Insights into the Oxygen Evolution Reaction on Graphene-Based Single-Atom Catalysts from First-Principles-Informed Microkinetic Modeling

Single-atom transition metals embedded in nitrogen-doped
graphene
have emerged as promising electrocatalysts due to their high activity
and low material cost. These materials have been shown to catalyze
a variety of electrochemical reactions, but their active sites under
reaction conditions remain poorly understood. Using first-principles
density functional theory calculations, we develop a pH-dependent
microkinetic model to evaluate the relative performance of transition
metal catalysts embedded in fourfold N-substituted double carbon vacancies
in graphene for the oxygen evolution reaction. We find that reaction
pathways involving intermediates co-adsorbed on the metal site are
preferred on all transition metals. These pathways lead to enhancements
in catalytic activity and broaden the activity peak when compared
with purely thermodynamics-based predictions. These findings demonstrate
the importance of investigating reaction pathways on graphene-based
catalysts and other two-dimensional (2D) materials that involve metal
active centers decorated by spectator intermediate species.