Operando Synthesis of High-Curvature Copper Thin Films for CO₂ Electroreduction.

As the sole metal that could reduce CO₂ to substantial amounts of hydrocarbons, Cu plays an important role in electrochemical CO₂ reduction, despite its low energy efficiency. Surface morphology modification is an effective method to improve its reaction activity and selectivity. Different from the pretreated modification method, in which the catalysts self-reconstruction process was ignored, we present operando synthesis by simultaneous electro-dissolution and electro-redeposition of copper during the CO₂ electroreduction process. Through controlling the cathodic potential and CO₂ flow rate, various high-curvature morphologies including microclusters, microspheres, nanoneedles, and nanowhiskers have been obtained, for which the real-time activity and product distribution is analyzed. The best CO₂ electro-reduction activity and favored C₂H₄ generation activity, with around 10% faradic efficiency, can be realized through extensively distributed copper nanowhiskers synthesized under 40 mL/min flow rate and -2.1 V potential.