In order to improve the photocatalytic activity of Bi₂WO₆ (BWO) under solar light irradiation, the introduction of oxygen vacancies has attracted wide attention owing to its simple synthesis method. However, the intrinsic link between oxygen vacancies and photocatalytic CO₂ reduction performance is still elusive. In this work, density functional theory (DFT) calculations combining with experimental measurements verify that oxygen vacancies are inclined to generate in [Bi₂O₂]²⁺ layers on BWO (010) surface, which results in narrowed band gap and improved electron-hole pair separation efficiency arising from the formation of Bi 6p impurity level. To the best of our knowledge, the reduction product CO is obtained via the reaction of CO₂ with •H, and the intermediate species include •COOH, •CO, •OH, and H₂O. Owing to BWO (010) surface chemical state variations, such as charge accumulation and depletion upon the introduction of oxygen vacancies, CO₂ and intermediate species change remarkably in adsorption configuration, and so do the reaction energy barriers with or without oxygen vacancies. Apparently, the rate-limiting step for the overall reaction is the transition from •COOH to •CO and •OH, and the corresponding activation barrier value is reduced from 2.83 eV to 1.91 eV, because C–O bond breaks more easily after the introduction of oxygen vacancies. This work provides a new enlightenment and insight into the role of oxygen vacancies in the process of reducing CO₂, and paves ways to design defective systems with higher photocatalytic activity.

为了提高Bi ₂ WO ₆ (BWO)在太阳光照射下的光催化活性，引入氧空位因其合成方法简单而受到广泛关注。然而，氧空位与光催化CO ₂还原性能之间的内在联系仍然难以捉摸。在这项工作中，密度泛函理论 (DFT) 计算结合实验测量验证了氧空位倾向于在 [Bi ₂ O ₂ ] ^{2+ 中产生}BWO（010）表面上的层，导致带隙变窄，提高了由 Bi 6p 杂质能级的形成引起的电子-空穴对分离效率。据我们所知，还原产物CO是通过CO ₂与•H反应获得的，中间物质包括•COOH、•CO、•OH和H ₂ O。由于BWO（010）表面化学状态变化，例如引入氧空位后的电荷积累和消耗，CO ₂和中间物种的吸附构型发生显着变化，有或没有氧空位的反应能垒也发生了显着变化。显然，整个反应的限速步骤是从•COOH 到•CO 和•OH 的转变，相应的激活势垒值从2.83 eV 降低到1.91 eV，因为引入后C-O 键更容易断裂氧空位。这项工作为氧空位在减少CO ₂过程中的作用提供了新的启示和见解，并为设计具有更高光催化活性的缺陷系统铺平了道路。