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-metal-free 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 H₂ production rate of 83 907 μmol h⁻¹ g⁻¹ with an apparent quantum efficiency of 22.5%, far exceeding those of bare CdS (1053 μmol h⁻¹ g⁻¹), CdS-RGO (12 177 μmol h⁻¹ g⁻¹), CdS-RGO-MoS₂ (29 268 μmol h⁻¹ g⁻¹), CdS:CoP (32 606 μmol h⁻¹ g⁻¹), CdS/CoP-RGO (54 259 μmol h⁻¹ g⁻¹) and CdS:Pt (12 478 μmol 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 H₂-evolution kinetics. We believe that this work provides invaluable information for the design of new, efficient sunlight-active noble-metal-free photocatalysts for hydrogen production through water-splitting.