Electroreduction of nitrate anions on cubic and polyoriented platinum nanoparticles modified by copper adatoms

Abstract

In this work, electroreduction of nitrate anions on bare and copper-modified platinum nanoparticles (Pt NPs) supported on glassy carbon is studied using cyclic voltammetry. Two types of Pt NPs are chosen for this purpose: unshaped (polyoriented) NPs and cubic NPs displaying the preferential (100) orientation of faces. The modification of cubic and polyoriented Pt NPs by copper adatoms with submonolayer coverages is performed in a controlled way in solutions containing small concentrations of Cu2+ ions, 10−5M. Nitrate reduction is studied first in copper-free solutions and then in the presence of 10−5M Cu2+. The transmission electron microscopy and voltammetric measurements of the cubic NPs indicate the presence of a significant amount of Pt(100) terraces on the surface of these NPs. In perchloric acid solutions containing 0.02M NaNO3 and 10−5M Cu2+, accumulation of copper adatoms on the NPs results in a fast increase in the currents of nitrate electroreduction. These reduction currents on the cubic NPs are up to three times higher than on the polyoriented NPs at Cu coverages of 0.20–0.35. The comparison of the data on Pt NPs with the data for single crystal electrodes with (100) terraces of different width (Pt(610), Pt(210)) shows that the behavior of NPs can be simulated on the basis of the data for single crystal faces with wide (cubic NPs) and narrow (unshaped NPs) (100) terraces. Thus, cubic NPs manifest rather a high electrocatalytic activity in the studied reaction of nitrate anion electroreduction, which is typical for single crystal surfaces with relatively wide Pt(100) terraces. At the same time, in comparison with macro single crystalline electrodes, these NPs are characterized by sufficiently higher stability, larger specific surface area, and flexibility in application.