Colloidal Design and Preparation of an Internal Electric Modulated Z-Scheme BiOI-CdS Heteronanostructure with Oxygen-Rich Vacancies

Photoelectrochemical (PEC) water splitting offers an ideal strategy for the development of clean and renewable energy. However, its practical implementation is often inhibited by the high recombination rate of photogenerated charge carriers and the instability of photoanodes. Introducing defect engineering (such as oxygen vacancies) and constructing internal electric field-modulated Z-scheme heteronanostructures (HNs) can be considered as effective approaches to overcome these obstacles. Herein, a flexible method is developed for synthesizing Z-scheme BiOI-CdS HNs with oxygen vacancies, which induce an internal electric field between ultrathin BiOI nanosheets and a CdS semiconductor. This Z-scheme mechanism significantly promotes the separation of photogenerated electron–hole pairs, thereby enhancing the PEC performance. The BiOI-CdS photoanode achieves a photocurrent density of 4.22 mA cm^–2 at 1.6 V vs RHE under AM 1.5G illumination (100 mW cm^–2), outperforming bare BiOI and CdS. Moreover, the photoanode exhibits exceptional stability with only a slight decrease of approximately in its initial photocurrent after a rigorous 4 h test, surpassing other counterparts in terms of durability. This work affords a better understanding of oxygen vacancies and the construction of highly efficient and stable Z-scheme photoanodes for feasible PEC application.