Preparation Of Graphene Composite Materials And Study Of Their Electrochemical Propertie

Graphene is an ideal substrate,often used for the growth of functional nanomaterials.In recent years,nanocomposites made of graphene（G）and transition metal oxides have attracted extensive attention in various fields due to their synergistic effects.Metal oxides can prevent graphene stacking and increase the surface area,which helps to form metal oxide nanostructures with uniformly dispersed and controllable morphology,and suppresses the structural changes and agglomeration of metal oxides.The oxygen-containing groups in graphene will ensure good electrical contact,interfacial interaction and bonding between graphene and metal oxides,shortening the ion diffusion path.The combination of the two can promote each other,learn from each other,and synergize.This work mainly prepares graphene composites and studies their applications in electrochemistry.（1）Graphene and alkylthiol-coated ruthenium composite nanoparticles（Ru@G,Ru@HT,Ru@DT,and Ru@OT）with different chain lengths were synthesized by reduction reaction,and were characterized by various physical properties.It is confirmed that their cores are Ru0 cores in the metallic state,and the periphery is coated with graphene and alkylthiols of different chain lengths.These nanoparticles are 2-5 nm in size and have good dispersibility.These nanoparticles were decorated on electrodes,and their electrochemical capacitive behaviors were explored by electrochemical methods,including cyclic voltammetry,galvanostatic charge-discharge,and electrochemical impedance spectroscopy.Due to the synergistic effect,Ru@G exhibits excellent supercapacitor behavior and electrochemical stability,with a specific capacitance of 1013 F·g^-1 at 0.004 V·s^-1 and a capacitance retention rate after 10,000 cycles94.9%,much higher than other Ru@thiol nanoparticles.（2）Polyvinylpyrrolidone（PVP）and graphene（G）modified iron oxide（Fe₂O₃）nanoparticles（Fe₂O₃-PVP-G）were prepared by hydrothermal method.The Fe₂O₃-PVP-G nanoparticles are uniformly distributed and the inner core is an elliptical Fe₂O₃-like structure.The electrocatalytic behavior of this nanomaterial towards p-nitrophenol（p-NP）was explored by electrochemical methods linear voltammetry（LSV）and electrochemical impedance spectroscopy（EIS）.The advantage of Fe₂O₃-PVP-G electrode is that the oxygen evolution reaction（OER）catalytic activity of Fe₂O₃ is preserved,and the doped hydrophilic groups can be enriched on the electrode surface.Compared with pure Fe₂O₃,Fe₂O₃-PVP-G has a smaller band gap and induced crystal planes.In the experiment,Fe₂O₃-PVP-G exhibited a higher p-NP oxidation current density,which was 10.4 times that of Fe₂O₃ at 1μM.The p H test showed that p-NP was oxidized to fatty acid,which is non-toxic and environmentally friendly.Due to the protection of PVP and G,Fe₂O₃-PVP-G has high catalytic stability,and the current retention rate reaches 88.5%after 15 days.（3）Iron phosphate（FePO₄）and iron phosphate composite graphene nanoparticles（FePO₄-G）were synthesized by a hydrothermal method,and characterized by various methods to confirm that they are well-dispersed nanoparticles with FePO₄ cores,and the FePO₄ core is coated with graphene.These nanoparticles were decorated on electrodes,and their electrochemical behaviors were explored by electrochemical methods,including cyclic voltammetry,galvanostatic charge-discharge,and electrochemical impedance spectroscopy.FePO₄-G-3 exhibits excellent supercapacitor behavior and electrochemical stability,with a specific capacitance of 271.3 F·g^-1 at 0.01 V·s^-1 and a capacitance retention of 99.23%after3000 cycles,which is far higher than other FePO₄-G nanoparticles.