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 2 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 2 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 2 ) hollow spheres with rich oxygen vacancies for CO 2 photoreduction. The synthetic route involves successive steps of the coating of CdS nanolayer on the prepared SiO 2 solid nanospheres, transformation of CdS into CdS-CuS through cation exchange reaction, the coating of amorphous TiO 2 nanoparticle layer on the SiO 2 @CdS-CuS solid nanospheres, and the simultaneous transformations of solid nanospheres to hollow nanospheres and amorphous TiO 2 nanoparticle layer to amine-functionalized anatase TiO 2 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 2 ultrathin nanosheets with rich oxygen vacancies exposes a greater number of active sites for CO 2 adsorption and increases incident light absorption and utilization. As anticipated, the optimal composite catalyst demonstrates much higher CO 2 reduction properties with a considerable CO yield (115.66 μmol g −1  h −1 ), 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.