Synthesis And Catalytic Properties Of The Modified Chitosan Metal Chelate Study

Fuel cells are considered as a 21th century's energy system due to their high efficiency and low pollution. Recently, aluminum-air fuel cell become the research project of general interest because aluminum is a kind of rich, cheap fuel and it is easy to be stored and transported. In this thesis, the present development, progress and main problems of aluminum-air fuel cells, air cathode and air cathode catalysts were shortly introduced .The synthetic conditions of PYCS, PRCS were studied, then the synthesized compounds were characterized by IR and XPS. The chelate of CoPYCS, NiPYCS, CuPYCS and CoPRCS were heat treated at different temperatures, and the effects of heat-treatment temperature on the structure of the metallic chelate were studied mainly by XPS. Catalytic activities of different catalysts were also studied mainly thorough testing the polarization curve and the discharge of air-cathode. The main results are as follows:(1)PYCS and PRCS were synthesized. In addition, the optimal conditions of condensation reaction between 2-pyridylaldehyde and chitosan were investigated and obtained by orthogonal experiments : swelling at 65℃, the molar ratio of chitosan to 2-pyridylaldehyde is 1/4, at pH 6.0, reacting 12h.(2)Metallic chelate CoPYCS, NiPYCS, CuPYCS and CoPRCS were synthesized, and the effects of the acidity and type of mediums, concentration of metallic ion and time of reaction on the ability of chelating metallic ions of PYCS resin were studied. The results indicated that: in the solvent NH₄NO₃, the chelate ability of Co(II) is the best at pH value about 6.0 and Ni(II) at about 6.5 respectively. In addition, in the solvent CH₃COOH-CH₃COONa, when pH value is about 6.5, Cu(II) also has the best chelation efficient. The obtained compounds were analyzed by IR.(3)The electrocatalytic properties of CoPYCS, NiPYCS, CuPYCS and CoPRCS for the oxygen reduction reaction were studied. Also the relationship between heat-treatment temperature and the catalytic activity were studied. It was found that the catalytic activity increased byheat-treated chelate and the catalytic activity of the CoPYCS heat-treated at 650 °C for the oxygen reduction is the highest. XPS measurements indicated that the enhanced activity is due to the existence of a CoN4 site. In addition, the catalytic activity of CoPRCS heat-treated at 900 °C for the oxygen reduction is the highest, also the XPS measurement indicated that the enhanced activity is mainly due to the existence of metallic atom clusters.