Oxygen Vacancy‐Mediated Exciton Effect in Hierarchical BiOBr Enables Dichotomy of Energy Transfer and Electron Transfer in Photocatalysis

Abstract

Using solar energy through green and simple artificial photosynthesis systems are considered as a promising way to solve the energy and environmental crisis. However, one of the important primary steps of photosynthesis, i.e., energy transfer, is long being ignored especially in inorganic semiconducting systems due to the small exciton binding energies. Herein, the simultaneous interrogation of the charge transfer and energy transfer steps in a photoexcitation process is proposed by utilizing few-layered nanosheet-assembled hierarchical BiOBr nanotubes with rich oxygen vacancies (OVs) as efficient multifunctional photocatalysts. Benefiting from the integrated 1D/2D structure and abundant OV defects, the excitonic effect strikes a delicate balance in the optimized BiOBr photocatalyst, showing not only improved charge carrier separation and transfer but also enhanced exciton generation. As a result, the hierarchical BiOBr nanotubes exhibit high efficiency toward photocatalytic CO 2 reduction with an impressive CO evolution rate of 135.6 µmol g −1 h −1 without cocatalyst or photosensitizer. The dominant reactive oxygen species of singlet oxygen ( 1 O 2 ) are discriminated for the first time, which originated from an energy transfer process, with electrophilic character, whereas the minor effect of superoxide anion radical ( • O 2 −) with a nucleophilic rate-determining step in the photocatalytic aerobic oxidation of sulfides.

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

“…Meanwhile, the [Br] − slabs with highly localized valence electrons display reduced electronic screening that further makes e – –h + pairs strongly tangled in energy, eventually evolving into excitons (Scheme b). To this end, strong excitonic effects in layered BiOBr with highly ordered out-of-plane symmetry constitute shackles for charge carrier-driven photocatalysis, including O 2 activation ,− and CO 2 reduction . The introduction of defects, , dopants, ,, and disordered domains into exciton-based 2D layered photocatalysts has been previously demonstrated to enable destabilization of bound excitons via establishing discontinuously distributed energy landscapes, thus promoting exciton dissociation.…”

Hierarchically porous CsPbBr3@HZIF-8 heterojunctions for high-performance photocatalytic degradation of antibiotics in high-salinity wastewater

“…As we know, in the photo-activation of molecular oxygen, two potential pathways exist for the generation of 1 O 2 . 41 The first involves energy transfer from excited semiconductors to the ground state O 2 , leading to the production of 1 O 2 . Alternatively, O 2 can initially acquire a photoexcited electron to form ˙O 2 − , which is subsequently oxidized to ˙O 2 − by photogenerated holes residing in the valence band.…”

UV‐to‐NIR Harvesting Conjugated Porous Polymer Nanocomposite: Upconversion and Plasmon Expedited Thioether Photooxidation

“…[43,56] The generation of O 2 *À and 1 O 2 was probed through absorption and electron paramagnetic resonance (EPR) spectroscopy (Figure S32-S39, Scheme S2-S5). [57] The decrease in the absorption peak of 1,3-diphenylisobenzofuran solution (DPBF, 1 O 2 scavenger) was faster under simultaneous irradiation of both green (λ ex = 540 nm) and NIR light compared to the only visible (green) and NIR light due to the rapid generation of 1 O 2 by UCÀ POPÀ Au and subsequent 1 O 2 -mediated oxidation of DPBF (Figure S34, Scheme S2). [37] Additionally, the distinct EPR triplet signals for 2,2',6,6'-tetramethylpiperidine-1-oxyl (TMPO) radical were observed for the oxidation of 2,2',6,6'-tetramethylpiperidine (TMP) in the presence of 1 In addition, the absorption and electron paramagnetic resonance (EPR) spectroscopy were carried out to elucidate the role of the individual components (UCNP, AuNP, and POP) in the generation of the reactive oxygen species (ROS).…”