Synthesis, Characterization And Studies Of Nickel, Copper, Cobalt And Molybdenum Complexes With Electrocatalytic Hydrogen Evolution

With the increasing of the environment pollution and energy crisis in 21 st, the development of green and renewable energy resources has persistently attracted remarkable attentions. Compared with the traditional fossil fuels, such as petroleum, coal, and natural gas, hydrogen has emerged as a clean and sustainable fuel because its high energy capacity, less pollution and recycling. An effective route to form H2 in high efficiency has been a subject of intense study in the word.In nature, hydrogenase enzymes can efficiently catalyze proton reduction to produce hydrogen using earth-abundant metals. However, these enzymes are difficult to obtain in sufficient amounts to adapt for commercial applications and their stability is often limited outside of their native environment. These considerations have led to the development of molecular catalysts in recent years. This study tried to probe new electro-catalysts through the design and synthesis of transition metal complexes with various and novel ligands.The main works in this thesis are following:1) Four ligands, 2,3-bis(2-hydroxybenzylideneimino)-2,3-butenedinitrile(H2LA), 2-pyridylamino-N,N-bis(2-methylene-4,6-difluorophenol)(H2LB), 2-pyridylamino-N,N-bis(2-methylene-4-methoxy-6-tert-butylphenol)(H2LC) and N,N-dimethylethylenediamino-N,N-bis(2,4-difluorophenol)(H2LD) were synthesized.2) Six complexes, [NiIILA] 1,[CuIILA] 2,[CoIL’(py)3][CoIIL’2] 3, [LBMoVI(O)2] 4, [LCMoVI(O)2] 5 and [LDMoVI(O)2] 6 were prepared and characterized.3) Investigation on the electrocatalytic performance of the obtained six complexes shows that they can act catalysts for generating hydrogen from acid or water. Furthermore, the six complexes demonstrate various hydrogen evolutions capabilities in acetic acid/aqueous buffer at different p H. The turnover frequency(TOF) reaches a maximum of 574(p H = 6.0), 1258(p H = 5.0), 3855(p H = 7.0), 756(p H = 6.0), 493(p H = 7.0) and 88 h-1(DMF) for complex 1, 2, 3, 4, 5 and 6, respectively.4) The possible catalytic mechanism for hydrogen evolution was also suggested.The study results show that the transition metal ions and the donor type and electronic properties of the ligands have significantly effect on the electrochemical hydrogen production capabilities, suggesting that a good catalyst for hydrogen evolution can be prepared by the adjustment the structure and electronic properties of ligand and the matching of metal ions and ligands. In particular, metal complexes with the electron-withdrawing groups in the ligands can increase catalytic hydrogen efficiency, while the electron-donating groups in the ligands will decrease the catalytic hydrogen efficiency. The evidence of the same UV-Vis spectra obtained from the beginning and ultimate electrochemical tests and the catalytic properties at different electrochemical periods of each electro-catalyst show that the six electro-catalysts have good stability and durability.