Restructuring at Au/AlOOH Interface Enables Enhanced CO2 Photoreduction by Synergistically Optimizing Charge Separation and H2O Activation

Abstract

Separating photoexcited holes in metallic nanostructure to drive H₂O oxidation reaction to balance the CO₂ photoreduction reaction is highly desirable, but challenging. The bottleneck lies in the sluggish kinetics of both photoexcited hole transfer and H₂O 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 CO₂ photoreduction through optimizing the Au 5d-band holes separation and H₂O activation. In situ and ex situ characterizations evidence restructuring at interfaces to form an ultrathin γ-Al₂O₃ nanolayer (≈2 nm thickness), which optimizes the energy band structure and promotes spontaneous transfer of photoexcited Au 5d-band holes to the valence band of AlOOH, and prolongs the lifetime of electrons available for CO₂ reduction on Au. Furthermore, hydroxyl vacancies generated during restructuring process are demonstrated to promote H₂O adsorption and lower the energy barrier for O₂ formation, supplying adequate protons for CO₂ protonation reduction and thereby boosting CO₂ 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.