Method of creating particle size distribution model, method of predicting degradation of fuel cell catalyst using the method of creating particle size distribution model, and method of controlling fuel cell using the method of predicting degradation of fuel cell catalyst

A degradation predicting method of predicting degradation of a catalyst metal of a fuel cell, comprising:

• determining a particle size range by determining a minimum particle size and a maximum particle size of a cluster of particles of the catalyst metal of which a particle size distribution is to be simulated, said cluster of particles comprising a plurality of particles of the catalyst metal;
• integrating the frequency of appearance of the particles in the determined particle size range, over an integration region defined by the minimum particle size as a starting point and the maximum particle size at an endpoint;
• dividing the integration region into a given number of regions through a first dividing operation, using the integral of the frequency of appearance, so that integrals obtained for the individual regions into which the integration region is divided are substantially equal, and determining particles sizes of division points at which the integration region is divided;
• determining the minimum particle size, the maximum particle size and the particle sizes of the respective division points, as typical points;
• obtaining a particle size distribution model by assuming a particle size distribution containing particles having the particle sizes of the respective typical points, said particle size distribution being plotted such that the frequency of appearance of the particles having the particle size of each of the typical points is equal to the integral obtained for each of the regions into which the integration region is divided at the typical points;
• and
• predicting degradation of the catalyst metal of the fuel cell, using the particle size distribution model.

A method of controlling a fuel cell, comprising:

• determining a particle size range by determining a minimum particle size and a maximum particle size of a cluster of particles of the catalyst metal of which a particle size distribution is to be simulated, said cluster of particles comprising a plurality of particles of the catalyst metal;
• integrating the frequency of appearance of the particles in the determined particle size range, over an integration region defined by the minimum particle size as a starting point and the maximum particle size as an endpoint;
• dividing the integration region into a given number of regions through a first dividing operation, using the integral of the frequency of appearance, so that integrals obtained for the individual regions into which the integration region is divided are substantially equal, and determining particles sizes of division points at which the integration region is divided;
• determining the minimum particle size, the maximum particle size and the particle sizes of the respective division points, as typical points;
• obtaining a particle size distribution model by assuming a particle size distribution containing particles having the particle sizes of the respective typical points, said particle size distribution being plotted such that the frequency of appearance of the particles having the particle size of each of the typical points is equal to the integral obtained for each of the regions into which the integration region is divided at the typical points;
• predicting degradation of the catalyst metal of the fuel cell, using the particle size distribution model;
• measuring a cell voltage of the fuel cell;
• measuring a cell resistance of the fuel cell;
• determining whether humidity control of the fuel cell is to be performed, based on a degree of the predicted degradation of the catalyst metal of the fuel cell, the measured cell voltage, and the measured cell resistance;
• and
• executing a first control mode in which control for reducing the humidity of the fuel cell is performed when the measured cell resistance is smaller than a predetermined resistance value, a second control mode in which control for increasing the humidity of the fuel cell is performed when the measured cell resistance is equal to or larger than the predetermined resistance value, and a third control mode in which control for increasing the humidity of the fuel cell is performed when it is predicted, from a result of degradation prediction of the catalyst metal of the fuel cell, that a surface area of a local portion of the fuel cell catalyst is reduced.