Positive effects of phosphotungstic acid on the in-situ solid-state polymerization and visible light photocatalytic activity of polyimide-based photocatalyst

Abstract

A series of H3PW12O40 (HPW)-containing polyimide (PI) hybrid composites (TPI) are prepared through in-situ solid-state polymerization using HPW, melem and pyromellitic dianhydride as precursors. The effect of HPW on the morphology, porosity, chemical structure, and optical and visible-light photocatalytic degradation efficiency of TPI composites are systematically investigated by various characteristic methods. By comparing the structure, property and photocatalytic activity of the TPI composites and the HPW-PI composites (prepared by the impregnation method), it indicates that HPW can promote the formation of CN bond in the five-membered imide rings between amines and anhydrides during the in-situ solid-state condensation process. Subsequently, the visible-light (λ > 400 nm) photocatalytic degradation efficiency of imidacloprid on TPI composites is also enhanced compared with the pristine PI because of the enhancement of the in-situ solid-state condensation reaction, photogenerated electron-hole separation efficiency and visible-light utilization efficiency after the introduction of HPW. The visible-light photocatalytic degradation rate constant k of 15% TPI composites prepared at 300 °C and 5% TPI composites prepared at 325 °C are about 10.33 and 2.42 times of the corresponding pristine PI, respectively. Compared with commercial P25, the photocatalytic degradation efficiency of 15% TPI-300 and 5% TPI-325 are about 4.58 and 5.13 times of P25 under visible light irradiation.