Vitamin B12, which we are used to getting from meat, fish and eggs, has unexpectedly proved useful in energy. A group of researchers from the University of Cordoba (Spain) has used it for the first time as a catalyst - a substance that speeds up a chemical reaction - for a rechargeable battery. The work was published in the Journal of Materials Chemistry A.
The device in question is a zinc-air cell. In such devices one of the electrodes "breathes" oxygen from the air, while the second is made of zinc. The Spanish scientists' prototype contains vitamin B12 (cobalamin) anchored on single-walled carbon nanotubes - microscopic tubes made of carbon. This design helps the electrochemical reaction proceed, because at the center of the vitamin molecule is cobalt in oxidation state III.
This is already the third biomolecule the team has tried as a catalyst: hemoglobin and catalase - iron-containing proteins - worked in their batteries earlier. The main achievement of the current project is that the B12 cell was made rechargeable. It withstood up to 250 charge and discharge cycles.
"We looked at the properties of natural materials in order to apply them in new batteries," explained one of the authors, Manuel Cano Luna. The difficulty was that vitamin B12 dissolves well in water, and the electrolyte in the cell is aqueous. To keep the vitamin from being washed out, it was attached to the nanotubes, imitating the way amino acids join together in proteins.
Zinc-air batteries are considered a promising replacement for lithium-ion ones: zinc is abundant and recyclable, oxygen is taken from the air, so the battery is lighter. Aqueous electrolytes do not burn, which increases safety. But operation requires an efficient catalyst that must also act in both directions - both during discharge and during charge. According to researcher Antonio Jesus Fernandez Romero, vitamin B12 "has shown that it meets the necessary conditions": during discharge it speeds up the reduction of oxygen to water, and during charge it speeds up the release of oxygen.
The authors emphasize that this is still a laboratory prototype, not a finished product. But it opens the way to cheaper and more sustainable energy storage systems that could be useful in the transition to renewable sources - for example, for storing their surpluses.