Environment of Metal-O-Fe Bonds Enabling High Activity in CO Reduction on Single Metal Atoms and on Supported Nanoparticles.

Single-atom catalysts are often reported to have catalytic properties that surpass those of nanoparticles, while a direct comparison of sites common and different for both is lacking. Here we show that single atoms of Pt-group metals embedded into the surface of FeO have a greatly enhanced interaction strength with CO compared with the FeO surface. The strong CO adsorption on single Rh atoms and corresponding low activation energies lead to 2 orders of magnitude higher conversion rates of CO compared to Rh nanoparticles. This high activity of single atoms stems from the partially oxidic state imposed by their coordination to the support. FeO-supported Rh nanoparticles follow the behavior of single atoms for CO interaction and reduction, which is attributed to the dominating role of partially oxidic sites at the FeO-Rh interface. Thus, we show a likely common catalytic chemistry for two kinds of materials thought to be different, and we show that single atoms of Pt-group metals on FeO are especially successful materials for catalyzed reactions that depend primarily upon sites with the metal-O-Fe environment.