Hydrothermal synthesis of Mo-C co-doped TiO2 and coupled with fluorine-doped tin oxide (FTO) for high-efficiency photodegradation of methylene blue and tetracycline: Effect of donor-acceptor passivated co-doping

Limited by the narrow photoresponse range and high electron-hole recombination rate, the photocatalytic efficiency of TiO2 is still far below what is expected. Herein, the Mo-C donor-acceptor passivated co-doping TiO2 ((Mo,C)-TiO2) was synthesized via a hydrothermal synthetic strategy, then it is coupled with FTO. The donor-acceptor co-doped TiO2 exhibit band gap reduction of ∼1.0 eV, and enable the nanoparticles to be photoactive in the visible light range. The band structure investigated by Mott-Schottky plots and valence band spectra reveal that doping induces an extended-tail-states near the valence band edges, which is responsible for the photoresponse in the visible light region. Density-functional theory (DFT) calculations manifest that donor-acceptor co-doping TiO2 exhibit both the advantages of the Mo, C mono-doped cases, and results in higher charge density in (Mo,C)-TiO2. The photoluminescence (PL) spectra and time-resolved PL spectra show that co-doping induced deep electron trap state in (Mo,C)-TiO2, confirmed by the surface photovoltage (SPV) spectroscopy, which enables accumulate long-lived photoinduced electrons and effectively suppresses the radiative electron-hole recombination. Meanwhile, FTO as the electronic receiver is beneficial for the charge carrier separation. As expected, the (Mo,C)-TiO2/FTO photocatalysts show a remarkably enhanced photocatalytic activity in the visible-light irradiation degradation of methylene blue (MB) and tetracycline (TC), up to ∼4 times higher than that of TiO2.