Electroless deposition of Pt on Ti - catalytic activity for the hydrogen evolution reaction

The deposition of platinum on titanium at open-circuit potential from an aq ueous 0.1 M HClO4 solution containing K2PtCl6 was studied. On freshly polis hed titanium, spontaneous deposition of platinum takes place through a disp lacement reaction between Ti(O) and dissolved Pt(TV). At very short times o f deposition, fine dispersions of platinum crystals were formed on titanium . At longer deposition times, the size of the platinum crystals increases w hereas their number decreases due to coalescence and agglomeration processe s. On titanium covered by a thin oxide film, the rate of deposition is very low and photocatalytic deposition of Pt on the TiO2 surface occurs simulta neously with the displacement reaction. The hydrogen evolution reaction (he r) was used as a probe reaction for testing both the catalytic activity and deposition conditions. There is evidence that the catalytic activity of th e Pt crystals for the her increases with decreasing crystal size. (C) 2000 Elsevier Science S.A. All rights reserved.