. Due to the fast kinetics, no measurable voltage losses are predicted for pure-H 2 /air proton exchange membrane fuel cell applications when lowering the anode Pt loadings from its current value of 0.4 mg pt /cm 2 to the automotive target of 0.05 mg pt /cm 2 .

Abstract: The energy efficiency of water electrolysis was considerably improved under a high magnetic field. This was proved by measuring the cell voltage, the IR-drop, and the electrode potentials for the electrolysis which was galvanostatically operated in alkaline (4.46 and 0.36 M KOH) and acidic (0.05 M H 2 SO 4 ) solutions. A large reduction in the cell voltage was achieved in a magnetic field, especially at a high current density. The decrease of the IR-drop, which was measured by the current interrupter method, depended on the concentration of electrolyte solutions. In a magnetic field, the oxygen overpotential was reduced more than the hydrogen overpotential.

Abstract: Ultrasensitive electrochemical detection of hydrazine using nanosized Au particles self-assembled on a sol−gel-derived 3D silicate network is described. The citrate-stabilized gold nanoseeds (GNSs) were self-assembled on the thiol groups of the silicate network, which was preassembled on a polycrystalline Au electrode. The size of the GNSs on the network was enlarged by a seed-mediated growth approach, and the GNSs were characterized by UV−visible spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and electrochemical measurements. The enlarged nanoparticles (GNEs) on the silicate network have a size distribution between 70 and 100 nm and behave as a nanoelectrode ensemble. This nanostructured platform is highly sensitive toward the electrochemical oxidation of hydrazine. A very large decrease in the overpotential (∼800 mV) and significant enhancement in the peak currents with respect to the bulk Au electrode were observed without using any redox mediator. The nanos...

Abstract: Cobalt sulfides have been known for more than 30 years to be active toward oxygen reduction, and cobalt selenides have shown less activity. In this paper, a theoretical analysis is made of the four-electron reduction reaction of oxygen to water over the mixed anion and cation (202) surface of the pentlandite structure Co9Se8, one of several selenide phases. Reversible potentials for forming adsorbed reaction intermediates in acid are predicted using adsorption energies calculated with the Vienna ab initio simulation program (VASP) and the known bulk solution values together in a linear Gibbs energy relationship. Comparison with an earlier theoretical analysis of pentlandite structure Co9S8 shows that the overpotential is predicted to be larger for the selenide by around 0.22 V. Cobalt selenide electrodes of unspecified stoichiometry were prepared chemically on glassy carbon discs, and polarization curves were measured using rotating discs. When heat-treated at 900 °C, the onset potential for O2 reduction ...

Abstract: PtRu (1 : 1) catalysts supported on low surface area carbon of the Sibunit family (SBET = 72 m2 g−1) with a metal percentage ranging from 5 to 60% are prepared and tested in a CO monolayer and for methanol oxidation in H2SO4 electrolyte. At low metal percentage small (<2 nm) alloy nanoparticles, uniformly distributed on the carbon surface, are formed. As the amount of metal per unit surface area of carbon increases, particles start coalescing and form first quasi two-dimensional, and then three-dimensional metal nanostructures. This results in a strong enhancement of specific catalytic activity in methanol oxidation and a decrease of the overpotential for CO monolayer oxidation. It is suggested that intergrain boundaries connecting crystalline domains in nanostructured PtRu catalysts produced at high metal-on-carbon loadings provide active sites for electrocatalytic processes.

Abstract: A room temperature ionic liquid N-butylpyridinium hexafluorophosphate (BPPF6) was used as a binder to make an ionic liquid modified carbon paste electrode (IL-CPE), which showed good characteristics such as simple preparation procedure, fast electrochemical response and good conductivity. The electrochemical oxidation of ascorbic acid (AA) on the new IL-CPE was carefully studied. The oxidation peak potential of AA on the IL-CPE appeared at 109 mV (vs. SCE), which was about 338 mV decrease of the overpotential compared to that obtained on the traditional carbon paste electrode (CPE) and the oxidation peak current was increased for about four times. The electrochemical parameters of AA on the IL-CPE were calculated with the charge transfer coefficient (α) and the electrode reaction rate constant (ks) as 0.87 and 0.800 s−1, respectively. Based on the relationship of the oxidation peak current and the concentration of AA a sensitive analytical method was established with cyclic voltammetry. The linear range for AA determination was in the range from 1.0×10−5 to 3.0×10−3 mol/L with the linear regression equation as Ip (μA)=−2.52–0.064C (μmol/L) (n=13, γ=0.9942) and the detection limit was calculated as 8.0×10−6 mol/L (3σ). The proposed method was free of the interferences of coexisting substances such as dopamine (DA) and amino acids etc., and successfully applied to the vitamin C tablets determination.

Abstract: Proton-conducting solid oxide fuel cells (H-SOFC), using a proton-conducting electrolyte, potentially have higher maximum energy efficiency than conventional oxygen-ion-conducting solid oxide fuel cells (O-SOFC). It is important to theoretically study the current–voltage (J–V) characteristics in detail in order to facilitate advanced development of H-SOFC. In this investigation, a parametric modelling analysis was conducted. An electrochemical H-SOFC model was developed and it was validated as the simulation results agreed well with experimental data published in the literature. Subsequently, the analytical comparison between H-SOFC and O-SOFC was made to evaluate how the use of different electrolytes could affect the SOFC performance. In addition to different ohmic overpotentials at the electrolyte, the concentration overpotentials of an H-SOFC were prominently different from those of an O-SOFC. H-SOFC had very low anode concentration overpotential but suffered seriously from high cathode concentration overpotential. The differences found indicated that H-SOFC possessed fuel cell characteristics different from conventional O-SOFC. Particular H-SOFC electrochemical modelling and parametric microstructural analysis are essential for the enhancement of H-SOFC performance. Further analysis of this investigation showed that the H-SOFC performance could be enhanced by increasing the gas transport in the cathode with high porosity, large pore size and low tortuosity.

Abstract: Electrochemical properties of double wall carbon nanotubes (DWNT) were assessed and compared to their single wall (SWNT) counterparts. The double and single wall carbon nanotube materials were characterized by Raman spectroscopy, scanning and transmission electron microscopy and electrochemistry. The electrochemical behavior of DWNT film electrodes was characterized by using cyclic voltammetry of ferricyanide and NADH. It is shown that while both DWNT and SWNT were significantly functionalized with oxygen containing groups, double wall carbon nanotube film electrodes show a fast electron transfer and substantial decrease of overpotential of NADH when compared to the same way treated single wall carbon nanotubes.

Abstract: Alkali lignin undergoes strong adsorption on polycrystalline gold electrodes. Subsequent oxidation in a sulfuric acid solution leads to a restructured redox-active polymer that shows features characteristic for surface confined species. Surface coverage of up to 4.40×10−10 mol cm−2 may be obtained depending on the adsorption time or lignin concentration in the adsorption solution. Using Laviron's approach the electron-transfer rate constant and the transfer coefficient were found to be 8.9 s−1 and 0.35, respectively. The formal potential of the redox couple shifted negatively with pH at a rate of ca. 60 mV/pH unit, suggesting a 2 e/2 H+ reaction. The redox couple was also found to be a good mediator for electrochemical ascorbic acid oxidation in neutral phosphate buffer with ca. 250 mV reduction of the oxidation overpotential.

Abstract: In this paper, the phenomenology of a formation of a honeycomb-like structure was considered. Copper deposits obtained at overpotential of 1000 mV were examined by scanning electron microscopy (SEM) technique. It was shown that two groups of craters or holes were formed by the electrodeposition at this overpotential. The origin of one group is associated with hydrogen evolution and the attachment of hydrogen bubbles at the surface area of an electrode. For the origin of the other group, a current distribution at the growing surface was very important. The effect of preparing a working electrode onto the formation of a honeycomb-like structure is also considered.