Self‐assembled vertical heterostructure with a high interface‐to‐volume ratio offers tremendous opportunities to realize intriguing properties and advanced modulation of functionalities. Here, a heterostructure composed of two visible‐light photocatalysts, BiFeO3 (BFO) and ε‐Fe2O3 (ε‐FO), is designed to investigate its photoelectrochemical performance. The structural characterization of the BFO‐FO heterostructures confirms the phase separation with BFO nanopillars embedded in the ε‐FO matrix. The investigation of band structure of the heterojunction suggests the assistance of photoexcited carrier separation, leading to an enhanced photoelectrochemical performance. The insights into the charge separation are further revealed by means of ultrafast dynamics and electrochemical impedance spectroscopies. This work shows a delicate design of the self‐assembled vertical heteroepitaxy by taking advantage of the intimate contact between two phases that can lead to a tunable charge interaction, providing a new configuration for the optimization of photoelectrochemical cell.
Metastable ε-Fe2O3 is a unique phase
of iron oxide, which exhibits a giant coercivity field. In this work,
we grew epitaxial ε-Fe2O3 films on flexible
two-dimensional muscovite substrates via quasi van der Waals epitaxy.
It turns out that twinning and interface energies have been playing
essential roles in stabilizing metastable ε-Fe2O3 on mica substrates. Moreover, the weak interfacial bonding
between ε-Fe2O3 and mica is expected to
relieve the substrate clamping effect ubiquitously encountered in
films epitaxially grown on rigid substrates, such as SrTiO3. It is anticipated that these flexible ε-Fe2O3 thin films can serve as a platform for exploring possible
interesting emergent physical properties and eventually be integrated
as flexible functional devices.
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