Giant batteries: Going with the flow

[NickB79]

http://www.economist.com/blogs/babbage/2014/01/giant-batteries

The solution Dr Huskinson and Dr Marshak propose, in a paper in Nature, is to use molecules called quinones, mixed with sulphuric acid, on one side of the membrane, and a mixture of bromine and hydrobromic acid on the other—and to make the electrodes out of carbon. Quinones are molecules composed of carbon, hydrogen and oxygen that ionise in similar ways to metals like vanadium. Anthraquinones—the class of quinone employed by Dr Huskinson and Dr Marshak—can be synthesised cheaply because their precursor, anthracene, is a component of crude oil. And anthraquinones already have industrial applications, for example in the paper-pulp industry, so an infrastructure to make them exists. The question was, would they be as good as vanadium in a battery?

Dr Huskinson and Dr Marshak found that, with a suitable material on the other side of the membrane—namely the bromine/hydrobromic acid mixture—they were. The anthraquinone they chose, called AQDS, reacts with the sulphuric acid in a way complementary, with a suitable transfer of hydrogen ions, to the way bromine turns into bromide ions, the non-hydrogen part of hydrobromic acid. And it does so without the need for a metal catalyst.