Operando reconstruction towards stable CuI nanodots with favorable facets for selective CO2 electroreduction to C2H4

Cu-based electrocatalysts with favorable facets and Cu+ can boost CO2 reduction to valuable multicarbon products. However, the inevitable Cu+ reduction and the phase evolution usually result in poor performance. Herein, we fabricate CuI nanodots with favorable (220) facets and a stable Cu+ state, accomplished by operando reconstruction of Cu(OH)(2) under CO2- and I--containing electrolytes for enhanced CO2-to-C2H4 conversion. Synchrotron X-ray absorption spectroscopy (XAS), in-situ Raman spectroscopy and thermodynamic potential analysis reveal the preferred formation of CuI. Vacuum gas electroresponse and density functional theory (DFT) calculations reveal that CO2-related species induce the exposure of the (220) plane of CuI. Moreover, the small size of nanodots enables the adequate contact with I-, which guarantees the rapid formation of CuI instead of the electroreduction to Cu-0. As a result, the resulting catalysts exhibit a high C2H4 Faradaic efficiency of 72.4% at a large current density of 800 mA cm(-2) and robust stability for 12 h in a flow cell. Combined in-situ ATR-SEIRS spectroscopic characterizations and DFT calculations indicate that the (220) facets and stable Cu+ in CuI nanodots synergistically facilitate CO2/*CO adsorption and *CO dimerization.