The Preparation Of Graphite Phase Carbon Nitride Composite Material And Its Electrochemical Performance

With the rapid development of the modern economy,the demand for non-renewable energy has increased sharply.The environmental issues such as energy crisis and greenhouse effect have gradually attracted people's attention,and the development of new energy and energy storage technologies is imperative.Among the existing energy storage devices,supercapacitors are considered to be the most promising energy storage devices due to their unique high electrochemical properties such as high power density,excellent coulombic efficiency and fast charge and discharge.Electrode materials are one of the main factors affecting the electrochemical performance of supercapacitors.An ideal electrode material with excellent electrochemical properties can be obtained by changing the chemical composition and microstructure of materials.Graphite phase carbon nitride?g-C₃N₄?is a two-dimensional nitrogen-containing carbon material,which has been widely used in energy storage systems such as catalysis,fuel cells,lithium ion batteries and super capacitors,due to its high density of nitrogen,chemical stability,low cost and environmental friendliness.Composite materials based on different materials can show synergistic effects in addition to their own properties,resulting in composites that exhibit superior performance over single materials.Combining g-C₃N₄ with other conductive materials can increase the reactive sites and conductivity of the composite to reveal the potential applications in the energy storage devicesIn this paper,the g-C₃N₄ composites were prepared for supercapacitor electrode materials and the electrochemical performances were investigated.The main contents are as follows:1.G-C₃N₄ nanosheets were prepared by a simple chemical oxidation method,and PEDOT:PSS@g-C₃N₄ composites were prepared by direct mixing g-C₃N₄ with PEDOT:PSS.By optimizing the mass ratio between PEDOT:PSS and g-C₃N₄,PEDOT:PSS@g-C₃N₄?1:5?electrode material with optimal electrochemical performance was obtained.The capacitance at a current density of 1 A g^-1 was 277 F g^-1,and the capacity retention after 5000 charge and discharge cycles was 94.2%.Through the nitrogen in g-C₃N₄ and the synergism between PEDOT:PSS and g-C₃N₄,the conductivity and charge transport are improved and the re-deposition of g-C₃N₄ is inhibited.Thus,the supercapacitor electrode material with excellent electrochemical performance,high coulombic efficiency,and high energy density has obtained.2.The SnS₂/g-C₃N₄ composites were prepared by in situ growth of g-C₃N₄ on SnS₂nanosheets through a simple hydrothermal method.By optimizing the mass ratio between g-C₃N₄ and SnS₂,the SnS₂/g-C₃N₄?SSCN-2?electrode material with optimal electrochemical performance was obtained.The capacitance at a current density of 0.5A g^-1 was 552 F g^-1,and the capacity retention after 15000 charge and discharge cycles was 95.8%.A symmetrical supercapacitor assembled by SSCN-2 exhibit a specific capacitance of 120 F g^-1 at a current density of 1 A g^-1,benefiting from the increased surface area and high quality heterostructure of the composites,accelerating the rate of electron transfer and electrochemical reaction.At the same time,the role of g-C₃N₄ as a support material avoids the accumulation of SnS₂ resulting in excellent cycle life.3.Based on SnO₂ has the advantages of high conductivity and wide voltage window,SnO₂/g-C₃N₄ composites were prepared by a simple hydrothermal reaction.By optimizing the mass ratio between g-C₃N₄ and SnO₂,the SnO₂/g-C₃N₄?SOCN-2?electrode material with the best electrochemical performance was obtained.The capacitance at a current density of 1 A g^-1 was 488 F g^-1,and the capacity retention after5000 charge and discharge cycles was 97.2%.A symmetric supercapacitor assembled by SOCN-2 has a capacitance value of 153 F g^-1 at a current density of 1 A g^-1.The synergistic effect between SnO₂ and g-C₃N₄ and the high-quality heterostructure enhance the electrochemical performance,while the g-C₃N₄ inhibits the stacking of SnO₂.In summery,the supercapacitor electrode material exhibits an excellent capacitance performance,high coulombic efficiency,high energy density and high cycle stability.