Fig. 1: Characterization of the copper electrocatalysts.

a Schematic illustration for the preparation of the HB Cu, MB Cu and LB Cu catalysts. TEM of the HB Cu (b), MB Cu (c), and LB Cu (d) catalysts before CO2RR, respectively. Scale bars, 100 nm. Insets show the particle size distribution of the corresponding catalysts. Source data are provided as a Source Data file. HRTEM images showing crystallographic information of HB Cu (e), MB Cu (f), and LB Cu (g) catalysts before CO2RR, respectively. Scale bars, 5 nm. Locally magnified images showing the magnified grain boundaries. Scale bars, 2 nm. HRTEM images showing crystallographic information of HB Cu (h), MB Cu (i), and LB Cu (j) catalysts after 30 min of CO2RR, respectively. Scale bars, 10 nm. Locally magnified images showing the magnified grain boundaries. Scale bars, 2 nm. The yellow and orange dashed lines circle the facet fragments of the Cu(111) and Cu2O(111), respectively, and the white dashed line highlights the interface boundary between the Cu(111) and Cu2O(111) facets.