MeOH-tolerant oxygen reduction catalysts

For DMFC systems, Pt cathodes are also used as the catalyst of choice however, given Pt s ability to reduce oxygen and oxidize methanol, this lack of selectivity makes them sensitive to methanol crossover from anode to cathode via the membrane. This methanol crossover can have a depolarizing effect on cathode performance, reducing overall cathode activity. To combat this, an extensive effort has been made to identify and develop selective oxygen/reduction catalysts unaffected by MeOH crossover. 

More recent research has focused on the binary Ru sulfides and selenides. Schulenberg et al. showed that modifying a Ru/C with Se (via H2Se03) improved activity by a factor of three. It was concluded that the Se inhibited surface oxide formation that limits active sites with Ru/C. Both catalysts showed some H2O2 formation at lower potentials (e.g., 3% at 

Oxygen/reduction polarization curves from RDE measurements for Ru,92MO(,Q8Se04, Ru/C, and Pt/C in 0.6 M H2SO4,60°C. (T. J. Schmidt et al.. Journal of the Electrochemical Society, 4 2620 (2000). Reproduced by permission of The Electrochemical Society.) 

Ruthenium/carbon catalysts have also been promoted by the addition of Fe. Bron et al. reported the addition of Fe to a preformed Ru/C catalyst via adsorption of Fe complexes, followed by heat treatment. They found an increase in oxygen reduction activity of three to five times over unmodified Ru/C. It was suggested that the surfaces of Ru particles were covered with FeN,Cy sites. As discussed previously, the Pd alloys have shown significant MeOH tolerance toward oxygen reduction and appear to have activities closest to that of Ft. 

The development of MeOH-tolerant cathode catalysts for DMFC is a key component for certain system arrangements. In particular, it is critical for 

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