Thermal effects - an alternative mechanism for plasmonic-assisted photo-catalysis

Recent experimental studies demonstrated that chemical reactions can be accelerated by adding metal nanoparticles to the chemical reactants and illuminate them at their plasmon resonance. It was claimed that the enhanced reaction rate occurs via the reduction in the activation energy driven by the plasmon-induced non-thermal (“hot”) electrons. In this contribution, we show that these claims are extremely unlikely to be correct and that instead, the faster chemical reactions are likely the result of mere heating. To do that, we derive a self-consistent theory of the electron distribution in metal nanostructures under continuous-wave illumination. We show [Dubi & Sivan, Light Sci. Appl., 2019] that only about one-billionth of the energy provided by the illumination goes to creating non-thermal (“hot”) electrons, and the rest goes to heating. Further, we develop a simple model based on the Fermi golden rule and the Arrhenius Law. We show [Sivan et al., Science, 2019; Dubi et al., Chem. Sci., 2020] that the alternative theory of illumination-induced heating can explain the experimental data to a remarkable agreement. Our results provide the first-ever comprehensive theory of plasmon-assisted photocatalysis and should become the basis for the analysis of future experiments.