| Direct methanol fuel cells (DMFCs) operate via direct electro-oxidation of methanol, thereby producing electricity without the complications of a reformer. This system simplicity ensures good scalability (portable electronics to transportation applications) while the relatively low operating temperature (60–130°C) ensures low emissions. Nonetheless, the voltage losses sustained in direct methanol electro-oxidation over Pt-based catalysts (2–5 nm Pt-Ru particles on carbon support) preclude its implementation in many applications. Nearly all half-cell experiments to-date (used to screen catalysts and determine reaction mechanisms) have occurred on solid metal electrodes, ambient temperatures, and elevated anode potentials (0.45–0.6 V rhe), which poorly reflect DMFC operating conditions.; A bench-scale electrochemical measurement has been developed for determining the mechanisms of methanol electro-oxidation on dispersed Pt catalysts at elevated temperatures and pressures (up to 100°C and 2 atm). The technique facilitates transient measurement of methanol electro-oxidation and formation of the poisoning CO adlayer through pulsed reactant injection. Independent measurement of individual reaction pathways (e.g. oxidation and thermal desorption of the poisoning CO adlayer) are also possible. The general effects of temperature, methanol concentration, and anode potential on the electro-oxidation mechanism will be discussed. Numerical modeling of the coupled transport/kinetic system provides estimates for pathways difficult to measure directly.; A novel, mini-deposition source has been used to prepare Ru adlayers on a Pt(111) substrate in ultra-high vacuum conditions. Characterization of both thick (15 ML) and sub-monolayer Ru adlayers by AES, TDS, and LEED indicates that Ru grows in a predominantly simultaneous multi-layer mode, which is epitaxial with the underlying substrate to some degree. The results indicate that the source is suitable for preparing model Pt-Ru surfaces for further elucidating the role of Ru oxides for nucleation oxygen species in electrochemical systems. |
