Synthesis of Polyaniline/C Supported Iron in Chemical Oxidative Polymerization for PEMFC Cathode Catalyst

• Main Author: Vuri Ayu Setyowati
• Other Authors: Wang-Chen Hao
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/23028212132564657505

碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 103 === The non-precious metal catalyst (NPMC) by using transition metal with nitrogen-doped carbon material shows the good activity of oxygen reduction reaction (ORR), which has the opportunity to replace the high-cost platinum catalyst in the proton exchange membrane fuel cell (PEMFC) in the recent studies. In this study, aniline hydrochloride was used asnitrogen source and XC72 was used as carbon support source during polymerization. During sample preparation, catalysts were pyrolyzed by different temperature for getting activity recovery. The highest ORR activity was obtained by pyrolysis at 700 oC. Furthermore, we have to consider the optimum amount of nitrogen and carbon supported catalyst The electrochemical method was used most of the time for analysis in order to determine the catalytic activity of ORR. In addition, some physical analysis techniques were used to identify the catalyst behavior. Some physical analysis such as SEM, XRD, Raman, XPS, XAS, FTIR were used to identify the catalyst behavior. Surface morphology information of catalysts were obtained by Field Emission Scanning Electron Microscope (FE-SEM). The crystalline peaks of various catalysts were determined by XRD. Thermal analysis such as Thermogravimetric Analysis (TGA) was employed for non-precious metal catalyst (NPMC). XPS also was used to determine the elemental percentages and identify the presence of N functional groups. Fourier transform infrared spectroscopy (FTIR) was used to identify the organic bonding of nitrogen and carbon The changing of iron coordination symmetry could be detected by variation pre-edge intensity based on XANES curves and the result confirms that iron oxidation states remain as Fe3+ after pyrolysis. Generally, Fe-PANI/C catalyst had good ability to be applied as cathode catalyst but particularly, the selected catalyst was shown the best properties for being catalyst and included the suitable parameter to synthesize material catalyst. 1:1 ratio of aniline and XC72 was used for the preparation of Fe-PANI/C catalyst and the Fe content was fixed to 7 wt.% for the preparation of Fe-N-C catalyst. The electrochemical analysis shows that FeCl3.6H2O mixed with polyaniline are the preferred iron precursor (FeCl3.6H2O-PANI/C) to get higher ORR activity than the others, which its electron-transfer number is around 3.99. The Raman spectrum of FeCl3.6H2O-PANI/C shows the ratio of G-band and D band (IG/ID) corresponding to the degree of graphitization. The low IG/ID on Raman spectra is caused by high nitrogen functionalities content. The percentage composition between C/N/Fe was determined by XPS spectra, showing the higher percentage composition of N element in FeCl3.6H2O-PANI/C. The N composition was made of pyrrolic N, cyanide, and quaternary N. The major N composition of FeCl3.6H2O-PANI/C is quaternary N about 57.73%. The XANES spectra of FeCl3.6H2O-PANI/C show that the oxidation state of central Fe is 3+ and the changing of coordination structure occur after pyrolysis. The stability tests of FeCl3.6H2O-PANI/C shows only 50 mV decay after 30000 cycle times. This result confirms that FeCl3.6H2O-PANI/C catalyst is applicable for cathode catalyst fuel cell.