Flexible PTh/GQDs/TiO2 composite with superior visible-light photocatalytic properties for rapid degradation pollutants

Abstract

Flexible fiber membranes for pollutant removal have received increasing attention due to their high adsorption performance and easy recycling characteristics. However, due to the lack of environmentally friendly regeneration, some adsorption membranes have low regeneration efficiency, especially in terms of chemical adsorption, so they lack reusability. This study prepares a series of conducting polymer [PAn (polyaniline) or PPy (polypyrrole) or PTh (polythiophene)] graphene quantum dots (GQDs, the size of GQDs is about 20 nm)/TiO₂ ternary fiber membranes via a facile electrospinning method with chemical deposition. Remarkably, this creates an anatase TiO₂ and π-conjugated system. The combination is beneficial to the photocatalytic degradation of organic pollutants, showing synergistic promotion in both the degradation rate and the degree of decomposition. The UV-vis test shows that the combination of GQDs broadens the optical response threshold of TiO₂, from near ultraviolet region excitation to visible region excitation. At the same time, the conductive polymer load further reduces the energy required for photogenerated electron transfer, which theoretically improves the degradation effect. Photocatalytic degradation tests showed that the PTh/GQDs/TiO₂ fiber membrane exhibited significant high photocatalytic activity of visible-light in the methylene blue (MB) and TC degradation. The degradation rate level is 92.90% and 80.58%, respectively and the MB removal is more than 4 times that of bare TiO₂ membrane. After photocatalytic regeneration four times, the regeneration efficiency can be maintained above 95%. Notably, various experimental results show that the interface charge transfer mechanism between GQDs/TiO₂ and PTh follows the Z-scheme heterojunction, which maximizes the retention of strong reducing electrons and oxidation holes. In the degradation, the active species of ·O₂⁻ and ·OH, make different contributions in the photocatalysts, which oxidize and break down the pollutant molecules into small molecules and then to harmless substances. According to the electronegativity difference of the material itself, PTh acts as electron acceptor in the degradation system, and TiO₂ fiber membrane doped with GQDs acts as electron donor. The present research, not only offers feasibility of the PTh/GQDs/TiO₂ flexible fiber membrane as an environment-friendly catalyst, but also motivates researchers to develop flexible fiber materials for future photocatalytic technology.