A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS Page: 4 of 11
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Fgwre t TEM Images with is of pit sle dlstlbulbcn histograms of 100 pmrtcwfor a) 2 nm, b) 2.5 nm, c) 3.5 nr, d) 7 nm, and e)11
nm Rh NPs. Asculb bar We 20 n except for the HRTEM irna. fj Rh 3d XPS spectre of he 2, 2.5, and 3 nrnm Rh NPa togter with
prevouly syntheslzed 7 and 11 nm Rh NPs, showing the increase In oddzld Rh a the pirtiie Eire dw=ra.
Fgure . a) Turnove Freqummy relative to Rh (oi Th 50 torO, 20 Torr 00. and 200 C dactha Ion engy (150 - 225*C) for CO
oddation Are bOh particle sih dependent. b) The the*keea of the odide sheLl scales with party size: 2 FM and 7 imi NP. are illusirated hte
with ie oxie layers shown to scale, as determined by APXPS.
Fg" 1 APXPS pecra of the Rh3dt pe whI reduced Rh (i07. eV) and oxidized Rh (3Oa2 .V, 3094 V). The ~of both
samples Initially reduce and then oxidize at higher temperalures. The 2 nim NPs are mr1 oxlized at all temperahna. The two Rh(X+) peaks
are atihuled to Rh aions in two diferdn aoldatjon slates or coordinated to a dlfferwd number of oxygen aloms.
Rgw A 0 1C asper of 2 rim and 7 nm Rh NPs In 500 Torr 02 (a and c) and during reaction (10 mTorr %, 20 rTorr CO) (b and d). When
exposed to both 02 and CO, a peak at higher binding emwrgy for . whieh is alihbuted to a RhO. spociu..
Keywords: heterogeneous culalyab - nanornaterals - X-ray specirowcopy - Rh { carbon rrnmxde
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Grass, Michael E.; Zhang, Yawen; Butcher, Derek R.; Park, Jeong Y.; Li, Yimin; Bluhm, Hendrik et al. A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS, article, September 15, 2008; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc930894/m1/4/: accessed April 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.