Adequately stabilized and exposed copper heterostructure for CO2 electroreduction to ethanol with ultrahigh mass activity

Adequately exposure of active sites to reactants is crucial in improving the actual catalytic activity in various electrocatalytic reactions. e.g., CO2 electroreduction. Herein, we construct abundant opening mesopores throughout carbon nanofibers via a simple O2 plasma treatment, which can simultaneously create a CO2-rich environment and expose Cu/CuxO sites to the reaction interface. The unique Cu/CuxO sites can generate a 70.7% Faradaic efficiency of C2H5OH at the 400 mA cm−2 current density. Moreover, this superior structure can significantly increase the number of active sites that actually participated in the reaction, and leads to an exceptional 8.4 A mg−1 Cu mass activity for C2H5OH, which is among the highest mass activity for C2H5OH ever reported. The DFT calculation and CO-TPD studies reveal that the created Cu/CuxO heterostructure provides adequate *CO coverages and lowers the energy barrier of the C–C coupling process for ethanol formation, in which the key ethanol intermediates are detected via the in-situ spectra investigations. This strategy can be easily applied to construct efficient catalysts in other electrocatalytic reactions.