A　cobalt-based　polyoxometalate,　Na7H10[Co-6(H2O)(2)(PW9O34)(2)(PW6O26)]center　dot　30H(2)O,　was　synthesized　by　a　simple　aqueous　solution　method.　It　showed　catalytic　activity　for　the　visible-light-driven　H-2　evolution　from　water　splitting　with　eosin　Y　as　the　photosensitizer　and　triethanolamine　as　the　electron　donor.　The　initial　rate　of　the　H-2　evolution　was　141　mu　mol　h(-1),　which　was　higher　than　that　of　Co2+　cations　(55　mu　mol　h(-1)).　The　efficient　catalytic　activity　was　attributed　to　that　the　[B-PW9O34](9-)　units　in　the　sample　act　as　electron　transmitters　to　accelerate　charge　transfer.　Moreover,　a　possible　mechanism　was　proposed　to　explain　the　H-2　evolution　from　water　splitting　in　the　present　system.　(C)　2015　Elsevier　B.V.　All　rights　reserved.