| In recent years,supercapacitors have been designed as a new type of energy storage device because of their high power density,fast charge and discharge,and excellent cycle life.Among them,Mn O2as a transition metal member has received more and more attention in the field of supercapacitors because of its abundant resource reserves,excellent theoretical specific capacitance(～1370 F?g-1),low price,and simple preparation methods.However,its low conductivity is about 10-5S?cm-1to10-6S?cm-1,which results in slow transmission of electrons and ions at the electrode and electrode electrolyte interface,which limits the wide application of Mn O2in the field of supercapacitors.Therefore,in this paper,three-dimensional porous graphite felt（GF）with low cost,stable chemical properties and good conductivity is used as the base material for the composite electrode.A seed-assisted method is used to induce the generation of strong and highly conductive one-dimensional titanium compound nano-skeleton array on GF,thereby increasing the accessibility of electrolyte and the speed of electron and ion diffusion and transportation.Then combined with Mn O2,the resulting composite electrode exhibits good energy storage characteristics and cycle stability.The preparation of the samples in this paper is as follows:First,GF is cut into 1cm×1 cm GF sheet as the substrate,and the impurities are removed by ultrasonic cleaning in a solution containing ethanol,acetone and deionized（DI）water.An aqueous solution containing 1.10 m L of titanium tetrachloride（Ti Cl4）and 48.90 m L of hydrochloric acid（HCl）was mixed with the GF sheet for 30 minutes to form titanium dioxide（Ti O2）seeds on the GF to generate seed graphite felt（SGF）.Then,a hydrothermal synthesis method is used to induce the one-dimensional Ti O2nanoarray on the surface of the SGF,and then a tube furnace high temperature urea-assisted nitridation is used to convert the Ti O2into titanium nitride（Ti N）.Finally,Ti O2/SGF and Ti N/SGF were immersed in a mixed solution consisting of 0.04 mol?L-1potassium permanganate（KMn O4）and 0.01 mol?L-1manganese sulfate（Mn SO4）,and heated at140°C for 12 hours.The Mn O2/Ti O2/SGF and Mn O2/Ti N/SGF composite electrode was finally prepared.In order to prove the successful preparation of MnO2/Ti N/SGF composite electrode.First,it was proved by field emission scanning electron microscope indicating that Ti O2seeds were formed on GF.Then,Raman and XRD were used to prove the formation of Ti O2,Ti N and Mn O2.Then the composite electrode material was further characterized by BET test.Finally,HR-TEM,SAED and XPS were used to study the crystal form of composite electrode materials.The prepared GF,Mn O2/GF,Ti O2/SGF,Ti N/SGF,Mn O2/Ti O2/SGF and Mn O2/Ti N/SGF electrodes were placed in 1 mol?L-1Na2SO4aqueous solution,respectively,and after a series of electrochemical,it was found that Mn O2/Ti N/SGF electrode has the best supercapacitor performance.The direct connection between Mn O2and titanide and titanide and SGF does not require adhesives,which effectively reduces the contact resistance between materials.The long tapered titanide nano-skeleton array with high conductivity provides high-speed transmission channels for electrons and ions,and has Good electrolyte accessibility.The Mn O2/Ti N/SGF electrode has a high specific capacity of 425.5 F?g-1during the test.In addition,the high-expansion coefficient Mn O2crystal and the low-expansion coefficient rigid titanide crystal form a benign synergy,so that the composite electrode material will not collapse due to the fragmentation of the local material in the long-term charge and discharge test,and the cycle performance of the electrode will increase.The specific capacity of the Mn O2/Ti N/SGF electrode is basically unchanged after 10,000 charge-discharge tests.These results undoubtedly show that the prepared Mn O2/Ti N/SGF composite electrode is an outstanding candidate for high-performance MnO2 supercapacitor. |
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