Cu-based electrocatalysts with favorable facets and Cu^(+)can boost CO_(2) 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 CO_(2)-and I--containing electrolytes for enhanced CO_(2)-to-C_(2)H_(4) 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 CO_(2)-related species induce the exposure of the(220)plane of Cu I.Moreover,the small size of nanodots enables the adequate contact with I^(-),which guarantees the rapid formation of Cu I instead of the electroreduction to Cu^(0).As a result,the resulting catalysts exhibit a highC2H4 Faradaic efficiency of 72.4%at a large current density of 800 m A cm^(-2) and robust stability for 12h in a flow cell.Combined in-situ ATR-SEIRS spectroscopiccharacterizations and DFT calculations indicate that the(220)facets and stable Cu^(+) in CuI nanodots synergistically facilitate CO_(2)/*CO adsorption and*CO dimerization.
