S. Hunyadi Murph, E.B. Fox, S.M. Serkiz, H. Colon-Mercado
Direct methanol fuel cells (DMFCs) have recently attracted much interest as a promising alternative to conventional batteries, especially in portable electronic devices. DMFCs, however, have several disadvantages including high cost, largely as a result of high precious metal catalyst loading requirements, slow kinetics, and methanol crossover. In order to overcome these problems there is a need to develop alternative catalysts with high surface area and lower cost as well as to develop novel membranes that reduce methanol crossover. We addressed these problems by producing nano-sized platinum materials with different morphologies (spheres, rods, cubes, hollow vs. full, core-shell) in order to maximize Pt catalytic activity on a mass basis and self-assembled them into Nafion membranes. We focused our attention on three specific types of nano-sized catalysts: (1) solid monometallic Pt nanospheres, (2) hollow Pt nanospheres and nanowires, and (3) core-shell Au-Pt nanorods and nanocubes. All these approaches allow fine tuning of size and shape of the Pt nanospheres simply based on the reactants and the seed concentrations. These reactions take place in air and water, are quick, economical and amenable to scaling up. The nano-catalysts were characterized by electron microscopy techniques, energy dispersive X-ray analysis, ICP-MS, and tested for DFMC applications.