Influence of Graphene and Copper on the Photocatalytic Response of TiO2 Nanotubes

Abstract

SSCI-VIDE+CARE:ECI2D+MHM:FDA:CGU:GBEInternational audience1D nanotubular TiO2 are known to improve photocatalytic performance compared to classical 3D particles. Combination of TiO2 nanotubes (NTs) with graphene oxide (GO) was previously envisaged to limit the recombination of e--h+ pairs (Appl. Cat. B 2017, 209, 203-213). Compared to non-reduced GO, improvement in activity was noticed if partially reduced GO was used due to a decrease in charge transfer resistance after partial reduction limiting the recombination phenomenon. If GO was totally reduced, the gain in activity was lost suggesting that the driving force for the injection of electrons from TiO2 to GO comes from the consumption of oxygen groups on graphene layers. The present study proposes an alternative for avoiding the consumption of photoelectrons through the addition of Cu NPs onto GO without contact with TiO2 NTs. Such a building is facilitated by the tendency of GO to wrap up around TiO2 NTs. Comparison was herein performed between Cu/TiO2 NTs and Cu/(R)GO/NTs systems. On Cu/TiO2 NTs, results show a stabilization of Cu NPs at a +I oxidation state due to a strong interaction with TiO2 NTs leading to a 80% increase in activity for formic acid (FA) degradation under UV. TiO2 NTs are also necessary in combination with Cu to acquire an enhanced photocatalytic response in the visible region or for the production of H2. Contrary to GO/TiO2 NTs, in the presence of Cu, addition of non-reduced GO leads to a 250% increase in activity compared to TiO2 NTs alone for FA photodegradation while the use of partially reduced GO leads to a similar photocatalytic response than with Cu/TiO2 NTs alone. This effect is due to a partial dislocation of the graphene layers wrapped around TiO2 NTs leading to a preferential relocation of Cu NPs directly onto TiO2 NTs