Abstract: A method of operating the fuel cell stack having an anode side and a cathode side by flowing hydrogen into the anode side and flowing air into the cathode side. The fuel cell produces electricity that is used to operate a primary electrical device. To shut down the stack in one embodiment, the primary electrical device is disconnected from the stack. The flow of air into the cathode side is stopped and positive hydrogen pressure is maintained on the anode side. The fuel cell stack is shorted and oxygen in the cathode side is allowed to be consumed by hydrogen. The inlet and outlet valves of the anode and the cathode sides are closed. Thereafter, the flow of hydrogen into the anode side is stopped and the flow of exhaust from the cathode side is stopped.

Abstract: At least one positive temperature coefficient element is used to efficiently control fuel cell voltage at startup and shutdown making the fuel cell more efficient and protecting the electro catalyst layer.

Abstract: A system and method for reducing cathode carbon corrosion during start-up of a fuel cell stack. If a long enough period of time has gone by since the last system shutdown, then both the anode side and the cathode side of the stack will be filled with air. If the system includes split sub-stacks, then a start-up sequence uses a fast hydrogen purge through each sub-stack separately so as to minimize the time of the hydrogen/air front flowing through the anode side of the stacks. The start-up sequence then employs a slow hydrogen purge through the sub-stacks at the same time. If the time from the last shutdown is short enough where a significant amount of hydrogen still exists in the cathode side and the anode side of the sub-stacks, then the fast hydrogen purge can be eliminated, and the start-up sequence proceeds directly to the slow hydrogen purge.

Abstract: A process for fabricating a unitized electrode assembly for a polyelectrolyte membrane is disclosed. The process includes providing a gas diffusion medium and a membrane electrode assembly, printing an adhesive on the gas diffusion medium, locating the gas diffusion medium relative to the membrane electrode assembly and pressing the gas diffusion medium and the adhesive against the membrane electrode assembly.

Abstract: At least one positive temperature coefficient element is used to efficiently control fuel cell voltage at startup and shutdown making the fuel cell more efficient and protecting the electro catalyst layer.

Abstract: A system and method for reducing cathode carbon corrosion during start-up of a fuel cell stack. If a long enough period of time has gone by since the last system shutdown, then both the anode side and the cathode side of the stack will be filled with air. If the system includes split sub-stacks, then a start-up sequence uses a fast hydrogen purge through each sub-stack separately so as to minimize the time of the hydrogen/air front flowing through the anode side of the stacks. The start-up sequence then employs a slow hydrogen purge through the sub-stacks at the same time. If the time from the last shutdown is short enough where a significant amount of hydrogen still exists in the cathode side and the anode side of the sub-stacks, then the fast hydrogen purge can be eliminated, and the start-up sequence proceeds directly to the slow hydrogen purge.

Abstract: A method of operating the fuel cell stack having an anode side and a cathode side by flowing hydrogen into the anode side and flowing air into the cathode side. The fuel cell produces electricity that is used to operate a primary electrical device. To shut down the stack in one embodiment, the primary electrical device is disconnected from the stack. The flow of air into the cathode side is stopped and positive hydrogen pressure is maintained on the anode side. The fuel cell stack is shorted and oxygen in the cathode side is allowed to be consumed by hydrogen. The inlet and outlet valves of the anode and the cathode sides are closed. Thereafter, the flow of hydrogen into the anode side is stopped and the flow of exhaust from the cathode side is stopped.

Abstract: Methods of producing an electrochemical conversion assembly comprising an electrochemical conversion cell are provided. The electrochemical conversion cells which comprises a membrane electrode assembly, first and second flowfield portions defined on opposite sides of the membrane electrode assembly, and, at least one vapor barrier layer disposed between the membrane electrode assembly and at least one of the flowfield portions. The method further includes selecting a desired mass transfer coefficient MTC for the at least one vapor barrier layer of at least about 0.05 cm and optimizing one or more of the porosity, the tortuosity, and the thickness of the vapor barrier layer to produce the desired MTC in the vapor barrier layer.

Abstract: A process for fabricating a unitized electrode assembly for a polyelectrolyte membrane is disclosed. The process includes providing a gas diffusion medium and a membrane electrode assembly, printing an adhesive on the gas diffusion medium, locating the gas diffusion medium relative to the membrane electrode assembly and pressing the gas diffusion medium and the adhesive against the membrane electrode assembly.