Ruthenium-Alloy Electrocatalysts with Tunable Hydrogen Oxidation Kinetics in Alkaline Electrolyte

• Published in: Journal of physical chemistry. C Vol. 119; no. 24; pp. 13481 - 13487
• Main Authors: St. John, Samuel, Atkinson, Robert W, Unocic, Raymond R, Zawodzinski, Thomas A, Papandrew, Alexander B
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18.06.2015
• Subjects: alloys; catalysts; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; metal nanoparticles; palladium; platinum
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.5b03284

High-surface-area ruthenium-based Ru x M y (M = Pt or Pd) alloy catalysts supported on carbon black were synthesized to investigate the hydrogen oxidation reaction (HOR) in alkaline electrolytes. The exchange current density for hydrogen oxidation on a Pt-rich Ru0.20Pt0.80 catalyst is 1.42 mA/cm2, nearly 3 times that of Pt (0.490 mA/cm2). Furthermore, Ru x Pt y alloy surfaces in 0.1 M KOH yield a Tafel slope of ∼30 mV/dec, in contrast with the ∼125 mV/dec Tafel slope observed for supported Pt, signifying that hydrogen dissociative adsorption is rate-limiting rather than charge-transfer processes. Ru alloying with Pd does not result in modified kinetics. We attribute these disparate results to the interplay of bifunctional and ligand effects. The dependence of the rate-determining step on the choice of alloy element allows for tuning catalyst activity and suggests not only that a low-cost, alkaline anode catalyst is possible but also that it is tantalizingly close to reality.