A reaction that puzzled scientists for 50 years has now been explained by researchers at Umeå University. Rapid structural snapshots captured how graphite transforms into graphite oxide during electrochemical oxidation, revealing intermediate structures that appear and disappear over time. The researchers describe this as a new type of oscillating reaction.
Oscillating chemical reactions are fascinating to watch and important for developing an understanding of how complex systems work, both in chemistry and in nature. Classical visual examples of such reactions show how the colors of a solution change back and forth, cycling through different states and producing a final product after each cycle.
Umeå researchers recently published a study in the scientific journal Angewandte Chemie, reporting a rather different and new type of oscillating reaction during electrochemical oxidation of graphite.
"It has been known for 50 years that some voltage oscillations spontaneously occur when a charge is applied to a graphite electrode immersed in sulphuric acid solution. The end product of this reaction is graphite oxide, a material consisting of layers of graphene oxide. However, what happens to the structure of the material during the reaction at every oscillation cycle had remained a complete mystery," says Alexandr Talyzin, Professor in the Department of Physics at Umeå University.
Thanks to new synchrotron methods, researchers can record X-ray diffraction scans in a matter of a few seconds, providing snapshots of the material's structure changes during oxidation. Surprisingly, the experiments revealed an intermediate phase with a specific structure that appears at one part of the cycle, disappears in the next stage and then reappears, repeating the cycle.
"Soon we realised that we had observed a new - to the best of our knowledge - type of oscillating reaction. What began as a detailed study of a particular chemical reaction suddenly appeared to be a lot more interesting from the point of view of fundamental chemistry. Bartosz Gurzeda, the first author of the study, also recorded a beautiful video showing periodic changes in the appearance of a sample every few minutes," says Alexandr Talyzin.
Oscillation reactions are happening inside all living beings but were once considered impossible in inorganic chemistry. This discovery expands our knowledge of chemical kinetics and reaction mechanisms and could lead to the development of new theories and models in chemistry.
The first theory explaining oscillating reactions earned Ilya Prigogine the Nobel Prize in 1977 and became a fundamental part of non-equilibrium thermodynamics, showing how order can emerge from chaos.
"We hope that new theories will be developed to explain this new type of oscillating reaction, which may lead to the discovery of new similar examples," says Alexandr Talyzin.
