Polycrystalline and Single‐Crystal Cu Electrodes: Influence of Experimental Conditions on the Electrochemical Properties in Alkaline Media

Abstract

Single and polycrystalline Cu electrodes serve as model systems for the study of the electroreduction of CO , CO and nitrate, or for corrosion studies; even so, there are very few reports combining electrochemical measurements with structural characterization. Herein both the electrochemical properties of polycrystalline Cu and single crystal Cu(1 0 0) electrodes in alkaline solutions (0.1 m KOH and 0.1 m NaOH) are investigated. It is demonstrated that the pre-treatment of the electrodes plays a crucial role in determining their electrochemical properties. Scanning tunneling microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry are performed on Cu(1 0 0) electrodes prepared under UHV conditions; it is shown that the electrochemical properties of these atomically well-defined electrodes are distinct from electrodes prepared by other methods. Also highlighted is the significant role of residual oxygen and electrolyte convection in influencing the electrochemical properties.

Ab Initio Cyclic Voltammetry on Cu(111), Cu(100) and Cu(110) in Acidic, Neutral and Alkaline Solutions

“…This is similar to the experiments by Schouten et al . We must note that CVs reported in the literature on Cu single‐crystalline electrodes depend strongly on both the surface pre‐treatment and the selected potential range . Recently, Engstfeld et al.…”

Structure‐Sensitivity and Electrolyte Effects in CO2 Electroreduction: From Model Studies to Applications

“…subjected a Cu(100) surface to successive cycles of Ar + sputtering and annealing under ultra‐high vacuum condition and at 1000 K, followed by direct transfer to the electrochemical cell, without exposure to the electrochemical cell. This protocol ensured high surface ordering as demonstrated by ex‐situ STM measurements, with terraces >50 nm in width (in comparison, an STM images suggest that other treatments, involving air‐transfer and without a thermal annealing step, yield much rougher surfaces) . They demonstrated that the slight discrepancy between the reported blank voltammograms in literature, particularly for Cu(100), was related to the presence of defects that are likely to be induced by conventional surface pre‐treatments involving electropolishing and exposure of the electrode in air (Figure D).…”

“…Different surface pre‐treatments can be applied to Cu(hkl) in order to ensure surface ordering under experimental conditions. These pre‐treatments usually consist of both mechanical and electrochemical polishing of the surface (Figure C) and transferring through air . However, there is still slight discrepancy between the different voltammetric profiles reported in literature for Cu(hkl).…”

“…The inset shows the STM image with sizes of 700 nm×700 nm and 4 nm×4 nm, respectively (Recorded with IT=1 nA, UT=0.1 V and IT=0.6 nA, UT=0.2 V, respectively). Reprinted with permission from Copyright (2018) WILEY‐VCH Verlag GmbH& Co. KGaA,Weinheim.…”

On the Possibilities and Considerations of Interfacing Ultra‐High Vacuum Equipment with an Electrochemical Setup

“…Cu(111) was chosen as a sample due to Cu being the only pure metal electrocatalyst which can catalyse the reduction of CO 2 to a range of different interesting products with a reasonable faradaic efficiency . Furthermore, the fundamental EC properties of Cu are still under debate . The electrolytes were picked as they are prevalent in the literature for these sample types.…”