Title: Atomic Structure of Pt₃Ni Nanoframe Electrocatalysts by in Situ X-ray Absorption Spectroscopy.

Abstract

Understanding the atomic structure of a catalyst is crucial to exposing the source of its performance characteristics. It is highly unlikely that a catalyst remains the same under reaction conditions when compared to as-synthesized. Hence, the ideal experiment to study the catalyst structure should be performed in situ. Here, we use X-ray absorption spectroscopy (XAS) as an in situ technique to study Pt₃Ni nanoframe particles which have been proven to be an excellent electrocatalyst for the oxygen reduction reaction (ORR). The surface characteristics of the nanoframes were probed through electrochemical hydrogen underpotential deposition and carbon monoxide electrooxidation, which showed that nanoframe surfaces with different structure exhibit varying levels of binding strength to adsorbate molecules. It is well-known that Pt-skin formation on Pt-Ni catalysts will enhance ORR activity by weakening the binding energy between the surface and adsorbates. Ex situ and in situ XAS results reveal that nanoframes which bind adsorbates more strongly have a rougher Pt surface caused by insufficient segregation of Pt to the surface and consequent Ni dissolution. In contrast, nanoframes which exhibit extremely high ORR activity simultaneously demonstrate more significant segregation of Pt over Ni-rich subsurface layers, allowing better formation of the critical Pt-skin. This work demonstratesmore » that the high ORR activity of the Pt₃Ni hollow nanoframes depends on successful formation of the Pt-skin surface structure.« less

Authors:

Becknell, Nigel ^[1]; Kang, Yijin ^[2]; Chen, Chen ^[1]; Resasco, Joaquin ^[1]; Kornienko, Nikolay ^[1]; Guo, Jinghua ^[3]; Markovic, Nenad M ^[2]; Somorjai, Gabor A ^[4]; Stamenkovic, Vojislav R ^[2]; Yang, Peidong ^[5]

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+ Show Author Affiliations

1. Univ. of California, Berkeley, CA (United States)
2. Argonne National Lab. (ANL), Argonne, IL (United States)
3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
4. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
5. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kavli Energy NanoScience Institute, Berkeley, CA (United States)

Publication Date:

Thu Dec 10 00:00:00 EST 2015

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1832458

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Journal of the American Chemical Society

Additional Journal Information:

Journal Volume: 137; Journal Issue: 50; Journal ID: ISSN 0002-7863

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Oxides; Platinum; Catalysts; Extended X-ray absorption fine structure; Nickel; Nanoframe; X‐ray absorption; Oxygen reduction; Platinum alloy