Oxygen Vacancy-Rich S-Scheme CeO2@Ni1–xCoxSe2 Hollow Spheres Derived from NiCo-MOF for Remarkable Photocatalytic CO2 Conversion

Photocatalytic CO2 conversion into chemicals has been a promising strategy to utilize sustainable solar energy and alleviate the greenhouse effect. Nonetheless, the achievements of these photocatalytic reactions are challenging. Herein, we present a strategy for the synthesis of hierarchical CeO2@Ni1–xCoxSe2 hollow spheres (HSs) including the successive steps of coating of the CeO2 nanolayer on SiO2 spheres, in situ growth of NiCo-MOF nanosheets, selenization reaction, and subsequent etching treatment. The hierarchical CeO2@Ni1–xCoxSe2 HSs exhibiting intimate interface contact between two nanoshells form an S-scheme heterojunction with fast charge/mass transport and excellent visible-light absorption, while maintaining the strong reducing power of electrons in the conduction band of Ni1–xCoxSe2 nanosheets and the strong oxidizing capacity of holes in the valence band of CeO2 HSs with oxygen vacancies. The S-scheme photogenerated charge transfer mechanism was testified by the work function and electron paramagnetic resonance measurements. These advantages make the optimized CeO2@Ni1–xCoxSe2 HS sample exhibit superior activity and high stability in photocatalytic CO2 reduction with a CO production rate of 25.93 μmol h–1 g–1. This work provides more opportunities to fabricate other hierarchical S-scheme semiconductor-based photocatalysts.