In situ tuning of the electronic structure of active sites is a long-standing challenge. Herein, we propose a strategy by controlling the hydrogen spillover distance to in situ tune the electronic structure. The strategy is demonstrated to be feasible with the assistance of CoO_x/Al₂O₃/Pt catalysts prepared by atomic layer deposition in which CoO_x and Pt nanoparticles are separated by hollow Al₂O₃ nanotubes. The strength of hydrogen spillover from Pt to CoO_x can be precisely tailored by varying the Al₂O₃ thickness. Using CoO_x/Al₂O₃ catalyzed styrene epoxidation as an example, the CoO_x/Al₂O₃/Pt with 7 nm Al₂O₃ layer exhibits greatly enhanced selectivity (from 74.3% to 94.8%) when H₂ is added. The enhanced selectivity is attributed to the introduction of controllable hydrogen spillover, resulting in the reduction of CoO_x during the reaction. Our method is also effective for the epoxidation of styrene derivatives. We anticipate this method is a general strategy for other reactions.

活性位点电子结构的原位调谐是一个长期存在的挑战。在这里，我们提出了一种通过控制氢溢出距离来原位调整电子结构的策略。在通过原子层沉积制备的 CoO _x /Al ₂ O ₃ /Pt 催化剂的帮助下，该策略被证明是可行的，其中 CoO _x和 Pt 纳米颗粒被中空的 Al ₂ O ₃纳米管隔开。从 Pt 到 CoO _x的氢溢出强度可以通过改变 Al ₂ O ₃厚度来精确定制。使用 CoO _x /Al ₂ O ₃以催化苯乙烯环氧化为例，当添加H ₂时，具有 7 nm Al ₂ O ₃层的 CoO _x /Al ₂ O ₃ /Pt表现出极大的选择性（从 74.3% 到 94.8%）。增强的选择性归因于引入可控的氢溢出，导致反应过程中 CoO _x的减少。我们的方法对苯乙烯衍生物的环氧化也很有效。我们预计这种方法是其他反应的一般策略。