Controlled formation of Ag-AgxO nanoparticles on the surface of commercial TiO2 based composites for enhanced photocatalytic degradation of oxalic acid and phenol

Tóth, Zsejke-Réka and Hernadi, Klara and Baia, Lucian and Kovács, Gábor and Pap, Zsolt (2020) Controlled formation of Ag-AgxO nanoparticles on the surface of commercial TiO2 based composites for enhanced photocatalytic degradation of oxalic acid and phenol. CATALYSIS TODAY. ISSN 0920-5861 (In Press)

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Abstract

The issues regarding the low stability of the Ag nanoparticles during the photodegradation processes are already well-known, being easily transformed to AgxO. On the other hand, the (photo)catalytic efficiency of TiO2 can be increased by modifying its surface with noble metal nanoparticles. Therefore, the present work focused on commercial TiO2 (Aldrich anatase and rutile) mixtures with well-defined ratios, applying Ag nanoparticles on the surface of the titania with or without using a reducing agent. The transformation of the Ag nanoparticles into AgO was monitored in the frame of the anatase and rutile content, while the transformation’s effect on the photocatalytic activity was examined (degradation phenol and oxalic acid under UV). It was concluded that the Ag nanoparticles deposited on the surface of rutile can increase the efficiency of charge separation while, present on the surface of the anatase, the formed amorphous AgO nanoparticles are behaving similarly. The tertiary and quaternary composites generally had higher photocatalytic efficiencies toward oxalic acid, than the corresponding commercial TiO2 mixtures. The low stability of the Ag nanoparticles was also found in our investigations, as the NPs are transformed into Ag2O, which can be re-transformed during the photocatalytic processes to Ag. On the other hand, the stability of the AgO is not affected during the aging period. Therefore, it can be assumed, that AgO is more stable on the surface of the anatase phase of the titania than the Ag and the Ag2O nanoparticles.

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