Improved photoelectrode performance of chemical solution-derived Bi₂O₃ crystals via manipulation of crystal...

Three-dimensional Bi₂O₃ crystals with various morphologies were successfully synthesized on F-doped tin oxide substrates with and without homoseed layers via chemical bath deposition (CBD) routes. The structural analysis reveals that control of the pH value of the reaction solution resulted in as-grown Bi₂O₃ crystals with nanosheet and plate morphologies. A lower pH value of the reaction solution engendered formation of a porous sheet-like morphology of Bi₂O₃; by contrast, a higher pH value of the reaction solution is favorable for formation of solid Bi₂O₃ plates on the substrates. Furthermore, a sputter coated Bi₂O₃ seed layer with dual α- and β-Bi₂O₃ phases plays an important role in the CBD-derived Bi₂O₃ crystallographic structures. The Bi₂O₃ crystals formed via CBD processes without a sputter coated Bi₂O₃ homoseed layer demonstrated a high purity in β-Bi₂O₃ phase; those grown with a homoseed layer exhibited a dual α/β phase. The photoactive performance results show that construction of an α/β-Bi₂O₃ homojunction in the CBD-derived Bi₂O₃ crystals substantially improved their photoactive performance. Comparatively, the porous Bi₂O₃ nanosheets with a dual α/β-Bi₂O₃ phase demonstrated the highest photoactive performance among various Bi₂O₃ crystals in this study. The superior photoactivity of the porous α/β-Bi₂O₃ nanosheets herein is attributed to their high light absorption capacity and photoinduced charge separation efficiency. The experimental results in this study provide a promising approach to design CBD-derived Bi₂O₃ crystals with desirable photoelectric conversion functions via facile morphology control and seed layer crystal engineering.