Singular characteristics and unique chemical bond activation mechanisms of photocatalytic reactions on plasmonic nanostructures

Abstract

The field of heterogeneous photocatalysis has almost exclusively focused on semiconductor photocatalysts. Herein, we show that plasmonic metallic nanostructures represent a new family of photocatalysts. We demonstrate that these photocatalysts exhibit fundamentally different behaviour compared with semiconductors. First, we show that photocatalytic reaction rates on excited plasmonic metallic nanostructures exhibit a super-linear power law dependence on light intensity (rate ∝ intensity(n), with n > 1), at significantly lower intensity than required for super-linear behaviour on extended metal surfaces. We also demonstrate that, in sharp contrast to semiconductor photocatalysts, photocatalytic quantum efficiencies on plasmonic metallic nanostructures increase with light intensity and operating temperature. These unique characteristics of plasmonic metallic nanostructures suggest that this new family of photocatalysts could prove useful for many heterogeneous catalytic processes that cannot be activated using conventional thermal processes on metals or photocatalytic processes on semiconductors.

Solar-Powered Plasmon-Enhanced Heterogeneous Catalysis

“…The average lifetime of the vibrationally excited states of adsorbates on metals corresponds to~10 −12 -10 −11 s. Linear-to-superlinear regime transition takes place for electron scattering events occurring at rates of 10 11 -10 12 s −1 or higher [13,31]. For instance, the rate of plasmonic ethylene epoxidation on Ag nanocubes exhibits linear dependence on intensity up to 300 mW cm −2 and a superlinear dependence above 300 mW cm −2 ( Figure 6C) [124]. The kinetic isotope effect, the second experimental signature of electron-driven reactions, is defined as the ratio between the rates of a reaction involving a light isotope with respect to the same reaction with a heavier one.…”

“…This opens the possibility to manipulate and control the reaction selectivity. Electron-driven reactions can be distinguished from phonon-driven processes due to (a) transition from linear to superlinear dependence of the reaction rate on the incident photon flux [13,31,124], and (b) higher kinetic isotope effect [31,125]. In metals, the rate of charge carrier formation is linearly dependent on the photon flux.…”

Plasmons on the edge ofMoS2nanostructures

“…The high catalytic activity of the MoS 2 nanoparticles has been directly linked to the presence of metallic edge states on the otherwise semiconducting MoS 2 nanoparticles [21]. Very recently, an observed extraordinary photocatalytic behavior of metallic nanoparticles has been shown to originate from the excitation * kiran@fysik.dtu.dk of LSPRs [22,23]. As we predict here, the metallic edge states on MoS 2 nanostructures can lead to the formation of highly localized 1D plasmons-a result that adds edge plasmonics to the list of this material's unique properties with potential applications within nanoplasmonics and photocatalysis.…”

Morphology‐controlled Electrodeposition of Copper Nanospheres onto FTO for Enhanced Photocatalytic Hydrogen Production

“…Conventional photocatalysts are almost exclusively focused on the study of inorganic semiconductor materials such as TiO 2 , [9][10][11][12][13][14] however, poor light absorption and the fast electron/hole recombination [15] limited the use of these photocatalysts. To overcome these problems, great efforts have recently been devoted to using plasmonic metallic nanostructures in the field of photocatalysis [16][17][18][19][20][21] due to their surface plasmon resonance property [22,23] which is beneficial for light absorption and increase of photogenerated charge carriers energy intensity under visible light irradiation. Dong et al found that Bi nanostructure exhibited a remarkable and stable photocatalytic activity due to its surface plasmon resonance.…”