Abstract
Plasmonic nanoparticles (NPs), particularly Au NPs, are potential candidates for photocatalysts because of their unique optical properties. The size of Au NPs plays a crucial role in effective light absorption, which is an important factor in photocatalytic reactions. Although Au NP-based photocatalysts have garnered significant researched interest, the size effect of Au NPs on a photocatalytic reaction has not been sufficiently studied. We characterized the effect of size on the photocatalytic activity of Au NPs of different sizes. We found that the absorption cross-section of the Au NPs gradually increased as the size of the Au NPs increased. However, the reaction rate for each size of NP was inversely proportional to the absorption cross-section. Based on the simulation results, we found that larger Au NPs have a higher scattering factor than that of smaller Au NPs. Consequently, the scattering effect of Au NPs hinders effective light absorption, resulting in slower reaction kinetics. These findings can contribute to the rational design of high-efficiency plasmonic photocatalysts.
Highlights
Plasmonic noble metal nanoparticles (NPs) have received significant attention because of their unique optical properties in the visible light region and their catalytic activity in the nanoscale regime [1,2,3,4]
The role of the plasmonic NPs is limited to a light-absorbing antennae, and the metal oxide NPs act as the reaction center by transferring electrons from metal NPs
Kim et al reported the harvesting of energetic charge carriers in Au NPs, the amount of activation energy that is reduced under plasmonic excitation, and the transference of excited electrons to the reaction substance through the insulating ligand in plasmonic Au photocatalysts [14,15,16]
Summary
Plasmonic noble metal nanoparticles (NPs) have received significant attention because of their unique optical properties in the visible light region and their catalytic activity in the nanoscale regime [1,2,3,4] These properties result from their localized surface plasmon resonance (LSPR) and are advantageous for their implementation as photocatalysts. Heterostructured plasmonic photocatalysts drive important chemical transformations such as the dissociation of H2, ethane epoxidation, water splitting, and reduction of CO2 to hydrocarbons [5,9,10,11,12] In such photocatalysts, the role of the plasmonic NPs is limited to a light-absorbing antennae, and the metal oxide NPs act as the reaction center by transferring electrons from metal NPs. the excited electron is generated only in metal NPs by light, the metal NP (mostly Au) itself is not considered as a potential plasmonic photocatalyst because the timescale of energy relaxation of photoexcited charge carriers is extremely small [13], and kinetically redundant in a chemical reaction. By correlating the reaction kinetics and extinction spectra of Au NPs of varying sizes, we found that the scattering effect could hinder the effective number of photons absorbed by the Au NPs
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