Direct Observation of Ni Nanoparticle Growth in Carbon-Supported Nickel under Carbon Dioxide Hydrogenation Atmosphere.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37504574.
- Also identified by DOI 10.1021/acsnano.3c03721 and PMC identifier 10416566.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Understanding nanoparticle growth is crucial to increase the lifetime of supported metal catalysts. In this study, we employ <i>in situ</i> gas-phase transmission electron microscopy to visualize the movement and growth of ensembles of tens of nickel nanoparticles supported on carbon for CO<sub>2</sub> hydrogenation at atmospheric pressure (H<sub>2</sub>:CO<sub>2</sub> = 4:1) and relevant temperature (450 °C) in real time. We observe two modes of particle movement with an order of magnitude difference in velocity: fast, intermittent movement (<i>v</i><sub>max</sub> = 0.7 nm s<sup>-1</sup>) and slow, gradual movement (<i>v</i><sub>average</sub> = 0.05 nm s<sup>-1</sup>). We visualize the two distinct particle growth mechanisms: diffusion and coalescence, and Ostwald ripening. The diffusion and coalescence mechanism dominates at small interparticle distances, whereas Ostwald ripening is driven by differences in particle size. Strikingly, we demonstrate an interplay between the two mechanisms, where first coalescence takes place, followed by fast Ostwald ripening due to the increased difference in particle size. Our direct visualization of the complex nanoparticle growth mechanisms highlights the relevance of studying nanoparticle growth in supported nanoparticle ensembles under reaction conditions and contributes to the fundamental understanding of the stability in supported metal catalysts.