Membraneless Fuel Cells
The lack of a membrane means they are cheaper but the size limits their use to portable applications which require small amounts of power.
By eliminating the membrane and delivering the reactants as a mixture, MRFCs can potentially be simpler and less costly than conventional fuel cell systems.
Meanwhile, the free electrons travel around the cell to power a given load and then combine with the oxygen and hydrogen at the anode to form water.
The most common method in the United States (95% of production) is via Gas reforming, specifically using methane,[2] which produces hydrogen from fossil fuels by running them through a high temperature steam process.
However, since these methods of hydrogen production are often energy and space intensive, it is often more convenient to use the chemicals directly in the fuel cell.
Another advantage over gaseous fuels, as in the H2-O2 cells, is that liquids are much easier to handle, transport, pump and often have higher specific energies allowing for greater power extraction.
Although hydrogen technology has significantly evolved, other fossil fuel based cells (such as DMFC's) are still plagued by the shortcomings of proton exchange membranes.
In solid oxide fuel cells, high temperatures are needed which require energy and can also lead to quicker degradation of materials.
LFFC's overcome the problem of unwanted crossover through the manipulation of the Reynolds number, which describes the behavior of a fluid.
By choosing the correct fuel and oxidizing agents in LFFC's, protons can be allowed to diffuse from the anode to the cathode across the interface of the two streams.
Membraneless fuel cells offer a cost advantage due to the lack of the electrolytic membrane.
A membraneless fuel cell is theoretically the better option since the diffusion interface across both fluids is extremely thin and using higher concentrations does not result in a drastic effect on crossover.
For example, pumps are required to maintain laminar flow while gas separators can be needed to supply the correct fuels into the cells.
By creating micro structures which form specific contact angles with water, fuel cannot be drawn backwards.
[8][9] Membraneless fuel cells are currently being manufactured on the micro scale using fabrication processes found in the MEMS/NEMS area.
In order to take advantage of hydrophobic effects, the surfaces need to be smooth to control the contact angle of water.
To produce these surfaces on a large scale, the cost will significantly increase due to the close tolerances which are needed.
For the fuel cell configuration with a carbon dioxide generating mechanism, the surface tension effects could also increase the pumping requirements drastically.
Therefore, in order to obtain more power, fuel cells must be connected in series or parallel (depending on whether greater current or voltage is desired).
For large scale building and automobile power applications, macro fuel cells can be used because space is not necessarily the limiting constraint.
The lack of a physical electrolytic membrane and energy dense fuels that can be used means that LFFC's can be produced at lower costs and smaller sizes.
