Design And Study Of Nickel、cobalt And Copper Complexes With Catalytic Properties For Hydrogen Generation

As the world is facing the major challenge from climate change,in 2020,our country officially put forward the strategic goal of peak carbon emission by 2030 and carbon neutrality by 2060.Now,the most important task is to realize the low-carbon transformation of the energy system,combine the objectives of ecological and environmental protection and energy revolution environmental protection and energy revolution,and achieve high-quality coordinated development of green,low-carbon and circular development.The energy transition requires the way of power generation transform fossil fuels to renewable energy sources such as hydrogen,solar and wind and to improve energy efficiency.Hydrogen energy,as an ideal energy carrier,has the advantages of high energy density,zero pollution and zero carbon emissions,and is one of the clean energy resources to alleviate the increasingly serious energy crisis.Catalysts are key to speeding up the production of hydrogen in an electrolytic cell and the decomposition of hydrogen in a fuel cell.This paper mainly focuses on the design、synthesis and research of catalysts for hydrogen generation and hydrogen oxidation:1.Synthesis,characterization and investigation catalytic properties of planar tetra coordinated nickel complex Ni ASO 1.After design,nickel complex Ni-ASO 1 is synthesized,and its structure is determined and characterized by ¹HNMR,single crystal diffraction,X-ray photoelectron spectroscopy（XPS）,infrared spectroscopy（IR）,X-ray powder diffraction（PXRD）and UV Vis.Based on the fact that nickel complexes supported salicylaldoxime ligand are rarely used in catalytic hydrogen production,we research the electrochemical behavior of Ni-ASO 1 and find that it has electrocatalytic proton reduction performance.In phosphoric acid buffer solution（p H=7.0）,the turnover frequency（TOF）of Ni-ASO 1 reaches to 1428 H₂（mol cat）^-1h^-1 at an overpotential of 837.6 m V.In the three component heterogeneous photocatalytic system composed of CdS NRs,H₂A and complex Ni-ASO 1,Ni-ASO can provide hydrogen for 50 h,with a TON of8138 moles H₂（moles catalyst）^-1 and the average AQY was 16.5%.The study shows that the catalyst complex Ni-ASO 1 has good stability in photocatalytic hydrogen production.2.Synthesis and research catalytic hydrogen production of water-soluble tridentate cobalt complex[（btep）Co Br₂]2.The SNS type ligand and complex 2 are designed and synthesized.Its structure is determined by single crystal diffraction,ESI-MS and powder X-ray diffraction.The photocatalytic and electrocatalytic hydrogen production properties of the complex are studied.In multiphase photocatalysis（λ=469 nm）,[（btep）Co Br₂]can work for 40 h,and the TON is9326 mol H₂（mol cat）^-1.When the overpotential was 837.6 m V,the TOF of the[（btep）Co Br₂]was 591.9 mol H₂（mol cat）^-1 h^-1.The molecular orbital energy of complex[（btep）Co Br₂]2 is calculated by DFT（Density functional theory）,which can provide a theoretical basis for the photocatalytic mechanism.3.Copper complexes[Cu（btep）Br₂]3 and[Cu（btep）Cl₂]4 are synthesized and the effect of halogen anions on catalytic activity is studied.The two complexes,[Cu（btep）Br₂]3 and[Cu（btep）Cl₂]4 supported by bis（methylthioether）pyridine（btep）have been designed and synthesized in our lab.Their structures have been characterized by various tests,such as single crystal X-ray diffraction and PXRD.And the effect of two complexes on the catalytic activities for electrochemical and photochemical driven hydrogen evolution have been researched.In heterogeneous photocatalysis,[Cu（btep）Br2]and[Cu（btep）Cl2]can catalyze hydrogen evolution with a TON of 6180 and 5094 mol H2（mol cat）^-1 during 48 h photolysis.Under an overpotential（OP）of837.6 m V,[Cu（btep）Br₂]3 and[Cu（btep）Cl₂]4 can electrocatalyze hydrogen evolution from a neutral buffer water with a turnover frequency（TOF）of 351.1 mol H₂（mol cat）^-1h^-1and 120mol H₂（mol cat）^-1h^-1,respectively.Electrochemical and photochemical investigations show that introduction of Br^-exhibits a much higher catalytic efficiency for hydrogen production than introduction of Cl^-with same metal center.4.The ligand bis-（2-pyridylmethyl）-2,2’-thiodiethanethiol（bptde）、complex[Ni（bptde）（MeCN）（ClO₄）₂]5 and[Cu（bptde）（ClO₄）₂]6 are prepared the effect of catalytic activity for hydrogen evolution is studied.Under an overpotential（OP）of 837.6 m V,[Ni（bptde）（MeCN）（ClO4）2]5 and[Cu（bptde）（ClO₄）₂]6 can electrocatalyze hydrogen evolution from a neutral phosphoric buffer with a TOF of 1372 mol H₂（mol cat）^-1h^-1and 478 mol H₂（mol cat）^-1h^-1,respectively.In photocatalysis,[Ni（bptde）（MeCN）（ClO4）2]5 can continuously catalyze the reduction of water for 60 h,with TON of 19676 mol H2（mol cat）^-1,and the average AQY is 19.86%.[Cu（bptde）（ClO₄）₂]6 can catalyze hydrogen evolution with a TON of 1542 mol H₂（mol cat）^-1during 36 h irradiation,and the average AQY is 4.71%.The experimental results show that catalytic activity of the nickel complex is much better than the copper complex with the same ligand NS₃N.At the same time,this work also provides a new perspective for the study of hydrogen evolution of ternary sulfide catalysts of other non-noble metals.5.Complexes[Co（bpy）₂（SCN）₂]7 and[Ni（bpy）₂（SCN）₂]8 are synthesized,and the effect of metal centers on catalytic hydrogen production is studied.We prepare two new complexes,[Co（bpy）₂（SCN）₂]7 and[Ni（bpy）₂（SCN）₂]8 by the ligand bis（methylthioether）pyridine（btep）.[Co（bpy）₂（SCN）₂]and[Ni（bpy）₂（SCN）₂]exhibit the electrocatalytic H₂ evolution in phosphoric buffer solution（p H=7）with 699.6 and 1,469mol H₂（mol cat）^-1h^-1 at overpotential as 837.6 m V,respectively.Under a blue light,[Co（bpy）2（SCN）2]catalyze the hydrogen evolution for 30 h with a maximum TON of 10544mol H₂（mol cat）^-1.[Ni（bpy）₂（SCN）₂]can produce H₂ with a TON of 15160 mol H₂（mol cat）^-1after irradiation for 72 h.The study shows[Ni（bpy）2（SCN）2]8 exhibits more efficient than[Co（bpy）2（SCN）2]7 for light-driven hydrogen generation.6.A new catalyst for both hydrogen evolution and oxidation,based on a nickel（II）complex,[Ni-en-P₂]（ClO₄）₂ 9,is designed.The planar tetra coordination nickel（II）complex,[Ni-en-P₂]（ClO₄）₂,is designed and provided by the reaction of Ni（ClO₄）₂ with ligand N,N’-bis[o-（diphenylphosphino）benzylidene]ethylenediamine（en-P₂）.[Ni-en-P₂]（ClO₄）₂ 9 can electro-catalyze hydrogen evolution from a neutral buffer（p H 7.0）,with a turnover frequency（TOF）of 1327 mol H₂（mol cat）^-1h^-1 under an overpotential of 836.6 m V.[Ni-en-P₂]（ClO₄）₂ 9 also can electro-catalyze hydrogen oxidation with a TOF of 111.7 s^-1 with H₂atmosphere in MeCN.Electrochemical investigations show that[Ni-en-P₂]（ClO₄）₂ 9 can catalyze hydrogen evolution reaction and hydrogen oxidation reaction.It shows that more efficient nickel electrocatalyst can be developed to replace noble metals to catalyze hydrogen production and hydrogen oxidation.