Early Stages of Platinum Electrodeposition on Highly Oriented Pyrolitic Graphite: Scanning Tunneling Microscopy Imaging and Reaction Pathway

Article abstract of DOI:10.1021/j100121a041

The early stages of Pt electrodeposition (0.675-0.620 V vs RHE) on highly oriented pyrolitic graphite (HOPG) from chloroplatinic acid at 25 deg C have been studied by ex-situ STM and SEM imaging complemented with electrochemical data.Nucleation and 3D growth of Pt initiate at HOPG surface defects.Large Pt agglomerates containing flat crystallites with well-defined geometries are found around HOPG steps.Pt crystallites formed by 1-2 nm size clusters become more compact as the electrodeposition potential is shifted negatively or the Pt electrodeposited charge is increased.High-resolution STM imaging reveals large uncovered HOPG areas with the nearest-neighbor C-C distance d = 0.24 +/- 0.02 nm and flat hexagonal Pt crystallites.Electrochemical data combined with STM imaging can be interpreted in terms of a diffusion-controlled Pt(IV) to Pt(II) reaction at HOPG and a surface reaction leading to Pt(0) at HOPG defects.