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 (Ti_xSn_1-xO₂) support was prepared via a solvothermal method with substitution of Ti⁴⁺ by Sn⁴⁺ in the TiO₂ lattice. Furthermore, the Ti_xSn_1-xO₂ was combined with conventional carbon black (Vulcan XC-72) to prepare a hybrid support (Ti_xSn_1-xO₂-C) for depositing Pt nanoparticles. The ratios of Sn vs. Ti in the solid-solution and Ti_xSn_1-xO₂vs. 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/Ti_0.9Sn_0.1O₂-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 Ti_0.9Sn_0.1O₂ 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 Ti_0.9Sn_0.1O₂-C is due to high content of OH group on Ti_0.9Sn_0.1O₂ along with the strengthened metal-supports interactions. Both promote the oxidation of poisoning CO absorbed on Pt active sites.