Preparation And Electrochemical Performance Of Chromium Nitride Nanomaterials

The super capacitor（SC_S）has the ability of fast charge/discharge,high output power and long cycle stability.It has a wide application prospect in the field of energy storage.However,the inherent low energy density of SC_S is difficult to meet the growing operation demand of various electronic products,which seriously hinders its application.In recent years,researchers have been devoted to the development of super capacitors with high energy density,mainly focusing on the optimization of the morphology and structure of electrode materials,the improvement of specific surface area and the selection of appropriate electrolytes.In this paper,the precursor of nano-sized chromium oxide（Cr₂O₃）was prepared by hydrothermal method,and the influence of hydrothermal conditions on the morphology and structure of nano-sized Cr₂O₃ was studied;the electrode material of nano-sized chromium nitride（CrN）was prepared by nitriding nano-sized Cr₂O₃ in ammonia gas,and the influence of morphology and electrolyte on its electrochemical performance was studied.The main research contents and results are as follows:（1）The influence of hydrothermal conditions（pH,temperature and time）on the phase and morphology of Cr₂O₃ was studied.The results showed that Cr₂O₃ nanoparticles with a size of about 50 nm were prepared under the conditions of pH 9,hydrothermal temperature 170℃and hydrothermal time 3 h.（2）Nano CrN electrode material was prepared by using granular nano Cr₂O₃ as precursor.The effects of nitriding temperature and time on the morphology and structure of CrN were studied,and the capacitance and electrochemical properties of CrN were investigated.The results show that the empty shell granular CrN is prepared at the nitriding temperature of 750℃and the nitriding time of 5 h.It is found that the specific capacitance increases first and then decreases with the increase of nitriding time.The electrochemical performance test showed that the electrode material of CrN（including Cr₂O₃ without nitriding）had the highest specific capacitance of 333.2 F/g（10mV/s）,and remained 84.7%of the initial capacitance after 5000charge discharge cycles.（3）The effects of aqueous electrolytes H₂SO₄,Na₂SO₄ and KOH on the electrochemical properties of CrN were studied.The results show that the voltage window is-0.2v-0.8v in acid and neutral electrolytes（1mol/L H₂SO₄,1mol/L Na₂SO₄）and-0.9v-0.1v in alkaline electrolytes（1mol/L KOH）.The electrochemical performance test results show that the maximum specific capacitance is 142.9 F/g in alkaline electrolytes,but only 72.4 F/g and 92.5F/g（10mV/s）in neutral and acid electrolytes.（4）Cr₂O₃（nano flake,porous sphere and layer）with different morphology was used as precursor to prepare nano flake,porous sphere and layer with precursor morphology.The effect of morphology on the electrochemical performance of porous spherical CrN was studied in alkaline electrolyte.The results show that the highest specific capacitance of porous spherical CrN is 213.2 F/g,and the specific capacitance of nano flake and layered CrN are82.4 F/g and 126.7 F/g（10mV/s）,respectively.In this paper,nano CrN with special morphology was successfully prepared by gas-solid reaction method,which has excellent electrochemical performance.The specific capacitance of nano CrN（including Cr₂O₃ without nitriding）obtained after nitriding for 2h is higher than that of pure Cr₂O₃ and CrN,which provides experimental basis for the application of transition metal CrN in super capacitor.