Electrocatalytic hydrogenation of C2H4 on PtO2 powder - A study of surfaceprocesses occurring at powder materials by cavity microelectrode

Taking the electrocatalytic hydrogenation of ethylene as an example, we sho w that the cavity microelectrode allows the study of the surface processes occurring on powder materials. The electrocatalytic current can be observed at scan rate (upsilon) up to a few tens of mV s(-1), while with a standard composite electrode, upsilon must be lower than a few fractions of mV s(-1 ). The extent of the scan rate range is around two to three magnitudes. The refore, it is possible to construct significant voltammogram characteristic s (peak intensity, peak potential, and peak area) scan rate profiles, which are related to processes underlying the electrocatalysis. However, their q uantitative exploitation needs a theoretical model, which can be built up b y (i) applying the chemical and electrochemical kinetics to the various inv olved processes and (ii) taking into account the geometry proper to a compo site electrode. Direct analysis of the model allows qualitatively explainin g the variation of the ratio electrolytic-current/H chemisorption current o bserved on cavity microelectrode vs. the scan rate, when compared to that o f the spherically shaped platinum electrode. (C) 2001 The Electrochemical S ociety. [DOI: 10.1149/1.1359206] All rights reserved.