Fuel cells are today the ultimate power source that the world of energy scientists craves about. The main issue with them is that they are expensive to make and to maintain. Some of their components get used with time and are very expensive to replace. That’s one of their issues. The other is that they need very pure hydrogen to work correctly and generate the highest amount of electricity out of their reactions.
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Fuel cells work this way: hydrogen is fed to the anode (+) of the cell, where the hydrogen atoms are split in protons and electrons by using a catalyst. The protons pass through the electrolyte from the middle of the fuel cell (between the anode and the cathode), to the cathode (-), and the electrons are forced through an electric circuit and form an electrical voltage between the anode and the cathode. Of course, this voltage drives our stuff (mp3 players, laptops, electric motors). The electron flow is instantaneous and electrons coming from the load (our device) rejoin at the cathode with the hydrogen protons and oxygen from the atmosphere, creating water. Of course, this operation is also done in the presence of another catalyst (platinum, for example – very expensive). So fuel cells are also a source of pure H2O.
Most fuel cells today are PEMFC type, standing for Polymer Electrolyte Membrane. The main issue with them is that their temperature cannot exceed 100°C and require very precise temperature measurement instrumentation and cooling systems (that also consume energy).
A startup company from Pasadena, CA, called Superprotonic, has come up with a new and revolutionary type of electrolyte for the fuel cell “sandwich”. It is a SAFC type electrolyte, standing for Solid Acid Fuel Cell.
What are solid acids? For an elaborate description on how solid acids work for the fuel cell, you may go here. For a simpler explanation, read on.
Solid acids have a salt-like structure, and are chemical intermediates between acids and salts. It is basically a substance called cesium bisulfate [½ Cs2SO4(salt) + ½ H2SO4(acid) => CsHSO4(solid acid)]. Solid acids have conductive properties to around 250°C, being able to carry the hydrogen protons from one side to another by an atomic hopping process, in which the hydrogen proton sticks to oxygen atoms consequently under certain conditions, until it reaches the other side.
The process looks like this:
It has been believed for a long time that solid acids used as electrolyte would dissolve in the water forming at the negative side of the fuel cell, but that’s just not true. At high temperatures, when water transforms into vapors, there’s no danger for the SAFC. They have actually been demonstrated as being quite stable over days of constant operation and multiple heating/cooling processes.
Aside from being able to operate at elevated temperatures, SAFCs have two other distinct advantages over PEMFCs:
- they are impermeable to gases (no loss of gas through unwanted cross-over);
- they transport “bare” protons through the membrane rather than inefficiently carrying over excess water molecules, as is the case with PEMFCs.
So now PEM fuel cells could easily be replaced with SAFCs, at little costs and great efficiency. Why there is so much silence around this subject, and why nobody hears of Superprotonics in a long time, is another story, interesting to be found out. Their site has not been updated from 2007, while other types of expensive PEM fuel cells have been invented and prospered since then. Are there interests in producing expensive stuff? I guess there are.
Finally, you may get a picture of what’s happening to a SAFC during its superprotonic transition from the animation below:
| 1. Room temperature 2. Beginning transition on left 3. Superprotonic on left side 4. More superprotonic on left side 5. Fully superprotonic 6. Reverse transitioned |
