Photoinduced Hydrogen Production With Dye Sensitized Semiconductor Systems Based On Cobalt Molecular Catalysts

In this paper, four cobalt complexes were synthesized and used as hydrogen-evolving molecular catalysts in non-precious photocatalytic H2 production systems with semiconductor as catalyst, Organic dyes as the photosensitizers, and triethylamine(TEA) as electron donor sacrificial agent. The main results are as follows:1. Four cobalt complexes [Co(phen)2(L)](abbreviated as Co L1-Co L4) were synthesized by using Co Cl2·6H2O, salicylic acid and 1,10-phenanthroline as the starting materials, and characterized by elemental analysis, IR and 1H NMR spectra.2. The above-mentioned four cobalt complexes were loaded onto Titania surface to obtain catalysts Co L/Ti O2. The hydrogen production performances were studied under visible light irradiation by using xanthene organic dyes as photosensitizer and triethylamine(TEA) as electron donor. The results showed that Co L2 was the most effective cocatalyst, and the maximum amount of hydrogen evolved for 50 mg 2wt%Co L2/Ti O2 achieved to 91 μmol within 6h under the optimal conditions of 4 μmol EY2-(alcohol-soluble), 5%(v/v) TEA and p H 11.0. In addition, the possible deactivation reason of the system was ascribed to the photolysis of sensitizer and desorption of Co L from Ti O2 surface.3. The above-mentioned four cobalt complexes were loaded onto g-C3N4 surface as hydrogen-evolving molecular catalysts. Similarly, the hydrogen production performances were also studied under visible light irradiation by using EY2-(alcohol-soluble) as photosensitizer and triethylamine(TEA) as sacrificial agent. It had been found that Co L3 was the most effective cocatalyst, and the maximum amount of hydrogen produced for 50 mg 2wt%Co L3/g-C3N4 was 72 μmol within 2.5h under the optimal conditions of 6 μmol EY2-, 7.5%(v/v) TEA and p H 11.0. The possible deactivation reason was attributed to the phtodegradation of sensitizer and partical desorption of Co L from g-C3N4 surface.