Synthesis, electrochemical property and photocatalytic H2 evolution of a novel binuclear complex under irradiation of visible light

Abstract

A new binuclear cobalt complex, namely [Co2(dmgH)4(μ-4,4′-bpy)Cl2](1), had been synthesized by the reaction of [Co(dmgH)(dmgH2)Cl2] with 4,4′-bipyridine(μ-4,4′-bpy) and characterized by IR, 1H 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 (λ>420nm). The maximum H2 yield of 1488.3±34.5μmol (160.0±3.7TON vs. 1) and H2 evolution rate of 744.2±17.3μmolh−1 were recorded under the optimal conditions with 1 of 3.7×10−4molL−1, EY2− of 4×10−4molL−1, TEOA of 20% (v/v) and pH 10 in 2h irradiation. Furthermore, the mechanism of H2 evolution in the homogeneous photolysis system was also briefly discussed. The electron transfer from the excited 1*EY2− to Co catalytic center of complex 1 in the designed system was also confirmed to be thermodynamically feasible.