Design,Synthesis And Photocatalytic Hydrogen Evolution Of Novel Photocatalysts Based On Co And Ni Complexes

A classical homogeneous photocatalytic hydrogen production system is typically composed of catalyst, photosensitizer and electron donor. Molecular device is a category of important compound linking photosensitizer and photocatalyst through covalent interaction, which can be used as photocatalyst to generate hydrogen under visible-light-driven. Up to now, most of the photocatalytic systems still employ noble metal(such as Pt, Pd, Ru, Rh) as catalyst or photosensitizer, and thus the study of the photocatalytic system based on non precious metal is very significant in this field.For this reason, in this paper, three molecular devices based solely on non precious metal have been systhesized by coupling cobalt complex with EY2-/ R-6G, and characterized by 1H-NMR and MS et al.. An efficient photocatalytic system was constructed for hydrogen production by using the target molecular device as photocatalyst, TEA as a sacrificial electron donor in CH3CN/H2O(v:v, 1:1). The maximum H2 evolution of 205.5±9.5μmol(for 1) was recorded under the optimal conditions with photocatalyst 1 of 4×10-4M, TEA of 25%(v/v) and pH 10.0 in CH3CN/H2O(v:v, 1:1) after 2.5h irradiation(λ>420 nm). Furthermore, the mechanism of H2 evolution in the homogeneous single-component photolysis system was also briefly discussed by fluorescence spectrum and cyclic voltammetry(CV).On the other hand, the type of nickel-sulful photocatalyst has attracted much attention in recent years because of its low cost, simple structure, good stability, and high H2 evolution activity under the visible light irradiation. However, the organic xanthene dyes is easily degraded by the light irradiation, resulting in the deactivation of photocatalytic system. Recently, water-soluble CdSe,CdTe quantum dots(QDs) as PS obtained high activity of H2 evolution.Herein, a new nickel quinolinethiolate complex and water-soluble MPA-CdSe QDs had been synthesized and characterized. For this purpose, the corresponding photocatalytic systems were constructed. Under the optimal conditions, 2105 TON H2 was observed in the first system, and in the second system a maximum hydrogen evolution of 3884 TON H2 was recorded. Furthermore, the mechanism of the first photocatalytic system was explored by fluorescence spectroscopy and CV, the results indicated that in the present system H2 production is due to the heterocoupling between Ni-H- and N-H~+.