Disperse Multimetal Atom-Doped Carbon As Efficient Bifunctional Electrocatalysts For Oxygen Reduction And Evolution Reactions: Design Strategies

Disperse metal atoms can boost the catalytic activities of carbon-based electrocatalysts for various important chemical reactions at the heart of clean energy conversion technologies, such as oxygen reduction reaction (ORR) or oxygen evolution reaction (OER), but there lacks fundamental understanding and design principle of the catalysts. Herein, we design new disperse metal atom catalysts with single-, dual-, and tri-metal sites coordinated by nitrogen and study their catalytic activities by using the density functional theory methods. The electronic structures, reaction free energies, reaction pathways, and over-potentials were calculated to predict the catalytic activities for OER and ORR. The results show that introducing heterogeneous metal sites can break the scaling factor, significantly enhancing the bifunctional catalytic activities. An intrinsic descriptor was found to well describe the catalytic activities and provide a better understanding of the local electrical field effects on catalytic activities. Among all the catalysts studied in this work, ZnCo metal pairs show the preeminent bifunctional catalytic activities. Dual-metal catalysts generally suppress the competing two-electron-transfer reaction (formation of H2O2) while facilitating the four-electron-transfer ORR and perform better than single- and tri-metal ones and the best commercial noble metal catalysts (e.g., Pt and RuO2). The predictions are consistent with the previous experimental results. This work provides a theoretical base for rational design of disperse metal atom catalysts with excellent bifunctional catalytic activities.