Efficient and Selective CO ₂ -to-Formate Conversion Using Waste Plastic-Derived Carbon Nanotube-Copper Catalysts

Electrochemical reduction of CO2 to formic acid (FA) offers a straightforward route for CO2 utilization and hydrogen (H2) storage. However, its widespread application is hindered by challenges such as low efficiency, poor catalyst stability, and scalability issues. In this study, we upcycled waste plastics into nitrogen-doped carbon nanotubes (N-pCNTs) and employed them as a support for copper (Cu) electrocatalysts in CO2 reduction. The resulting N-pCNT/Cu catalyst exhibited improved performance, achieving 82% formate selectivity at a low applied potential and sustaining a high current density of over 400 mA cm–2. Moreover, it demonstrated stable operation, maintaining over 75% formate selectivity for more than 50 h in a flow cell. Density functional theory calculations revealed that N-defect sites in the CNT framework modulate the electronic structure of Cu, strengthening CO2 adsorption and stabilizing key *OCHO intermediates. This cooperative Cu–N interaction provides a unique reaction pathway distinct from that of conventional Cu catalysts, thereby enhancing both activity and durability. This innovation not only advances scalable e-fuel production but also aligns with global efforts to reach a net-zero carbon future.