Surface-Plasmon-Mediated Hydrogenation of Carbonyls Catalyzed by Silver Nanocubes under Visible Light

Abstract

Plasmonic nanoparticles are exciting and promising candidates for light-activated catalysis. We report herein the use of plasmonic nanocubes for the activation of molecular hydrogen and the hydrogenation of ketones and aldehydes via visible light irradiation at 405 nm, corresponding to the position of the plasmon band of the nanocubes, at 80 °C. Only 1 atm of molecular hydrogen is required to access, using catalytic amounts of silver, primary, and secondary alcohols, with complete chemoselectivty for CO over CC reduction. The resulting catalytic system was studied over a scope of 12 compounds. Exposure to other wavelengths, or absence of light failed to provide activity, thus proving a direct positive impact of the plasmonic excitation to the catalytic activity. By varying the irradiation intensity, we studied the relationship between plasmon band excitation and catalytic activity and propose a potential reaction mechanism involving plasmon-activated hot electrons. This study expands the scope of reactions catalyzed by free-standing plasmonic particles and sheds light on H2 activation by silver surfaces.

Water splitting catalyzed by titanium dioxide decorated with plasmonic nanoparticles

“…Tian and Tatsuma [40] suggested that upon excitation due to the SPR, charge separation is accomplished by transfer of photo-excited electrons from Au NPs to the TiO 2 conduction band and that such a charge separation was facilitated by the Schottky barrier formed by their interface. Following this early work, supported Au NPs were found to be applicable for various chemical transformations including of the oxidation of formaldehyde, alcohols, and amines to imines, C−C and amine-alkyne-aldehyde couplings, hydroamination of alkynes, oxidative degradation of phenol, oxidative aldehyde-amine condensation to amide, and hydroxylation of benzene, as well as the production of hydrogen or oxygen gas from organic molecules [41][42][43].…”

“…They observed a sharp increase of activity compared to bare TiO 2 and showed that rational control of shape and size, and thus change in SPR, resulted in a modification of the wavelength at which photoactivation occurs. Ag NPs, both in supported and unsupported forms, have otherwise been used for organic transformations, including alkene epoxidation, and carbonyl hydrogenation [43,63,64]. The Linic group applied this principle to the PEC water splitting, using Ag nanocubes onto nitrogen-doped TiO 2 .…”

Reaction Pathway Dependence in Plasmonic Catalysis: Hydrogenation as a Model Molecular Transformation

“…However, it was observed that the reaction rate when SiO 2 was employed as support was enhanced by almost two‐fold relative to TiO 2 . This principle has also been employed to achieve the localized surface plasmon resonance activation of H 2 and drive reduction reactions using Ag nanocubes as catalysts . Interestingly, palladium concave nanocubes have been investigated as plasmonic catalysts for the hydrogenation of styrene .…”

“…[1][2][3][4] In this case, gold [5] and silver [6] nanoparticles, which support localized surfacep lasmonr esonance excitation in the visible and nearinfrared range, are usually employed as catalysts. [3,[7][8][9][10] The utilization of copper and aluminumn anoparticles as catalysts has also received attention. [11][12][13][14] Plasmonic nanocatalysis has become attractive towards the development of more environmentally friendly processes because it enables the utilization of visible/solar light as ag reen energy input to drivea nd control av ariety of transformations.…”

“…[46,47] This principle has also been employed to achieve the localized surface plasmon resonance activation of H 2 and drive reduction reactions using Ag nanocubes as catalysts. [10] Interestingly, palladium concave nanocubes have been investigated as plasmonic catalysts for the hydrogenation of styrene. [48] In this case, however,i tw as shown that localized surfacep lasmon resonance-excited hot electrons led to ad ecrease in catalytic activities.…”