Surface enrichment of Pt in stable Pt-Ir nano-alloy particles on MgAl2O4 spinel in oxidizing atmosphere

Li, Wei -Zhen; Nie, Lei; Cheng, Yingwen; Kovarik, Libor; Liu, Jun; Wang, Yong

doi:10.1016/J.CATCOM.2017.01.012

Title: Surface enrichment of Pt in stable Pt-Ir nano-alloy particles on MgAl₂O₄ spinel in oxidizing atmosphere

Journal Article · Fri Jan 13 00:00:00 EST 2017 · Catalysis Communications

DOI:https://doi.org/10.1016/J.CATCOM.2017.01.012· OSTI ID:1342224

Li, Wei -Zhen ^[1]; Nie, Lei ^[1]; Cheng, Yingwen ^[1]; Kovarik, Libor ^[1]; Liu, Jun ^[1]; Wang, Yong ^[2]

Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Washington State Univ., Pullman, WA (United States)

With the capability of MgAl₂O₄ spinel {111} nano-facets in stabilizing small Rh, Ir and Pt particles, bimetallic Ir-Pt catalysts on the same support were investigated in this paper, aiming at further lowering the catalyst cost by substituting expensive Pt with cheaper Ir in the bulk. Small Pt-Ir nano-alloy particles (< 2 nm) were successfully stabilized on the spinel {111} nano-facets as expected. Interestingly, methanol oxidative dehydrogenation (ODH) rate on the surface Pt atoms increases with oxidizing aging but decreases upon reducing treatment, where Ir is almost inactive under the same reaction conditions. Up to three times enhancement in Pt exposure was achieved when the sample was oxidized at 800 °C in air for 1 week and subsequently reduced by H₂ for 2 h, demonstrating successful surface enrichment of Pt on Pt-Ir nano-alloy particles. Finally, a dynamic stabilization mechanism involving wetting/nucleation seems to be responsible for the evolution of surface compositions upon cyclic oxidizing and reducing thermal treatments.

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Research Organization:: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Biological and Environmental Research (BER)