Asymmetric Associate\nConfiguration of Nb Single Atoms\nCoupled Bi–O Vacancy Pairs Boosting CO<sub>2</sub> Photoreduction

Precisely designing the atomic coordination structure\nof the catalytic\ncenter is highly desired to lower the energy barrier of CO<sub>2</sub> photoreduction. The present work shows that engineering Nb single\natom coupled Bi–O vacancy pairs (<i>V</i><sub>Bi–O</sub>) into Bi<sub>24</sub>O<sub>31</sub>Br<sub>10</sub> (BOB) atomic\nlayers can create a preferential local asymmetric structure. This\nconfiguration can result in a stronger local polarization electric\nfield and thus prolong the carrier lifetime, as proved by ultrafast\ntransient absorption spectroscopy. Meantime, this unique Nb SA-<i>V</i><sub>Bi–O</sub> associate favors the formation of\nstrong chemical interaction between key *COOH intermediate and catalytic\ncenter, thus lowering the energy barrier of the rate-limiting step.\nBenefiting from these features, a high CO generation rate of 76.4\nμmol g<sup>–1</sup> h<sup>–1</sup> for CO<sub>2</sub> photoreduction can be achieved over Nb SA-<i>V</i><sub>Bi–O</sub> BOB atomic layers in pure water, roughly 5.4\nand 92.7 times higher than those of BOB atomic layers or bulk BOB,\nrespectively. This work discloses an important paradigm for designing\nsingle atom coupled defect associates to optimize photocatalysis performance.