Kinetic Implication from Temperature Effect on Hydrogen Evolution Reaction at Ag Electrode

Hydrogen evolution reaction （HER） at polycrystalline silver electrode in 0.1 mol/L HClO4 solution is investigated by cyclic voltammetry in the temperature range of 278-333 K. We found that at electrode potential φa,app decreases with φ, while pre-exponential factor A remains nearly unchanged,which conforms well the prediction from Butler-Volmer equation. In contrast, with φ nega-tive shifts from the onset potential for HER to the potential of zero charge （PZC≈-0.4 V）, both Ea,app and A for HER increase （e.g., Ea,app increases from 24 kJ/mol to 32 kJ/mol）. The increase in Ea,app and A with negative shift in φ from -0.25 V to PZC is explained by the increases of both internal energy change and entropy change from reactants to the transition states, which is correlated with the change in the hydrogen bond network during HER. The positive entropy effects overcompensate the adverse effect from the increase in the activation energy, which leads to a net increase in HER current with the activation energy negative shift from the onset potential of HER to PZC. It is pointed out that entropy change may contribute greatly to the kinetics for electrode reaction which involves the transfer of electron and proton, such as HER.

Performance of Ag_(2)O/Ag Electrode as Cathodic Electron Acceptor in Microbial Fuel Cell

An Ag2O/Ag electrode was prepared through the electrochemical oxidation of sterling silver. This electrode was used as a cathodic electron acceptor in a microbial fuel cell （MFC）. The Ag2O/Ag electrode was characterized by scanning electron microscopy, X-ray powder diffraction and linear sweep voltammetry. The maximum voltage output of the MFC with the AgaO/Ag cathode was maintained at between 0.47 and 0.5 V in 100 cycles, indicating the good regenerative capacity of the Ag2O/Ag electrode. The overpotential loss for silver oxide was 0.021-0.006 V, and the maximum power output, open circuit potential and short circuit current of the MFC were 1.796 W m^-3, 0.559 V and 9.3375 A m^-3, respectively. The energy required for electrochemical reoxidation ranged from 40% to 55% of the energy produced by the MFC. Results indicated that the AgeO/Ag electrode could be used as a cathodic electron acceptor in MFCs with excellent stability.

Effects Of Ultrasound On Voltammetric Measurements At An Ag Cylinder Electrode

In this paper,the voltammetric behaviours of Ag cylinder electrode in 1 mol/dm(3) KOH solution have been investigated in the presence of ultrasound irradiation. The results based on the CV, EIS and polarization measurements showed that ultrasound could enhance the mass transport, inhibit the oxygen evolution and increase the exchange current.

Impedance characteristics for solid Ag/AgCl electrode used as recording electric field generated by vessels in seawater

Ag/AgCl electrode has been prepared using pressed powder techniques. In order to verify the feasibility of this type of electrode used as detecting electric field generated by vessels in seawater, its characteristics of DC resistance, low frequency AC impedance, and receiving impedance in artificial seawater have been studied by polarization measurements, low frequency electrochemical impedance spectra, the open and short circuit cell conditions. The results show that the electrode can keep a low resistance when it responses the weak electrostatic field in seawater. The AC impedance of the electrode decreases as the frequency of the signal increasing. The receiving impedance decreases when the frequency of external field increases too. The valid detection bandwidth is determined by the properties of the impedance and the reactions occurring on the surface of the electrode.

Rayleigh relaxation of pyrazine, pyridine and piperidine molecules adsorbed on the roughened Ag electrode by light beating technique

The light beating technique (intensity correlation algorithm) was employed to analyze the Rayleigh scattering from the roughened Ag electrode in very dilute (10^(-4)M) pyrazine, pyridine and piperidine aqueous solutions containing KCl (0.1 M). The relaxation time is longer when the applied voltages are between-0.4 V and-0.8 V(vs. SCE) where the Raman effect also shows greater surface enhancement. Also observed was that for the piperidine case the relaxation time reaches its maximum at the more negative applied voltage. The origin of the relaxation is attributed mainly to the desorp- tion process of the pyrazine. pyridine and piperidine molecules off the roughened Ag electrode. An. electrostatic model was also proposed for the interpretation of these experimental observations.

Preparation and Properties of Embeddable Ag/Ag Cl Gelling Reference Electrode for Rebars Corrosion Monitoring in Concrete

Reference electrodes are a key part for corrosion monitoring and measurement of rebars in concrete. A reference electrode that can be buried in concrete is fabricated by using Ag/Ag Cl electrode and methyl cellulose gelling electrolyte. The stability, repeatability and anti-polarization of the reference electrode are investigated; the influences of the inner electrolyte loss, exterior OH- contamination, and temperature on the potential of the reference electrode are also investigated in this paper. The results show that the reference electrode has good stability, repeatability, and antipolarization. The influences of inner electrolyte loss, exterior OH- contamination, and temperature on the potential of the reference electrode are minimal. Therefore, it can be used for corrosion monitoring and measurement of rebars in concrete.

Monitoring Chloride Concentrations in Concrete Pore Solutions Using Silver/Nano-silver Chloride Sensors

Corrosion of reinforcing steel is a major cause for degradation of concrete structures,especially when exposed to chloride ions.Thus,the Silver/Nano-silver Chloride (SNSC) electrodes as sensors of chloride concentration were prepared and encapsulated carefully.The properties of the electrode were studied by emerging them in a series of concrete pore solutions with different admixed KCl contents.These SNSC sensors show that good stability in concrete pore solutions at room temperature.Polarization disposal can shorten the stabilized period of the sensors.The electrochemical tests indicate the SNSC sensors with desirable linearity and reproducibility.The response time of SNSC sensors is short enough for monitoring the chloride ions concentration in concrete structures.The good performance of SNSC sensors indicate that they could be embedded in the concrete structures in the future.

In-situ measurement of the dissolved S^(2-) in seafloor diffuse flow system: sensor preparation and calibration

The preparation approach and calibration result of an improved type of ion selective electrode （ISE）, which is used to measure the total dissolved S^2-, are introduced in this paper. The improved Ag/Ag2S electrode uses silver wire as the substrate, which is surrounded by electric polymer containing superfine silver powder. After the stabilization of the epoxy-resin, Ag2S layer was formed by chemical reaction with 0.2 mol/L （NH4）2S solution for 5 min. With Ag/AgC1 as reference electrode, the Ag/Ag2S electrode can be used to measure dissolved S^2-. The correlation between the measured potentials and the logarithm of dissolved S^2- is found to be linear, within range of the concentration of dissolved S^2- from 10^-2-10-7 mol/L. The slope of the regression line between measured potential and logarithm of dissolved S^2- is about -27.7, which agrees well with the theoretical Nernst value -29.6. Furthermore, the performance of the improved Ag/Ag2S electrode, such as the response time, sensitivity and stability, greatly outweighs the conventional Ag/Ag2S electrode.

Thermodynamic Foundation for High Temperature Electrochemistry

Thermodynamic concepts required for the thermodynamic calculation of the potentials of electrodes for high temperature applications are briefly reviewed. A thermodynamic approach to the calculation of half cell potentials and the standard chemical potential of an electron at high temperatures which are related to the Standard Hydrogen Electrode(SHE) is discussed. As examples, an external Ag/AgCl reference electrode and a YSZ(Ag|O_2) pH sensor for high temperature applications are analyzed by using the thermodynamic approach to derive a high temperature pH measurement equation. The two electrodes are employed to measure high temperature pH and the measured pH was compared with the calculated pH by using a solution chemistry method. Concepts and principles for electrode kinetics are also briefly introduced and a modification to the Tafel equations is suggested.

Monitoring Biosignals with Low Cost Wearable Sensors

With the increase of aging population, we have been witnessing a decline in the quality of life influenced by numerous social, cultural and economic factors. Several studies have addressed these facts and some emerging technologies are capable of monitoring and anticipating these problems. With the advance in the development of smart textiles, it＇s possible to use these technologies in the acquisition of biosignals, which allows obtaining a better comfort regarding the use of smart clothes over traditional Ag/AgCI electrodes. In this way, it is possible to monitor for longer periods reducing the discomfort to the user. This paper reports the development of a low cost sensor with the capability of monitoring the electrical activity of the heart, measuring the heart rate and body temperature and is applied in the scenario： health ＆ wellbeing, targeting the continuous measurement of vital signs.

Improved Ag-Si interface performance for Si solar cells using a novel Te-based glass and recrystallization process of Ag

In order to prove that the Te-based glass frit could be applied to Ag pastes to fabricate Ag electrode and elucidate the reactions among Ag,the frit,and the Si wafer,the Te-based glass and Ag pastes with different contents of glass frit(0 wt%,1 wt%,3 wt%,5 wt%,and 7 wt%)were prepared.The microstructures of Ag electrodes and the phase analysis of interface between Ag electrodes and the Si wafer were investigated using scanning electron microscopy(SEM)coupled with energy-dispersive X-ray spectroscopy(EDX)and X-ray diffraction(XRD).When the content of glass frit is 3 wt%,the Ag electrode has good adhesion with Si wafer.What’s more,Ag crystallites and metallic Te could be found on the Si wafer.These results suggest that the TeO_(2) in the glass frit could react with SiNx anti-reflecting coating(ARC)and Si to serve as a medium for forming Ag crystallites.

Structure of water at ionic liquid/Ag interface probed by surface enhanced Raman spectroscopy

The potential-dependent adsorption behavior of water and ionic liquid was probed by surface-enhanced Raman spectroscopy （SERS） at the Ag electrode surface in the ionic liquids containing water with different concentrations. The configuration of water at the ionic liquid/electrode interface and the relationship between the potential of zero charge （pzc） and the molar frac- tion of water were deduced through the changes in the vibrational frequency of OH stretching mode. A small Stark effect value was determined in the system with lower molar fraction of water. With the increase of the water concentration, the OH stretching vibrational frequency gradually shifted to the high wavenumber region, the pzc was also moved positively, and the Stark effect value of OH stretching vibrational mode increased. It reached about 76 cm-1 V-I in the 1 tool L-1 [BMIM]Br aqueous solution. These differences were mainly contributed by hydrogen bonding and the configuration of water in the ionic liquid solution. In the solution with lower water content, water molecules existed at the interface layer through hydrogen bond- ing with cations, while in the higher content solution, the intermolecular hydrogen bonding between water molecules was strengthened and the possibility of the direct interaction between the water molecule and electrode surface increased.

Application of Te-Based Glass in Silicon Solar Cells

（90-x）TeO2-xZnO-lOBi203 （x = 15, 17.5, 20 and 22.5, in mol%） and 70TeOz-2OZnO-（10-y）Bi2O3-y Na2O （y = 1, 3, 5, 7, and 10, in mol%） glasses, and the corresponding Ag paste were prepared in order to prove that the Te-based glass frit could be applied to Ag pastes to fabricate Ag electrode. The relationship between structure and properties of the glasses was analyzed. The effects of glass frit on the microstructure, adhesion force, and resistivity of the Ag electrode were studied. The microstructure of Ag electrodes and the phase analysis of interface between Ag electrodes and the Si wafer were investigated using SEM and XRD. Finally, the 70TeO2-20ZnO-5Bi2O3-5Na2O glass showed better performance in the paste. What is more, Ag crystallites could be found on the Si wafer. These results suggested that the Te-based glass frit could react with SiNx anti-reflecting coating and Si to serve as a medium for forming Ag crystallites.