Water promoted structural evolution of Ag nanocatalysts supported on alumina

• Published in: Nano research Vol. 16; no. 7; pp. 9107 - 9115
• Main Authors: Liu, Conghui, Li, Rongtan, Wang, Fei, Li, Kun, Fan, Yamei, Mu, Rentao, Fu, Qiang
• Format: Journal Article
• Language: English
• Published: Beijing Tsinghua University Press 01.07.2023
• Subjects: Aluminum oxide; Atmosphere; Atomic/Molecular Structure and Spectra; Biomedicine; Biotechnology; Catalysis; Catalysts; Chemical reduction; Chemistry and Materials Science; Condensed Matter Physics; Dispersion; Ethanol; Evolution; Materials Science; Metals; Migratory species; Nanocatalysis; Nanoclusters; Nanoparticles; Nanotechnology; Nanowires; Oxidation; Particle size; Research Article; Room temperature; Selective catalytic reduction; Silver; Sintering; Transitional aluminas; Ag nanocatalyst; spontaneous aggregation; water effect; oxidative dispersion
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-023-5735-6

Water is often involved in many catalytic processes, which can strongly affect structural evolution of catalysts during pretreatments and catalytic reactions. In this work, we demonstrate a promotional effect of H 2 O on both oxidative dispersion and spontaneous aggregation of Ag nanocatalysts supported on alumina. Ag nanoparticles supported on γ-Al 2 O 3 and Ag nanowires on Al 2 O 3 (0001) can be dispersed into nanoclusters via annealing in O 2 above 300 °C, which is accelerated by introduction of H 2 O into the oxidative atmosphere. Furthermore, the formed highly dispersed Ag nanoclusters are subject to spontaneous aggregation in humid atmosphere at room temperature. Ex situ and in situ characterizations in both powder and model catalysts suggest that formation of abundant surface hydroxyls and/or water adlayer on the Al 2 O 3 surface in the H 2 O-containing atmosphere facilitates the surface migration of Ag species, thus promoting both dispersion and aggregation processes. The aggregation of the supported Ag nanostructures induced by the humid oxidative atmosphere enhances CO oxidation but inhibits selective catalytic reduction of NO with C 3 H 6 . This work illustrates the critical role of H 2 O in structure and catalytic performance of metal nanocatalysts, which can be widely present in heterogeneous catalysis.