Insights into (Mn/Fe/Co)M–N–C dual-atom catalysts for the oxygen reduction reaction: the critical role of structural evolution†

Abstract

Single-atom catalysts (SACs) based on metal–nitrogen–carbon (M–N–C) compounds have been identified as a potential substitute for Pt-based oxygen reduction reaction (ORR) catalysts due to their facile availability and low cost. M₁M₂–N–C based dual-atom catalysts (DACs) may be utilised to regulate the active site and optimise their ORR activity. Accordingly, M₁M₂–N₆–C₁₄ (M₁ = Mn, Fe, Co; M₂ = late transition metals) DACs were constructed within a graphene slab. M₁M₂–N–C is more stable than the corresponding M₁–N–C and M₂–N–C due to the affinity between M₁ and M₂. Furthermore, the ORR activity of FeM–N–C (M = late transition metals), MnM–N–C (Co, Ru, Rh, Os, Ir, and Re) and CoM–N–C (M = Cu, Zn, Pd, and Pt) is enhanced in comparison to that of Fe–N–C, due to the modified electronic properties. In comparison to other active ORR electrocatalysts, FeCu–N–C is positioned at a relatively high level on the volcano plot. To gain further insight into the dynamic stability of FeCu–N–C under working conditions (*OOH, 80 °C), an ab initio molecular dynamics simulation was employed. The accelerated structural evolution of the FeCu–N–C electrocatalyst resulted in the Cu atom being pulled out of the N–C substrate plane. Nevertheless, the resulting Fe(vacancy)–N–C and Fe(vacancy)–NH–C electrocatalysts have been observed to retain high ORR activity and stability. The findings of this study have significant implications for the design of DACs.