In this work, a 2D hybrid CdS nanosheets(NSs)/MoS2 layered heterojunctions were successfully synthesized by a two-step hydrothermal method and subsequent ultrasonic treatment. The results showed that the loading ultrathin MoS2 NSs as co-catalysts could significantly boost the photocatalytic H-2-evolution activity of CdS NSs. It is demonstrated that the optimized 2D CdS NSs/MoS2 (1.0 wt%) layered heterojunctions could achieve the highest photocatalytic H-2-evolution activity of 1.75 mmol g(-1) h(-1) from an aqueous solution containing sulfide and sulfite under visible light, which is 2.03 times as high as that of the pristine CdS NSs. It is believed that the deposition of ultrathin MoS2 NSs and intimate 2D-2D coupling interfaces are mainly responsible for the excellent H-2-evolution performance of 2D CdS NSs/MoS2 layered heterojunctions, owing to the effectively promoted separation and transportation of charge carriers and the enhanced following surface H-2-evolution kinetics. Interestingly, the lactic acid and formic acid have also been demonstrated to be better sacrificial reagents than the Na2S/Na2SO3, for the photocatalytic H-2 evolution over the 2D CdS NSs/MoS2 layered heterojunctions. It is hoped that the strategy of 2D-2D interfacical coupling based on CdS NSs can become a general strategy to improve the H-2-evolution activity over various kinds of conventional semiconductor NSs. (C) 2016 Elsevier B.V. All rights reserved.