Environment of Metal–O–Fe Bonds Enabling High Activity in CO2 Reduction on Single Metal Atoms and on Supported Nanoparticles

Abstract

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 Fe₃O₄ have a greatly enhanced interaction strength with CO₂ compared with the Fe₃O₄ surface. The strong CO₂ adsorption on single Rh atoms and corresponding low activation energies lead to 2 orders of magnitude higher conversion rates of CO₂ compared to Rh nanoparticles. This high activity of single atoms stems from the partially oxidic state imposed by their coordination to the support. Fe₃O₄-supported Rh nanoparticles follow the behavior of single atoms for CO₂ interaction and reduction, which is attributed to the dominating role of partially oxidic sites at the Fe₃O₄–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 Fe₃O₄ are especially successful materials for catalyzed reactions that depend primarily upon sites with the metal–O–Fe environment.