Catalytic Hydrogen Production Using A Cobalt Catalyst Bearing A Phosphinoamine Ligand

The use of clean energy to replace traditional fossil energy is a major problem that needs to be solved to achieve sustainable development of human society.Hydrogen is an ideal energy carrier,and the product of combustion is water without pollution.Plants split water into oxygen(O2)by photosynthesis under mild conditions,while releasing protons(H+)and electrons(e').Less bacteria and green algae use their own hydrogenase protein to rapidly couple H+ and electron e-into H2 for their own metabolism.Artificially simulating photosynthesis in nature decomposing water into H2 and O2 directly,which is considered to be one of the effective ways to achieve hydrogen energy utilization.Precious metal catalysts(platinum,rhodium)exhibit very high activity in photocatalytic hydrogen production,but their high cost and lack of reserves limit the practical application.The metal cobalt complex has good catalytic hydrogen production activity,and the development of stable metal cobalt catalyst for high-efficiency hydrogen production reaction has been a research hotspot in this field.In order to simulate the synergistic effect of hydrogenase-catalyzed"rmetal-ligand"in proton reduction,this paper introduces N or O atoms in the inner coordination layer of pentamethylcyclopentadiene cobalt complex as basic site binding/transfer Protons,synergistic metal centers to catalyze proton reduction to produce hydrogen.Using the synthesized metal cobalt complex as catalyst,we investigated its hydrogen production activity under electrocatalytic and photocatalytic conditions and developed a photocatalytic reduction hydrogenation reduction reaction of styrene compounds.The photoinduced electron transfer process mechanism between the semiconductor and the catalyst,the specific results are as follows:1.Two metal pentamethylcyclopentadienyl cobalt complexes Cp*Co(1,2-Ph2PC6H4NH2)Cl(1)and Cp*Co(1,2-Ph2PC6H4NMe2)Cl(2)were synthesized with the 1,2-Ph2PC6H4NH2 and 1,2-Ph2PC6H4N(Me)2 ligands.Complexes were characterized by nuclear magnetic resonance,mass spectrometry and X-ray single crystal diffraction.The electrochemical activity and stability of the complexes were investigated by cyclic voltammetry.The results show that the TOF of 1 catalytic proton reduction is 924 s-1 and the complex 2 is 505 s-1 under electrocatalytic conditions.2.The photocatalytic hydrogen production performance of complexes 1 and 2 was studied under the condition of visible light irradiation with CdSe quantum dots as sensitizer.Photoelectric test results demonstrate a rapid electron transfer process between the quantum dots and the catalyst.It was found that the photon-catalyzed TON number of hydrogen production of catalyst 1 reached 10,000(quantum yield?55.51%);the TON number of hydrogen production of catalyst 2 was about 6000.The synthesized complex is used as a cocatalyst in the photocatalytic system.The difference in activity between the complexes 1 and 2 in the photocatalytic system indicates that NH2 is more suitable as a basic site than the NMe2 group.Participate in the reduction reaction of protons.3.Based on the established photocatalytic hydrogen production system,a hydrogenation reduction system of photocatalytic styrene compounds based on complex 1 was developed.The Ru(bpy)32+was used as the sensitizer and the ascorbic acid was used as the electron sacrificial.Under the visible light irradiation,the hydrogenation reduction product of the styrene compound was obtained,yield:70%.