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.
Bibliographical noteFunding Information:
This work was supported by National Research Foundation of Korea (NRF) grants funded by the Korean government (MEST and MSIP) (2013R1A1A2009575 and 2014R1A4A1001690). This research was also supported in part by the Global Research Laboratory Program [Grant No. 2009-00439] and the Max Planck POSTECH/KOREA Research Initiative Program [Grant No. 2011-0031558] through the MEST's NRF funding. Finally, this study was financially supported by the 2016 Post-Doc. Development Program of Pusan National University.
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