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

Abstract

Carbon supported binary Pt–Ti alloys were investigated for application in methanol electro-oxidation (MOR) and oxygen electro-reduction reactions (ORR). Various compositions of Pt 100− x Ti x /C ( x = 0, 25, 50, and 75) catalysts were synthesized by sequential impregnation of Pt and Ti followed by annealing at 900 °C for 30 min under H 2/Ar flow. X-ray diffraction results showed formation of the Pt 3Ti intermetallic phase in Pt 50Ti 50 and Pt 25Ti 75 catalysts after annealing at 900 °C. The Pt 50Ti 50/C-900 and Pt 25Ti 75/C-900 catalysts (the ‘-900’ designation indicates the catalyst was annealed at 900 °C) exhibited 103% ( 87.4 mA m g Pt − 1 ) and 198% ( 128 mA m g Pt − 1 ) higher MOR activity, respectively, than in the Pt/C-900 catalyst ( 43.0 mA m g 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 Pt 50Ti 50/C-900 and Pt 25Ti 75/C-900 catalysts exhibited 32.3 and 30 .2 μ A c m Pt − 2 , respectively, which were 171 and 154% higher than the 11.9 μ A c m 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 Pt 50Ti 50/C-900 and Pt 25Ti 75/C-900 catalysts both exhibited poor ORR activity.