Apparent transfer coefficient for ORR at polycrystalline platinum under convection conditions: a potential modulation study

作者：Mostafa Ehab; Baltruschat Helmut^*

来源：Journal of Solid State Electrochemistry, 2013, 17(7): 1861-1867.

DOI：10.1007/s10008-013-2147-7

• ac voltammetry
• Adsorption
• Electrocatalysis
• Impedance spectroscopy
• Oxygen reduction

The oxygen reduction reaction has been studied in the thin-layer flow through cell at polycrystalline platinum in 0.5 M H2SO4 at different flow rates. The apparent transfer coefficient (alpha%26apos;) and the corresponding Tafel slope have been calculated using the previously introduced ac voltammetry method [1, 2]. In addition to the correction of the high electrolyte resistance in the thin-layer cell, the contribution from other adsorption processes presented by the adsorption resistance has been also subtracted. The effect of increasing convection on the obtained alpha%26apos; and Tafel slopes has been examined and it was found that the apparent cathodic transfer coefficient is 0.5 (corresponding to a Tafel slope of -120 mV dec(-1)) in all cases independent of the flow rate or frequency, suggesting that the first electron transfer to oxygen is the rate-determining step. The difference between Tafel slopes obtained here, i.e., by ac voltammetry method, and that obtained from usual Tafel slopes is due to the potential dependence of oxygen adsorbates, which in the method used here is-at least in part-separated from the potential dependence of the rate constant.

• 出版日期2013-7