Thousand-hour salt precipitation-free CO2-to-ethylene electrosynthesis at high current densities

Salt precipitation remains a bottleneck in scaling carbon dioxide (CO2) electroreduction to ethylene (C2H4), as it blocks gas transport, induces electrode flooding, and causes rapid performance degradation. Identifying electric field-driven cation accumulation and the consequent hydrophobicity loss as key factors, here, we show a wettability-engineered Cu-based electrode that decouples hydrophobicity from electronic conductivity. The electrode incorporates in situ embedded Cu active sites within an insulating, hydrophobic polymer matrix, forming localized “hydrophobic trap”. This architecture preserves interfacial hydrophobicity under operation, suppresses cation accumulation, and confines locally generated OH⁻ ions to sustain an alkaline microenvironment for C-C coupling. The optimized electrode achieves a faradaic efficiency of 75.9% for C2H4 at 1.2 A cm−2 in a flow cell, and operates for over 1000 h in a membrane electrode assembly electrolyzer. The electrode maintains high productivity under low CO2 concentrations and in the presence of flue gas impurities. Techno-economic analysis confirms the feasibility of this strategy. The development of robust catalysts that could work under high current densities brings promise but is a challenge in CO2 electroreduction. Here, the authors report a wettability-engineered electrode design for ethylene electrosynthesis that operates over 1000 h without salt precipitation.