Formation and evolution of AuxPd1-x model catalysts under gaseous environments and variable temperature within an ETEM - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2023

Formation and evolution of AuxPd1-x model catalysts under gaseous environments and variable temperature within an ETEM

Résumé

Networks of nanoparticles (NPs) with well-controlled characteristics (size, composition, inter-distance) can be obtained by the di-block copolymer approach; an amphiphilic di-block copolymer dissolved in toluene yields a system of inverse micelles whose core can be charged with metallic precursors to yield such networks. The latter can be used as model catalysts when tranferred to flat surfaces. The formation of individual NPs within the cores and the stability of the networks with increasing temperature under reactive gases have yet to be investigated. To do so we used an Environmental TEM (Titan ETEM/G2, TFS) operated at 300kV, under gas pressures upto 10 mbar during heating under oxygen and CO, together with a WildFire sample-holder with dedicated heating MEMS-microchips (DENSsolutions). We used PS-b-P2VP di-block copolymer micelles metallized with HAuCl4 and Pd(CH3COO)2 precursors to obtain Au-rich and Pd-rich AuxPd1-x systems. The precursors selectively bind with N-functions in the P2VP cores to form bimetallic seeds as it was previously established in the case of PdAg NPs [1]. Monolayers of controlled AuxPd1-x core-metallized micellar solutions were deposited by spin-coating on the microchips. Safe illumination conditions were deduced from preliminary irradiation tests to minimize electron-beam influence during the observations. In the case of Au80Pd20, the bimetallic seeds within the P2VP cores (Fig.1) begin to sinter around 350°C and unique NPs are eventually formed around 500°C, under oxygen; this is consistent with the decomposition temperature range of the PS-b-P2VP copolymer [2]. The NPs network is stable upto 900°C. Approaching the gold melting temperature (1064°C) the NPs begin to decompose without affecting the network frame. Regarding Au20Pd80, under oxygen, the seeds begin to sinter around 300°C and, at 450°C, NPs demixing is observed leading to Janus NPs (Au-rich/PdO; Fig.2); the latter are readily reduced upon CO exposure and bimetallic NPs reform. The stability of the bimetallic NPs networks seems to be driven by the intrinsic properties of the metals composing them. We thank the METSA network for support and the CLYM for access to the ETEM. References: [1] E. Ehret et al., Nanoscale, 7 (2015), p.13239 [2] T. Orhan Lekesiz et al., J. Anal. Appl. Pyrolysis, 106 (2014), p.81
Fichier non déposé

Dates et versions

hal-04146467 , version 1 (30-06-2023)

Identifiants

  • HAL Id : hal-04146467 , version 1

Citer

F. Cadete Santos Aires, E. Ehret, B. Domenichini, L. Burel, T. Epicier. Formation and evolution of AuxPd1-x model catalysts under gaseous environments and variable temperature within an ETEM. 18ème Colloque de la SFµ, Jul 2023, Rouen, France. ⟨hal-04146467⟩
18 Consultations
0 Téléchargements

Partager

Gmail Facebook X LinkedIn More