Graphite felt has good stability, the unit cost of large surface area, good permeability of the advantages of electrode materials used in direct methanol fuel cell flow, but because of its poor hydrophilicity, electrochemical activity is not high, which greatly limits its application. Therefore, we try to improve the electrochemical properties of carbon atoms by changing the electronic structure of carbon atoms. Although the nitrogen doped graphite felt has been reported sporadically, the research on the nitrogen doped graphite felt used as the cathode of direct flow methanol fuel cell is still in the blank.

　　With the energy and environmental problems become more and more prominent, the research and development of green, pollution-free new energy has been attached great importance by the enterprises and the government. Fuel cell is a kind of clean energy which can directly convert the chemical energy into electric energy.

　　The graphite felt has the advantages of good stability, large surface area per unit cost and good fluid permeability, but its application is limited because of its poor hydrophilicity and low electrochemical activity. Therefore, it is hoped that the surface treatment can improve its electrochemical performance. Commonly used acid treatment, heat treatment, electrochemical oxidation, rare earth ion modification methods.

　　The electrode material is one of the key factors to restrict the development of the liquid flow battery. It needs to meet the requirements of high conductivity, large surface area, high selectivity to a specific reaction, good electrochemical activity, good chemical stability and so on. The main researches are metal, composite and carbon. The metal electrode has good conductivity, excellent mechanical properties, high electrochemical activity, but the stability in the anode region is poor and expensive, it is not suitable for large-scale applications; composite electrode material is a polymer and conductive carbon mixing, drying and tabletting after prepared, while improving the conductivity, oxidation but the need to overcome the polymer at high temperature; carbon electrode mainly include carbon cloth, graphite, carbon fiber and graphite felt, good stability and low cost, but the graphite, carbon fiber and carbon cloth used as electrode, a few cycles, the electrode surface is damaged, only the graphite felt electrode is the present study is more and more widely used as electrode material.

　　Polyacrylonitrile (PAN) based graphite felt , made of PAN precursor in an inert gas in high temperature and antipyretic have a variety of forms, such as continuous products, carbon fiber, short carbon fiber and short carbon fiber. It has many applications in engineering because of its excellent physical and chemical properties and electrical conductivity. Continuous carbon fibers are often used in resin matrix composites as reinforcements.

　　The most widely used short cut carbon fiber is a small amount of chopped carbon fiber mixed with concrete, forming carbon fiber concrete, which has a variety of functional characteristics such as pressure sensitivity, temperature sensitivity, thermoelectric and electrothermal effects. Based on the above features, carbon fiber reinforced concrete materials can be used in the temperature and deformation self diagnosis and adaptive aspects of concrete structures, such as intelligent deicing and snow melting system of concrete pavement [5]. But the production process of continuous carbon fiber is relatively complex, the price is higher; and the short cut carbon fiber mixed with concrete, need the chopped carbon fiber completely uniformly dispersed in the concrete, it is a big problem in materials, the functional properties of carbon fiber reinforced concrete material is affected, especially the heating effects the size based conductive network formation in carbon fiber, namely by carbon fiber components reduce the concrete resistance and Joule heat.

　　Graphite felt is a soft cloth formed by the bonding of chopped carbon fibers, and each fiber forms a conductive network with each other. In the concrete smart materials, because the carbon fiber felt easily cut into the desired shape size, sample only need to be paved in concrete.

　　PAN based graphite felt with electrothermal effect good and stable; the thermal efficiency of carbon fiber of different types are different, therefore, can choose the optimal thickness, to achieve efficient and economic purposes; in a certain temperature range, the temperature stability of PAN based graphite felt the rise and the input power is proportional to the input power can be selected according to the need the temperature rise; graphite felt with a temperature sensitive effect, linear resistivity increased with the temperature of graphite felt decreases, this effect can be used for temperature detection structure; combined with temperature sensitive effect and heating effect, is expected to realize the adaptive temperature regulating structure.

　　Ammonia decomposition produced by urea nitrogen doping on graphite felt, preparation of nitrogen doped graphite felt, compared with nitrogen doped graphite felt and graphite felt has more excellent electrochemical performance, and doping temperature and doping time have influence on the electrochemical activity of graphite felt.

　　Proton exchange membrane fuel cell (PEMFC) has many advantages, such as high power density, low working temperature, fast start and long service life, but hydrogen storage is used as fuel.

　　Graphite felt is the main cathode material of direct flow methanol fuel cell, and its performance is very important for direct flow methanol fuel cell. Graphite felt has the advantages of good stability, large surface area under unit cost, good fluid permeability, etc. but its application is limited because of its poor hydrophilicity and low electrochemical activity.

　　Commonly used acid treatment, heat treatment, electrochemical oxidation, nitrogen doping and other methods. Due to nitrogen doping not only improves the surface chemical activity of graphite felt, but also on the electronic structure of regulation, so in recent years, nitrogen doped graphite felt in many electrochemical devices exhibited electrocatalytic properties better than graphite felt no nitrogen doping of this study is based on previous achievements.

　　The ammonia produced by hydrolysis of urea by nitrogen doping treatment on graphite felt, has an important influence on the electrochemical activity of the cathode temperature,nitrogen doping does not change the crystal structure of graphite felt, but will affect the crystallite parameter.

　　there will not be much affected the overall morphology of nitrogen doped under certain conditions on the graphite felt mat, the nitrogen content of graphite are improved in nitrogen doped after nitrogen increased mainly pyrrolic nitrogen and pyridine type nitrogen, indicating the increase of no contribution even inhibit the electrochemical activity of graphite nitrogen on graphite felt, pyrrolic nitrogen and pyridine type nitrogen is the main reason to enhance the electrochemical activity of graphite felt the.

　　All vanadium redox flow battery (VRB battery, VRB) is a new type of green environmental protection battery, has the advantages of high efficiency, long service life, safe and reliable, can be used as a large energy storage device, the wind, hydro, solar and other unstable energy into electrical energy storage to be used as a backup power supply has a wide application prospect.

　　The hydrophilic and electrochemical activity of PAN based (PAN) graphite felt is poor and the graphite felt needs to be modified to be better used in vanadium battery. In order to improve the electrochemical activity of graphite felt, the two cerium oxide was modified on graphite felt by ethanol solution method and sol gel method. Two cerium oxide has the capability of storing and releasing oxygen and the diffusion capacity of fast oxygen vacancies, which is the most active catalyst in rare earth oxides.

　　Modified graphite felt, in the battery testing of the highest coulomb efficiency can reach 95%, energy efficiency is also close to 90%.Surface deposition method on the surface of graphite felt with catalytic activity of metal, is another kind of modified graphite felt. On the surface of graphite felt were introduced into manganese, cobalt and nickel three metals, and physical and electrochemical properties test of modified graphite felt. The results showed that the modified surface of graphite fiber functional changes, wettability of graphite felt, to improve its electrochemical activity. Battery test results show that the coulomb efficiency can reach 90%.

　　Graphite felt is a great ratio of carbon fiber surface area, can provide a larger electrochemical reaction for the electrochemical reaction, while the graphite felt has strong oxidation and corrosion resistance, and in addition to the conductive properties of itself, because the graphite felt electrode can be compressed, as battery assembly, contact resistance and bipolar in the small, compared with the metal electrode, the cost is relatively low, is a kind of ideal electrode material.

　　Vanadium battery as the current strong momentum of development of green energy storage battery, has broad prospects for development in large-scale energy storage. However, in the process of vanadium battery research, the research of electrode materials is one of the key constraints. The electrode material must have the characteristics of stability, performance in strong acid medium and low resistivity, good conductivity, high mechanical strength, high electrochemical activity, and electrode materials at present is not up to the above requirements, can not meet the actual needs of the long-term work of vanadium battery.

　　Carbon materials due to its good conductivity and corrosion resistance, many researchers of various carbon materials by charge discharge experiments in vanadium electrolyte, found that graphite rods, graphite plate as cathode in the etching phenomenon, glassy carbon material surface electrochemical irreversibility, polyacrylonitrile based graphite felt the best performance. Through the experiment, it is very important to the polyacrylonitrile based graphite felt electrode surface modification.

　　Polyacrylonitrile based carbon fiber with high strength, high modulus, high temperature resistance, corrosion resistance, fatigue resistance, low coefficient of a series of excellent creep resistance, electrical conductivity, heat transfer and thermal expansion.

　　At present, the domestic market is not on the sale of carbon felt carbon felt, because the main use is as a thermal insulation material. The raw materials of PAN based carbon fiber carbon fiber is non graphitic structure, carbon content more than 90%, the carbon fiber in 10m.Cm resistivity magnitude, the resistivity is relatively large, and the carbon fiber surface energy is low, and the water wettability, contact angle, surface is hydrophobic, and without any the carbon fiber is not suitable for vanadium battery electrode.

　　Processing time should not be more than 2 hours, and the electrochemical activity of graphite felt will decrease with the increase of treatment time in the process of acid treatment of graphite felt.