Assembling ultrathin nickel hydroxide nanosheets on cadmium sulfide hollow spheres for enhanced CO₂ photoreduction

The controllable hollow sphere, serving as an excellent light-trapping cavity, represents one of the most appealing structures in photocatalytic CO₂ reduction but is plagued by limited catalytic active sites. Herein, we report an in situ self-assembly strategy to decorate cadmium sulfide hollow spheres (CdS HS) with ultrathin nickel hydroxide (Ni(OH)2) nanosheets to boost CO₂ photoreduction. The as-grown CdS@Ni(OH)₂ photocatalyst affords a higher CO yield of 3.12 mmol g^-1h⁻¹ and a good apparent quantum efficiency (AQE) of 2.05 % compared with the pristine CdS HS (0.38 mmol g^-1h⁻¹). The superior performance could be assigned to the unique hollow nanostructure and the synergistic effect between CdS HS and Ni(OH)₂ nanosheets. The interior CdS HS strengthens the multiple light reflections that leads to optimized light harvesting. The ultrathin Ni(OH)₂ nanosheet shell effectively prevents photocorrosion of CdS while providing a suitable local chemical environment that promotes CO₂ adsorption and activation. Additionally, the close contact interface of CdS@Ni(OH)₂ facilitates efficient separation and migration of photoinduced electrons and holes, thus boosting photocatalytic kinetics. This study presents a facile route for the controllable engineering of hollow microreactors toward CO₂ photoreduction and sheds light on the structure-dependent photocatalytic mechanisms.