Methanol-resistant cathodic oxygen reduction catalysts for methanol fuel cells

Efforts were made to simplify the structure of Ru-based catalysts, and to t ailor industrially practicable methanol insensitive oxygen reduction cataly sts both by thermolysis of Ru-carbonyls in organic solvents and by modified preparation techniques of Ru colloids. Selective catalysis was found to be essentially independent of the chalcogene (Se) used which, however, is a c rucial factor for facilitating efficient electron transfer. All preparation s contained Ru-metal particles of nm size, the surfaces of which were modif ied by carbonyl and carbido-carbonyl complexes or carbon compounds. The rol e of carbon as ligand to Ru clusters stabilizing the Ru interface against o xidation and in promoting catalytic electron exchange via nonbonding Ru d-s tates is theoretically analysed in a model calculation. An analogy is drawn to a biological Fe - only hydrogenase centre in order to discuss projected key experiments for optimizing reduction catalysis: the stabilization of s mall, inherently unstable catalytic metal clusters by CO or CN and their li nking via electron bridges such as S and Se to electron reservoirs (metal c olloids).