Nitrate electroreduction is studied on Pt(S)-[n(100) x(110)] stepped platinum single crystals with 2, 4, and 6 atoms wide terraces modified by copper adatoms. The electrodes were modified by electrodeposition of Cu-ad in a 0.1M HClO4 thorn 0.020 M NaNO3 thorn 10(-5)M Cu(ClO4)(2) solution by cycling the potential in the range of 50-350 mV, simultaneously with nitrate reduction. The peak of dissolution of copper adatoms in the nitrate solution is shifted in the positive direction, as compared to the nitrateefree solution, due to the stabilization of copper adatoms by adsorbed NO. This shift is not observed for Pt(210) with the terrace width of only 2 atoms: an increase in the terrace width results in the growing peak shift. The rate of nitrate electroreduction on modified electrodes increases by up to two orders of magnitude and grows at low copper coverages at an increase in the terrace width in the sequence of Pt(210) < Pt(410) < Pt(610). An increase in the surface coverage by copper adatoms causes redistribution of adatoms in the adsorption layer. In this case, the differences in the nitrate reduction rate decrease, but the sequence of Pt (210) < Pt (410) < Pt (610) is still preserved. The full surface coverage by Cuad cannot be obtained in this working solution by potential cycling in the range of 50-350mV. (C) 2018 Elsevier Ltd. All rights reserved.