Well-ordered Pt(111) single-crystal electrodes are inactive towards CO2 reduction. Cycling the electrode in the Pt oxide region induces disorder on the surface. characterized by the presence of hydrogen adsorption states at 0.12 V and 0.26 V, which indicate the presence of domains with the geometry of (110) and (100) surfaces. In parallel with this, the electrode activity for CO2 reduction is increased. After interaction of CO2 with the perturbed Pt(111) surface, the suppression of the adsorption states corresponding to the defects indicates their important role in the electrode activity. The latter cannot be reached by simply introducing ordered (100) step rows on the (111) surface, as demonstrated by the limited activity of the vicinal Pt(211) and Pt(755) surfaces.