Method of operation fuel cell system and fuel cell system

The feeding of oxidizing agent and fuel gas into the respective cathode (33) and anode (32), are continued for a predetermined time period, after the fuel cell and a load (306) are disconnected. The feeding of the oxidizing agent and fuel gas is stopped, so as to control the operation of the fuel cell, such that the cell voltage exceeds a threshold voltage of 0.9V for less than 10 minutes. Independent claims are also included for the following: (1) fuel cell; and (2) fuel cell system.