Transition metal-N₄ embedded black phosphorus carbide as a high-performance bifunctional electrocatalyst for ORR/OER

Designing highly active electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is an important challenge in energy conversion and storage technology. In this work, based on computational screening over doping of 23 kinds of transition metals (TMs), we use first-principles study to explore the ORR and OER activity of TM-N₄ embedded black phosphorus carbide monolayer (b-PC). The results show that its catalytic performance highly depends on the number of electrons in the d orbital and the number of valence electrons of introduced TM atom. Moreover, we found that Co-N₄-bPC (η_ORR = 0.31 V; η_OER = 0.22 V), Rh-N₄-bPC (η_ORR = 0.33 V; η_OER = 0.62 V), and Ir-N₄-bPC (η_ORR = 0.21 V; η_OER = 0.21 V) can be promising candidates as bifunctional catalysts for both the ORR and OER and can be comparable or superior to TM-N₄-graphene in terms of overpotential. They experience no structural distortion at 500 K. Moreover, the exfoliation energy of b-PC is lower than that of graphene, and these three promising candidates show much lower formation energy than TM-N₄-graphene. Our study provides a systematical method for designing and developing high performance 2D material-based single atom catalysts (SACs) beyond graphene.