<p>Two-dimensional (2D) nanomaterials have emerged as highly efficient co-catalysts in the field of photocatalytic water splitting, due to their distinct physicochemical features. Herein, a novel 2D nanomaterial, ultrathin FePS₃ nanosheets, is prepared by an ultrasound-assisted delamination process in organic solvent, followed by the in situ construction of CdS nanosheet/FePS₃ nanosheet hierarchical heterojunction via the solvothermal method. It is notable that the designed CdS/FePS₃ photocatalyst demonstrates an efficient hydrogen-producing performance up to 7565&#xa0;μmol&#xa0;g⁻¹&#xa0;h⁻¹ for hydrogen production reaction (HER) under visible-light illumination, which is almost 8 times higher than that of bulk CdS. The enhancement in HER performance is attributed to the synergy of accelerated interfacial charge transfer, high specific surface area, and extended visible-light absorption originating from as-synthesized conductive few-layer FePS₃ nanosheets. Furthermore, the charge transfer pathway of the constructed 2D CdS/2D FePS₃ heterojunction is unveiled by in situ atomic force microscopy with Kelvin probe force microscopy (AFM-KPFM), in situ X-ray photoelectron spectroscopy (XPS), and photoelectrochemical measurements. This study offers new insight into the rational design and controllable synthesis of FePS₃-based composite photocatalytic systems for efficient photocatalytic hydrogen production.</p> Graphical abstract <p></p>