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

A simple method is described for preparing ultrathin films of carbon-supported platinum nanoparticles on gold and other substrates for examination by electrochemical infrared reflection-absorption spectroscopy (EC-IRAS) in which the anomalous "antiabsorbance" 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 thorough rinsing. The Pt monolayer-level films prepared by this means exhibit largely positive unipolar absorbance bands for CO adlayers, whereas an anomalous inverted band component appears for thicker films, especially those featuring high Pt nanoparticle loadings. These findings demonstrate the value of the film preparation tactic for exploring the electrocatalytic properties of C/Pt materials by using combined electrochemical and EC-IRAS measurements.