A research team from Tulane University in the United States recently announced the latest results, revealing for the first time at the atomic scale the underlying reasons why gold is extremely resistant to oxidation and does not easily lose its luster. Research shows that some atoms on the surface of gold will spontaneously rearrange when encountering oxygen, forming a structure similar to an "invisible shield", which significantly hinders the chemical reaction between oxygen molecules and gold.
For a long time, it has been generally believed that gold is not easy to change color, mainly because the interaction between gold atoms and oxygen is weak. Matthew Montemore, associate professor of chemical engineering at Tulane University, points out that this traditional explanation is incomplete. Their research found that on the two most common gold surface structures, surface atoms are restructured and rearranged into a more stable arrangement, thereby greatly increasing gold's resistance to oxidation reactions.
Montemore and co-author Santu Biswas, a postdoctoral researcher in the Department of Chemical and Biomolecular Engineering, used computer simulations to model in detail the process by which oxygen molecules come into contact with two common gold surfaces. The results show that if the atoms on the gold surface remain unrearranged, oxygen molecules are more likely to be split and react with the gold. Once the surface is restructured, the reaction rate between gold and oxygen will be reduced by about a billion to a trillion times, which is equivalent to forming a barrier that almost blocks oxidation at the atomic level.
This work provides a new physical and chemical explanation for gold's long-term tarnishing, and further explains why gold jewelry and other gold products can maintain a stable appearance for long periods of time, even hundreds of years. At the same time, this mechanism also has important implications for catalysis science. At present, gold-based catalysts have been used in some industrial oxidation reactions, but gold's "innate resistance" to the cleavage of oxygen molecules limits its reactivity in chemical production and energy applications to a certain extent.
Catalytic systems using a combination of gold and palladium have been used in the production of chemical products such as vinyl acetate. Gold catalysts have also been studied for use in areas such as automobile exhaust carbon monoxide removal and propylene oxide preparation. Montemore said that if gold could be "tricked" in a way that makes it easier to split oxygen molecules, gold could become an efficient catalytic material for a variety of important industrial reactions. The new idea proposed in this study is to fundamentally change its surface geometry to improve reactivity by preventing or reversing the atomic reconstruction of gold surface.
In the past, efforts to improve the catalytic performance of gold have focused on alloying it with other metals or supporting nanoscale gold particles on oxide supports. The latest results suggest that directly designing the geometric structure of the gold surface and controlling its atomic arrangement pattern may become another effective way to improve the reactivity of gold. The related paper is titled "Role of Reconstruction in the Inertness of Gold toward Oxygen" and has been published in Physical Review Letters.