Noble-Metal-Free Ultrathin CdS-NiFeS 2D-2D Heterojunction Nanosheets for Significantly Enhanced Photocatalytic Hydrogen Evolution

To effectively restrain the charge recombination of bulk CdS, which dominantly limits the photocatalytic activity, ultrathin CdS-NiFeS two-dimensional (2D)-2D heterojunctions are well designed with the creation of tight interfaces, where NiFeS nanosheets derived from layered double hydroxides possess tunable work functions and hydrogen evolution overpotentials. The optimized CdS-2% NiFe_0.1S photocatalyst presents an excellent hydrogen generation activity of 626.7 μmol/h (10 mg catalysts, equivalent to 62.67 mmol/g/h), which is fairly high among noble-metal-free CdS-based catalysts. The greatly enhanced catalytic performance can be ascribed to the following synergetic effects. This ultrathin 2D-2D heterostructure formed between CdS and NiFeS establishes sufficient contact interfaces, shortens the charge transport distance, and efficiently accelerates the electron transfer from CdS to NiFeS, which possesses a large work function. Moreover, the bimetallic NiFeS cocatalyst evidently decreases the reaction barrier, provides abundant active sites, and then facilitates H₂ generation. This research may offer new inspirations to develop 2D nanomaterials for outstanding photocatalytic performance.