Leveraging Interlayer Interaction in M-N-C Catalysts for Enhanced Activity in Oxygen Reduction Reactions

Atomically dispersed metal-nitrogen-carbon (M-N-C) materials are deemed promising catalysts for the oxygen reduction reaction (ORR) in fuel cells. Yet the multilayer nature of M-N-C has been largely neglected in computational analysis. To bridge the gap, we conducted a first-principles investigation using bilayer M-N-C models (TMN/G-TMN/G, TM = Mn, Fe, Co, Ni, Cu, G = graphene, x, y = 3 or 4), where the TMs on the top serves as the active center. While in-plane TMN₄ at the bottom has a minimal impact on the ORR, out-of-plane TMN₃ substantially influences the adsorption free energy of OH through a strong interlayer bonding interaction. By leveraging interlayer interactions, we appreciably lowered the overpotential of selected TMN₄ (TM = Co, Ni, Cu) and achieved a minimum of 0.40 V on CoN₄/G-CuN₃/G. Constant potential calculations revealed weak dependence of OH binding energy on external voltage and obtained results comparable to constant charge calculation. This study provided new physical insight into modulating naturally occurring multilayer M-N-C catalysts.