(177d) Elucidating the Roles of Nanoparticle Clustering and Equilibrium Heating in Plasmonic Catalysts Under Continuous Broadband Illumination

Plasmonic metal nanoparticles have garnered interest due to their unique ability to harvest low intensity light via the excitation of localized surface plasmon resonance (LSPR). The decay of LSPR yields radiative scattering and non-radiative absorption of photons, the latter contributing to efficient charge carrier generation within the particles. These charge carriers may subsequently thermalize, leading to heating of the particle and its surrounding environment. These nonthermal and photothermal processes, respectively, can be utilized to drive light-mediated chemistry on the surfaces of plasmonic nanoparticles [1, 2, 3]. Gaining insight into the relative influence of these processes has become exceedingly relevant, because each process may have distinct consequences for the rational design of reaction-specific catalysts [4].

In this work, we shed light on the relative contributions of these effects by characterizing photothermal equilibrium catalyst heating under continuous broadband illumination. We first introduce a new photoreactor platform which facilitates superior thermal and photothermal temperature and reaction characterization. Next, we employ this reactor to compare reaction rate enhancement for CO oxidation over plasmonic Ag/Al₂O₃ catalysts. By varying the Ag weight loading, we explore the role of equilibrium heating and collective effects emerging from increasing particle density and clustering on the support. Pairing experimentally obtained in-operando temperature measurements and reaction rate data, we show that the contribution of photothermal equilibrium heating at low to moderate loadings cannot exclusively explain the extent of rate enhancement. Instead, only at high weight loadings do we observe significant contributions from collective effects.

References

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2. Aslam, U., Rao, V.G., Chavez, S. & Linic, S., Nat. Catal. 9, 656-665 (2018).
3. Aslam, U., Chavez, S. & Linic, S., Nanotechnol. 12, 1000–1005 (2017).
4. Linic, S., Chavez, S. & Elias, R. Nat. Mater. 20, 916–924 (2021).