Electrodeposited platinum revisited: Tuning nanostructure via the deposition potential

Pt nanostructured materials composed of nm-sized Pt crystallites interconnected via grain boundaries are prepared by electrochemical deposition on Au and glassy carbon substrates from aqueous chloride solutions of hexachloroplatinic acid under potentiostatic mode at various potentials (0.025-0.550 V versus RHE). These samples may be considered as model electrode materials for the investigation of the influence of structural defects in electrocatalysis. Nanostructure and morphology of electrodeposited materials are analyzed with X-ray diffractometry and scanning electron microscopy. Considerable distortions of Pt lattice are detected, which are revealed by the decreased lattice parameter and significant microstrains. These lattice distortions increase with the decrease of the deposition overvoltage, and are the highest in the region of kinetically controlled electrodeposition. The deposition potential can be thus used as a tool to tune the nanostructure of supported Pt. Defectiveness is found to correlate with the degree of surface screening estimated from the difference of the calculated and the experimental surface areas. Screening is found to result from both the crystal coalescence and the existence of nanopores. Continuous potential cycling is accompanied by restructuring of both nanoparticles and intergrain boundaries, but does not fully relax lattice compression. (c) 2006 Elsevier Ltd. All rights reserved.