The alchemy is a thousand years old. Gold was once considered one of the least reactive metals. How can one improve the activity and selectivity of Au catalysts? Is an interstitial solid solution catalyst a feasible strategy? Can a C-Au interstitial catalyst be formed? Can interstitial C atoms change the electronic structure of Au? Can the electronic structure of Au be expressed in one parameter? Can this parameter serve as a descriptor for the selective hydrogenation activity of the Au catalyst, and thereafter pave the way for the design of a catalyst?

In order to try to answer these questions, we propose a carbon inverse doping strategy to obtain C-Au interstitial solid solution catalysts supported on ordered mesoporous carbon. We put great effort into confirming the interstitial C atoms in the Au lattice and their effects on the electronic structure of Au as well as the hydrogenation activity:

1. Interstitial C atoms lead to an expansion of the Au lattice.
2. C diffusion that leads to a rearrangement of electron density may be dominant in causing charge transfer from the surface to the Au clusters.
3. With the increase of C content, the d charge of Au increases from 0.061 to 0.192 e.
4. With the increase of the d charge of Au, the adsorption activation entropy of 3-nitrostyrene is significantly changed and the hydrogenation activity is increased. The turn-over frequency (TOF) of the interstitial catalyst is 3 times that of a commercial Au/TiO₂ catalyst, and the selectivity remains above 99%. A good linear dependence between d charge and turn-over frequency is found. Therefore, the d charge density of Au can be used as a descriptor.

The production of an interstitial solid solution is a good strategy for the production of highly efficient metal catalysts. If you are interested in this work, you can read our article in Nature Communications:https://doi.org/10.1038/s41467-020-18322-x.