Synthesis and characterization of methanol tolerant Pt/TiOx/C nanocomposites for oxygen reduction in direct methanol fuel cells

Pt/TiOx/C nanocomposites have been synthesized by depositing hydrated titanium oxide on carbon-supported Pt (Pt/C), reducing H2PtCl6 with sodium formate on carbon-supported hydrated titanium oxide (TiO2/C), and simultaneously depositing hydrated titanium oxide and reducing H2PtCl6 with formate on carbon support, followed by heat treatment at 500 and 900degreesC in 90% Ar-10% H-2 mixture. The catalytic activity for oxygen reduction was evaluated in half cells with sulfuric acid electrolyte and in single direct methanol fuel cells (DMFC). Tolerance to methanol was studied with half cells containing sulfuric acid mixed with methanol. Charge transfer resistance and electrochemical active surface area of the Pt/TiOx/C catalysts were studied with impedance and cyclic voltammetry measurements. Both the synthesis methods and heat treatments influence the catalytic activity, and some of the Pt/TiOx/C composites exhibit higher catalytic activity than Pt/C. The Pt/TiOx/C catalysts also exhibit better methanol tolerance than Pt/C. The mechanism for the enhanced catalytic activity of Pt/TiOx/C is discussed. (C) 2004 Elsevier Ltd. All rights reserved.