Supported Vanadium Oxide as a Photocatalyst in the Liquid Phase: Dissolution Studies and Selective Laser Excitation

Abstract

Supported vanadium oxide species are tested for their capability to perform photocatalytic methyl orange degradation in the aqueous phase. Excitation is performed with a frequencytripled (λ = 270 nm) or frequency-doubled (λ = 405 nm) Ti: sapphire laser in a newly designed 15 ml photoreactor. Photocatalytic activity in dye degradation is only observed at 270 nm excitation, indicating that larger vanadium oxide structures (V 2 O 5 nanoparticles, decavanadates) are either not present in sufficient quantities, or not active in the reaction. Reference experiments exclude pure photodegradation of the dye. It is found that a major part of the supported vanadium oxide species becomes detached from the silica support, and a very small fraction detaches from alumina. Considerations of the aqueous phase chemistry of dissolved vanadate ions allow to identify the formed dissolved species to be predominantly H 2 VO 4 À ions. These doubly protonated monovanadates are the main active species in the photocatalytic reaction, together with small anchored species on alumina.

Monitoring Catalytic 2-Propanol Oxidation over Co3O4 Nanowires via In Situ Photoluminescence Spectroscopy

“…9,15,17 An optical spectroscopy tool, which has so far hardly been used for in situ investigations of catalytic gas phase processes (only a few studies on photocatalysis exist 18,19 ) is photoluminescence (PL) spectroscopy. With PL spectroscopy, electronic transitions of metal oxide catalysts, 20,21 active surface sites 22,23 or molecules at the metal oxide gas phase interface 24,25 can be excited and detected. PL spectroscopy shows a high sensitivity to smallest concentrations, even for fluorescent molecules with low quantum yields.…”

“…26 By using specific excitation wavelengths reaction products as well as the catalyst itself including its active surface centers can be selectively excited and their signals seperately detected. 22 In this way, a specific sub-component of a catalytic process can be monitored with high sensitivity and quite locally at the catalyst surface without affecting the catalytic process.…”

Enhanced photocatalytic activity of V2O5 /g-C3N4 /ZnO nanocomposite for efficient degradation of Amoxicillin, Chlorpyrifos and Methylene blue

“…Heterostructured composites, particularly combining g-C3N4 with other semiconductors, show promise by enhancing charge carrier separation. However, problem still arises, such as electrons reducing and holes oxidation, emphasising the ongoing need for creative solutions including g-C3N4-derived photocatalysts [31,32].…”

Monitoring Catalytic 2-Propanol Oxidation over Co3O4 Nanowires via In Situ Photoluminescence Spectroscopy

“…An optical spectroscopy tool, which has so far hardly been used for in situ investigations of catalytic gas phase processes (only a few studies on photocatalysis exist , ), is photoluminescence (PL) spectroscopy. With PL spectroscopy, electronic transitions of metal oxide catalysts, , active surface sites, , or molecules at the metal oxide gas phase interface , can be excited and detected. PL spectroscopy shows a high sensitivity to smallest concentrations, even for fluorescent molecules with low quantum yields .…”

“…For acetone molecules (PL quantum yield ∼0.12%) a detection limit of 65 ppm was determined in an air gas flow . By use of specific excitation wavelengths, reaction products as well as the catalyst itself including its active surface centers can be selectively excited and their signals separately detected . In this way, a specific subcomponent of a catalytic process can be monitored with high sensitivity and quite locally at the catalyst surface without affecting the catalytic process.…”