Finding optimal surface sites on heterogeneous catalysts by counting nearest neighbors

CATEGORY: HETEROGENEOUS CATALYSTS 
Finding optimal surface sites on heterogeneous catalysts by counting nearest neighbors

Type	Journal Article
Author	Federico Calle-Vallejo
Author	Jakub Tymoczko
URL	http://www.sciencemag.org/content/350/6257/185
Volume	350
Issue	6257
Pages	185-189
Publication	Science
Date	10/09/2015
Abstract	A good heterogeneous catalyst for a given chemical reaction typically has only a single specific type of surface site that is catalytically active. Methodologies such as Sabatier-type activity plots determine optimal adsorption energies to maximize catalytic activity. However, these are difficult to use as guidelines to devise new catalysts. Authors introduce coordination-activity plots that predict the geometric structure of optimal active sites. The method is illustrated on the oxygen reduction reaction catalyzed by platinum. Sites with the same number of first-nearest neighbors as (111) terraces but with an increased number of second-nearest neighbors are predicted to have superior catalytic activity. Authors have used this rationale to create highly active sites on platinum (111), without alloying and using three different affordable experimental methods. Accounting for surface coordination The exploration of heterogeneous catalysts using first-principles calculations can be daunting because the large number of atoms and possible surface geometries. Calle-Vallejo et al. describe a simpler metric for assessing optimal reactivity: a weighted average of surface coordination that includes second-nearest neighbors. The calculations identified three approaches for introducing cavity sites into the platinum(111) surface to improve its performance for the oxygen reduction reaction used in fuel cells.