Abstract
This paper reports about the results of our analysis concerning the problem of a decline in the electricity generation performance of the fuel cell, resulting from the use of hydrogen fuel containing impurities in fuel cell vehicles. The specific details of our investigation were as follows.
1) Analytic methods that utilize poisoning estimation coefficients and poisoning prediction formulas were proposed.
2) The development mechanism of CO poisoning in the fuel cell were analyzed.
3) The dependency of CO poisoning on mixed CO concentration, operating pressure and operation temperature were investigated.
The results obtained from this research can be summarized as follows. a) A poisoning estimation formula has been proposed that focus attention on adsorption of CO onto the catalyst electrode and oxidation dissociation. The proposed estimation formula can estimate electricity generation performance, when the concentrations of impurities mixed within fuel are changed discretionarily under constant operating temperature conditions. This formula was applied to analysis once its validity had been clearly shown through comparison with experimental results. b) A poisoning coefficient concept was proposed that allows quantitative comparison of the degree of poisoning under fixed operating temperature conditions when various gases with impurities and various catalyst electrodes are utilized, and was then applied to our analysis. c) At times when a high concentration of CO is mixed within the fuel, it is now clearly evident that there is no significant increase in performance caused by an increase in operating pressure, regardless of whether the Pt Catalyst or the Pt-Ru Catalyst is used. This is presumed to be a result of the fact that when the pressure is increased, the electron dissociative reaction is encouraged, but simultaneously the amount of CO adsorbed onto the electrode of the catalyst also rises. d) It has been made transparent that increasing the operating temperature can significantly reduce the CO poisoning problem. Further, the poisoning reduction effect achieved when utilizing the Pt-Ru Catalyst, not only comes into effect when operating at normal temperature ranges, but is also effective at times of low temperature.