Oxygen-Vacancy-Mediated Exciton Dissociation in BiOBr for Boosting Charge-Carrier-Involved Molecular Oxygen Activation

Abstract

Excitonic effects mediated by Coulomb interactions between photogenerated electrons and holes play crucial roles in photoinduced processes of semiconductors. In terms of photocatalysis, however, efforts have seldom been devoted to the relevant aspects. For the catalysts with giant excitonic effects, the coexisting, competitive exciton generation serves as a key obstacle to the yield of free charge carriers, and hence, transformation of excitons into free carriers would be beneficial for optimizing the charge-carrier-involved photocatalytic processes. Herein, by taking bismuth oxybromide (BiOBr) as a prototypical model system, we demonstrate that excitons can be effectively dissociated into charge carriers with the incorporation of oxygen vacancy, leading to excellent performances in charge-carrier-involved photocatalytic reactions such as superoxide generation and selective organic syntheses under visible-light illumination. This work not only establishes an in-depth understanding of defective structures in photocatalysts but also paves the way for excitonic regulation via defect engineering.

Theory‐Guided Defect Tuning through Topochemical Reactions for Accelerated Discovery of UVC Persistent Phosphors

“…The positron lifetime spectra of both samples exhibit three fitted lifetime components (Figure c, Table 1 ). The longest component (τ 3 ) can be tentatively attributed to large voids such as vacancy clusters . Based on the calculated positron lifetimes ( Table 2 ), the shortest lifetime component (τ 1 ) can be ascribed to the positron trapped at oxygen divacancies ( V O3,1 , V O3,2 , and V O3,4 ; a class of defects due to the loss of two oxygen atoms from the [PO 4 ] unit), while the component (τ 2 ) can be assigned to vacancy associates ( V PO1‐4 ) ( Figure ).…”

BiOCl/BiOBr Heterojunction with Rich Oxygen Vacancies Induced by Ultraviolet and Its Enhanced Photocatalytic Performance

“…As well known, OVs can easily produce in BOX (X = Cl, Br, I) under UV‐light irradiation which can be attributed to weak bond energy and long bond length of Bi–O bond. Meanwhile, defect energy levels under conduction band of BiOBr and BiOCI,, which induced by oxygen vacancies, can act as electronic capture centers to suppress the recombination of photogenerated electron–hole pairs as well as further expand the light‐responsive . Moreover, abundant surface dangling bonds generated by the coordination‐unsaturated character of OVs can act as active sites, which not only promote the adsorption of the substrate but also facilitate the adsorption‐desorption of the intermediates .…”

“…Wang verified that OVs can not only accelerate the excitons dissociate into free carriers as well as promote its separation and migration, but also enhance the redox ability of the BiOBr‐OV nanoplates . BiVO 4 /BiOCl heterojunction successfully prepared by hydrochloric acid treatment, which exhibits outstanding PEC performance attributed to the high charge separation efficiency in the heterojunction interface originate from the type II band alignment .…”

Defective [Bi2O2]2+ Layers Exhibiting Ultrabroad Near‐Infrared Luminescence

“…[1] In this pursuit, the incorporation of intrinsic or extrinsic atomic defects in structures that either exhibit naturally occurring vacancies or those with synthetically or postsynthetically introduced vacancies has been established as ap owerful approacht ot he finetuning of the properties of aw ide range of functional materials. Many of today's prominentm aterials, such as high-transition-temperature superconductors, [2,3] solar-drivenp hotocatalysts, [4][5][6][7] photovoltaic materials, [8] metal-organic frame-works, [9][10][11] and ferroelectrics, [12][13][14] are imperfect systems with defect-induced, locally broken periodic structures,i nw hich imperfection plays ap ivotal role in governing, or at least affecting, their physiochemicalproperties. [15][16][17][18][19][20] Materials consisting of as equence of infinitely repeating stacksof[Bi 2 O 2 ] 2 + layers,such as bismuth-based cupratesuperconductors, bismuth oxyhalides, and Aurivillius phases, have attracted intensivea ttention because they exhibit an array of tantalizing properties, such as superconductivity,p hotocatalytic, photoluminescence (PL),a nd ferroelectricity.…”