Watching water

Using a new and improved imaging instrument at the US

(NIST), scientists can survey water inside hydrogen fuel cells. This capability is key to making the technology practical for powering future automobiles.

With visualization powers 10 times better than those achieved previously, researchers can “see” water production and removal in fuel cells under a range of simulated operating conditions, from arctic cold to desert heat.

‘This as-it-happens, inside view is essential because fuel-cell performance depends on a delicate balance,’ explained NIST physicist Muhammad Arif, who leads the NIST team that developed the instrument. ‘Too little - or too much - water can shut it down.’

In fuel cells, which are stacks of battery-like devices, water is the by-product of the chemical process that uses electrons stripped from hydrogen molecules to generate electricity. With the newly commissioned Neutron Imaging Facility, water quantities smaller than one microgram are revealed, and details as small as 0.02mm can be discerned in images. Even better spatial resolution is expected.

Outputs are akin to CAT scans. Images are recorded at a rate of up to 30 frames per second, or 30 times faster than the first-generation instrument that NIST built to demonstrate the usefulness of neutron imaging for fuel cell research.

The ability to look inside fuel cells--through their maze-like solid housing--is achieved with cone-shaped beams of neutrons. Unlike X-rays, neutrons can pass nearly unimpeded through the solid encasements, but they interact strongly with hydrogen. As a result, neutron beams are highly sensitive probes of water, since each molecule contains two hydrogen atoms and one oxygen atom.

Located at NIST's Center for Neutron Research, the research station is operated as a national user facility, open to scientists from industry, universities, and government agencies. It is jointly funded by NIST, the US Department of Energy and General Motors.

Additional Information on the instrument, including how to apply to use it, can be found here.