Environment of Metal-O-Fe Bonds Enabling High Activity in CO 2 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 Fe ₃ O ₄ have a greatly enhanced interaction strength with CO ₂ compared with the Fe ₃ O ₄ surface. The strong CO ₂ adsorption on single Rh atoms and corresponding low activation energies lead to 2 orders of magnitude higher conversion rates of CO ₂ compared to Rh nanoparticles. This high activity of single atoms stems from the partially oxidic state imposed by their coordination to the support. Fe ₃ O ₄ -supported Rh nanoparticles follow the behavior of single atoms for CO ₂ interaction and reduction, which is attributed to the dominating role of partially oxidic sites at the Fe ₃ O ₄ -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 Fe ₃ O ₄ are especially successful materials for catalyzed reactions that depend primarily upon sites with the metal-O-Fe environment.