Electrospun polymer nanofibers coated with TiO2 hollow spheres catalyze for high synergistic photo-conversion of Cr(VI) and As(III) using visible light

Abstract

TiO2@PAN nanofibers with inorganic (TiO2 hollow spheres, PAN: polyacrylonitrile) and organic (pre-carbonized polyacrylonitrile) ordered co-combinations were exposed to Cr(VI) and As(III) under visible light irradiation (λ > 420 nm). Relative photocatalytic activity was as follows: TiO2@PAN-3(30 mg) > TiO2@PAN-4(40 mg) > TiO2@PAN-2(20 mg) > TiO2@PAN-1(10 mg) > PAN. TiO2@PAN-3 with 30 mg TiO2 hollow spheres exhibited a high photo-conversion rate (99% Cr(VI) photo-reduction efficiency and 83% As(V) formation rate) and stability (five cycles) relative to PAN and the other samples. The new insights of synergistic effect between Cr(VI) and As(III) provided a reference way for handling complex water pollutants. A series of instrumental analysis techniques demonstrated the electron-hole separation efficiency in TiO2@PAN-3. Electron Paramagnetic Resonance (EPR) of TiO2@PAN-3 depicted a stronger DMPO/·OH adduct signal. Furthermore, the smallest arc radius diameter was found on the TiO2@PAN-3 composite electrode Electrochemical Impedance Spectroscopy (EIS) Nyquist plot, which suggests that the TiO2@PAN-3 interface has minimal charge transfer resistance. In addition, TiO2@PAN-3 exhibited the lowest Photoluminescence (PL) intensity, indicating it displays the highest electron-hole separation efficiency. Based on these results, we envisage the future construction of TiO2@PAN-3 photocatalysts with high Cr(VI) photo-reduction (99%) and As(III) photo-oxidation performance, and high stability (the photo-reduction rate was still reached 82% after five cycles) for the removal of heavy metals from actual water samples.