Ascorbic-acid-assisted in-situ construction of S-scheme CuO/Cu2O hetero-nanosheets with active Cu(II)-O-Cu(I) bridges for efficient CO2 photoreduction

Abstract

Efficient charge transfer across interfaces is highly desirable, but remains challenging in engineering semiconductor heterojunctions for photocatalysis. In this work, hybrid hetero-nanosheets (HNSs) of CuO/Cu2O bridged with interfacial Cu(II)-O-Cu(I) have been constructed via an in-situ topotactic transformation strategy, in which CuO nanosheets are partially reduced by ascorbic acid and transformed into Cu2O. The interfacial Cu(II)-O-Cu(I) bridges are found to provide fast transfer channels for photogenerated carriers transporting from CuO to Cu2O in an S-scheme pathway, leading to enhanced separation of photogenerated carriers. Furthermore, the bond bridges can tune the kinetic and thermodynamic processes of the CO2-to-CO conversion at interfacial Cu(I) catalytic sites by altering the rate-determined step and shifting downwards d-band center of the Cu(I) sites. Owing to the interfacial Cu(II)-O-Cu(I) bridges, the optimized CuO/Cu2O HNSs significantly expedite the CO2 photoreduction to CO, delivering a CO2 conversion rate of 22.14 μmol g−1 h−1 with a CO selectivity of 94.4%, outperforming the state-of-the-art copper oxide-based photocatalysts. This work demonstrates an effective in-situ topotactic transformation strategy to create interfacial bond bridges at heterogeneous interfaces for boosted photocatalysis as well as the critical roles of interface catalytic sites for CO2 conversion.