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% NiFe0.1S photocatalyst presents an excellent hydrogen generation activity of 626.7 mu mol/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.