Hot‐Electron‐Induced Photothermal Catalysis for Energy‐Dependent Molecular Oxygen Activation

Abstract

Hot electrons activate reactants and reduce the activation energy barrier (Ea) of a reaction through electron donation. However, a comprehensive understanding of the intrinsic driving force of this electron‐donating effect is lacking, let alone the precise manipulation of electron donation processes. Herein, the essential and promotional role of hot electron energy on the electron‐donating effect was elucidated using molecular oxygen activation (MOA) as a model reaction. Through providing an available electron source to the conventional photo‐thermal conversion system, the high energy carried by hot electrons was liberated and greatly enhanced the electron donation towards the LUMO (π*) orbit of O2. The energy was also transferred to O2 and elevated the potential energy surface (PES) of MOA, which was reflected by the enhanced formation of superoxide oxygen anions. As predicted, the Ea of MOA decreased by 45.1 % and exhibited a substantial light dependence, demonstrating that MOA became energy‐efficient due to improved exploitation and conversion of photon energies.

Local Growth Mediated by Plasmonic Hot Carriers: Chirality from Achiral Nanocrystals Using Circularly Polarized Light

“…Plasmonic NCs and their hybrids are also useful as photosensitizing elements in photocatalysis, serving as nanoantennas that concentrate light energy and transfer it to drive chemical transformations. − This can be mediated through different mechanisms, with charge transfer events being particularly interesting because they can initiate redox reactions or favor the evolution of a reaction by reducing its activation energy. − Charge transfer can occur by either the direct interfacial excitation of a carrier between a metal and its environment , or the separate processes of carrier excitation and injection. − The diagram in Figure a presents this latter mechanism, in which the role of surfaces in the excitation of high-energy excited carriers is very important, because they allow the promotion of an electron within the conduction band by satisfying the constraints of conservation of momentum in the process of photon absorption. − Only high-energy excited electrons, to which we will refer as “hot electrons” (HE) hereafter, will be susceptible to leaving the metal. Consequently, when considering the design of plasmonic systems for plasmon-based catalysis, we should consider their capacity for exciting large numbers of hot carriers at the NC’s interfaces .…”

Determining the Reaction Mechanisms of Photo‐Thermo Synergetic Processes by Kinetic Investigations

“…Qu et al. suggested that the high intensity and short wavelength can reduce the apparent activation energy of phenol oxidation utilizing MoS 2 /TiO 2 , revealing that photo‐induced hot electrons play dominantly role in promoting the reactants activation (Figure 3a) [21] . They proposed that the light can help to generate the electron‐hole pairs in MoS 2 and TiO 2 composite, and the photo‐induced electrons in MoS 2 would transfer to the conduction band of TiO 2 and inject the lowest unoccupied molecular orbital (LUMO) orbits of O 2 , thus promoting the O 2 activation while the holes from TiO 2 would trap electrons from H 2 O that possibly emigrated to the valance band of MoS 2 and experienced a recombination with part of electrons causing heat emission.…”

“…[20] Qu et al suggested that the high intensity and short wavelength can reduce the apparent activation energy of phenol oxidation utilizing MoS 2 /TiO 2 , revealing that photo-induced hot electrons play dominantly role in promoting the reactants activation (Figure 3a). [21] They proposed that the light can help to generate the electron-hole pairs in MoS 2 and TiO 2 composite, and the photo-induced electrons in MoS 2 would transfer to the conduction band of TiO 2 and inject the lowest unoccupied molecular orbital (LUMO) orbits of O 2 , thus promoting the O 2 activation while the holes from TiO 2 would trap electrons from H 2 O that possibly emigrated to the valance band of MoS 2 and experienced a recombination with part of electrons causing heat emission. Also, Liu et al found that the apparent activation energies in non-thermal reaction catalyzed by Rh nanotubes decorated TiO 2 (Rh-c/TiO 2 ), Rh nanotubes modified Al 2 O 3 (Rh-c/ Al 2 O 3 ) and Rh nanoparticles decorated TiO 2 (Rh-s/TiO 2 ) are less than the apparent activation energies of thermal reaction determined over Rh-c/TiO 2 , Rh-c/Al 2 O 3 and Rh-s/TiO 2 catalysts [19] (Figures 3b and d).…”

“…For example, Amal et al utilized Au decorated TiO 2 as the active component to selectively oxidize C 2 H 5 OH into CH 3 CHO under photo-thermo reaction conditions at low reaction temperature and different light irradiation wavelengths, which showed that the lightenhanced reaction rate for Au/TiO 2 was higher than that of the product formation rate over TiO 2 . And they showed that the reaction rate of Au/TiO 2 under UV light was greater than that under visible light, indicating that probably the light-enhanced reaction rate under visible light was owing to the synergistic effect between photo-induced hot electrons and external heat [21] Copyright 2021 Wiley-VCH; b) the product generation rate in thermal reaction for Rh nanotubes decorated TiO 2 (Rh-c/TiO 2 ), Rh nanotubes modified Al 2 O 3 (Rh-c/Al 2 O 3 ) and Rh nanoparticles decorated TiO 2 (Rh-s/TiO 2 ) as a function of temperature; c) the product evolution rate as a function of reaction temperature and light intensity; Reproduced with permission. [22] Copyright 2020 Wiley-VCH.…”

Investigation into Enhanced Catalytic Performance for Epoxidation of Styrene over LaSrCoxFe2–xO6 Double Perovskites: The Role of Singlet Oxygen Species Promoted by the Photothermal Effect

“…Oxygen activation is essential to trigger heterogeneous catalysts for catalytic epoxidation of styrene under aerobic conditions . Electron transfer from the catalyst surface to oxygen is believed to be the key step to oxygen activation . From this point of view, the advantage of photocatalysis in generating hot electrons is that it is a good alternative and supplement to thermalcatalysis for promoting oxygen activation.…”