BiVO4/PANI composite with p-n heterostructure for enhanced photocatalytic activity towards Cr(VI) reduction

A novel p-n heterostructure BiVO4/polyaniline (BiVO4/PANI) composite was prepared via a hydrothermal route with a subsequent oxidative polymerization of aniline (ANi) monomer by adjusting the ANi/BiVO4 mass ratio. The structure, morphology, optical and photoelectric properties of the as-prepared materials were determined by various characterization techniques, while their photocatalytic activities for Cr(VI) reduction were evaluated under visible-light illumination. Comparing to the BiVO4, the BiVO4/PANI composites had a significantly enhanced Cr(VI) photoreduction activity. The optimum BiVO4/PANI(0.25) exhibited a high Cr(VI) reduction activity (99.6% after 120 min) and good cycle stability (95.1% Cr(VI) removal at the 5th cycle), which reduction efficiency was around 17.5 times higher than that of the BiVO4. The enhanced photocatalytic performance was described to the synergistic effect between PANI and BiVO4 as well as the p-n heterostructure. The conductive PANI as h(+) transporter and light acceptor produced more photogenerated carriers and provided a fast electron transport path to accelerate the migration of photogenerated e(-)-h(+) pairs, and the semiconductor BiVO4 gave the fine structure stability. At the same time, the p-n heterostructure promoted the separation of photogenerated eh(+) pairs. Furthermore, the possible mechanism for Cr(VI) photoreduction was proposed according to the various characterizations and experiment results.