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.