2020 Volume 61 Issue 10 Pages 1949-1957
The surface morphological changes of electrodeposited Pt–75 at% Cu (Pt–75Cu) nanoparticles under potential cycling were investigated by identical-location scanning electron microscopy. The electrodeposited nanoparticles consisted of numerous nuclei (∼3 nm in diameter) that agglomerated to form larger secondary particles (30–50 nm). Upon immersion in sulfuric acid, Pt shells formed on the surfaces of the Pt–75Cu nanoparticles due to the selective dissolution of Cu. Although around 40% of the Cu was dissolved from Pt–75Cu, no noticeable surface morphological changes were observed. Thereafter, Pt–75Cu was subjected to potential cycling between 0.05 and 1.0 V, whereupon surface smoothing of the nanoparticles due to the surface diffusion of Pt was observed. Conversely, when Pt–75Cu was potential-cycled between 0.05 and 1.4 V, the particle diameters of the nanoparticles drastically decreased and the nuclei on the surface completely disappeared owing to Pt dissolution and re-deposition. The heat-treated nanoparticles developed numerous pores on their surfaces during immersion and the initial stage of potential cycling. However, their final morphologies were found to be similar to those of the non-heated sample. The formation of pores can be explained by the coarsening of nuclei by heat treatment.
This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 84 (2020) 244–252. Abstract and captions of figures are slightly changed.
