MACROCYCLIC REDOX PROMOTERS FOR METHANOL OXIDATION

CONTAMINATION OF THE PLATINUM (PT) SPECIES IN METHANOL OXIDATION ANODES BY OXIDIZED METHANOL RESIDUES IS A MAJOR OBSTACLE TOWARD DEVELOPING LONG LIFE METHANOL FUEL CELLS. RESEARCH IN THIS PHASE I PROJECT FOCUSES ON THE ATTACHMENT OF VARIOUS MACROCYCLIC AQUA COMPLEXES OF CERTAIN TRANSITION METALS CAPABLE OF UNDERGOING CONSECUTIVE OXIDATIONS TO THE HYDROXO- AND OXO- STATES AT POTENTIALS CLOSE TO METHANOL OXIDATION ON PT. THESE SPECIES FORM AN INTACT PROMOTER COREON WHICH PT IS DEPOSITED. THE STRONG ELECTRONIC INTERACTIONS BETWEEN THE OXO-METAL SPECIES AND THE ORGANIC RESIDUE ON PT ARE EXPECTED TO RESULT IN THE REMOVAL OF THE ABSORBED ORGANIC FROM THE PT. THE MECHANISM ALSO INVOLVES OXYGEN ATOM TRANSFER TO PT SITES. THESE PROMOTER SPECIES HAVE DISTINCTIVE REDOX CHEMISTRY AND AFFINITY FOR CARBON MONOXIDE AND OTHER SPECIES. THIS APPROACH, IN CONTRAST TO SIMPLY USING VARIOUS OXIDE PROMOTERS (WHICH OFTEN SHOW IRREVERSIBLE REDOX BEHAVIOR) WILL ENHANCE UNDERSTANDING OF THE PROMOTER ACTION AND HELP IN THE DESIGN OF ELECTRODES OF LONG-TERM STABILITY.