Atmosphere-dependent stability and mobility of catalytic Pt single atoms and clusters on gamma-Al2O3

Caroline Dessal (1) , Alexis Sangnier (2) , Céline Chizallet (2) , Christophe Dujardin (3) , Franck Morfin (1, 4) , Jean-Luc Rousset (1, 5) , Mimoun Aouine (1, 6) , Matthieu Bugnet (7) , Pavel Afanasiev (1, 5) , L. Piccolo (1, 5)

1 IRCELYON - Institut de recherches sur la catalyse et l'environnement de Lyon
2 IFPEN - IFP Energies nouvelles
3 UCCS - Unité de Catalyse et Chimie du Solide - UMR 8181
4 ING - IRCELYON-Ingéniérie, du matériau au réacteur
5 CATREN - IRCELYON-Catalyse Hétérogène pour la Transition Energétique
6 MICROSCOPIE - IRCELYON-Microscopie
7 MATEIS - Matériaux, ingénierie et science [Villeurbanne]

Atomically dispersed metals promise the ultimate catalytic efficiency, but their stabilization onto suitable supports remains challenging owing to their aggregation tendency. Focusing on the industrially-relevant Pt/-Al2O3 catalyst, in situ X-ray absorption spectroscopy and environmental scanning transmission electron microscopy allow us to monitor the stabilization of Pt single atoms under O2 atmosphere, as well as their aggregation into mobile reduced subnanometric clusters under H2. Density functional theory calculations reveal that oxygen from the gas phase directly contributes to metal-support adhesion, maximal for single Pt atoms, whereas hydrogen only adsorbs on Pt, and thereby leads to Pt clustering. Finally, Pt cluster mobility is shown to be activated at low temperature and high H2 pressure. Our results highlight the crucial importance of the reactive atmosphere on the stability of single-atom versus cluster catalysts.

Keywords: Atmosphere-; catalytic; Al 2O3

Domains: Catalysis; Environmental and Society

Caroline Dessal, Alexis Sangnier, Céline Chizallet, Christophe Dujardin, Franck Morfin, et al.. Atmosphere-dependent stability and mobility of catalytic Pt single atoms and clusters on gamma-Al2O3. Nanoscale, 2019, 11 (14), pp.6897-6904. ⟨10.1039/C9NR01641D⟩. ⟨hal-02142310⟩