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- ItemSupported Vanadium Oxide as a Photocatalyst in the Liquid Phase: Dissolution Studies and Selective Laser Excitation(2021) Kortewille, Bianca; Pfingsten, Oliver; Bacher, Gerd; Strunk, JenniferSupported vanadium oxide species are tested for their capability to perform photocatalytic methyl orange degradation in the aqueous phase. Excitation is performed with a frequency-tripled (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 (V2O5 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 H2VO4− ions. These doubly protonated monovanadates are the main active species in the photocatalytic reaction, together with small anchored species on alumina.
- ItemVerification of impurity-related photocatalytic activity of insulating oxide supports(Amsterdam : Elsevier, 2021) Kortewille, Bianca; Springer, Armin; Strunk, JenniferPhotocatalysts composed of vanadium oxide species supported on commercial MgO and ZrO2 are investigated in selective methanol oxidation. Both support oxides are insulators, so the vanadium oxide species are expected as sole active component in photocatalysis. However, the pure supports showed considerable activity: Bare MgO was more active than MgO-supported vanadia catalysts, and ZrO2 showed intermediate activity. By various characterization methods, the presence of TiO2 (anatase) in the MgO support, and the presence of Zn, possibly as ZnO, in ZrO2 is demonstrated. The present study highlights that photocatalysts containing commercial supports must be carefully checked for impurity-related photocatalytic performance. © 2021 The Authors