Molybdenum　sulphide　has　emerged　as　a　promising　electrocatalyst　for　hydrogen　evolution　reaction　(HER).　Toward　further　improving　its　activity,　tremendous　efforts　have　been　made　to　preferentially　expose　active　edge　sites　of　molybdenum　sulphide-based　catalysts　by　engineering　their　surface　structure.　In　this　work,　3D　arrays　of　molybdenum　sulphide　nanosheets　were　synthesized　by　hydrothermal　treatment　of　Mo　mesh　in　aqueous　thiourea　solution.　Their　compositional,　morphological　and　structural　properties　as　well　as　electrocatalytic　activities　were　investigated　in　details.　The　results　reveal　that　3D　arrays　of　molybdenum　sulphide　nanosheets　demonstrate　an　enhanced　HER　activity　with　a　low　onset　overpotential　of　120　mV　and　a　Tafel　slope　of　46　mV/dec,　which　is　superior　to　that　of　2D　arrays　molybdenum　sulphide　nanosheets　grown　on　Mo　foil.　The　high　activity　for　HER　can　be　ascribed　to　the　superstructure　of　the　catalysts　with　a　large　fraction　of　edge　sites　and　a　high　surface　area.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.