Shape-dependent electrocatalysis:: ammonia oxidation on platinum nanoparticles with preferential (100) surfaces

A shape-dependent electrocatalysis for the ammonia oxidation reaction is reported. Pt nanoparticles with different (100) preferentially oriented surface structures were synthesised. Cyclic voltammetry of the Pt nanoparticles is presented and the "so-called" hydrogen adsorption/desorption process is used as structure sensitive reaction to obtain qualitative information about the surface structure of the nanoparticles. While Pt nanoparticles prepared in microemulsion show a voltammetric profile very similar to that characteristic of a polyoriented surface, colloidal Pt nanoparticles appear to be (100) preferentially oriented. The electrochemical activity of these nanoparticles for ammonia oxidation in basic medium was studied. The results show that the anodic current density is very sensitive to the existence of Pt(100) domains. Thus oxidation current densities seven times higher can be obtained among the different nanoparticles, showing the importance of controlling the surface structure of the nanoparticles for the development of an active electrocatalyst for ammonia oxidation. (C) 2004 Elsevier B.V. All rights reserved.