Reversal of the photoinduced majority carriers in polypyrrole by semiconductor-insulator-semiconductor heterostructure and related highly-efficient photoreduction of Cr(VI)

Abstract

Abstract The development of visible-light-responsive photo-reductant with organic conjugated-polymers is considered as a promising and efficient way to solve the current environmental pollution and energy crisis. In this work, we reports the Fe3O4@SiO2@Polypyrrole nanocomposite with semiconductor-insulator-semiconductor (S-I-S) heterostructure, which exhibited a distinct reversal of the majority-carriers' type of polypyrrole under irradiation. In addition, the photochemical activity of polypyrrole was effectively enhanced by ~2 times via capacitance effect derived from this heterostructure. In fact, quenching experiments revealed that the reaction pathway of polypyrrole could be subverted from photoinduced hole to mainly electron by this heterostructure. The contribution ratio of photoinduced electron in Fe3O4@SiO2@Polypyrrole’s reaction system was evaluated via the photodegradation tests, which was ~73%. As a contrast, photoinduced hole was the only active species in polypyrrole’s system. As a result, the heterostructural Fe3O4@SiO2@Polypyrrole exhibited an excellent photoreduction ability toward Cr(VI) with its enhanced photo-electron productivity, the removal ratio of Cr(VI) was 99.2% after 90 min irradiation under model sunlight. Generally, this study provides a novel strategy for designing and fabricating highly-efficient photo-reductant with a low-cost and easy way, which can be further used for the elimination of Cr(VI) in wastewaters under mild conditions.