Lignin dubbed as supergreen fuel for fuel cells

Lignin has been used for the first time in a fuel cell paving way for supergreen fuel cells.

Researchers from the Laboratory of Organic Electronics at Linköping University developed the fuel cell that uses lignin, which is a cheap by-product from paper manufacture and one of the most common biopolymers. Lignin is cheap and readily available biopolymer that consists of a large number of hydrocarbon chains woven together, which can be broken down in an industrial process to its energy-rich constituent parts, benzenediols. One of these, catechol makes up 7% of lignin.

Researchers at the Organic Energy Materials group at LiU, led by Professor Xavier Crispin, have discovered that this type of molecule is an excellent fuel for use in fuel cells.

The fuel most often used in tradition fuel cells is hydrogen gas, which reacts with oxygen from the air. The chemical energy is converted in the fuel cell to electricity, water and heat. However, 96% of the hydrogen produced worldwide is from non-sustainable sources, and is accompanied by carbon dioxide emission.

Other fuels used in fuel cells are ethanol and methanol, but these produce also carbon dioxide as a by-product. The electrodes necessary to attract the fleeing electrons are usually made from platinum, which is both expensive and scarce.

Benzenediols, however, are aromatic molecules, and metal electrodes cannot be used in fuel cells based on benzenediols since the reactions are slightly more complex. The researchers instead use electrodes made from the popular conducting polymer PEDOT:PSS. This polymer has the interesting property of conducting electricity, while at the same time having a surplus of protons. This means that it functions as both electrode and proton conductor.

The chemical energy of the fuel is converted to electricity without carbon dioxide being formed.

The researchers have calculated that the amount of electricity produced by the new fuel cell is approximately the same as the current ethanol-based and methanol-based fuel cells.