Erbium Single Atom Composite Photocatalysts for Reduction of CO2 under Visible Light: CO2 Molecular Activation and 4f Levels as an Electron Transport Bridge

Abstract It is still challenging to design a stable and efficient catalyst for visible‐light CO 2 reduction. Here, Er 3+ single atom composite photocatalysts are successfully constructed based on both the special role of Er 3+ and the special advantages of Zn 2 GeO 4 /g‐C 3 N 4 heterojunction in the photocatalysis reduction of CO 2 . Especially, Zn 2 GeO 4 :Er 3+ /g‐C 3 N 4 obtained by in situ synthesis is not only more conducive to the tight junction of Zn 2 GeO 4 and g‐C 3 N 4 , but also more favorable for g‐C 3 N 4 to anchor rare‐earth atoms. Under visible‐light irradiation, Zn 2 GeO 4 :Er 3+ /g‐C 3 N 4 shows more than five times enhancement in the catalytic efficiency compared to that of pure g‐C 3 N 4 without any sacrificial agent in the photocatalytic reaction system. A series of theoretical and experimental results show that the charge density around Er, Ge, Zn, and O increases compared with Zn 2 GeO 4 :Er 3+ , while the charge density around C decreases compared with g‐C 3 N 4 . These results show that an efficient way of electron transfer is provided to promote charge separation, and the dual functions of CO 2 molecular activation of Er 3+ single atom and 4 f levels as electron transport bridge are fully exploited. The pattern of combining single‐atom catalysis and heterojunction opens up new methods for enhancing photocatalytic activity.