Hydrophobic, Ultrastable\nCu<sup>δ+</sup> for\nRobust CO<sub>2</sub> Electroreduction to C<sub>2</sub> Products at\nAmpere-Current Levels

Copper (Cu) is the only known material that can efficiently\nelectrocatalyze\nCO₂ to value-added multicarbon products. Owing to the instability\nof the Cu^δ+ state and microscopic structure in reactions,\nCu catalysts are still facing big challenges with low selectivity\nand poor durability, particularly at high current densities. Herein,\nwe report a rational one-step surface coordination approach for the\nsynthesis of Cu dendrites with an ultrastable Cu^δ+ state and hydrophobicity (Cu CF), even after exposure to air for\nover 6 months. As a result, Cu CF exhibited a C₂ FE of\n90.6% at a partial current density of 453.3 mA cm^–2 in a flow cell. A 400 h stable electrolysis at 800 mA and even a\nground-breaking stable operation at a large industrial current of\n10 A were achieved in the membrane electrode assembly (MEA) form.\nWe further demonstrated a continuous production of C₂H₅OH solution with 90% relative purity at 600 mA over 50 h in\na solid-electrolyte reactor. Spectroscopy and computation results\nsuggested that Cu(II) carboxylate coordination species formed on the\nsurface of Cu CF, which ensured the stability of the Cu^δ+ state and hydrophobicity. As a result, rich active sites and a stable\nthree-phase interface on the catalyst surface were achieved, along\nwith the optimized *CO adsorption strength and adsorption configuration.\nThe mixed *CO adsorption configurations on Cu CF made the *CO dimerization\nprocess easier, which promoted the conversion of CO₂ to\nC₂ products. This work provides a promising paradigm for\nthe design and development of Cu-based catalysts with ultrahigh stability\nunder industrial current densities.