Three-dimensional hierarchical PANI/Bi₂S₃ nanoflowers heterojunction for enhanced photoelectrochemical water splitting

Highlights: • 3D hierarchical Bi₂S₃ nanoflowers synthesized by hydrothermal route. • Implementation of a facile and low cost two-step procedure to synthesize PANI/Bi₂S₃ nanocomposite at RT. • Rational design and fabrication of 3D hierarchical PANI/Bi₂S₃ photoanode for visible light induced PEC water splitting. • Demonstration of ~5 fold increased photocurrent density by PANI/Bi₂S₃ than that of Bi₂S₃ photoanode. • Enhanced PEC performance achieved due to staggered Type-II heterojunction and faster charge transport. -- Abstract: The fabrication of the semiconductor photoanode with good chemical stability, sufficient light harvesting ability, and fast charge carrier separation and transportation capability is crucial for efficient photoelectrochemical (PEC) water splitting. Herein, we designed the nanocomposite based photoelectrode which is integrated by hydrothermally grown 3D hierarchical nanoflowers (NFs) of bismuth sulfide (Bi₂S₃) and conducting polymer polyaniline (PANI). The as-fabricated PANI/Bi₂S₃ photoanode has demonstrated much enhanced photocurrent density (~6.95 mA/cm² at 0.8 V vs. NHE), which is ~5 fold higher in comparison to Bi₂S₃ photoanode (~1.30 mA/cm² at 0.8 V vs. NHE). Also, the PANI/Bi₂S₃ photoanode has exhibited profoundly increased charge separation and injection efficiency of ~78.31% and ~90.18%, respectively. Furthermore, ~3 fold increased incident photon-to-current conversion efficiency (IPCE) value is achieved by PANI/Bi₂S₃ as compared to the Bi₂S₃ photoanode. The rational design of hierarchical semiconductor heterojunction, improved visible light absorption, efficient separation of photogenerated charge carriers, and faster charge transport properties altogether account for the enhanced PEC performance of the fabricated PANI/Bi₂S₃ photoanode. A possible schematic model for the significantly enhanced activity of the PANI/Bi₂S₃ photoanode for solar light induced PEC water splitting has also been explicated. These findings would provide new opportunities for understanding, exploration, and advancement of different other novel 3D hierarchical nanostructures based systems in the area of energy conversion, harvesting, and storage in the future.