Rapid visible light photocatalytic reduction of Cr6+ in aqueous environment using ZnO-PPy nanocomposite synthesized through ultrasonic assisted method

An efficient and cost-effective nanocomposite, zinc oxide-polypyrrole (ZnO-PPy) was synthesized via a simple ultrasonic technique. The as-prepared ZnO-PPy nanocomposite was characterized and confirmed by various analytical techniques such as XRD, FT-IR, UV-DRS, SEM and elemental mapping analysis. The ZnO-PPy nano-composite has been shown to be highly efficient reduction of toxic Cr6+ to Cr3+ under visible light compared to pure ZnO. The better photocatalytic activity is due to the visible light active PPy covered on the surface of ZnO, which can accelerate and separate the electron and hole pairs and reduce the recombination. In the ZnO-PPy nanocomposite system, the photocatalytic reduction rate constant and percentage were observed at k = 0.2572 min(-1) and 99.2 % and the catalysts shows higher efficiency even after four cycles. Interestingly, the effect of foreign ions (cations and anions) and reaction pH were optimized and discussed. Meanwhile, the ZnO-PPy nanocomposite charge transfer mechanism were investigated through photocurrent and impedance analysis. This work demonstrates that a simple ultrasonic method efficiently utilized for the preparation of nanocomposite and its applications.