Platinum Metals Review - Volume 46, Issue 4, 2002

The direct methanol fuel Cell (DMFC) is a low temperature fuel cell operating at temperatures of 30 to 130°C. The DMFC is powered by a liquid fuel (usually considered essential for transport uses) and is therefore regarded by some as the ideal fuel cell system. In this paper, the DMFC is compared to the hydrogen-fuelled proton exchange membrane fuel Cell (PEMFC) which was discussed in detail in the January and July issues. While a typical DMFC is less efficient than a PEMFC, work to improve its performance with new electrocatalyst materials for utilisation in the membrane electrode assemblies has proved successful. This work is described here and some possible commercial uses for the DMFC are also considered.

Non-trivial structural changes and phase transformation kinetics have been found to occur in Palladium-hydrogen and Palladium-metal-hydrogen systems during relaxation processes as hydrogen is released. In the Palladium-hydrogen system these changes take place in stages: an incubation period, a period of fast degassing, a period of stabilisation, and a post-stabilisation period. In Palladium-metal-hydrogen systems the structural changes and phase transformations are non-monotonous (oscillating or stochastic). Time dependent kinetics have been observed over periods of up to tens of thousands of hours. An hypothesis based upon non-equilibrium thermodynamics and hydrogen interaction factors between matrix defects and atoms in the Palladium systems is proposed to explain the phenomena.