The photo is sourced from rscf.ru
Germanium is a silvery-white semi-metal widely used in optics, as well as in production of electronics and chemical catalysts. The starting material for its production is germanium oxide – a white crystalline powder containing impurities and characterised by low solubility: only 4.3 grams of the substance is dissolved in one litre of water. Therefore, the synthesis of germanium requires special purification, as well as the use of a large volume of water or high concentration alkali solutions.
The scientists from the Kurnakov Institute of General and Inorganic Chemistry of the RAS tried to solve this problem. They used ammonium peroxogermanate to obtain germanium oxide, a colourless crystalline powder retaining its properties at the temperatures up to 70 degrees Celsius. Solubility of the resulting germanium oxide reached 100 grams per 1 liter of water, and its mass was almost 100% of the mass of the primary ingredients. The scientists of the IGIC RAS used this substance to synthesise composites used for creation of the anodes for lithium-ion batteries.
To obtain the composites, the authors of the study dissolved germanium oxide in water, and then added ethanol. Due to this, the nanoparticles of the substance formed a thin uniform film on the substrate, which was graphene oxide, a carbon material, which when heated, is able to impart the composite the properties of graphene characterised by high electrical conductivity. The intermediate material was heated to 300 degrees Celsius, and then processed with a stream of dry ammonia at the temperature of 700 degrees Celsius, which eventually made possible obtaining of germanium nitride.
The scientists at each stage of the study synthesised samples with different ratios of germanium and graphene compounds (80/20, 50/50 and 20/80), and then measured their electrochemical properties with lithium-ion battery electrodes. The experiments have shown that low content germanium samples are most preferable as they show good stability with a large number of charge-discharge cycles.
“Germanium is still an expensive resource for industrial use, but germanium itself and its compounds possess a lot of useful properties. We have managed to achieve high yields of the final product, which significantly reduces the cost of the process… We plan to synthesise other interesting germanium compounds or materials based on them, which can be used, for example, in gas sensors, as electrodes not only for lithium-ion batteries, but also for sodium- and potassium-ion ones and supercapacitors,” the Russian Science Foundation quotes Alexander Medvedev, one of the authors of the study, PhD in chemical sciences, senior researcher at IGIC RAS.
