Analysis of effective surface area for electrochemical reaction derived from mass transport property

Abstract

The effective surface area, eff S , for electrochemical reaction at a Pt electrode was analyzed using mass transport property as a probe. This parameter is different to the socalled electrochemical surface area (ECA), which is usually obtained from the amount of protons which are underpotentially deposited, UPD H , or by CO stripping. The analysis was done using both experimental and numerical methods. In experiments, a rotating disk electrode (RDE) was used under the conditions where the Pt surface can be partially covered by Pt oxides or CO. For numerical analysis, three mass transport models based on diffusion, convection and convective-diffusion were used. As a result, it was found that it is possible to estimate eff S from the change in Koutecky-Levich slope at high rotation speeds. The analysis suggests that eff S does decrease notably from relatively low potential (around 0.4 V), even though it is not obvious in measured currents as the effect is masked by the low rates of mass transport. The analysis also suggests that there is a large difference in eff S with different methods, namely, estimation from the amount of Pt oxides and the analysis derived from mass transport property.Keywords: Effective surface area; RDE; HOR; catalyst Research highlights ▶ Estimation of effective surface area was possible by analyzing mass transport. ▶ Inactive domain size could also be estimated from the analysis. ▶ Effectiveness decreased notably from relatively low potential unlike Pt oxide growth.

An Evaluation of Biofield Treatment on Thermal, Physical and Structural Properties of Cadmium Powder

“…Similar results of particle size reduction in titanium and antimony had been reported by our group in previous studies [11,12]. Moreover, in nickelcadmium batteries, cadmium is used as negative electrode plate, which oxidised and release electrons during discharging, thus reduction in particle size of cadmium powder after biofield treatment may increases the specific energy of batteries [32,33] Furthermore, Iden et al reported that increase in surface area improves the kinetics of electrochemical reactions in batteries [34]. Thus, it is assumed that biofield treated cadmium could be more useful in electrochemical application as compared to control.…”

General Models for the Electrochemical Hydrogen Oxidation and Hydrogen Evolution Reactions: Theoretical Derivation and Experimental Results under Near Mass-Transport Free Conditions

“…Although there is much work in the literature assessing the performance of platinum toward the hor/her it is now well recognized that mass transport masks the true activity of platinum for this reaction, and the measured “exchange current densities” are too low in many papers. , This effect is illustrated in Figure in which the her/hor polarization plots are presented for a range of different electrochemical techniques transformed into specific activity (current density per real surface area). These techniques cover a wide range of mass transport regimes, in increasing order from microelectrodes with high surface area platinum catalyst ( R f = 30) in contact with Nafion or acid, a 50 μm platinum microelectrode ( R f ≈1) in contact with aqueous acid, to a Pt rotating disk electrode ( R f ≈ 1, 7200 rpm) in contact with 0.1 mol dm –3 HClO 4 , to a single platinum particle (450 nm in diameter) in acid to results obtained utilizing our floating electrode technique , ( R f ≈ 1) for an electrode in 1 mol dm –3 HClO 4 . It is clear that there is a significant spread of results, but what is also clear is that mass transport effects occur even when the electrode is polarized at potentials at which the current is a small fraction of the mass transport limited current.…”

Driving electrochemical reactions at the microscale using CMOS microelectrode arrays

“…This alteration in the diffusion field and detection volume affects the mass transport of ions to the electrode surface. 32…”

“…This alteration in the diffusion field and detection volume affects the mass transport of ions to the electrode surface. 32 Evaluating these fluorescence emissions 30 s after the voltage was applied and using the calibration curve to convert the fluorescence ratio to pH, yields the result shown in Fig. 4B.…”