title: Suppression of Hydrogen Evolution by Oxygen Reduction in Nanoporous Electrocatalysts.
abstract: Electroreduction of small molecules in aqueous solution often competes with the hydrogen evolution reaction (HER), especially if the reaction is driven even moderately hard using a large overpotential. Here, the oxygen reduction reaction (ORR) was studied under proton diffusion-limited conditions in slightly acidic electrolytes: a model system to study the relative transport kinetics of protons and reactants to an electrocatalyst and the relationship between transport and catalytic performance. Using dealloyed nanoporous nickel-platinum (np-NiPt) electrodes, we find the hydrogen evolution reaction can be completely suppressed even at high overpotentials (-400 mV vs RHE). In addition, the mechanism of oxygen reduction can be changed by using buffered versus unbuffered solutions, suggesting the reaction selectivity is associated with a transient rise (or lack thereof) in the interface pH at the np-NiPt surface. Independently controlling reactant transport to electrocatalyst surfaces at high overpotentials exhibited a surprisingly rich phenomenology that may offer a generalizable strategy to increase activity and selectivity during electroreduction reactions.
authors.affiliation: Department of Materials Science and Engineering, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Ellen E
authors.identifier: 0000-0003-2624-9245
authors.initials: EE
authors.lastname: Benn
authors.affiliation: Department of Materials Science and Engineering, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Bernard
authors.initials: B
authors.lastname: Gaskey
authors.affiliation: Department of Materials Science and Engineering, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Jonah D
authors.initials: JD
authors.lastname: Erlebacher