Hydrothermal evolution, optical and electrochemical properties of hierarchical porous hematite nanoarchitectures

Hollow or porous hematite (α-Fe₂O₃) nanoarchitectures have emerged as promising crystals in the advanced materials research. In this contribution, hierarchical mesoporous α-Re₂O₃ nanoarchitectures with a pod-like shape were synthesized via a room-temperature coprecipitation of FeCl₃ and NaOH solutions, followed by a mild hydrothermal treatment (120°C to 210°C, 12.0 h). A formation mechanism based on the hydrothermal evolution was proposed. β-FeOOH fibrils were assembled by the reaction-limited aggregation first, subsequent and in situ conversion led to compact pod-like α-Re₂O₃ nanoarchitectures, and finally high-temperature, long-time hydrothermal treatment caused loose pod-like α-Re₂O₃ nanoarchitectures via the Ostwald ripening. The as-synthesized α-Re₂O₃ nanoarchitectures exhibit good absorbance within visible regions and also exhibit an improved performance for Li-ion storage with good rate performance, which can be attributed to the porous nature of Re₂O₃ nanoarchitectures. This provides a facile, environmentally benign, and low-cost synthesis strategy for α-Re₂O₃ crystal growth, indicating the as-prepared α-Re₂O₃ nanoarchitectures as potential advanced functional materials for energy storage, gas sensors, photoelectrochemical water splitting, and water treatment.