Roughness of electrode

Nevertheless, despite the fact that the theory [84] looks convincing, we think it doubtful that the electrode surface roughness alone, without any additional conditions imposed, should not only cause the frequency dispersion of the capacitance, but also provide for its characteristic potential dependence, described by the Schottky theory. Moreover, a well-substantiated conclusion was drawn recently that the roughness of electrode surface does not necessarily cause the emergence of a CPE in the electrode s impedance [88],... 

Lifetime test for oxygen electroreduction electrode/XPS, electrochemical impedance spectroscopy) Ag KOH solution Catalyst preparation not given. Porous PTFE bonded gas diffusion layer is prepared by cold rolling method 12-15% performance loss of cell voltage in 5000 h of operation time due to decrease of the surface roughness of electrode and PTFE degradation effect. Wagner et al. (2003)... 

Figure Bl.22.6. Raman spectra in the C-H stretching region from 2-butanol (left frame) and 2-butanethiol (right), each either as bulk liquid (top traces) or adsorbed on a rough silver electrode surface (bottom). An analysis of the relative intensities of the different vibrational modes led to tire proposed adsorption structures depicted in the corresponding panels [53], This example illustrates the usefiilness of Raman spectroscopy for the detennination of adsorption geometries, but also points to its main limitation, namely the need to use rough silver surfaces to achieve adequate signal-to-noise levels.

Immersion electrodes are the most common glass electrodes. These are roughly cylindrical and consist of a barrel or stem of inert glass that is sealed at the lower end to a tip, which is often hemispherical, of special pH-responsive glass. The tip is completely immersed in the solution during measurements. Miniature and microelectrodes are also used widely, particularly in physiological studies. Capillary electrodes permit the use of small samples and provide protection from exposure to air during the measurements, eg, for the determination of blood pH. This type of electrode may be provided with a water jacket for temperature control. 

The in situ methods more commonly used to obtain the surface roughness R = SRa/S8ram (where and Sgeom are the working surface and the geometric area, respectively) of electrodes are10 24 63 73 74 218 (1)... 

The dependence of the C,E curves for a solid metal on the method of electrode surface preparation was reported long ago.10 20 67 70 219-225 in addition to the influence of impurities and faradaic processes, variation in the surface roughness was pointed out as a possible reason for the effect.10 67,70 74 219 For the determination of R it was first proposed to compare the values of C of the solid metal (M) with that of Hg, i.e., R = C-M/c-Hg 10,74.219-221 data at ff=0 for the most dilute solution (usually... 

The electrical double-layer structure and fractal geometry of a pc-Ag electrode have been tested by Se vasty an ov et al.272 They found that the geometrical roughness of electrochemically polished pc-Ag electrodes is not very high (/pz 1.5 to 1.25), but the dependence of Chtr curves on cej, as well as on/pz, is remarkable (C, =30 to 80 fi cm-2 if/pz =1.5 to 1.0). 

Later, polished and unpolished pc-Pb electrodes were studied600 and the Parsons-Zobel plots at c > 0.005 M NaF were found to be linear, with the value of/re = 1.15 for the polished electrode. At c 0.005 M NaF, nonlinear Parsons-Zobel plots, which are characteristic of solid pc electrodes, were observed. The Ch a curves, calculated for polished pc-Pb taking into account the roughness of the surface (Cf ° = 0.26 F m-2, cr = 0.18 F m 2), were compared with those obtained on the basis of the GCSG theory for liquid Hg. C, E curves were obtained for NaF + H20 solutions with the addition of various amounts of thiourea (TU). The... 

Borisova et al. A diffuse-layer minimum was found in the C, E curves, but the capacitance dispersion was appreciable and the value of C at Emib for Cd was higher than that calculated using the C, E curve for Hg 10,220,221 jt was notect10 that one of the reasons for this was the roughness of the pc-Cd surface. Therefore, Cd, Pb, and T1 electrodes were remelted in an inert atmosphere to give solidified drop electrodes. The capacitance dispersion was somewhat lower, but the difference between calculated and experimental capacitance was still substantial.221... 

Electrochemically polished and chemically treated Cd(0001), Cd(10T0)t Cd(l 120), Cd(lOTl), and Cd(ll2l) electrodes have been studied by impedance and cychc voltammetry by Lust et al.152 153 249 664 665 a slight variation of capacitance (3 to 6%) has been observed with v. In the case of chemically treated electrodes, a somewhat higher (5 to 10%) dependence of C on v has been explained by the geometric roughness of the electrode surface. 

In recent years, many types of double-layer capacitors have been built with porous or extremely rough carbon electrodes. Activated carbon or materials produced by carbonization and partial activation of textile cloth can be used for these purposes. At carbon materials, the specific capacity is on the order of 10 J,F/cm of trae surface area in the region of ideal polarizability. Activated carbons have specific surface areas attaining thousands of mVg. The double-layer capacity can thus attain several tens of farads per gram of electrode material at the surfaces of such carbons. 

A Specular X-ray reflection While the specular X-ray reflection (SXR) approach is again a means of probing solid coatings at the atomic level, it does have the advantage that the model obtained at the surface can include information on the atomic-scale roughness of the buried , i.c. usually inaccessible, electrode/surface layer interface. 

To quantitatively characterize the surface roughness of the Pt films, the rms roughness cr of the electrodes was evaluated and the resulting values are indicated in Figures 10a, 10b and 10c, respectively. From the comparison between height fluctuation of all the film... 

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