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19Current study reports the facile synthesis of Ag/MoS 2 nanocomposite 20 photocatalyst for visible-light driven hydrogen gas evolution. The MoS 2 nanoflakes 21 were hydrothermally prepared and then decorated with Ag nanoparticles (NPs) by 22 simple chemical reduction process at room temperature. Detailed 23 characterizations had been carried out to probe the physical structure and 24 properties of the as-synthesized nanocomposite. The nanocomposite shows 25 enhanced visible-light absorption and pronounced quenching of 26 photoluminescence intensity as compared to that of pure MoS 2 . The 27 photocatalytic hydrogen gas evolution experiments reveal that the Ag NPs can act 28 as efficient co-catalyst for MoS 2 nanoflakes and subsequently improve the 29 hydrogen gas evolution rate. Ag-loading dependent photocatalytic tests indicate 30 that the 20 wt%-Ag/MoS 2 nanocomposite exhibits the highest photocatalytic 31 activity with hydrogen gas evolution of 179.5 µmol H 2 /g cat , which is enhanced by 32 95% if compared to that of commercial MoS 2 nanopowder (92.0 µmol H 2 /g cat ). The 2 possible mechanisms that contribute to the improvement of visible-light driven 34 photocatalytic performance for nanocomposite are proposed. 35 36Instead, the excitons that formed upon absorbing incident photon can further split 62 the water molecules into its constituents. Therefore, photocatalysis hydrogen 63 3 generation through suspension remain attractive since it is well-complement with 64 the worldwide initiative toward the implementation of the technology, which is 65 anticipated to fully harness the sunlight from mother nature as one of highly 66 abundance natural resource. 67As part of two-dimensional materials, graphene also has gained significant 68 popularity for photocatalysis applications, where it has been greatly used as 69 matrix that is able in prolong the charge-carrier lifetimes. 7 In contrast to the 70 graphene, MoS 2 appear to be a semiconductor by itself and had been repeatedly 71 proved to exhibit tunable bandgap energy that is strictly dependent on the atomic 72 thickness. The bandgap values can be maneuvered from 1.9 eV (direct bandgap) 73 for a single layer MoS 2 nanosheet, down to 1.2 eV (indirect bandgap) for 74 multilayer MoS 2 nanoflakes, in which both of these bandgap are well-correspond 75 to the light absorption in the visible-(450-700 nm) and infrared-region (700-1400 76 nm), respectively. 8 As a result, MoS 2 would become one of the ideal candidates to 77 be used as visible-and infrared-active optical material for photo-energy 78 engineering including photosplitting of water. 79 In terms of the structural characteristic, MoS 2 generally exists in expanded 80 two-dimensional sheet-like structure 8, 9 . Such expanded planar nature not only 81 renders highly-exposed surface area for it, but it is also propitious to be employed 82 as a matrix in supporting other inorganic nanoparticles (NPs) to form new class of 83 nanocomposite with value added features that are highly-suitable for specific 84 application...