Wide spectra-responsive Polypyrrole-Ag3PO4/BiPO4 co-coupled TiO2 nanotube arrays for intensified photoelectrocatalysis degradation of PFOA

Abstract

As a persistent organic pollutant, perfluorooctanoic acid (PFOA) has been paid more and more attention because of its persistence, immunotoxicity and bioaccumulation. In this study, we constructed a novel photoelectrocatalysis (PEC) system for the removal of PFOA from the aquatic environment, based on TiO2 nanotube arrays (TNTs) coated by Polypyrrole-Ag3PO4/BiPO4 (Ppy-AB) n-p-n heterostructure. The three-dimensional Ppy-AB@TNTs photoelectrode shows excellent sunlight-driven photocatalytic performance, PEC stability, and efficient PFOA removal ability. The introduction of Ppy effectively reduced photocorrosion of Ag3PO4 and accelerated electron transfer of BiPO4. Under simulated sunlight irradiation and biased potential of 2 V (vs. Ag/AgCl), the removal of 100 mg/L PFOA (60 mL) reached 92.5% and defluorination was 64.8% after 3 h PEC treatment. The degradation pathway of PFOA was investigated based on the intermediates tested by HPLC-MS, and the results indicated that PFOA was decomposed by stepwise losing − CF2 − units. Notably, the PEC degradation mechanism and heterostructure electron transfer pathway were investigated by experimental study and density functional theory (DFT) calculation. Furthermore, the excellent reusability of Ppy-AB@TNTs heterojunction photoelectrode implied its great potential for efficient degradation of PFOA in practical industrial PFOA-containing wastewater.