Asymmetric Associate Configuration of Nb Single Atoms Coupled Bi–O Vacancy Pairs Boosting CO2 Photoreduction

Precisely designing the atomic coordination structure of the catalytic center is highly desired to lower the energy barrier of CO₂ photoreduction. The present work shows that engineering Nb single atom coupled Bi–O vacancy pairs (V_Bi–O) into Bi₂₄O₃₁Br₁₀ (BOB) atomic layers can create a preferential local asymmetric structure. This configuration can result in a stronger local polarization electric field and thus prolong the carrier lifetime, as proved by ultrafast transient absorption spectroscopy. Meantime, this unique Nb SA-V_Bi–O associate favors the formation of strong chemical interaction between key *COOH intermediate and catalytic center, thus lowering the energy barrier of the rate-limiting step. Benefiting from these features, a high CO generation rate of 76.4 μmol g^–1 h^–1 for CO₂ photoreduction can be achieved over Nb SA-V_Bi–O BOB atomic layers in pure water, roughly 5.4 and 92.7 times higher than those of BOB atomic layers or bulk BOB, respectively. This work discloses an important paradigm for designing single atom coupled defect associates to optimize photocatalysis performance.