An organometallic deposition of ruthenium adatoms on platinum that self poisons at a specific surface composition.: A direct methanol fuel cell using a platinum–ruthenium adatom anode catalyst

The organometallic precursor Ru4(μ-H)4(CO)12 (1) reacts with dihydrogen (60 atm, room temperature hexane as solvents, 3 h) over either blacked Pt gauze or Pt black powder to deposit Ru adatoms (Ruad) and CO on the Pt surface. The deposition is self-poisoned by adsorbed CO, stopping when a specific coverage of Pt by CO is reached. The results from the electrooxidation of the adsorbed CO, from base voltammograms recorded in aqueous sulfuric acid, from exhaustive anodic stripping of Ruad, and from the potentiodynamic and potentiostatic electrooxidation of MeOH, all show that the deposition self-poisons after ca. 0.05 surface equivalents (moles Ruad vs. moles Pt surface) of Ruad are deposited on blacked Pt gauze. The deposition over Pt black powder self-poisons after depositing ca. 0.10 surface equivalents of Ruad. A direct CH3OH fuel cell using the resulting black Pt–Ruad powder was constructed by hot-pressing the catalyst into a Nafion® membrane. Contrary to expectations, the Pt–Ruad catalyst did not lose significant amounts of surface Ru during either hot pressing the membrane electrode assembly, nor during operation of the fuel cell at 90 °C.