Active site structure and methane oxidation reactivity of bimetallic Pd and Pt nanoparticles

[Display omitted] •Oxidizing atmosphere converts PdPt particle to Pt-rich core-PdO shell structure.•PdO shell with underneath Pt core is highly effective for C–H activation of CH4.•Adsorption of H2O/SO2 derived species increases effective CH4 activation barriers.•Kinetically relevant C–H cleavage on...

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Published in:Applied catalysis. A, General General, 2022-01, Vol.629, p.118290, Article 118290
Main Authors: Yang, Yifei, Lee, Jaekyoung, Dorakhan, Roham, Nie, Haoyu, Fu, Guangshi, Quarantotto, Alessandro, Howe, Jane Y., Chin, Ya-Huei (Cathy)
Format: Article
Language:English
Subjects:
Bimetallic nanoparticles
Bimetals
Core-shell nanoparticles
Dynamic structural analysis
Methane
Methane oxidation
Nanoparticles
Oxidation
Oxygen consumption
Palladium
PdO
PdPt alloy
Platinum
SO2 poisoning
Structural dynamics
Turnover rate
Water inhibition
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Summary:[Display omitted] •Oxidizing atmosphere converts PdPt particle to Pt-rich core-PdO shell structure.•PdO shell with underneath Pt core is highly effective for C–H activation of CH4.•Adsorption of H2O/SO2 derived species increases effective CH4 activation barriers.•Kinetically relevant C–H cleavage on Pt core-PdO shell with or without H2O/SO2.•Pt-rich core-PdO shell cluster is more resistant to H2O than SO2 comparing to PdO. Kinetic, oxygen uptake, microscopic, and spectroscopic studies shed light on the structural dynamics of PdPt bimetallic catalysts and their methane oxidation rates. Reductive treatments lead to Pd0Pt0 nanoparticles distributed in sizes and Pt:Pd ratios. Oxidative treatments, including treatments in CH4-O2 reaction mixture, lead the Pd, as the more oxophilic metal, to migrate onto the surfaces and undergo bulk oxidation, forming a thin PdO shell covering the underneath Pt-rich core. Residing on the PdO shell are Pd2+-O2− site pairs that are highly effective for C–H activation in methane—the CH4 turnover rates are the highest at 0.3 Pt:Pd ratio and the C–H activation barrier decreases from 64 to 37 kJ mol−1 as the Pt:Pd ratio increases from 0 to 1. H2O and SO2 impurities increase the effective barrier to 58 and 116 kJ mol−1, respectively, but such effects remain much smaller than on unpromoted PdO.
ISSN:0926-860X
1873-3875
DOI:10.1016/j.apcata.2021.118290