A new binuclear cobalt complex, namely [Co-2(dmgH)4(mu-4,4 '-bpy)Cl-2](1), had been synthesized by the reaction of [Co(dmgH)(dmgH(2))Cl-2] with 4,4 '-bipyridine(mu-4,4 '-bpy) and characterized by IR, H-1 NMR, CV. An efficient homogeneous photocatalytic system was constructed by combination of noble-metal-free cobalt complex as catalyst, Eosin Y dye (EY2-) as photosensitizer and TEOA as sacrificial reagent under visible-light irradiation (lambda > 420 nm). The maximum H-2 yield of 1488.3 +/- 34.5 mu mol (160.0 +/- 3.7 TON vs. 1) and h(2) evolution rate of 744.2 +/- 17.3 mu mol h(-1) were recorded under the optimal conditions with 1 of 3.7 x 10(-4) mol L-1, EY2- of 4 x 10(-4)mol L-1, TEOA of 20% (v/v) and pH 10 in 2 h irradiation. Furthermore, the mechanism of H-2 evolution in the homogeneous photolysis system was also briefly discussed. The electron transfer from the excited (l)*EY2- to Co catalytic center of complex 1 in the designed system was also confirmed to be thermodynamically feasible. (C) 2014 Elsevier Ltd. All rights reserved.