Construction of CdS@Ti₃C₂@CoO hierarchical tandem p-n heterojunction for boosting photocatalytic hydrogen production in pure water

Highly efficient and direct photocatalytic H₂ evolution from water splitting is a hopeful route to convert solar energy into renewable and storable chemical energy. However, it's still a challenging task to eliminate the constraint of sacrificial agents. Herein, by integrating the architecture guidance and energy band engineering into the design conception, a novel CdS@Ti₃C₂@CoO hierarchical tandem p-n heterojunction photocatalytic system is designed and prepared for the first time. Ti₃C₂ nanosheets not only solve the compatibility problem between CdS and CoO but also function as a bridge to consolidate them into a special tandem p-n heterojunction where two secondary internal electric fields are set up and combined into the strong internal electric field existing in the p-n heterojunction. The triple-internal electric field can dramatically boost the separation efficiency of photogenerated charge carriers and realize the regulation of their spatial motion. This specific photocatalytic system exhibits superior photocatalytic performance with a H₂ evolution activity of 134.46 μmol·h⁻¹·g⁻¹ and excellent stability without any sacrificial agents. Our work introduces a potential avenue to design efficient photocatalysts by constructing multi-hierarchical systems toward practical application in solar energy conversion.