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Microstructure of Bimetallic PtPd Catalysts under Oxidizing Conditions
Author(s) -
Johns Tyne R.,
Gaudet Jason R.,
Peterson Eric J.,
Miller Jeffrey T.,
Stach Eric A.,
Kim Chang H.,
Balogh Michael P.,
Datye Abhaya K.
Publication year - 2013
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201300181
Subject(s) - catalysis , bimetallic strip , oxidizing agent , oxide , materials science , microstructure , carbon monoxide , chemical engineering , xanes , metal , high resolution transmission electron microscopy , extended x ray absorption fine structure , inorganic chemistry , metallurgy , chemistry , nanotechnology , absorption spectroscopy , organic chemistry , transmission electron microscopy , spectroscopy , engineering , physics , quantum mechanics
Diesel oxidation catalysts (DOCs), which decrease the amount of harmful carbon monoxide (CO), nitrogen oxide (NO), and hydrocarbon (HC) emissions in engine exhaust, typically utilize Pt and Pd in the active phase. There is universal agreement that the addition of Pd improves both the catalytic performance and the durability of Pt catalysts. However, the mechanisms by which Pd improves the performance of Pt are less clear. Because these catalysts operate under oxidizing conditions, it is important to understand these catalysts in their working state. Herein, we report the microstructure of PtPd catalysts that are aged in air at 750 °C. After 10 h of aging, EXAFS and XANES analysis show that the Pt is fully reduced but that almost 30 % of the Pd species are present as an oxide. HRTEM images show no evidence of surface oxides on the metallic PtPd particles. Instead, the PdO is present as a separate phase that is dispersed over the alumina support. Within the metallic particles, Pt and Pd are uniformly distributed and there is no evidence of core–shell structures. Therefore, the improved catalytic performance is likely associated with the co‐existence of metallic Pt and Pd on the catalyst surface.