Facet-selective deposition of ultrathin Al2O3 on copper nanocrystals for highly stable CO2 electroreduction to ethylene.

Catalysts based on Cu nanocrystals (NCs) for electrochemical CO 2 -to-C 2+ conversion with high activity have been a subject of considerable interest, but poor stability and low selectivity for a single C 2+ product remain obstacles for realizing sustainable carbon-neutral cycles. Here, we used the facet-selective atomic layer deposition (FS-ALD) technique to selectively cover the (111) surface of Cu NCs with ultrathin Al 2 O 3 to increase the exposed facet ratio of (100)/(111), resulting in a faradaic efficiency ratio of C 2 H 4 /CH 4 for overcoated Cu NCs 22 times higher than that for pure Cu NCs. Peak performance of the overcoated catalyst (Cu NCs/Al 2 O 3 -10C) reaches a C 2 H 4 faradaic efficiency of 60.4% at a current density of 300 mA cm -2 in 5 M KOH electrolyte, when using a gas diffusion electrode flow cell. Moreover, the Al 2 O 3 overcoating effectively suppresses the dynamic mobility and the aggregation of Cu NCs, which explains the negligible activity loss and selectivity degradations of Cu NCs/Al 2 O 3 -10C shown in stability tests.