Hydrogen.gov | B. Direct Methanol Fuel Cells

B. Direct Methanol Fuel Cells

Description: The most common type of direct hydrocarbon fuel cell is the Direct Methanol Fuel Cell (DMFC). In DMFCs, oxygen from the surrounding air is reduced at the cathode, as with PEMFCs, except that liquid methanol instead of hydrogen is the fuel oxidized directly at the anode. Thus a DMFC system does not require a hydrogen storage tank or reformer. On the other hand, by comparison to a PEMFC, a DMFC requires higher precious metal loading (higher cost) and offers lower power density, although the methanol fuel does provide higher energy density. DMFCs have been designed up to 5 kW. DMFCs may be suitable for smaller (< 0.5 kW) consumer electronics applications. A related type of fuel cell, the Direct Propane Fuel Cell, has a similar design and operating characteristics, while cryogenic propane has a higher energy density than methanol.

1. Materials and Component Design

a) Oxidation catalysts
Goals: Resistance to methanol, Reduced Pt loading on membrane

b) Membranes
Goal: Reduce methanol crossover; High volume, low cost manufacturing cost; Low precious-metal c content

i. Low-cost manufacturing, including ink-jet printing of catalysts on membrane electrode assemblies.

c) Integrated, direct hydrocarbon microcells
Description: All the components for making a micro, modular fuel cell (the electrocatalyst of cathode and anode, the separator or the membrane electrolyte, and the current collectors) can be integrated into a single fiber or cell structure. The hydrogen-containing fuel passes through each microcell connected in electrical series, resulting in a combined power production suitable for portable applications.

2. System Analysis

a) Fluid handling
Description: Miniature technology for an on-board unit

i. Flow channel design

ii. Flow modeling

b) System model
Description: Develop a validated system model, with periodic benchmarking, of the integrated fuel cell power system, subsystems, and components.

c) Testing

i. Single cell

ii. Sub-scale (0.5-kW) fuel cell stack.

3. Applications

a) Portable electronics
Description: Miniature power packs for cell phones and laptops.

i. Hybrid ultracapacitor-DMFC units
Description: Could provide 5x the energy density of battery packs.

b) Stand-alone power units
Description: Direct Propane Fuel Cells for telecommunications applications.

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