Charge Transfer Resistance Of Electrode Research Articles

Synthesis and electrochemical performance of Li3V2(PO4)3−xClx/C cathode materials for lithium-ion batteries

The Cl-doping Li3V2(PO4)3/C (LVP/C) cathode materials were synthesized by a sol–gel method. The effects of Cl-doping amount on electrochemical properties, structure and morphology of Li3V2(PO4)3/C were studied by electrochemical impedance spectroscopy, cyclic voltammetry, X-ray diffraction, FTIR spectrum and scanning electron microscopy. The results indicate that the Li3V2(PO4)2.88Cl0.12/C composite presents an excellent discharge capacity as high as 106.95mAhg−1 after 80 cycles at 8C. The same monoclinic structure of Li3V2(PO4)2.88Cl0.12/C sample can be obtained from XRD analysis while the particle size is smaller than that of pristine sample (x=0). The FTIR results further confirm the substitution of Cl− for PO43−. The reasons for the relatively enhanced capability are attributed to the decreased polarization and the reduced charge transfer resistance of electrode, with the suitable Cl-doping amount of x=0.12.

Optimization of TiO2 nanoparticle mixed PEDOT–PSS counter electrodes for high efficiency dye sensitized solar cell

Poly(3,4-Ethylendioxythiophene)–Poly(Styrene Sulfonate) (PEDOT–PSS) mixed with titanium dioxide (TiO2) nanoparticles was coated on conductive glass substrate by a doctor blading method and used as dye-sensitized solar cell (DSSC) counter electrodes. The energy conversion efficiency is significantly improved after TiO2 nanoparticle incorporation. This improvement is attributed to an increase in counter electrode catalytic activity and a decrease in counter electrode charge transfer resistance. These phenomena were observed using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS), respectively. The efficiency of polymer-TiO2 based DSSCs varied with the ratio of small (~25nm) to large (~100nm) TiO2 nanoparticles. The highest efficiency (~8.49%) was obtained with a ratio of 30% large to 70% small (wt/wt) nanoparticles inTiO2 electrodes. This efficiency is superior to that of Pt DSSC (~7.50%).

Non-dimensional analysis of PEM fuel cell phenomena by means of AC impedance measurements

AC impedance or electrochemical impedance spectroscopy (EIS) is becoming a fundamental technique used by researchers and scientists in proton exchange membrane (PEM) fuel cell analysis and development. In this work, in situ impedance measurements are presented for a series of operating conditions in a 50 cm 2 fuel cell. The electrode charge transfer resistance was determined from the corresponding arcs of the Nyquist diagrams. The analyses were performed for H 2/O 2 and H 2/air operation at different stoichiometric factors and reactant gases humidification. Characteristic time scales of charge transfer processes at the different operating conditions were estimated from the corresponding Bode plots. These values were used for a non-dimensional analysis of the different fuel cell electrochemical and transport processes, namely electrochemical reaction versus GDL reactant transport. Fuel cell adapted Damkhöler numbers are thus presented, where the results indicate that the GDL diffusion transport is the limiting process for the cases under analysis, especially when air is used as oxidant. Additional analysis of channel convective mass transport versus GDL diffusive mass transport is also presented.

Electrochemical Characteristics of $LaNi_5$ Electrode Fabricated by Ni and Cu Electroless Plating Techniques

The effect of electroless Ni and Cu plating on , type hydrogen storage alloy was investigated by the various electrochemical techniques such as constant current charge-discharge test, cyclic voltammeoy, and a.c. impedance spectroscopy. Scanning electron microscopy and X-ray diffraction test were conducted for phenomenological logical analyses. Cyclic Voltammetry results show that activation characteristics, cycle life and reaction ,rate were improved through electroless Ni and Cu plating. Compared with bare the charge transfer resistance of electrode was greatly reduced as charge-discharge cycle increases. Therefore, electroless Ni and Cu plating on alloy tends to accelerate the early activation, increasing the cyclic lift of electrode.

Electrochemical impedance study of the degradation of organic-coated copper

Electrochemical impedance spectroscopy (EIS) was used to study the corrosion behavior of organic-coated copper plate. The organic coatings of commercial lacquer or epoxy Epon resin 828 (Shell Co.) were evaluated in 0.5 M sodium chloride solutions. It was found that the coating was saturated with water after a short period of time and a rapid increase of coating capacitance and decrease of resistance were observed. The penetration of water molecules and electrolytes within the organic coating proceeds in three steps. Firstly, water diffuses into the coating and saturates the free volume of the coating, causing a rapid rise of capacitance. Secondly, the electrolytes penetrate within the voids into the metal–coating interface and the corrosion of metal intensifies; the coating resistance R p and electrode charge transfer resistance R ct decrease gradually during this period. The last period of time corresponds to the constant R p and R ct plateaus followed by decreases of these resistances due to a loss of adhesion of polymer film on the copper substrate. The EIS procedure developed in the study proved to be useful to characterize the degradation behavior of the copper–coating system.

Inhibition of Electrochemical Reactions at Gold Surfaces by Grafted, Highly Fluorinated, Hyperbranched Polymer Films

We report the synthesis and passivation properties of surface-grafted, highly fluorinated, hyperbranched poly(acrylic acid) (PAA) films that contain up to 50 atom % F. These films are very hydrophobic (water contact angle of up to 114°) and block electrochemical reactions on gold electrodes. Cyclic voltammetry in basic solution shows that while an electrode covered with a three-layer PAA (3-PAA) film mimics an assembly of microelectrodes, a fluorinated three-layer PAA (3-PAA/F) film blocks nearly all electron transfer to the gold surface. The charge transfer resistance of electrodes covered with a 3-PAA/F film is about 40 times greater than that for an electrode covered with a nonfluorinated 3-PAA film. 3-PAA/F films are initially 10 times more blocking than C16SH SAMs. Additionally, while the SAM is desorbed by electrochemical cycling, 3-PAA/F films are still highly blocking after ten potential sweeps over a 1.5 V range. Thus fluorinated PAA films are promising candidates for corrosion-inhibiting coatings.