Infrared reflection-absorption properties of platinum nanoparticle films on metal electrode substrates: control of anomalous opticaleffects

A simple method is described for preparing ultrathin films of carbon-suppor ted platinum nanoparticles on gold and other substrates for examination by electrochemical infrared reflection-absorption spectroscopy (EC-IRAS) in wh ich the anomalous "anti-absorbance" properties commonly observed for metal particle arrays can be minimized as well as controlled. The tactic involves physical deposition as an aqueous suspension, followed by drying and thoro ugh rinsing. The Pt monolayer-level films prepared by this means exhibit la rgely positive unipolar absorbance bands for CO adlayers, whereas an anomal ous inverted band component appears for thicker films, especially those fea turing high Pt nanoparticle loadings. These findings demonstrate the value of the film preparation tactic for exploring the electrocatalytic propertie s of C/Pt materials by using combined electrochemical and EC-IRAS measureme nts. (C) 2001 Elsevier Science BN. All rights reserved.