Facile tailoring of Co-based spinel hierarchical hollow microspheres for highly efficient catalytic conversion of CO₂

High-performance and low-cost photocatalysts are of significance to artificial photosynthetic systems for converting of CO₂ into CO and other value-added products. In this work, we developed a controllable and scalable self-templated approach to fabricate hierarchical Co-base spinel hollow microspheres for visible light-driven CO₂ reduction with a Ru-based sensitizer. The hollow microspheres are assembled by ultrathin nanosheets using Ni-Co-hydroxides as the morphology-conserved precursor. A series of characterization techniques were conducted to investigate structural features of the prepared Co-base spinel hollow spheres. Owing to the integration of the specific microstructure, functional Ni/Co species and oxygen vacancies, Co-base spinel hollow spheres possess enhanced CO₂ adsorption ability, more active sites, and efficient transfer and separation of photoexcited electrons. The high CO-evolving rate (27.7 μmol h^-1) and selectivity (84.4%) manifest desirable performance of Co-base spinel hollow spheres for CO₂ photocatalytic reduction. The findings suggest that such spinel-structured bimetallic oxides hierarchical hollow spheres, facilely synthesized via the proposed self-templated method, are efficient for photocatalytic CO₂ reduction.