Multi-shelled　micro-/nanomaterials　with　complex　hollow　structures　have　been　regarded　as　a　promising　kind　of　advanced　catalysts　for　energy　conversion　owing　to　their　large　specific　surface,　increased　active　sites,　and　shortened　paths　of　charge　transfer.　Herein,　a　series　of　double-shelled　transition　metal　chalcogenides　(Ni-Co-MoSx,　Co-MoSx,　and　Ni-MoSx)　with　ball-in-ball　hollow　structures　have　been　synthesized　by　converting　corresponding　metal-glycerol　spherical　precursor　with　the　assistance　of　(NH4)2MoS4　under　a　facile　solvothermal　condition.　In　this　process,　(NH4)2MoS4　acted　as　a　multifunctional　vulcanizator,　which　could　conveniently　afford　Mo　and　S　elements　at　the　same　time,　and　the　mass　ratio　of　the　precursor　to　(NH4)2MoS4　played　an　indispensable　role　in　preparing　the　uniform　hollow　sphere　with　satisfactory　morphology　and　catalytic　performance.　Noteworthily,　compared　with　ternary　Co-MoSx　and　Ni-MoSx,　the　quaternary　Ni-Co-MoSx　ball-in-ball　nanospheres　demonstrated　much　enhanced　catalytic　properties　in　accelerating　the　reduction　of　triiodide　in　dye-sensitized　solar　cells　(DSSCs)　and　the　electrochemical　hydrogen　evolution　reactions　(HERs)　due　to　the　advantages　of　multi-elements,　moderated　surface　texture,　and　larger　surface　area.　Specifically,　a　prominent　power　conversion　efficiency　of　9.63%　was　achieved　by　the　DSSC　assembled　with　Ni-Co-MoSx　counter　electrode　(CE),　which　was　much　superior　to　that　of　Pt　CE　(8.28%).　Besides,　Ni-Co-MoSx　showed　a　low　η10　of　93.4　mV　and　a　small　Tafel　slope　of　55.0　mV　dec−1　when　employed　as　electrocatalysts　for　HER　in　0.5　M　H2SO4.　©　2019　Elsevier　B.V.