Electroless deposition of Pt on Ti Part II. Catalytic activity for oxygen reduction

The reduction of oxygen on electroless deposited platinum on a freshly poli shed titanium electrode was studied in aqueous 0.1 M HClO4 and 0.2 M NaOH s olutions, utilising the rotating-disc electrode technique. TEM studies show that at short deposition times Pt is highly dispersed on titanium. At long er deposition times the degree of dispersion decreases due to coalescence a nd agglomeration processes and larger clusters are formed. The kinetics of oxygen reduction were affected substantially by the time of Pt deposition o n Ti at the open-circuit potential. A kinetic analysis of the current -pote ntial curves was made in the kinetically controlled region in the form of T afel plots and in the mixed kinetic-diffusion control region in the form of Koutecky-Levich plots. The catalytic activity of the Pt crystals decreases with increasing deposition time. The results were interpreted in terms of the effect of the Pt crystal size. The larger the Pt particles the lower th e catalytic activity. The role of titanium oxide formation and the electron ic effects were also discussed. (C) 2001 Elsevier Science B.V. All rights r eserved.