Theoretical insights of penta-M2N4 for oxygen reduction electrocatalysis

Abstract

The excellent oxygen reduction reaction (ORR) activity of the nitrogen-coordinated metal site (the “MN4” site) makes them promising candidates. Hence, extending a similar family is of great importance for the development of the ORR catalysts. In this work, we investigate ten penta-M2N4 (M = Ni, Pd, Pt, or Rh) by considering their stability, activity, and selectivity for the ORR performance based on first-principles calculations. Our results show that all the penta-M2N4 (p-M2N4) are dynamically and thermally stable and are promising for synthesis and application in the ORR. The 2e− ORR process overpotentials of p-NiPdN4 (Ni site) and p-PdRhN4 (Pd site) are estimated to be 0.07 V and 0.14 V, respectively, showing comparable activities to the well-known CoN4-C. For the 4e− ORR, p-Rh2N4 (Rh site), p-NiRhN4 (Ni site), and p-PdRhN4 (Rh site) are identified as candidates with excellent ORR performance. Moreover, a structure–activity relationship between the electronic properties and the catalytic performance is established, and the orbital hybridization induced by alloying plays a crucial role in modulating the selectivity in ORR. Our study provides valuable insights for the design of ORR catalysts.