Fig. 2: Surface faceting observed after quasi in situ pulsed CO2RR (an activated surface was achieved by structural modification of a Cu(100) surface after a pulsed CO2RR for 15 min).
a, LEEM image (electron energy E0 = 48 eV) after EC pulsing during the CO2RR between −1 VRHE and +0.6 VRHE, 1-s cycle ending at +0.6 VRHE. The images were obtained after experimental protocols where the ending pulse is indicated in red. Scale bar, 1 μm (applies to all images). b, XPEEM image (hν = 933 eV, E0 = 2 eV) on the same area as a displaying shadowing effects. c, Schematic representation of the observed shadowing effect for the truncated pyramid shape, based on the X-ray incidence angle and sample orientation, as observed in (b). d, LEEM image (electron energy E0 = 2.4 eV) for a sample exposed to EC pulses during the CO2RR between −1 VRHE and +0.8 VRHE, ending at +0.8 VRHE. e, XPEEM image (hν = 933 eV, E0 = 2 eV) on the same area as d displaying shadowing effects. f, Schematic representation of the observed shadowing effect for the pyramid shape, based on the X-ray incidence angle and sample orientation, as observed in (e). g, Atomistic representation of copper planes forming (n10) facets, where different atom colours represent atoms in different atomic planes. h, Graphic representation of height–angle effects in PEEM. Some areas appear brighter or darker as a consequence of the facet inclination in relation to the X-ray illumination. i, Overview cartoon of the square structures in g formed during pulsed CO2RR on the (001) surface.
