Gm Global Technolgoy Operations, Inc.

Giner Electrochemical Systems, LLC

Joerg Roth

Jeanette E O'Hara

Michael R Schoeneweiss

Han Liu

Mark F Mathias

Anthony B LaConti

Thomas A Trabold

Chunxin Ji

Bhaskar Sompalli

Bernd Krause

Robert McDonald

John Forchione

Thomas J McCallum

David Wood

A diffusion media for use in a fuel cell stack and that is adjacently aligned with lands of a reactant plate of the fuel cell stack. The diffusion media includes a sheet having a permeable material with a thickness. A plurality of water transport pores are defined through the sheet. Each of the pores has a pore diameter that is greater than 1.5 times the thickness.

Water transport features for diffusion media

A fuel cell that includes specially configured bipolar plates that separate the reactant gas flow field in an active area of the fuel cell into a primary flow channels and a secondary channels. In one embodiment, the primary flow channels are in use over the entire operating range of the fuel cell and the secondary flow channels are only in use at high cell current outputs. At low power demands, the primary channels operate at a voltage below 0.8 volts and provides a gas current density of more than 0.2 A/cm. The secondary flow channels have no gas supply and operate at mass transport limited conditions. Because of this design, voltage cycling is significantly reduced or eliminated, thus increasing the life of the fuel cell.

Reduction of voltage loss by voltage cycle through the use of specially formed bipolar plates

A diffusion media and a process for its fabrication are provided for addressing issues related to water management in electrochemical cells and other devices employing the diffusion media. In accordance with one embodiment of the present invention, a process for fabricating a diffusion media is provided. A diffusion media substrate is provided comprising a porous fibrous matrix defining first and second major faces. The substrate comprises an amount of carbonaceous material sufficient to render the substrate electrically conductive. A mesoporous layer is applied along at least a portion of one of the first and second major faces of the substrate. The mesoporous layer is applied to the substrate by providing a coating comprising a hydrophobic component, a hydrophilic component, and a pore forming agent. The substrate is free of fluorinated polymers outside of regions of the substrate carrying the mesoporous layer. The pore forming agent is decomposed such that the mesoporous layer is more porous than the diffusion media substrate.

Untreated diffusion media with mesoporous layer and devices incorporating the same

A gas diffusion electrode and method of making the same. According to one embodiment, the electrode comprises a support layer, a first cushioning layer positioned on top of the support layer, a second cushioning layer positioned on top of the first cushioning layer, and a catalyst layer positioned on top of the second cushioning layer. The support layer is a mechanically stable, electrically-conductive, gas porous substrate, such as carbon fiber paper. The first cushioning layer, which is also gas porous, comprises a non-woven mat of electrically-conductive, chemically-inert fibers, preferably carbon nanofibers, bound together with a polymeric binder, such as polytetrafluoroethylene. The second cushioning layer is similar to the first cushioning layer, except that carbon black or a similar electrically-conductive, chemically-inert particulate material is included in addition to or instead of the fibrous material for the purpose of fine-tuning pore size.

Gas diffusion electrode and method of making the same

A diffusion media and a scheme for spatially varying the parameters of the diffusion media to address issues related to water management in electrochemical cells and other devices employing the diffusion media are provided. A device is configured to convert a hydrogenous fuel source to electrical energy and comprises an electrochemical conversion assembly, first and second reactant inputs, first and second product outputs, and first and second diffusion media. The device is configured such that a mesoporous layer is carried along at least a portion of a major face of one of the first and second diffusion media substrates. The mesoporous layer comprises a hydrophilic carbonaceous component and a hydrophobic component. The mesoporous layer occupies a substantially greater portion of one of the high or low HO regions of the device, relative to the other of the high or low HO region of the device.

Spatially varying diffusion media and devices incorporating the same

A porous diffusion media according to the present invention is positioned against a catalyst layer of the membrane electrode assembly, the porous matrix comprises carbon paper, and the water transfer particles comprise carbon fibers or powders. Relatively high and relatively low water transfer particle density regions alternate across the porous diffusion media. A first major face of the media may be collectively more hydrophilic than the second major face and the second major face may be collectively more hydrophobic than the first major face. The diffusion media is positioned against the catalyst layer along the first major face of the diffusion media and against a flow field of the fuel cell along the second major face of the diffusion media. The porous diffusion media comprises hydrophobic material disposed along the second major face of the diffusion media.

Diffusion media, fuel cells, and fuel cell powered systems

The present invention discloses various methods in which a quality of a diffusion media for use in a fuel cell assembly can be qualitatively evaluated. The material constant, an internal contact angle, a ratio of high and low energy pores, and an external contact angle can be calculated for the diffusion media and compared to a predetermined standard to evaluate the quality of the diffusion media.

Method of making a gas diffusion media and quality controls for same

Gas diffusion media for use in fuel cells are provided that contain a pattern of deposited hydrophobic polymer such that less than 100% of the surface of the diffusion media is covered with hydrophobic polymer. The media are made by first wetting a sheet of carbon fiber paper in an aqueous emulsion of the hydrophobic polymer. The wetted sheet is contacted with a pattern member containing one or more openings oriented to correspond to a predetermined or desired pattern of hydrophobic polymer deposition. While still in contact with the pattern member, the sheet is heated or otherwise treated to cause evaporation of the water from the sheet. Evaporation while in contact with the pattern member takes place in such a way that hydrophobic polymer is concentrated in the sheet at the openings of the pattern member by the process of evaporation.

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Trebur, Germany

Joerg Roth