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

• A binuclear complex [Co2(dmgH)4(μ-4,4′-bpy)Cl2](1) was synthesized and characterized.
• Electrochemical property and photocatalytic H2 evolution of 1 was evaluated.
• Photolysis system composed of 1 of 3.7 × 10−4 M, EY2− of 4 × 10−4 M and TEOA of 20 vol%.
• The maximum H2 yield of 1479.9 μmol was recorded at pH10 in irradiation 2 h.
• The electron transfer from 1*EY2− to 1 was confirmed to be thermodynamically feasible.

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 > 420 nm). The maximum H2 yield of 1488.3 ± 34.5 μmol (160.0 ± 3.7 TON vs. 1) and H2 evolution rate of 744.2 ± 17.3 μmol h−1 were recorded under the optimal conditions with 1 of 3.7 × 10−4 mol L−1, EY2− of 4 × 10−4mol L−1, TEOA of 20% (v/v) and pH 10 in 2 h 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.

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