Stabilized Cu δ+ -OH species on in situ reconstructed Cu nanoparticles for CO 2 -to-C 2 H 4 conversion in neutral media.

Achieving large-scale electrochemical CO 2 reduction to multicarbon products with high selectivity using membrane electrode assembly (MEA) electrolyzers in neutral electrolyte is promising for carbon neutrality. However, the unsatisfactory multicarbon products selectivity and unclear reaction mechanisms in an MEA have hindered its further development. Here, we report a strategy that manipulates the interfacial microenvironment of Cu nanoparticles in an MEA to suppress hydrogen evolution reaction and enhance C 2 H 4 conversion. In situ multimodal characterizations consistently reveal well-stabilized Cu δ+ -OH species as active sites during MEA testing. The OH radicals generated in situ from water create a locally oxidative microenvironment on the copper surface, stabilizing the Cu δ+ species and leading to an irreversible and asynchronous change in morphology and valence, yielding high-curvature nanowhiskers. Consequently, we deliver a selective C 2 H 4 production with a Faradaic efficiency of 55.6% ± 2.8 at 316 mA cm -2 in neutral media.