Study On Covalent Strategy Heterogeneous Molecular Catalysts And Their Photocatalytic Hydrogen Production Performance

With the rapid development of the global economy,people’s demand for energy is increasing.However,the massive consumption of fossil fuels has caused energy shortages and the greenhouse effect,seriously affecting the sustainable development of human society.The development of clean and renewable energy is the ideal way to solve the current energy crisis and environmental hazards.Among these,the photocatalytic splitting of water to produce hydrogen energy has attracted considerable attention,which can directly convert the inexhaustible solar energy on Earth into storable chemical energy under the action of catalysts,providing an effective strategy for solving energy and environmental problems.The photocatalysts are the most critical part of this,as they require a wide absorption range,high charge separation efficiency,long term stability and strong redox capability to meet the requirements of photocatalytic applications.Therefore,designing and synthesizing efficient photocatalysts is the key to realizing solar to hydrogen energy.In this work,two polymeric materials based on heterogeneous metal complexes were designed and synthesized,their structure and morphology were characterized,the photocatalytic hydrogen-producing performance of the polymer investigated,and the catalytic mechanism speculated by experiment.The specific content of the research is divided into two parts,as follows:（1）Ruthenium organic polymers（Ru-P）were synthesized by polymerizing phenanthroline ruthenium complexes with 4,4’-diethynylbiphenyl via Sonogashira Coupling and used in photocatalytic decomposition of water reactions.The structure,morphology and optical properties of the polymer were characterized using X-ray diffraction,Ultra-high resolution field emission scanning electron microscopy,Fourier infrared,Raman spectroscopy and other tests.Photocatalytic experiments showed that the photocatalytic decomposition of Ru-P in CH₃CN/H₂O（v:v=4:1）mixture resulted in an aquatic hydrogen production rate of 411μmol·g^-1·h^-1.Further in situ photo-deposition of 3 wt%Pt in the reaction system to form Ru-P/Pt composites increased the hydrogen production rate to 1259μmol·g^-1·h^-1.The result of photoelectrochemical experimental results showed that Ru-P/Pt had a greater photocurrent density and lower impedance compared to Ru-P,and thus exhibited better charge separation efficiency,resulting in a significant increase in photocatalytic decomposition of aquatic hydrogen activity.（2）Two metal-organic polymers,Co-Salen-P and Fe-Salen-P,were synthesized by polymerizing Salen-type metal complexes with 1,3,6,8-tetraynylpyrene through a Sonogashira Coupling and used in the photocatalytic decomposition of water reactions.The structure,morphology and optical properties of the polymers were characterized using X-ray diffraction,Ultra-high resolution field emission scanning electron microscopy,Fourier infrared and transient fluorescence tests.The results of photocatalytic experiments showed that the two metal-organic polymers have good photocatalytic hydrogen production performance,with a rate of 492μmol·g^-1·h^-1 for Co-Salen-P within 5 h of light exposure,which is higher than that of Fe-Salen-P(50μmol·g^-1·h^-1).The photochemical experiments showed that the Co-Salen-P catalyst had more pronounced fluorescence burst,stronger photocurrent response,smaller impedance,longer fluorescence lifetime and therefore better photogenerated electron-hole separation efficiency compared to Fe-Salen-P,thus significantly improving the photocatalytic decomposition of aquatic hydrogen activity.