Identifying Dynamic Structural Changes of Active Sites in Pt-Ni Bimetallic Catalysts Using Multimodal Approaches

Deyu Liu, Yuanyuan Li, Matthew Kottwitz, Binhang Yan, Siyu Yao, Andrew Gamalski, Daniel Grolimund, Olga V. Safonova, Maarten Nachtegaal, Jingguang G. Chen, Eric A. Stach, Ralph G. Nuzzo, Anatoly I. Frenkel

Research output: Contribution to journalArticle

Abstract

Alloy nanoparticle catalysts are known to afford unique activities that can differ markedly from their parent metals, but there remains a generally limited understanding of the nature of their atomic (and likely dynamic) structures as exist in heterogeneously supported forms under reaction conditions. Notably unclear is the nature of their active sites and the details of the varying oxidation states and atomic arrangements of the catalytic components during chemical reactions. In this work, we describe multimodal methods that provide a quantitative characterization of the complex heterogeneity present in the chemical and electronic speciations of Pt-Ni bimetallic catalysts supported on mesoporous silica during the reverse water gas shift reaction. The analytical protocols involved a correlated use of in situ X-ray Absorption Spectroscopy (XAS) and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), complimented by ex-situ aberration corrected Scanning Transmission Electron Microscopy (STEM). The data reveal that complex reactions occur between the metals and support in this system under operando conditions. These reactions, and the specific impacts of strong metal-silica bonding interactions, prevent the formation of alloy phases containing Ni-Ni bonds. This feature of structure provides high activity and selectivity for the reduction of CO2 to carbon monoxide without significant competitive levels of methanation. We show how these chemistries evolve to the active state of the catalyst: bimetallic nanoparticles possessing an intermetallic structure (the active phase) that are conjoined with Ni-rich, metal-silicate species.

Original languageEnglish (US)
Pages (from-to)4120-4131
Number of pages12
JournalACS Catalysis
Volume8
Issue number5
DOIs
StatePublished - May 4 2018

Keywords

  • DRIFTS
  • STEM
  • XAS
  • bimetallic nanoparticles
  • catalysis
  • nickel
  • platinum
  • reverse water gas shift

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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    Liu, D., Li, Y., Kottwitz, M., Yan, B., Yao, S., Gamalski, A., Grolimund, D., Safonova, O. V., Nachtegaal, M., Chen, J. G., Stach, E. A., Nuzzo, R. G., & Frenkel, A. I. (2018). Identifying Dynamic Structural Changes of Active Sites in Pt-Ni Bimetallic Catalysts Using Multimodal Approaches. ACS Catalysis, 8(5), 4120-4131. https://doi.org/10.1021/acscatal.8b00706