Development of custom made bimetallic alloy model systems based on platinum - rhodium for heterogeneous catalysis

JOURNAL OF ALLOYS AND COMPOUNDS

卷:786

Article

Kumar, Susmit¹  Waller, David²  Fjellvag, Helmer¹  Sjastad, Anja Olafsen¹ 

[1] Univ Oslo, Ctr Mat Sci & Nanotechnol, NO-0315 Oslo, Norway

[2] Yara Norge AS, Yara Technol Ctr, NO-3905 Porsgrunn, Norway

关键词: Solid state diffusion;    Platinum;    Rhodium;    Bimetallic alloys;    Kirkendall effect;   

DOI  :  10.1016/j.jallcom.2019.02.026

来源: Elsevier

【 摘 要 】

The current study extends the insight into solid-state diffusion in alloys of the Platinum Group Metals (PGMs). Thereby, we pave the way for tailor making surface compositions of binary platinum (Pt) - rhodium (Rh) model catalysts, with deposited rhodium layers on the surface of Pt single crystals (SCs) as the starting point. Platinum single crystals with (100), (110) and (111) orientations were studied by scanning electron microscopy (SEM) and energy dispersive X - ray spectroscopy (EDS). In addition, X - ray Photoelectron spectroscopy (XPS) characterization was carried out on Pt(110). The crystallographic orientation has a prominent effect on diffusion characteristics. The slowest moving Kirkendall - plane was observed for Pt(110) at x(K) = 250 nm from reference point x(0), while, the fastest for Pt(100) was at x(K) = 450 nm, indicating that the inter-diffusion rate with respect to orientation increases in the sequence Pt(110) < Pt(111) < Pt(100). The diffusion coefficient of Rh into Pt is of the order similar to 10(-17)-10(-18 )m(2)/s, whereas it was slightly less than similar to 10(-19) m(2)/s for Pt into Rh; albeit comparable to the vacancy diffusion rate from Pt into Rh. Our experimental findings show good agreement with calculated inter-diffusion coefficients using Darken analysis. A theoretical direction is proposed for improved fitting of data. (C) 2019 Elsevier B.V. All rights reserved.

【 授权许可】

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