Multi-heterointerface charge transfer in amine-functionalized cadmium sulfide-copper sulfide@titanium dioxide hollow spheres with rich oxygen vacancies for carbon dioxide photoreduction.

Photocatalytically reducing CO into high-value-added chemical materials has surfaced as a viable strategy for harnessing solar energy and mitigating the greenhouse effect. But the inadequate separation of the photogenerated electron-hole pair remains a major obstacle to CO photoreduction. Constructing heterostructure photocatalysts with efficient interface charge transfer is a promising approach to solving the above problems. Herein, a straightforward synthetic strategy is developed to fabricate amine-functionalized cadmium sulfide-copper sulfide@titanium dioxide (CdS-CuS@TiO) hollow spheres with rich oxygen vacancies for CO photoreduction. The synthetic route involves successive steps of the coating of CdS nanolayer on the prepared SiO solid nanospheres, transformation of CdS into CdS-CuS through cation exchange reaction, the coating of amorphous TiO nanoparticle layer on the SiO@CdS-CuS solid nanospheres, and the simultaneous transformations of solid nanospheres to hollow nanospheres and amorphous TiO nanoparticle layer to amine-functionalized anatase TiO nanosheets with rich oxygen vacancies via the hydrothermal reaction process in the presence of ethylenediamine. In the composite catalyst, the formed multi-heterointerfaces among the different components accelerate charge separation and transport. Moreover, the formed hollow spherical structure covered with amine-functionalized TiO ultrathin nanosheets with rich oxygen vacancies exposes a greater number of active sites for CO adsorption and increases incident light absorption and utilization. As anticipated, the optimal composite catalyst demonstrates much higher CO reduction properties with a considerable CO yield (115.66 μmol g h), surpassing that of the control catalysts (single component and bicomponent). This research offers a versatile synthetic method to synthesize excellent catalysts aimed at the production of solar fuels.