4 research outputs found
Catalytic Activity of Platinum Monolayer on Iridium and Rhenium Alloy Nanoparticles for the Oxygen Reduction Reaction
No full textA new type of electrocatalyst with a core–shell
structure
that consists of a platinum monolayer shell placed on an iridium–rhenium
nanoparticle core or platinum and palladium bilayer shell deposited
on that core has been prepared and tested for electrocatalytic activity
for the oxygen reduction reaction. Carbon-supported iridium–rhenium
alloy nanoparticles with several different molar ratios of Ir to Re
were prepared by reducing metal chlorides dispersed on Vulcan carbon
with hydrogen gas at 400 °C for 1 h. These catalysts showed specific
electrocatalytic activity for oxygen reduction reaction comparable
to that of platinum. The activities of Pt<sub>ML</sub>/Pd<sub>ML</sub>/Ir<sub>2</sub>Re<sub>1</sub>, Pt<sub>ML</sub>/Pd<sub>2layers</sub>/Ir<sub>2</sub>Re<sub>1</sub>, and Pt<sub>ML</sub>/Pd<sub>2layers</sub>/Ir<sub>7</sub>Re<sub>3</sub> catalysts were, in fact, better than
that of conventional platinum electrocatalysts, and their mass activities
exceeded the 2015 DOE target. Our density functional theory calculations
revealed that the molar ratio of Ir to Re affects the binding strength
of adsorbed OH and, thereby, the O<sub>2</sub> reduction activity
of the catalysts. The maximum specific activity was found for an intermediate
OH binding energy with the corresponding catalyst on the top of the
volcano plot. The monolayer concept facilitates the use of much less
platinum than in other approaches. The results with the Pt<sub>ML</sub>/Pd<sub>ML</sub>/Ir<sub>2</sub>Re electrocatalyst indicate that it
is a promising alternative to conventional Pt electrocatalysts in
low-temperature fuel cells
Enhancing Oxygen Reduction Reaction Activity via Pd−Au Alloy Sublayer Mediation of Pt Monolayer Electrocatalysts
No full textNew Pt monolayer electrocatalysts were prepared using galvanic displacement of a copper monolayer deposited at underpotentials on a Pd core. By performing underpotential deposition twice, two monolayers were deposited, forming a core−shell structure with double shells. The double shells consist of an outermost shell of Pt monolayer and a sublayer shell of Pd−Au alloy. It was found that by adjusting the compositions of the alloy sublayer, it is possible to mediate the oxygen reduction reaction (ORR) activity of the Pt catalysts. An alloy with 10% (atomic) Au was found to be the most active among the catalysts tested. Furthermore, the catalysts showed good cycling stability that may be due to stabilizing effect of Au. Since different alloys can be used as the sublayer for mediation, this work may open up various opportunities to tailor electrocatalysts for best ORR activity
