Locally Asymmetric BiOBr for Efficient Exciton Dissociation and Selective O₂ Activation toward Oxidative Coupling of Amines

Abstract

Two-dimensional (2D) layered photocatalysts with highly ordered out-of-plane symmetry usually display robust excitonic effects, thus being ineffective in driving catalytic reactions that necessitate unchained charge carriers. Herein, taking 2D BiOBr as a prototype model, we implement a superficial asymmetric [Br−Bi−O−Bi] stacking in the out-of-plane direction by selectively stripping off the top-layer Br of BiOBr. This local asymmetry disrupts the diagnostic confinement configuration of BiOBr to urge energetic exciton dissociation into charge carriers and further contributes to the emergence of a surface dipole field that powers the subsequent separation of transient electron−hole pairs. Distinct from the symmetric BiOBr, which activates O 2 into 1 O 2 via an excitonmediated energy transfer, surface asymmetric BiOBr favors selective O 2 activation into •O 2− for a broad range of amine-to-imine conversions. Our work here not only presents a paradigm for asymmetric photocatalyst design but also expands the toolkit available for regulating exciton behaviors in semiconductor photocatalytic systems.

Fast and Efficient Piezo-Photocatalytic Mineralization of Ibuprofen by BiOBr Nanosheets under Solar Light Irradiation

“…Figure S.2 shows the photoluminescence spectrum of the synthesized material. The signal at around 420 nm is observed, analogous to the literature data . This band corresponds to the band-edge emission and can be assigned to free e – –h + recombination.…”

“…The signal at around 420 nm is observed, analogous to the literature data. 38 This band corresponds to the band-edge emission and can be assigned to free e − −h + recombination. The low intensity of the signal can be related to the lower recombination efficiency of e − and h + .…”

Electric effects reinforce charge carrier behaviour for photocatalysis

“…Surface asymmetric photocatalysis in the out-of-plane direction was achieved by selectively stripping the top Br layer of BiOBr. 118 This local asymmetry disrupted the diagnostic confinement structure of BiOBr, prompting the dissociation of high-energy excitons into charge carriers and further contributing to the emergence of a surface dipole field, which powers the subsequent separation of transient electron–hole pairs. Heterojunction engineering can achieve edge charge density disorder near the interface, thereby facilitating exciton dissociation and enhancing charge carrier-dominated photocatalytic reactions (Fig.…”