Influence of Co-Deposited Hydrogen on Microstructure of Electrodeposited Platinum Films from Chloro-Complex Solution

The influence of co-deposited hydrogen on microstructure of electrodeposited platinum (Pt) films was investigated using thermal desorption spectroscopy, X-ray diffraction and transmission electron microscopy. The Pt films were potentiostatically electrodeposited on a gold foil from a tetrachloroplatinate(Ⅱ) solution at 0.1 ∼ -0.3 V vs. Ag/AgCl. From the thermal desorption spectra of hydrogen, a broad desorption peak at around 650 K was observed in the Pt films deposited at 0.1 ∼ ‐0.2 V vs. Ag/AgCl, and a pronounced desorption peak at around 500 K was observed in the Pt films deposited at -0.3 V vs. Ag/AgCl. As the deposition potential was more negative, the current efficiency of Pt deposition was lower and the hydrogen concentration of Pt films was higher. These electrodeposited Pt films were consisted of fine grains of 9 - 17 nm, and the lattice parameter decreased with increasing hydrogen concentration. After heat treatment at 500 K, reduction of lattice contraction and increase in grain size were observed in the Pt films with higher hydrogen concentrations. The increase in grain size by the heat treatment was larger as the hydrogen concentration of Pt films was higher. Thus, it is clear that such grain growth observed in the electrodeposited Pt films was enhanced by hydrogen-induced superabundant vacancies.