Synthesis Of Pincer Complex-bridged Porphyrin Conjugated Polymers And The Application In Electrocatalytic Water Splitting

In recent years,the excessive exploitation and utilization of fossil fuels have caused a series of problems such as environmental pollution and energy shortages.The development of clean,environmentally friendly renewable energy sources(electric energy,solar energy,wind energy,etc.)is urgently needed.Among them,the technology of catalyzing water splitting hydrogen production through electrochemical and photoelectrochemical methods has attracted extensive attention.The development of efficient and stable electrocatalysts has become the focus of attention.To this end,we designed and synthesized four porphyrin conjugated polymers formed by covalent bond bridged by pincer complexes and tested their electrocatalytic water splitting performance.The main research contents are as follows:1.On the basis of the synthesis of metal pincer complexes and metalloporphyrin molecules,we designed and synthesized four pincer complexes bridged porphyrin conjugated polymers(Cu Por-Ru N₃ CP,Cu Por-N₃ CP,H₂Por-Ru N₃ CP and H₂Por-N₃ CP).The structure of monomer molecules and the successful synthesis of the polymers were determined by characterization methods such as ultraviolet-visible spectroscopy,mass spectrometry,infrared spectroscopy(FT-IR),XPS valence band spectroscopy,thermogravimetry,and elemental analysis.2.The four polymers(Cu Por-Ru N₃ CP,Cu Por-N₃ CP,H₂Por-Ru N₃ CP and H₂Por-N₃ CP)and the monomers(Cu Por and Ru N₃)have been combined with graphene oxide and then their electrocatalytic hydrogen evolution reaction performance have been conducted in 0.5 M H₂SO₄ solution.The results show that under the same conditions,Cu Por-Ru N₃ CP exhibits the best electrocatalytic HER activity(?=76 m V at j=10 m A cm^-2).The experimental results show that Cu Por-Ru N₃ CP has a smaller Tafel slope and a larger electrochemical active area(ECSA),which indicates that it has faster kinetics and smaller charge transfer resistance during the hydrogen evolution reaction.Considering that there exists a porphyrin ring structure similar to the leaf green photosensitive component in Cu Por-Ru N₃,the photo-assisted electrocatalytic activity of Cu Por-Ru N₃ was studied.The results show that the photo-assisted electrocatalysis can further reduces the overpotential of the Cu Por-Ru N₃ for hydrogen evolution reaction.The overpotential of the Cu Por-Ru N₃ polymer at 10 m A cm^-2 current density reduced from 73 m V to 46 m V after the light source is added.Further studies have proved that the external light source can induce more electrons to flow to the Ru center,improving the electron transfer ability of Cu Por-Ru N₃ and speeding up the kinetic process to enhance its electrocatalytic HER performance,confirming that Cu Por-Ru N₃ is a good photosensitive electrocatalyst.3.In order to further expand the application of the porphyrin conjugated polymer,we conducted the electrocatalytic oxygen evolution reaction performance test in 1 M KOH after the polymer and graphene oxide were mixed.The results showed that under the same conditions,Cu Por-Ru N₃ CP showed the best electrocatalytic OER activity(j=10 m A cm^-2 at?=442m A),and the current density did not decrease significantly after 20 hours electrolysis.