Cu2O nanocubes/TiO2 heterostructure and its adsorption and photocatalytic properties for tetracycline removal

Abstract

A simple and fast route for the synthesis of a heterostructure made of cuprous oxide nanocubes and titanium dioxide, as an efficient tetracycline (TC) adsorbent, was reported. The heterostructure has been characterized by X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), selected area electron diffraction (SAED), and diffuse reflectance spectroscopy (DRS). The TC adsorption capacity of the Cu2O NCs/TiO2 heterostructure was measured in dark through TC removal from an aqueous medium. Furthermore, Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) were performed before and after the adsorption process to evidence the adsorption of TC on the Cu2O NCs/TiO2 surface. Additional TC removal tests with visible light irradiation were carried out to distinguish between the adsorption and photocatalytic processes on Cu2O NCs/TiO2 heterostructure. Also, electron paramagnetic resonance (EPR) measurements were carried out using DMPO as a trapping agent to investigate formation of reactive oxygen species (ROS). Interestingly, there is no detectable ROS production by the Cu2O NCs/TiO2 heterostructure. The results permit the assumption that the TC removal is fully due to adsorption. Furthermore, these results contribute to clarifying a divergence in the literature regarding the production of electron/hole (e−/h+) pairs by Cu2O NCs under visible light.