A method for recovering performance of a fuel cell stack includes 1) a first pulse operation process including i) generating a hydrogen pumping reaction in a cathode by applying a current to the cathode after a supply of air to the cathode stops and ii) maintaining an OCV (open circuit voltage) by again supplying air to the cathode after the hydrogen pumping is performed, 2) a pole substitution process of substituting a pole of the fuel cell stack, and 3) a second pulse operation process including iii) generating the hydrogen pumping reaction in the cathode after the pole substitution, and iv) maintaining the OCV (open circuit voltage) by supplying air to the cathode after the pole substitution after the hydrogen pumping is performed.

A fuel cell system according to one embodiment performs refresh control of an electrode catalyst of a fuel cell, by reducing a stack voltage as a voltage of the fuel cell to a refresh voltage at which the electrode catalyst is activated. The system includes the fuel cell that generates electric power by an electrochemical reaction using fuel gas and oxidation gas, a stack voltage sensor that sensors the stack voltage, and a controller that controls power of the fuel cell. When a high load demand that makes the stack voltage lower than a given voltage is made on the fuel cell, the controller causes the fuel cell to deliver power commensurate with the high load demand, and performs refresh control when the stack voltage becomes lower than the given voltage through the above control.

A fuel cell system of the present disclosure performs a first and a second catalyst activation process, and the first catalyst activation process is performed where a flow rate of the air supplied to the fuel cell by the air compressor is reduced to be less than that before the refresh control is performed while keeping an amount of a current drawn from the fuel cell by the fuel cell converter at the same value as that before the refresh control is performed, and the second catalyst activation process is performed where the value of the current drawn from the fuel cell by the fuel cell converter is increased to be greater than that before the refresh control is performed while keeping the flow rate of the air supplied to the fuel cell by the air compressor at the same value as that before the refresh control is performed.

Disclosed is a stack for simulating a cell voltage reversal behavior in a fuel cell. The stack is configured to have a structure in which a separator of a portion of a plurality of cells in the stack have an inlet of a hydrogen flow field partially blocked to induce hydrogen starvation only in the portion of the plurality of cells.

An automated method or procedure for detecting a permeability state of a membrane of a fuel cell stack is provided. The procedure is sensitive enough to detect a defective membrane, and is accurate enough to enable correct maintenance of the fuel cell stack. The fuel cell stack is formed of a stack of electrochemical cells each having an anode and a cathode sandwiching a polymeric ion-exchange membrane therebetween. The fuel cell stack includes a fuel gas supply system on the anode side of the electrochemical cells, and includes an oxidant gas supply system on the cathode side of the electrochemical cells.

A fuel cell system is disclosed. The fuel cell system has at least one fuel cell stack which is arranged in a housing. The housing has at least one ventilation connection to the surroundings or to another volume. The ventilation connection has a valve device.

The following disclosure relates to methods of identifying defects (e.g., short circuits) in a membrane of an electrolytic cell. The following disclosure further relates to methods of repairing such a defect in the membrane of the electrolytic cell, particularly without having to disassemble the membrane from adjacent components of the electrolytic cell.

Disclosed is a stack for simulating a cell voltage reversal behavior in a fuel cell. The stack is configured to have a structure in which a separator of a portion of a plurality of cells in the stack have an inlet of a hydrogen flow field partially blocked to induce hydrogen starvation only in the portion of the plurality of cells.

System and methods for reducing carbon corrosion in a fuel cell system are presented. Particularly, the disclosed systems and methods may be utilized in connection with preventing the formation of a propagating H.sub.2-Air interface within the fuel cell system. In certain embodiments, the disclosed systems and methods may utilize an electrochemical pump disposed in a cathode loop of the fuel cell system configured to remove oxygen that intrudes into the fuel cell system. In further embodiments, pumps may be included in an anode and a cathode loop of the fuel cell system that may allow for circulation of certain gases to prevent the formation of an H.sub.2-Air front with the system.

A fuel cell system that employs a process for minimizing corrosion in the cathode side of a fuel cell stack in the system by combining cathode re-circulation and stack short-circuiting at system shut-down and start-up.