Study Of Based Nitrogen Doped Carbon Materials’ Electrochemical Properties

According to the full development of the society in recent years, a severe shortage of fossil energy has been in our country, due to the advantages of low cost, high specific energy, high power density, long cycle life, a wide range of application, supercapacitors and fuel cells have get the keen attention of research workers. Electrocatalyst occupies a decisive position in the anodic reaction of supercapacitors and the cathode reaction- oxygen reduction reaction(ORR) of fuel cells. To date, platinum and its alloys are the most effective ORR catalysts, whereas, the disadvantages of high cost, crossover effect and poor durability seriously limit their widespread commercialization. Hence, searching for nonprecious-metal and even metal-free catalysts with comparable or superior catalytic performance and commercial availability has attracted considerate attention from both industrial and academic researchers. In recent years, due to their high electrical conductivity, low cost and long cycling life, carbon materials have become the research topic as an alternative electric catalyst to Pt and its alloy. For example, graphene nanosheets(GNS) and carbon nanotubes(CNTs) have shown the bright future in supercapacitors, fuel cells and chemo/biosensing. The main contents of this paper are as follows:(1) Using graphene oxide(GO), oxidized multiwalled carbon nanotubes(O-CNTs) and ammonia as precursors, obtained nitrogen- doped grapheme /carbon nanotube nanocomposites(N-GOx@CNTy) by a hydrothermal process at a low temperature(180 °C). The micrograph and composition of N-GOx@CNTy nanocomposites characterized by scanning electron microscopy(SEM) and X-ray diffraction(XRD), fourier transform infrared spectroscopy(FTIR) and Raman spectroscopy respectively. And its super-capacitive properties under alkaline condition were tested by cyclic voltammetry(CV) and galvanostatic charge/discharge(GCD). The results showed that: The hydrothermal method has not destroyed the structure of carbon nanotubes and graphene, and successfully synthesized nitrogen doped graphene-carbon nanotube nanocomposites with well dispersed. Catalyst N-GO1@CNTs2 shows the best of supercapacitor, and the performance is dozens of times higher than that of untreated carbon nanotubes and graphene.(2) Using multiwalled carbon nanotubes(CNTs) dopamine and Tris-(hydroxymethyl)-aminomethane as precursors, obtained nitrogendoped carbon nanotubes(N-CNTs) by the heat treatment method of high temperature. The micrograph and composition of N-CNTs characterized by scanning electron microscopy(SEM) 、 transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS) respectively. And the performance of oxygen reduction under alkaline condition were tested by cyclic voltammetry(CV) 、 rotating disk electrode(RDE) and rotating ring disk electrode(RRDE). The results showed that: The method of heat treatment has not destroyed the structure of carbon nanotubes, and successfully synthesized nitrogen doped carbon nanotubes with well dispersed. It had successfully coated with a layer of thin film in the surface of carbon nanotubes, which had well solved the difficult problems of poor dispersion of carbon nanotubes. It has been verified that the 900 ℃and the dopamine concentration of 2 mg/mL is the best heat treatment temperature and the best concentration of coating; And the sample 2 mg/mL N-CNTs-900 showed a process close to 4etransfer, good stability and a good resistance to methanol oxidation. This all explained that the sample 2 mg/mL N-CNTs-900 has a good performance for oxygen reduction.(3) Using multiwalled carbon nanotubes(CNTs) 、 dopamine 、anhydrous ferric chloride(FeCl3) and Tris-(hydroxymethyl)-aminomethane as precursors, obtained nitrogen-doped carbon quantum dots(N-CQDs) by the heat treatment method of high temperature. The micrograph and composition of N-CNTs characterized by scanning electron microscopy(SEM)、transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy(XPS) respectively. The reaction mechanism of anhydrous ferric chloride and carbon nanotubes was analysis by TGA test. And the performance of oxygen reduction under alkaline condition were tested by cyclic voltammetry(CV) 、rotating disk electrode(RDE) and rotating ring disk electrode(RRDE). The results showed that: The method of heat treatment has successfully synthesized nitrogen doped carbon quantum dots. When the quality ratio of the anhydrous ferric chloride and the carbon nanotubes is to 2:1, the sample N-CQDs showed the best performance for oxygen reduction. And the sample N-CQDs showed a process close to 4e- transfer, good stability and a good resistance to methanol oxidation. This all explained that the sample N-CQDs has a comparable performance to Pt/C for oxygen reduction.