Published in Nature: CSIRO scientists have co-developed a new type of membrane that has the potential to significantly boost the performance of fuel cells in electric vehicles.
Many applications that require the separation of charged particles use polymeric membranes.
An example are proton-exchange membrane fuel cells (PEMFCs), which could potentially replace conventional batteries in electric cars.
Their potential advantage is that they very efficiently convert chemical energy stored in hydrogen into electricity: at the anode of the fuel cells electrons are split off from hydrogen, then positively charged hydrogen ions and there electrons separately flow to the cathode where a reaction with oxygen takes place to produce water.
The problem is, though, that the flow of hydrogen ions requires the polymeric membranes to stay wet.
This is currently done by placing the fuel cells alongside a radiator, water reservoir and a humidifier, but this comes at the cost of large amounts of space and power.
To find a better solution, the team led by researchers from China's Hanyang University took to nature, specifically to the ordinary cactus. There little pores, or stomata, open in the night to allow the take up of water in the night, and close during the day to minimise transpiration.
In a similar way, the researchers applied a water repellent surface coating onto the fuel cell membranes. The coating has nanometre-scale cracks allowing the water generated during the electrochemical reaction to transpire. But when the membranes start to dry out they shrink, which causes the cracks to close thus retaining the water and keeping the membrane hydrated.
The coating removes the need for bulky external equipment to keep the membranes wet, and it makes the fuel cells up to four times more efficient in hot and dry conditions.
The researchers also believe that their coating could improve other applications using hydrated polymer membranes, including devices for water treatment and gas separation.