Enhancing the activity of a metallic nanoparticle catalyst through localized plasmon resonance excitation on its surface

Abstract

The article examines the impact of plasmon excitation on the surface of a spherical metallic nanoparticle on its catalytic properties, specifically the efficiency of hot electron generation (activity). The physical mechanisms behind the enhancement of catalytic activity under resonant excitation of surface plasmons are described. A mathematical model is proposed within the classical approximation to describe the relationship between the optical and catalytic properties of metallic nanoparticles. The model accounts for volumetric, surface, and radiative mechanisms of electron relaxation in the nanoparticle, as well as the Hagen–Rubens approximation for the absorption coefficient, which is valid within the studied frequency range. Numerical results obtained within the framework of the proposed model include frequency dependences of the real and imaginary parts of the nanoparticle’s dielectric function, the absorption efficiency, the Fowler parameter, and the efficiency of hot electron generation. An explanation is provided for the similarity in the frequency dependence curves of the real and imaginary parts of the dielectric function, the absorption coefficient, and the Fowler parameter for silver nanoparticles of varying radii. A comparison is made between the obtained numerical results and experimental findings by other researchers regarding the spectral dependences of hot electron generation efficiencies for nanoparticles made of various metals and silver nanoparticles of different radii. The study investigates the extrema of the frequency dependences of hot electron generation efficiency, finding that the number and spectral positions of the extrema significantly depend on the radius and material of the nanoparticles. It is demonstrated that the highest maximum corresponds to a frequency close to the surface plasmon resonance frequency. Practical recommendations are developed for selecting materials for spherical nanoparticles to be used as photocatalysts in the optical frequency range to enhance the efficient utilization of solar energy.