Abstract
The effect of the nanostructure of electrodeposited palladium mesoparticles on the oxygen electroreduction reaction (oerr) in acid media is studied by electrochemical techniques combined with scanning tunneling microscopy, tapping-mode atomic force microscopy, and scanning electron microscopy. Palladium mesoparticles supported on highly oriented pyrolytic graphite (HOPG) exhibit a remarkable electrocatalytic enhancement, i.e., a decrease in the cathodic overvoltage on the order of 0.25 V, as compared to polycrystalline palladium electrodes. For a similar particle size, the largest electrocatalytic activity is obtained by use of quasi-two-dimensional (2D) ramified palladium particles and electrodeposited palladium charges exceeding 3 mC cm-2. For these particles, experimental results show that the electrocatalytic enhancement of the oerr can be related to the combined influence of the nanostructure of 2D branching on the HOPG and traces of oxygen-containing adsorbates that induces local perturbation of ele...
Highlights
Metal nano/mesoparticles are of interest due to their unique physical, chemical, and electrochemical properties, making them of importance in many technical applications
Significant progress in this direction has been made showing that the high activity requires a minimum metal particle size that should be compatible with bulk physicochemical properties of metal nano/mesoparticles
This process at palladium mesoparticles would be assisted by a weakening of the O-O bond strength at molecular oxygen adsorbates
Summary
Metal nano/mesoparticles are of interest due to their unique physical, chemical, and electrochemical properties, making them of importance in many technical applications. Noble metal islands at the nanometer to micrometer range have been produced on different substrates to be used in heterogeneous catalysis and electrocatalysis These materials have attracted great interest due to their potential applicability in relation to fundamental aspects of electrochemistry[1] and to many reactions of both industrial and environmental importance.[2,3,4]. In recent years a great effort has been made to attain a predictive understanding of the relationship between the shape and structure of metal particles of low dimensionality and their catalytic activity Significant progress in this direction has been made showing that the high activity requires a minimum metal particle size that should be compatible with bulk physicochemical properties of metal nano/mesoparticles. In contrast to this progress, the fabrication of metal nano/mesoparticles still remains rather empirical because some fundamental aspects of those processes yielding particles with preselected dimensionality, shape, and size at the nanometer scale are not fully dominated
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