Hierarchical dandelion-flower-like cobalt-phosphide modified CdS/reduced graphene oxide-MoS2 nanocomposites as a noble-metal-free catalyst for efficient hydrogen evolution from water

Abstract

Commercial applications of sustainable photocatalytic hydrogen production via water-splitting, an important future source of renewable energy, are hindered by the high price and scarcity of the requisite noble metal co-catalysts. This problem could be overcome by developing highly active and durable noble-metalfree photocatalysts. Herein, a new solar-light-active noble-metal-free catalyst featuring dandelion-flower-like cobalt-phosphide embedded with CdS nanostructures grown on reduced graphene oxide (RGO)-MoS2 nanosheets was designed, and its photocatalytic hydrogen production activity was evaluated in water under simulated sunlight irradiation using lactic acid as a sacrificial reagent. The results show that the optimized CdS/RGO-MoS2@CoP photocatalyst exhibited an efficient H-2 production rate of 83907 mu mol h(-1) g(-1) with an apparent quantum efficiency of 22.5%, far exceeding those of bare CdS (1053 mu mol h(-1) g(-1)), CdS-RGO (12 177 mu mol h(-1) g(-1)), CdS-RGO-MoS2 (29 268 mu mol h(-1) g(-1)), CdS: CoP (32 606 mu mol h(-1) g(-1)), CdS/CoP-RGO (54 259 mu mol h(-1) g(-1)) and CdS:Pt (12 478 mu mol h(-1) g(-1)) nanostructures. The proposed mechanism for the enhancement of the photocatalytic hydrogen evaluation rate of CdS/MoS2-RGO@CoP is based on the efficient separation of photogenerated electron-hole pairs. In the nanocomposite, the wrapped RGO nanosheets serve as good electron collectors and transporters. Meanwhile, the MoS2 and CoP nanostructures serve as a co-catalyst and electron acceptor, respectively, for the effective separation of the photo-charge carrier from the bare nanostructures, thereby decreasing the probability of electron-hole recombination at the interface of the nanocomposites and further stimulating the surface H-2-evolution kinetics. We believe that this work provides invaluable information for the design of new, efficient sunlight-active noble-metalfree photocatalysts for hydrogen production through water-splitting.