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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 Cuad in a 0.1 M HClO4 + 0.020 M NaNO3 + 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 nitrate–free 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)

The initial stages of Cu deposition at low overpotentials have been studied on the Pt(100) and Pt(111) basal faces and stepped surfaces Pt(610), Pt(410) of platinum single crystal electrodes. The process includes formation of a Cuad adlayer, an epitaxial monolayer of a two dimensional phase and three dimensional copper crystallites on the (100) terraces, while on the Pt(111) face the two dimensional Cu layer is absent as in this case 3-fold coordination of deposited Cu atoms probably cannot provide sufficient decrease in surface energy of the system. At high enough cathodic overpotentials, the 3D-phase of copper is formed on the monolayer of copper adatoms Pt(111)-Cuad. The Stranski-Krastanov mechanism of nucleation and growth is realized on all the studied electrodes. Financial support from the Russian Foundation for Basic Research (project no. 14-03-00530), MINECO (CTQ2013-44083-P) and Generalitat Valenciana (PrometeoII/2014/013) (Feder, Spain) is gratefully acknowledged.

The kinetics of copper underpotential deposition on stepped Pt(hkl) electrodes with controlled width of (111) terraces in acidic solutions of copper sulfate with 0–200 mM of acetonitrile (AcN) has been studied by means of cyclic voltammetry. In the presence of AcN Cu UPD process is hindered both at (100) steps and (111) terraces of Pt(171515) and Pt(755) faces due to blocking of the electrode surface with organic molecules, strongly adsorbed at the steps and nearby ones. The decoration of (110) steps with copper adatoms is slightly accelerated for Pt(775) electrode in the solution with 0.04 mM AcN. Increase in AcN concentration leads to inhibition of the UPD process. The difference in behavior of the stepped platinum electrodes is controlled by competitive adsorption of AcN, (bi)sulfate and Cu atoms at the step sites. AcN adsorption at (100) steps is stronger as compared with (110) ones. Keywords: Copper, Stepped single crystal, Adsorption, Acetonitrile

The electrochemical behavior of adsorbed NO molecules on a Pt(100) electrode has been studied in perchloric acid solutions by means of cyclic voltammetry. According to the literature data, a saturated NO adlayer with a coverage of ∼0.5 monolayers (MLs) is formed under open circuit conditions in an acidic nitrite solution as a result of a disproportionation reaction. The saturated adlayer is stable in the potential range of 0.4–0.9 V vs. a reversible hydrogen electrode in 0.1 M HClO4. NO molecules are oxidized at 0.9–1.1 V with the formation of adsorbed nitrite anions, and they can be reduced to ammonia at potentials less than 0.4 V. In this paper it has been shown that the adlayer stability depends on the surface coverage and extent of ordering. An unsaturated NO adlayer demonstrates NO ↔ NH3 redox transformations at 0.5–0.8 V. Financial support from the Russian Foundation for Basic Research (project no. 10-03-00427), MICINN (CTR2010-1624)(Feder), and Generalitat Valenciana (Prometeo/2009/045)(Feder, Spain) is gratefully acknowledged.