Band alignment and enhanced photocatalytic activation for α-Bi2O3/BiOCl (0 0 1) core–shell heterojunction

• Bi2O3/BiOCl (0 0 1) has been successfully synthesized by in situ chemical transformation.
• The prepared sample Bi2O3/BiOCl (0 0 1) is core–shell heterojunction.
• Definitive VB and CB of Bi2O3/BiOCl were experimentally confirmed by VB offset.

In order to develop low-cost photocatalyst, commercial Bi2O3 was utilized as raw material to prepare α-Bi2O3/BiOCl core-shell heterojunction via a facile in situ chemical transformation method. To clarify experimentally the band alignment relationships between the α-Bi2O3 and BiOCl (0 0 1), the α-Bi2O3/BiOCl (0 0 1) core–shell heterojunction band offsets were analyzed by X-ray photoelectron spectroscopy (XPS). Here based on energy gaps, valence band values of α-Bi2O3 and BiOCl (0 0 1), core levels difference of Bi 4f in α-Bi2O3/BiOCl (0 0 1) heterojunction, we demonstrate that band alignment of ∼0.28 eV exists between α-Bi2O3 and BiOCl with α-Bi2O3 possessing the higher valence band potential or electron affinity which is a driving force of valence band holes from α-Bi2O3 to BiOCl (0 0 1). While, the electrons in conduction band were driven to migrate through conduction band potential difference (0.49 eV) from BiOCl (0 0 1) to α-Bi2O3.

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