Coupling monoclinic Pb2(CrO4)O with Mn3O4 quantum dots as oxygen vacancies-rich S-scheme photocatalysts for visible-light-driven photocatalytic CO2 reduction with H2O

Simulating natural photosynthesis to convert CO 2 and H 2 O into fuels achieving overall reaction is a promising solution for addressing environmental problems and energy crises. Constructing an S-scheme catalyst of two or more catalytic sites with rapid electron transfer and strong redox capability may be an effective strategy for coupling photocatalytic CO 2 reduction and H 2 O oxidation. Here, an oxygen vacancies-rich S-scheme semiconductor photocatalyst composed of monoclinic lead chromate oxide (Pb 2 (CrO 4 )O) coupled with Mn 3 O 4 quantum dots (QDs) (Pb 2 (CrO 4 )O@Mn 3 O 4 QDs) are synthesized and tested for photoconversion of CO 2 with H 2 O under visible light. Through the integration of Pb 2 (CrO 4 )O with Mn 3 O 4 QDs, the photocatalytic C1-evolution rate on Pb 2 (CrO 4 )O@Mn 3 O 4 QDs is radically increased by 6.0 and 8.1 times, which is much faster than that of pristine Pb 2 (CrO 4 )O and Mn 3 O 4 . The origin of the greatly raised activity is revealed by advanced characterizations, and in situ X-ray photoelectron spectroscopy (XPS) confirms the electron transport pathway in Pb 2 (CrO 4 )O@Mn 3 O 4 QDs with light illumination, unveiling the efficient spatial separation/transfer of charge carriers in oxygen vacancies-rich Pb 2 (CrO 4 )O@Mn 3 O 4 QDs S-scheme heterojunction. Consequently, powerful photoelectrons and holes accumulate in the Mn 3 O 4 conduction band and Pb 2 (CrO 4 )O valence band, respectively, exhibiting prolonged long lifetimes and facilitating their involvement in CO 2 photoreduction and H 2 O photooxidation through altering the interfacial charge dynamics.