Stable <scp> CO ₂ </scp> electroreduction to <scp> CH ₄ </scp> at an engineering‐relevant scale enabled by confined Cu nanoclusters

Abstract Electrocatalytic CO 2 methanation is a promising strategy for renewable energy storage but remains limited by low selectivity and insufficient stability under industrially relevant conditions. Here, a confined Cu atom‐cluster catalyst anchored on a nitrogen‐rich carbon framework (Cu AC/NC) is reported, synthesized via a scalable supramolecular precursor strategy that precisely controls Cu aggregation at the atomic‐cluster scale. In a flow‐cell configuration, Cu AC/NC achieves a CH 4 Faradaic efficiency of ~70% with a partial current density of 316.1 mA cm −2 . In situ spectroscopic analyses reveal that cluster confinement tailors the local reaction microenvironment, facilitating *CO protonation and deep hydrogenation of CO 2 . Deactivation mechanisms in alkaline and acidic electrolytes, as well as under pulsed electrolysis, are systematically examined. By balancing activity and stability, a pure‐H 2 O‐fed system is identified, enabling stable, carbonate‐free operation in scalable membrane electrode assemblies while sustaining methane production at engineering‐relevant current density.