Single rhodium atom embedded two dimensional MoSi2N4: A promising electrocatalyst for oxygen reduction reaction

It is essential to develop electrocatalysts that exhibit excellent performance in the oxygen reduction reaction (ORR) for electrochemical energy applications. Recently, MoSi2N4 monolayer has been synthesized and attracted widespread interest. Herein, we constructed a series of structures by embedding transition metal (TM = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ir, Pt and Au) atom into MoSi2N4 with N vacancy (VN-MSN), denoted as TM@VN-MSN, and investigated their ORR activity systematically by first-principles calculations. It is found that TM@VN-MSN systems are stable and there is charge transfer between TM atom and MoSi2N4. After screening, Rh@VN-MSN has the best ORR catalytic activity with an overpotential of 0.35 V, even lower than that of classical Pt (1 1 1). Furthermore, an implicit solvation model is used to evaluate the solvent effect. The volcano plots and scaling relations are established based on free energies of intermediates, and verified ΔG*OH can use as a descriptor to explore the ORR activity on TM@VN-MSN. Moreover, d-band center theory and crystal orbital Hamilton populations (COHP) are used to reveal the ORR activity origin. This work not only provide a promising method for designing a new type of MoSi2N4-based ORR catalysts, but also expands its application in the field of electrocatalysis.