Nano-Confined Carbon Channels Enable Efficient Acidic CO₂ Electrolysis to Ethylene

Acidic electrochemical CO₂ reduction reaction (CO₂RR) offers a promising route for carbon utilization by mitigating carbonate formation that commonly occurs in alkaline and neutral electrolytes. However, efficient CO₂-to-C₂H₄ 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 C₂H₄ Faradaic efficiency of 70% at 400 mA cm^{- 2}, while sustaining a total C₂ 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 CO₂RR conditions. This work highlights nano-confined carbon channels as an effective interfacial engineering strategy for acid-tolerant CO₂RR and provides a sustainable pathway for upcycling waste plastics into functional carbon modifiers for efficient CO₂-to-C₂H₄ conversion.