Electrodeposited Pt and Pt-Sn nanoparticles on Ti as anodes for direct methanol fuel cells

Electro-oxidation of methanol was studied on titanium supported nanocrystallite Pt and Pt_x-Sn_y catalysts prepared by electrodeposition techniques. Their electro-catalytic activities were studied in 0.5mol/L H₂SO₄ and compared to those of a smooth Pt, Pt/Pt and Pt-Sn/Pt electrodes. Platinum was deposited on Ti by galvanostatic and potentiostatic techniques. X-ray diffractometer (XRD) and energy dispersive X-ray (EDX) techniques were applied in order to investigate the chemical composition and the phase structure of the modified electrodes. Scanning electron microscopy (SEM) was used to characterize the surface morphology and to correlate the results obtained from the two electrochemical deposition methods. Results show that modified Pt/Ti electrodes prepared by the two methods have comparable performance and enhanced catalytic activity towards methanol electro-oxidation compared to Pt/Pt and smooth Pt electrodes. Steady state Tafel plots experiments show a higher rate of methanol oxidation on a Pt/Ti catalyst than that on a smooth Pt.  Introduction of a small amount of Sn deposited with Pt improves the catalytic activity and the stability of prepared electrode with time as indicated from the cyclic votlammetry and the chronoamperometric experiments. The effect of variations in the composition for binary catalysts of the type Pt_x-Sn_y/Ti towards the methanol oxidation reaction is reported. Consequently, the Pt_x-Sn_y/Ti (x∶y (8∶1), molar ratio) catalyst is a very promising one for methanol oxidation.