title: Composite Ni/NiO-Cr2O3Catalyst for Alkaline Hydrogen Evolution Reaction.
abstract: We report a Ni-Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline electrolyte. The HER kinetics of numerous binary and ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni-Cr materials which exhibit metallic Ni as well as NiOxand Cr2O3phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to numerous binary and ternary Ni-alloys, including Ni-Mo materials. It is likely that at adjacent Ni/NiOxsites, the oxide acts as a sink for OHads, while the metallic Ni acts as a sink for the Hadsintermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiOxcontent and that the Cr2O3appears to stabilize the composite NiOxcomponent under HER conditions (where NiOxwould typically be reduced to metallic Ni0). Furthermore, in contrast to Pt, the Ni(Ox)/Cr2O3catalyst appears resistant to poisoning by the anion exchange ionomer (AEI), a serious consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI.
authors.affiliation: Northeastern University Center for Renewable Energy Technology (NUCRET), Northeastern University, Boston, Massachusetts 02115, United States.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Bates
authors.affiliation: Northeastern University Center for Renewable Energy Technology (NUCRET), Northeastern University, Boston, Massachusetts 02115, United States.
authors.forename: Qingying
authors.initials: Q
authors.lastname: Jia
authors.affiliation: Northeastern University Center for Renewable Energy Technology (NUCRET), Northeastern University, Boston, Massachusetts 02115, United States.
authors.forename: Nagappan
authors.initials: N
authors.lastname: Ramaswamy
authors.affiliation: Northeastern University Center for Renewable Energy Technology (NUCRET), Northeastern University, Boston, Massachusetts 02115, United States.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Allen
authors.affiliation: Northeastern University Center for Renewable Energy Technology (NUCRET), Northeastern University, Boston, Massachusetts 02115, United States.
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Mukerjee