Ethanol Solution Plasma Loads Carbon Dots onto 2D HNb3O8 for Enhanced Photocatalysis

Kinetic pathways of sub-bandgap induced electron transfer in Ag/TiO2 and the effect on isopropanol dehydrogenation under gaseous conditions

Electron transfer and its kinetics play a major role in the photocatalysis of metal/semiconductor systems. Using in situ photoconductances, in situ photoabsorption, and photoinduced spectroscopic techniques, the present research aimed to gain a deep insight into electron transfer pathways and their kinetics for Ag/TiO2 systems under sub-bandgap light illumination and gaseous conditions. The results revealed that electrons generated in TiO2 can transfer to Ag nanoparticles at fast rates, and plasmon-generated electrons in Ag nanoparticles can also transfer to TiO2. However, it was found that plasmon-assisted hot electron transfer efficiency is much lower than the electron transition from the valence band to the conduction band of TiO2. Rather than plasmonic active spots, the results showed that Ag nanoparticles acted as co-catalyst sites bridging electron transfer to recombination in a methanol-containing N2 atmosphere. As a result, photocatalytic isopropanol dehydrogenation was decreased. Independent of Ag decorations, it was also indicated that isopropanol dehydrogenation mainly occurred over TiO2 surfaces; therefore, Ag nanoparticles did not increase photocatalytic activities. Our results may provide a different viewpoint on sub-bandgap light-induced Ag/TiO2 photocatalysis under gaseous conditions; this may also facilitate the understanding of the photocatalytic mechanism of metal/semiconductor systems.

Plasmonic Au Nanoparticle of a Au/TiO2-C3N4 Heterojunction Boosts up Photooxidation of Benzyl Alcohol Using LED Light

Plasmonic Au nanoparticles (NPs) employing localized surface plasmon resonance excitation have exhibited superior visible light absorption for many organic transformations. In this work, we prepared a ternary composite catalyst comprising plasmonic Au NPs and a 2D/2D TiO₂-C₃N₄ heterojunction via a photoreduction method of chloroauric acid in the presence of TiO₂-C₃N₄. The introduction of plasmonic nanogold particles embedded onto the TiO₂ surface of the TiO₂-C₃N₄ heterojunction can significantly improve the photocatalytic performance during photooxidation of benzyl alcohol to benzaldehyde under mild conditions (1 bar air, white LED irradiation at ambient temperature). The productivity over Au/TiO₂-C₃N₄ (0.25 mmol_reacted BA g_cat.^-1 h^-1) is found to be ∼5.6, 8.3, and 8.2-fold of these over the Au/TiO₂, TiO₂-C₃N₄, and C₃N₄-Au-TiO₂ heterojunctions, respectively. Trapping experiments and electron spin resonance (ESR) spectroscopy confirm that the superoxide (^·O₂^-) and hydroxyl radicals (^·OH) act as the reactive oxygen species during photooxidation. Furthermore, the experimental results combined with density functional theory calculations reveal that the chemisorbed benzyl alcohol population, surface oxygen vacancies, and lifetime of photoexcited electrons and holes are largely improved by plasmonic Au NPs. This study on nanogold composites provides some hints for developing new efficient and practical photocatalysts.