Synthesis of PPy/RGO-based hierarchical material with super-paramagnetic behavior and understanding its robust photo current driven by visible light

Abstract

In this work, a PPy/RGO-based hierarchical material, Fe3O4@Pt@PPy@RGO, was constructed by enveloping hollow Fe3O4 microspheres and Pt nano-particles (NPs) into polypyrrole (PPy) shell, and then binding the core-shell nano-composites with graphene oxide (GO) membranes by UV irradiation for 12 h, which simultaneously reduced GO membranes to reduced graphene oxide (RGO). Photo-current detection show that visible light illumination triggered robust photo current from the PPy/RGO-based hierarchical material. Applying additional voltages did no harm to the hierarchical material, but enhanced its photo currents up to 5 times. Based on Raman, XPS and water contact angle test, it is clarified that the robust visible-light-driven performance of Fe3O4@Pt@PPy@RGO is attributed to the synergistic interactions between PPy and RGO. On one hand, its visible-light-driven performance stems from energy level matching and strong π-π stacking interaction between PPy and RGO. Driven by visible light irradiation, photo electrons were excited from PPy and injected into RGO spontaneously. Those injected photo-electrons migrated through RGO membranes rapidly to form photo current. On the other hand, its robust electron transporting and high structural stability originated from strong π-π conjugating between PPy and RGO, which alleviated surface stress in RGO and PPy to make the hierarchical material exhibit low surface energy and strong interfacial binding. Protected by PPy shell, hollow Fe3O4 microspheres maintained their super-paramagnetic nature in Fe3O4@Pt@PPy@RGO, making the hierarchical material exhibit low magnetic remanence and low coercive force at room temperature. The Fe3O4@Pt@PPy@RGO could be dispersed into water to form magnetic fluid, and separated from the fluid conveniently for recycling use by weak magnetic attraction.