C2N-graphene supported single-atom catalysts for CO2 electrochemical reduction reaction: mechanistic insight and catalyst screening

Abstract

Single-atom catalysts (SACs) have emerged as an excellent platform for enhancing catalytic performance. Inspired by the recent experimental synthesis of nitrogenated holey 2D graphene (C₂N-h2D) (Mahmood et al., Nat. Commun., 2015, 6, 6486–6493), we report density functional theory calculations combined with computational hydrogen electrode model to show that C₂N-h2D supported metal single atoms (M@C₂N) are promising electrocatalysts for CO₂ reduction reaction (CO₂ RR). M confined at pyridinic N6 cavity promotes activation of inert OCO bonds and subsequent protonation steps, with *COOH → *CO → CHO predicted to be the primary pathway for producing methanol and methane. It is found that *CO + H⁺ + e⁻ → *CHO is most likely to be the potential determining step; breaking the scaling relation of *CO and *CHO binding on M@C₂N SACs may simply be a rare event that is sensitively controlled by the detailed geometry of the adsorbate. Among twelve metals screened, M@C₂N SACs where M = Ti, Mn, Fe, Co, Ni, Ru were identified to be effective in catalyzing CO₂ RR with lowered overpotentials (0.58 V–0.80 V).