Hydrothermal Deposition of Metal Sulfide Heterojunction Thin Films for Photoelectrochemical Water Splitting

Metal sulfides represent a broad class of materials with considerable potential for applications in photovoltaic devices and energy technologies. However, the low‐temperature synthesis of high‐quality metal sulfide thin films remains a formidable challenge. Hydrothermal deposition, known for its versatility and cost‐efficiency, has been successfully employed to synthesize a variety of materials, yet its application in the preparation of metal sulfide thin films has not been extensively explored. In this study, we develop a hydrothermal deposition method to synthesize five distinct types of metal sulfide thin films, each with well‐defined phases and compositions. As a case study, CdS/Bi2S3 thin film was selected and evaluated as photoanode for photoelectrochemical water splitting. Through O‐doping and the modification of an ultrathin MoO3 overlayer, the photocurrent density was significantly enhanced from 1.52 mA cm‐2 (CdS/Bi2S3) to 2.27 mA cm‐2 (CdS/O‐Bi2S3), and further to 2.84 mA cm‐2 (CdS/O‐Bi2S3/MoO3) at 1.23 V vs. reversible hydrogen electrode under AM 1.5G illumination. This methodology is expected to advance both fundamental and applied research on metal sulfides.