Tailoring local structures of atomically dispersed copper sites for highly selective CO₂ electroreduction

Abstract

Atomically-dispersed copper sites coordinated with nitrogen-doped carbon (Cu–N–C) can provide novel possibilities to enable highly selective and active electrochemical CO₂ reduction reactions. However, the construction of optimal local electronic structures for nitrogen-coordinated Cu sites (Cu–N₄) on carbon remains challenging. Here, we synthesized the Cu–N–C catalysts with atomically-dispersed edge-hosted Cu–N₄ sites (Cu–N₄C₈) located in a micropore between two graphitic sheets via a facile method to control the concentration of metal precursor. Edge-hosted Cu–N₄C₈ catalysts outperformed the previously reported M–N–C catalysts for CO₂-to-CO conversion, achieving a maximum CO Faradaic efficiency (FE_CO) of 96%, a CO current density of –8.97 mA cm^–2 at –0.8 V versus reversible hydrogen electrode (RHE), and over FE_CO of 90% from –0.6 to –1.0 V versus RHE. Computational studies revealed that the micropore of the graphitic layer in edge-hosted Cu–N₄C₈ sites causes the d-orbital energy level of the Cu atom to shift upward, which in return decreases the occupancy of antibonding states in the *COOH binding. This research suggests new insights into tailoring the locally coordinated structure of the electrocatalyst at the atomic scale to achieve highly selective electrocatalytic reactions.

Keywords

atomic local structure / density functional theory / electrochemical CO ₂ reduction / metal nitrogen-doped carbon / single-atom catalyst

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