New insights on the enhanced non-hydroxyl radical contribution under copper promoted TiO2/GO for the photodegradation of tetracycline hydrochloride

TiO2/graphene oxide (GO) as photocatalyst in the photo -degradation of multitudinous pollutants has been extensively studied. But its low photocatalytic efficiency is attributed to the high band gap energy which lead to low light utilization. Cu-TiO2/GO was synthesized via the impregnation methods to enhance the catalytic performance. The Cu-TiO2/GO reaction rate constant for photo -degradation of pollutants (tetracycline hydrochloride, TC) was about 1.4 times that of TO2/GO. In 90 min, the removal ratio of Cu-TiO2/GO for TC was 98%, and the maximum degradation ratio occurred at pH S. After five cycles, the removal ratio of Cu-TO2/GO still exceeded 98%. UV-visible adsorption spectra of Cu-TiO2/GO showed that its band gap was narrower than TiO2/GO. Electron paramagnetic resonance (EPR) spectra test illustrated the generation rate of O-2- and OH was higher in Cu-TiO2/GO system than TiO2/GO and TiO2 system. The contribution sequence of oxidative species was O-2- > holes (h+) > OH in both TiO2/GO and Cu-TiO2/GO system. Interestingly, the contribution of OH in Cu-TiO2/GO was less than that in TiO2/GO during the photo -degradation process. This phenomenon was attributed to the better adsorption performance of Cu-TiO2/GO which could reduce the accessibility of TC to OH in liquid. The enhanced non-hydroxyl radical contribution could be attributed to that the more other active species or sites on (nearby) the surface of Cu-TiO2/GO generated after doping Cu. These results provide a new perspective for the tradition metal-doped conventional catalysts to enhance the removal of organic pollutants in the environment. (C) 2020 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

Cu-doped TiO2/GO composite photocatalyst shows enhanced photocatalytic activity with better degradation efficiency for tetracycline hydrochloride. The Cu-TiO2/GO has a narrower band gap and higher generation rate of oxidative species compared to TiO2/GO. Additionally, Cu-TiO2/GO demonstrates better adsorption performance and contributes to the non-hydroxyl radical generation during photodegradation.