Fig. 2

Structural characterization of pre-catalysts and Cu adparticles. a–c SEM/TEM images of oxide pre-catalysts. The scale bars are 2 μm in a, 200 nm in both b and c. d Schematic illustration of Cu adparticle growth from in-situ CO-RR. e–g SEM/HRSEM and h–j TEM/HRTEM images of Cu adparticle electrocatalysts obtained under CO-RR at −0.44 V vs. RHE in 1 M KOH. The scale bars are 500 nm in e, 200 nm in h, 50 nm in both f and i, 20 nm in both g and j, 2 nm in the inset of j