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Catalysis made faster through hole migration

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In a recent paper in the journal Proceedings of the National Academy of Sciences USA, researchers from IISER Pune and Rice University studied a fascinating mechanism for catalysis. Their results offer clues to a more directed approach for designing new catalysts.

Catalysts help accelerate a chemical reaction while not being consumed in the reaction and find certain place in industrial applications. Over the last decade, nanoparticles have come to be widely explored for their catalytic properties.

“A paper that came out a couple of years ago in Nature Chemistry discovered that catalytic reactions on metal nanoparticles show cooperative effect, which seemed to allow communication across a nanocatalyst. This was a very interesting observation and caught our attention,” said Dr. Srabanti Chaudhury, faculty member in the Chemistry department at IISER Pune. Along with her PhD student Bhawakshi Punia and collaborator Prof. Anatoly Kolomeisky from Rice University, Dr. Chaudhury chose to develop a theory to explain the cooperative behaviour, wherein a reaction in one segment of a nanorod triggered the reaction in a neighbouring segment of the rod.

Bhawakshi Punia Shrabanti Chaudhary
Bhawakshi Punia Dr. Srabanti Chaudhury

Previous researchers showed that formation of holes, which are positively charged regions deficient in electrons, was associated with the cooperative behaviour. In the present work, this became the starting point of investigation for the team.

They set out to develop a theory beginning with the production of holes until their decay, with the goal of addressing the question ‘what happens between the production and decay and how does this help in catalysis’.

To study the dynamics of the holes, the team developed a simple analytical pen-and-paper model, which is a common approach in chemical physics to understand reaction dynamics, and tested the model through simulations. In the method they applied, the team considered that at each catalytic site, as the local concentration of holes increases, the holes spread to a less crowded neighbouring site, and this movement continues. Thus, through the migration of holes, the catalytic reaction at one site triggers catalysis at another site.

The team studied how long the charged holes last and how far on the nanorod is it possible for this hole-based communication be carried out. They studied the effect of electric charge on the route of migration. The team found their theoretical predictions to be in good agreement quantitatively with the experimental data.

“Taking such a simple model and getting a quantitative picture was what made it very special,” says Dr. Chaudhury. “Our theoretical predictions suggest that one can design new catalysts where it will be possible to create such local concentrations of holes and the holes might diffuse faster to trigger more catalysis,” she says speaking about the possibilities for future studies.

This research was supported by funds from SERB-CRG, PMRF and NSF.

A news release on this by the Rice University is here and has also been featured in Materials Today.

Article citation:

Bhawakshi Punia, Srabanti Chaudhury*, and Anatoly B. Kolomeisky* (2022). Microscopic mechanisms of cooperative communications within single nanocatalysts. Proceedings of the National Academy of Sciences USA 119(3):e2115135119.