Study On Non-noble Metal Complexes Catalysts For Photocatalytic Hydrogen Production

Photocatalytic hydrogen production from water is a clean, environmental and recyclable energy transformation way of hydrogen production. The system produces hydrogen from water after a series of complicated reacation by the catalyst under the irradiation.Based on the literatures, 2-Pyridinethiol, 2,2′-bipyridine and 1,10-phenanthroline were used as ligand and Co, Mn and Fe were used as metal ions. Six complexes Co(bpy)(pyS)2(M1), Co(phen)(pyS)2(M2), Mn(bpy)(pyS)2(M3), Mn(phen)(pyS)2(M4), Fe(bpy)(pyS)2(M5) and Fe(phen)(pyS)2(M6) were synthesized and characterized by elemental analysis, 1H-NMR spectroscopy and electrospray ionization mass spectrometry(ESI-MS). The effects of reaction conditions on performance of catalysts were researched, the reasons of deactivation and reaction mechanism of homogeneous photocatalysis system were also studied.In this paper, the systems consisted of catalysts, electron donor and photosensitizer. The conditions of the system such as catalysts and its concentration, electron donor and its concentration, photosensitizer and its concentration, pH value of the system, solvent and its concentration, were explored and determined the optimum conditions for hydrogen production. According to experimental results, the performance of the catalysts shows M1>M2>M6> M5>M3>M4 under the same reaction conditions. The optimized conditions of M1 was catalyst=0.02 mM,fluorescein(Fl)=2.0 mM,pH=11.6,TEA(5% v/v)in CH3CH2OH/H2O(1:1 v/v). With the increase of reaction time, the performance of the catalyst showed a trend of increasing first and then decreasing under the optimum reaction conditions. The maximum hydrogen production of M1 was 261.1μmol in 25 th huors.The result of experiments found that the decomposition of complexes were the main reason which the homogeneous photocatalysis system deactivated. In another, the fluorescein was more stable and longer lifetime under irradiation when the system contained catalyst. On this basis, to study the reaction mechanism of the homogeneous photocatalytic system, M1 and M2 were chose to be experimental subject firstly. The result illustrated that it is feasible for electron transfer from the single state of fluorescein to M1 or M2 according to thermodynamics. The oxidative quenching of single state fluorescein is the dominant way of electron-transfer.