A CoP/CdS/WS₂ p-n-n tandem heterostructure: A novel photocatalyst for hydrogen evolution without using sacrificial agents

In this work, a photocatalyst with a built-in p-n-n tandem heterostructure is designed and fabricated by combining CdS with n-type WS₂ nanosheets and p-type CoP nanoparticles. The p-n-n tandem heterostructure allows different favorable properties from each participating compound to be combined, prolonging the lifetimes of photogenerated electrons, providing surface redox sites and increasing the photostability. Photocatalytic hydrogen evolution activity of CoP/CdS/WS₂ without using sacrificial agents is measured to be 9.16 μmol g^-1 h^-1. Moreover, it can be used as a bifunctional photocatalyst for degrading pollutants and producing hydrogen at the same time (43.51 μmol g^-1 h^-1). This work opens a new way for designing efficient photocatalysts without using sacrificial agents and combining energy conversion with environmental remediation effectively.