As　a　promising　alternative　to　Pt,　molybdenum　carbides　have　been　widely　used　in　many　domains.　Herein,　we　develop　a　co-catalyst　with　a　2D　lamellar　structure,　in　which　MoC　quantum　dots　are　embedded　in　a　carbon　membrane　uniformly　(MoC-QDs/C).　With　the　introduction　of　MoC-QDs/C,　the　flower-like　MoC-QDs/C/ZnIn2S4　composite　shows　an　unprecedented　enhancement　of　photocatalytic　performance,　compared　with　that　of　pure　ZnIn2S4.　The　optimal　hydrogen　generation　rate　of　MoC-QDs/C/ZnIn2S4　is　almost　48　times　as　much　as　that　of　pure　ZnIn2S4.　Besides,　the　enhancement　mechanism　is　also　demonstrated　that　MoC-QDs/C　can　accelerate　carriers＇　separation　and　decrease　the　overpotential　of　hydrogen　evolution　effectively　during　the　photocatalytic　water　splitting　process.　Moreover,　this　study　not　only　provides　a　high-efficiency　and　potential　co-catalyst　for　photocatalytic　H2　production,　but　also　is　expected　to　come　up　with　a　new　design　scheme　for　a　transition　metal　carbide-containing　co-catalyst.　©　2018　The　Royal　Society　of　Chemistry.