UV-A light-assisted gas-phase formic acid decomposition on photo-thermo Ru/TiO2 catalyst

Abstract

Although solar energy is considered as one of the ideal abundant sources of renewable energy to be integrated into catalytic processing, photonic and thermal excitations were perceived till recently as independent strategies in overcoming Arrhenius-type activation energy barriers in catalytic reactions. However, this dual-mode excitation of catalysts is receiving a growing interest nowadays due to promising evidence of synergy effects. A Ru/TiO2 photo-thermo-catalyst was prepared according to a UV-A light photo-assisted synthesis method allowing a fine control of the Ru nanoparticle size distribution, and the influence of a combined photonic (UV-A) and thermal activation on its performances in the gas phase decomposition of formic acid into hydrogen was investigated. The results showed that a dual photonic/thermal excitation in a onepot operation allows to increase the formic acid conversion and consequently the production of hydrogen vs. the reaction in the dark, the enhancement being all the more pronounced as the irradiance is high. The combined excitation allowed to drive the reaction at lower temperatures 2 upon irradiation while maintaining a similar conversion level. This low-temperature shift was all the more marked as the irradiance was high, and was accompanied by a strong increase in the selectivity to hydrogen. The change in both conversion and selectivity patterns suggested the implication of the light-excited electrons in the non-plasmonic Ru nanoparticles for conducting the reaction through an alternative low-energy transition state, with a lowering of the apparent energy activation, rather than a mechanism of localized-heat delivery.

Fermi-level shift, electron separation, and plasmon resonance change in Ag nanoparticle-decorated TiO2 under UV light illumination

“…[13][14][15][16] The co-catalysts include oxides, sulfides, carbides, and metals. Furthermore, metallic nanoparticles, such as Ag, 17 Au, 18 Pt, 19 Pd, 20 and Ru, 21 have been widely used in photocatalysis employing TiO 2 and other semiconductors. Numerous studies have shown that the photoinduced electrons in TiO 2 can transfer to metallic nanoparticles in a very short time, and thus the charge carriers are effectively separated.…”

Semiconductor Nanomaterial Photocatalysts for Water-Splitting Hydrogen Production: The Holy Grail of Converting Solar Energy to Fuel

“…Titanium oxide is regarded as the first semiconductor for photocatalyst-based water splitting [ 16 ], but because of a large band gap (3.2 eV) [ 110 ], it can only utilize UV radiation [ 111 ], which accounts for only a small portion of the solar spectrum. Still, many studies improved upon TiO 2 photocatalysts.…”

Efficiency of thermo–photocatalytic production of hydrogen from biomolecules: a multifaceted perspective

“…43 A similar reaction mechanism but from formic acid as the initial reactant instead of an alcohol has been shown to occur with Ru/TiO 2 . 71 As for the methanol case, the formate type species, decarbonylation type reactions leading to CO as well as the generation of carbon dioxide were promoted under thermo-photo conditions.…”