Seal of approval

A UK electro-chemical specialist is claiming a newly-developed membrane represents a significant step towards commercially viable fuel cells.


ITM Power said the new material, for use in proton exchange membrane cells (PEMs) that use methanol as their fuel, could drastically reduce the cost of the systems.


The only existing reliable membrane material for use in PEMs is Nafion, which is manufactured by global chemical giant DuPont at a cost of $500 per square metre, said ITM.


The UK company claims to have developed an innovative hydrocarbon polymer membrane, which not only has three times the ionic conductivity of Nafion but costs $5 per square metre.


One of the problems with fuel cell membranes is that the methanol can leak through to the other side of the chamber — known as methanol crossover — and ITM said its material also performs well in this regard.


The ITM membrane will enable the cells to be based on alkaline chemistry. This produces higher catalytic activity than acid and means that expensive platinum could be replaced by palladium as the catalyst on the fuel side, which is about a quarter of the cost.


Cambridgeshire-based ITM carried out the research as part of a DTI-funded project. Development of the material is a further boost for ITM, which recently launched what is claimed to be the first flexible fuel cell sufficient for use as an individual power pack for emergency services.


One of the key differences between the new cell and more conventional approaches is that it uses two liquids and so requires no air. This means that it can be operated in areas where there is little oxygen, whereas conventional fuel cells cannot. As it is completely sealed it could even work under water, or in the pressurised cabin of an aircraft. The fuel cell uses sodium borohydride solution as the fuel and hydrogen peroxide as the oxidant. Sodium borohydride carries about 50 per cent more energy per kilo than methanol.


According to chief executive Jim Heathcote, the device can create 20W of power continuously for more than three days, which is the minimum target for a fuel cell set by the UK and US military.


Unlike conventional fuel cells, using a liquid means that it is possible to adjust various characteristics such as hydration control, PH, and their ionic conductivity, claimed Heathcote.


The cell’s key attribute is its flexibility. Existing fuel cell designs use hard electrodes that are sensitive to vibration and crack easily. ITM’s cell manages to get around this problem as it can be initially moulded in any shape and is then flexible enough to bend to conform to the shape required in use, said Heathcote.


This would mean it could be carried comfortably on an operator’s back if used as a personal power pack for the military or civilian emergency services. It is also suitable for use by the emergency services as it is immune to environmental factors such as high levels of CO2 or smoke, which would adversely affect a conventional air-breathing fuel cell.


The entire cell is produced using ITM’s proprietary ‘one-stop’ process. Liquids are poured into a mould that contains the membrane and the catalyst. The whole pack is then introduced into a gamma radiation chamber, where the liquids solidify in situ as the monomers in the liquid become flexible polymers.


‘This is a fundamental architectural shift in fuel cell design,’ claimed Heathcote. ’It is more advanced than a direct alcohol fuel cell and has massive potential for the future.’