Effect of Ti addition to Pt/C catalyst on methanol electro-oxidation and oxygen electro-reduction reactions

Carbon supported binary Pt-Ti alloys were investigated for application in methanol electro-oxidation (MOR) and oxygen electro-reduction reactions (ORR). Various compositions of Pt100-xTix/C (x = 0, 25, 50, and 75) catalysts were synthesized by sequential impregnation of Pt and Ti followed by annealing at 900 degrees C for 30 min under H-2/Ar flow. X-ray diffraction results showed formation of the Pt-3 Ti intermetallic phase in Pt50Ti50 and Pt25Ti75 catalysts after annealing at 900 degrees C. The Pt50Ti50/C-900and Pt25Ti75/C-900 catalysts (the '-900' designation indicates the catalyst was annealed at 900 degrees C) exhibited 103% (87.4 mA mg(Pt)(-1)) and 198% (128 mA mg(Pt)(-1)) higher MOR activity, respectively, than in the Pt/C-900 catalyst (43.0 mA mg(Pt)(-1)) at 0.7 V (vs. reversible hydrogen electrode (RHE)). These two catalysts also showed high ORR activity. From a specific activity basis, the Pt50Ti50/C-900 and Pt25Ti75/C-900 catalysts exhibited 32.3 and 30.2 mu A cm(Pt)(-2), respectively, which were 171 and 154% higher than the 11.9 mu A cm(Pt)(-2) value of the Pt/C catalyst at 0.8 V (vs. RHE). Methanol-tolerant ORR activity was also investigated, but in the presence of methanol, the Pt50Ti50/C-900 and Pt25Ti75/C-900 catalysts both exhibited poor ORR activity. (C) 2009 Elsevier B.V. All rights reserved.