First-Principles Landscape of Single Atomic Catalysts to Metal Catalysts

Catalyzing oxygen reduction toward water, while generating electrical energy, holds great potential in scaling eco-friendly energy conversation and storage technologies. Current studies have largely focused on single iron atomic catalysts and carbon-supported platinum nanoparticles. Consequently, the exploration of alternative catalysts has been restricted, leaving a wealth of potential undiscovered. Here, we reported a transition from metallic to covalent bonding in carbon-supported transition metal catalysts (TM@Cs), which can explain the formation of two high-activity regions that are centered around iron single atomic catalysts and Pt-NPs. In addition to the classical scaling relation (ΔG*OOH = ΔG*OH + 3.2), we identified a novel scaling relation (ΔG*OOH = 1.55ΔG*OH + 0.77) between *OOH and *OH adsorption energy, dictating the presence of the second oxygen reduction reaction (ORR) pathway. TM@Cs with a higher metal-to-covalent bond ratio demonstrate a strong adsorption, favoring this new ORR pathway and suggesting inferior activity compared to that along the traditional ORR pathway. By increasing the covalent bonds in TM@Cs, it is likely to diminish the adsorption strength, thereby transitioning from this new pathway back to the conventional pathway and showing an activity improvement. This work provides a deep understanding of carbon-supported metal catalysts in designing effective catalysts.