Preparation and visible-light photocatalytic activity of PMDA/PDA linear polyimide

Abstract

The photocatalytic oxidation ability of polyimide is weak because of the relatively low valence band (VB). The valence band potential of the PMDA/PDA linear polyimide is +2.45 eV, showing that it has strong oxidizing property and strong oxidative degradation ability without constructing heterojunction.In order to prepare a kind of polyimide with high visible-light photocatalytic activity,linear polyimide (PI) with strong oxidizability is prepared by two-step method using pyromellitic dianhydride（PMDA） and p-phenylenediamine （PDA） as raw materials and ethanol as co-solvent. The chemical composition, microstructure and photoelectrochemical properties of PI are investigated by scanning electron microscopy (SEM), fourier infrared spectroscopy (FTIR),UV-vis diffuse reflectometer (UV-vis DRS), fluorescence spectrometer (PL) and X-ray photoelectron spectroscopy (XPS). The band gap width, Homo potential and lowest unoccupied molecular orbital (LUMO) potential of PI are measured.The results show that the main photocatalytic active center of the obtained polyimide is found to be photogenerated holes through a series of experiments. The photocatalytic activity of polyimide is evaluated by photodegradation of Rhodamine B, and the degradation efficiency of the as-prepared polyimide is three times as that of the commonly used photocatalyst g-C3N4. Therefore, PMDA/PDA linear polyimide is a kind of polyimide with high visible-light photocatalytic activity and high photocatalytic stability.

Keywords

• semiconductor material
• polyimide
• pyromellitic dianhydride
• phenylenediamine
• rhodamine b
• photocatalytic degradation