Restructuring at Au/AlOOH Interface Enables Enhanced CO 2 Photoreduction by Synergistically Optimizing Charge Separation and H 2 O Activation

Abstract Separating photoexcited holes in metallic nanostructure to drive H 2 O oxidation reaction to balance the CO 2 photoreduction reaction is highly desirable, but challenging. The bottleneck lies in the sluggish kinetics of both photoexcited hole transfer and H 2 O oxidation. Herein, this work demonstrates that the in situ reconstruction of n ‐type wide‐bandgap AlOOH‐supported Au nanoparticle heterogeneous photocatalyst, triggered by thermal and photothermal cooperative effect during photocatalytic reactions, facilitates the efficient CO 2 photoreduction through optimizing the Au 5 d ‐band holes separation and H 2 O activation. In situ and ex situ characterizations evidence restructuring at interfaces to form an ultrathin γ‐Al 2 O 3 nanolayer (≈2 nm thickness), which optimizes the energy band structure and promotes spontaneous transfer of photoexcited Au 5 d ‐band holes to the valence band of AlOOH, and prolongs the lifetime of electrons available for CO 2 reduction on Au. Furthermore, hydroxyl vacancies generated during restructuring process are demonstrated to promote H 2 O adsorption and lower the energy barrier for O 2 formation, supplying adequate protons for CO 2 protonation reduction and thereby boosting CO 2 photoreduction efficiency. This study offers valuable insights into the underlying mechanisms of utilizing n ‐type semiconductors to separate photoexcited d ‐band holes in metal nanoparticles.