Sn-doped TiO2 modified carbon to support Pt anode catalysts for direct methanol fuel cells

Catalyst supports are known to play important role in governing overall catalyst activity and durability. Here, a new type of SnO2–TiO2 solid solution (TixSn1-xO2) support was prepared via a solvothermal method with substitution of Ti4+ by Sn4+ in the TiO2 lattice. Furthermore, the TixSn1-xO2 was combined with conventional carbon black (Vulcan XC-72) to prepare a hybrid support (TixSn1-xO2–C) for depositing Pt nanoparticles. The ratios of Sn vs. Ti in the solid-solution and TixSn1-xO2 vs. XC-72 were systematically optimized in terms of their performance as supports for methanol oxidation. Compared to Pt/TiO2–C and commercial Pt/C catalysts, the best performing Pt/Ti0.9Sn0.1O2–C catalyst exhibited the highest activity, evidenced by methanol oxidation and CO stripping experiments. The well-dispersed Pt nanoparticles (2–3 nm) are mostly deposited on the boundaries of Ti0.9Sn0.1O2 and carbon blacks. Formation of the special triple junction structure can play an important role in improving Pt utilization with increased electrochemical active surface areas (ESA) of Pt. In addition, the enhanced activity for Pt supported on Ti0.9Sn0.1O2–C is due to high content of OH group on Ti0.9Sn0.1O2 along with the strengthened metal-supports interactions. Both promote the oxidation of poisoning CO absorbed on Pt active sites.