Impact of the Experimental Parameters on Catalytic Activity When Preparing Polymer Protected Bimetallic Nanoparticle Catalysts on Activated Carbon.

Content Provider	Europe PMC
Author	Paris, CharlieB. Howe, Alexander G. Lewis, Richard James Hewes, Daniel Morgan, David J. He, Qian Edwards, Jennifer K.
Copyright Year	2022
Abstract	Sol immobilizationis used to produce bimetallic catalysts withhigher activity to monometallic counterparts for a wide range of environmentaland commercial catalytic transformations. Analysis of complementarysurface characterization (XPS, Boehm’s titration, and zetapotential measurements) was used to elucidate alterations in the surfacefunctionality of two activated carbon supports during acid exposure.When considered in parallel to the experimentally determined electrostaticand conformational changes of the polymer surrounding the nanoparticles,an electrostatic model is proposed describing polymer protected nanoparticledeposition with several polymer–carbon support examples described.Consideration of the electrostatic interactions ensures full depositionof the polymer protected nanoparticles and at the same time influencesthe structure of the bimetallic nanoparticle immobilized on the support.The normalized activity of AuPd catalysts prepared with 133 ppm H2SO4 has a much higher activity for the direct synthesisof hydrogen peroxide compared to catalysts prepared in the absenceof acid. Detailed characterization by XPS indicates that the surfacebecomes enriched in Au in the Au–Pd samples prepared with acid,suggesting an improved dispersion of smaller bimetallic nanoparticles,rich in Au, that are known to be highly active for the direct synthesisreaction. Subsequent microscopy measurements confirmed this hypothesis,with the acid addition catalysts having a mean particle size ∼2nm smaller than the zero acid counterparts. The addition of acid didnot result in a morphology change, and random alloyed bimetallic AuPdnanoparticles were observed in catalysts prepared by sol immobilizationin the presence and absence of acid. This work shows that the depositionof polymer protected AuPd nanoparticles onto activated carbon is heavilyinfluenced by the acid addition step in the sol immobilization process.The physicochemical properties of both the polymer and the activatedcarbon support should be considered when designing a bimetallic nanoparticlecatalyst by sol immobilization to ensure the optimum performance ofthe final catalyst.
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Journal	ACS Catalysis [ACS Catal]
Volume Number	12
DOI	10.1021/acscatal.1c05904
PubMed Central reference number	PMC9016708
Issue Number	8
PubMed reference number	35465244
e-ISSN	21555435
Language	English
Publisher	American Chemical Society
Publisher Date	2022-03-30
Access Restriction	Open
Rights License	Permits the broadest form of re-use including for commercial purposes, provided that author attribution and integrity are maintained (https://creativecommons.org/licenses/by/4.0/). © 2022 The Authors. Published by American Chemical Society
Subject Keyword	carbon characterization sol immobilization nanoparticles gold−palladiumcatalyst hydrogen peroxide direct synthesis
Content Type	Text
Resource Type	Article
Subject	Chemistry Catalysis