Three-time "Jugend forscht" state champion prepares for the national finals at Hochschule Offenburg

Annika Obert had actually only intended to test the vitamin C content of the fruits and vegetables from her parents’ garden in Steinach. In the process, however, the research-enthusiastic student at the Marta-Schanzenbach High School in Gengenbach discovered the inorganic color pigment Prussian Blue. Its oxidized form, Prussian Brown, reverts to Prussian Blue upon contact with vitamin C (ascorbic acid). In addition, the pigment also reacts to electrical energy. And so the now 16-year-old came up with the idea of developing an environmentally friendly battery (accumulator) based on Prussian Blue at the Xenoplex Student Research Center in Gengenbach.

“The electrodes and electrolytes in most batteries today contain lithium, which comes primarily from South America. But these reserves are finite, and mining often takes place under conditions that are harmful to the environment and inhumane. Furthermore, lithium’s toxic and highly flammable properties complicate disposal and currently make recycling unprofitable in many cases,” Annika Obert explains the situation. The electrodes of her “Berlin White-Blue-Green-Brown” battery therefore consist of graphite foil, which can be obtained and disposed of in Europe in sufficient quantities without causing significant environmental damage. This foil is immersed in a solution of Berlin Brown. Through electrolysis, Prussian Blue then precipitates as a solid onto the foil, which is subsequently dried. When the battery is charged, the layer on one electrode turns white, while the layer on the other changes from green to brown; when discharged, both layers turn blue again. However, to make optimal use of the energetic properties of Prussian blue, the amount of deposited color pigment and a surface structure of the dried layer that is as smooth as possible are crucial. Using the scanning electron microscope at the Physics Service Center in the Center for Learning and Teaching at Hochschule Offenburg, Annika Obert, with the help of Dr. Pascale Müller, examined the surface structure of numerous electrodes that had been dried at different temperatures and using different methods. “Unfortunately, it turned out that cracks were present under all drying conditions,” the 16-year-old summarizes the results.

But the three-time state winner of the “Jugend forscht” competition in the field of chemistry isn’t discouraged by this and now plans to look for other ways to optimize the process. There’s still some time left until the 61st National Finals, which will take place from May 28 to 31 in Herzogenaurach. And perhaps Annika Obert, who already won second prize in the chemistry category last year, will take home the national title this time around.