The Proton Exchange Membrane (PEM) fuel cell was developed in the mid 1950’s at General Electric’s Research Laboratories. Little was done with this discovery until GE was approached by NASA to develop a new power source for the Gemini space missions. NASA could not launch enough batteries into orbit to last through the entire mission, so new technology was needed to achieve the power density required to stay within mission weight restrictions. GE supplied PEM fuel cells for the Gemini program and they used hydrogen and oxygen to generate the power for the space capsule.
Further to the work with NASA, The US Navy, working with GE, began testing PEM electrolyzer cells in 1972. About the time the Navy first commissioned their first PEM electrolyzer, General Electric sold this division to United Technologies where the program continues at Hamilton Sundstrand.
Nafion film from Dupont (the conductive membrane) is coated with catalysts to produce what is known as a Membrane Electrode Assembly or MEA. It is called this because the metal catalyst on both sides of the membrane become the positive and negative electrodes in the cell. The membrane material itself is a Teflon-based plastic that has sulfonic acid groups attached to the Teflon structure.
(Refer to diagram on right) On the oxygen side of the cell or anode, water is circulated and that is used as the feedstock to make the hydrogen and it is also used for cooling purposes. When the DC current is applied to the cell, the water is split into OXYGEN, PROTONS, and ELECTRONS. The oxygen is swept out of the cell by the circulating water.
The protons enter the membrane as an electrical charge as they are attracted to the negative electrode or cathode that is bonded to the opposite side of the membrane. The oxygen stays on the waterside and does not mix with the hydrogen. The oxygen is swept out of the cell with water circulation. Meanwhile, the electrons flow through the power supply circuit outside of the cell and rejoin the protons at the electrode surface. They combine to form a molecule of pure hydrogen. This Hydrogen is then pressurized by a backpressure regulator and sent to your process.
In Proton’s Hydrogen Generation process (as described above) Hydrogen is under high pressure and oxygen is under low pressure, oxygen can NEVER leak into the product hydrogen, keeping the plant safe.