Surface reconstruction of copper foil via electrochemical etching to proliferate CH4 production from CO2 electroreduction

Electrocatalytic CO2 reduction (eCO2R) to CH4 is a prospective approach for producing high value-added fuels. In this work, an effective approach was proposed by surface reconstruction using copper foil to facilitate eCO2R to CH4. The copper foil surface reconstruction was achieved via electrochemical etching in dilute phosphoric acid. Comprehensive characterizations suggested that the crystallinity and chemical binding energy states of the copper foil were well preserved after surface reconstruction, but the arrangement of copper atoms on the surface was adjusted. Etching time for 80 s was the most preferable condition, obtaining a uniform valley pattern structure with abundant grain boundaries, reporting the highest CH4 Faraday efficiency of 68.84% which was an order of magnitude higher compared to green foil counterpart. The relevant partial current density, CH4 production rate, and half-cell power conversion energy were measured to be −16.32 mA cm−2, 0.174 μmol s−1 cm−2, and 28.8% respectively from eCO2R at −1.3 V (vs. RHE). The in-situ ATR-IR spectroscopy confirmed that the surface reconstructed copper foil can significantly strengthen the adsorption of the *CO intermediate, facilitating its further hydrogenation to produce CH4 instead of dimerization to give C2 products. This work expanded the method of surface modification for copper foil via electrochemical etching and realized the regulation of geometric morphology on catalyst surface to obtain the desired performance for CO2 electroreduction reaction. [Display omitted] •Electrochemical etching for copper foil surface reconstruction was proposed.•Constructed valley pattern structures on copper foil increased grain boundaries.•Highest FECH4 of 68.84% was achieved via 80 s etching, tenfold improved.•Mechanism of eCO2R to CH4 over Cu-80s was confirmed via in-situ ATR-IR.