Triadic Sites Drive Tandem CO ₂ ‐to‐Ethanol Conversion by Steering *CO Coverage and *COH Intermediate Formation

Abstract

ABSTRACT Single metal‐coordinated nitrogen‐doped carbon (M 1 ‐NC) materials hold great promise for electrocatalytic CO 2 reduction, yet the precise modulation of their nitrogen configurations to steer ethanol selectivity remains a formidable challenge. Here, we designed Cu 1 ‐NC anchored on a carbon support featured with a high pyrrolic‐N to pyridinic‐N ratio (CuN 4 /pr‐h‐NC), which enables an exceptional Faradaic efficiency (FE) of 79.6% for ethanol. Experimental and theoretical studies reveal that pyrrolic‐N and pyridinic‐N synergize with Cu sites to form novel triadic sites, which regulate the potential‐determining step (PDS) from the traditional C–C coupling step to the protonation step of *CO to *COH. Pyrrolic N boosts *CO surface coverage, after which *CO migrates to neighboring pyridinic N sites for hydrogenation to *COH. The resulting *COH readily couples with another *CO at the single Cu site, driving selective ethanol formation. Due to the single‐metal‐surface‐independence of PDS, this mechanism extends to metals traditionally considered inactive for C–C coupling (M = Fe, Co, Ni, Zn). A positive correlation is observed between the ethanol FE and the pyrrolic N/pyridinic N ratio across the series, with ZnN 4 /pr‐h‐NC reaching 71.8% at –0.5 V versus RHE. This work establishes an ensemble site engineering strategy to rationally steer CO 2 to ethanol pathways for M 1 ‐NC electrocatalysts.