Nano‐Confined Carbon Channels Enable Efficient Acidic CO 2 Electrolysis to Ethylene

ABSTRACT Acidic electrochemical CO 2 reduction reaction (CO 2 RR) offers a promising route for carbon utilization by mitigating carbonate formation that commonly occurs in alkaline and neutral electrolytes. However, efficient CO 2 ‐to‐C 2 H 4 conversion under strongly acidic conditions remains challenging because copper‐based catalysts suffer from severe corrosion and competitive hydrogen evolution reaction (HER). Herein, we report a nano‐confined‐channel‐modified copper catalyst fabricated through flash Joule heating‐driven rapid pyrolysis of waste polypropylene. The resulting graphitized carbon forms abundant nanoscale confined channels on the copper surface, creating a protective and microenvironment‐regulating interface that suppresses catalyst corrosion while maintaining accessible Cu active sites. As a result, the catalyst achieves a C 2 H 4 Faradaic efficiency of 70% at 400 mA cm − 2 , while sustaining a total C 2 Faradaic efficiency exceeding 80% over 200–700 mA cm − 2 . Molecular dynamics simulations and in situ characterizations reveal that the nano‐confined carbon interface promotes local K + accumulation, enriches reaction intermediates, and establishes a locally high‐pH microenvironment, thereby suppressing the HER and favoring C─C coupling during acidic CO 2 RR conditions. This work highlights nano‐confined carbon channels as an effective interfacial engineering strategy for acid‐tolerant CO 2 RR and provides a sustainable pathway for upcycling waste plastics into functional carbon modifiers for efficient CO 2 ‐to‐C 2 H 4 conversion.