U7Co 3d impurity energy level mediated photogenerated carriers transfer in Bi₂S₃/ZnS:Co/TiO₂ photoanode

Photogenerated carriers' transfer efficiency as one of the most important criteria determines the efficiency of a photoanode for photoelectrochemical (PEC) water splitting. Energy barrier-free charge transfer of photogenerated carriers is achieved in a core–shell heterostructure of Bi2S3/ZnS:Co/TiO2, in which the arrayed TiO2 nanorods are covered with the Co doped ZnS inner layer and the Bi2S3 outer layer. The dual-shell structure ensures high photoconversion efficiency in PEC water splitting. The impurity energy state of Co in ZnS connects the conduction band edges of Bi2S3 and TiO2 to convey photogenerated electrons, without electrons hopping to Zn orbits at higher energy positions. The ABPE value of 1.07% at 1.23 V vs. RHE demonstrates the improved photoconversion efficiency of Bi2S3/ZnS:Co/TiO2 heterostructure. This work offers a photoanode construction strategy for the enhancement of the PEC water splitting via introducing impurity energy states at interlayer for barrier-free photogenerated charge migrating.