Hydrogen fuel cell mystery cracked

There are many great things in life that don’t need to be fully understood to appreciated. David Lynch films, American football and how the proton exchange membrane in hydrogen fuel cells works are prominent examples.

But at least scientists at the U.S. Department of Energy’s Ames Laboratory have gone someway to solving the latter, according to Science Daily.

“From nuclear magnetic resonance (NMR), we know that Nafion® molecules have a rigid backbone structure with hair-like ‘defects’ along the chain,” [Ames Laboratory scientist] Schmidt-Rohr said, “but we didn’t know just how these molecule were arranged. Some have proposed spheroidal water clusters, others a web-like network of water channels.”

“Our theory is that these hydrophobic [water-hating] backbone structures cluster together,” he continued, “to form long rigid cylinders about 2.5 nanometers in diameter with the hydrophilic ‘hairs’ to the inside of the water-filled tubes.”

Though the cylinders in different parts of the sample may not align perfectly, they do connect to create water channels passing through the membrane material, which can be 10’s of microns thick. It’s this structure of relatively wide diameter channels, densely packed and running mostly parallel through the material that helps explain how water and protons can so easily diffuse through Nafion®, “almost as easily as water passing through water,” Schmidt-Rohr said.

So now you know.