The reactivity of platinum microelectrodes

Abstract

Despite the widespread application of ultramicroelectrodes (UMEs), the customary method of their electrochemical characterization via outer sphere redox probing has serious limitations. In this study we provide additional insights into this subject by measuring not only outer sphere redox couples, but also blank voltammetries and the reactivity towards various catalytic reactions of Pt UMEs. The data for the UMEs are compared to those for macroscale Pt electrodes that can be flame-annealed. Although the reactivity is similar for reactions that are rather insensitive to the surface structure (and/or composition), UMEs perform much worse for more surface sensitive catalytic reactions. This effect can be explained by the UMEs being contaminated much faster, though it remains to be established if the origin of this contamination lies in the preparation method or in the impurities in the (high-purity grade) chemicals used. Our study recommends that catalytic reactivity measurements on ultramicroelectrodes should always be accompanied by blank voltammetries and the results have to be interpreted extremely carefully.

Absence of CO2 electroreduction on copper, gold and silver electrodes without metal cations in solution

“…A blank voltammogram of the Pt-UME can be seen in Fig. 4c, which shows the expected voltammetric features of a clean polycrystalline platinum surface 30 . The polycrystalline gold, copper and silver samples used were also characterized before the measurements, as shown in Fig.…”

Modification of Microelectrode Arrays with High Surface Area Dendritic Platinum 3D Structures: Enhanced Sensitivity for Oxygen Detection in Ionic Liquids

“…Given the rough nature of the deposits obtained from electrodeposition, the electroactive surface area (ESA) of each electrode was calculated using cyclic voltammograms (CVs) recorded in 0.5 M H 2 SO 4(aq) . Figure 3 shows CVs in 0.5 M H 2 SO 4 for all nine surfaces used in this study, scanned between the oxygen evolution and hydrogen evolution potentials, showing the characteristic behavior observed on platinum electrodes in H 2 SO 4 [ 40 , 41 ]. There are three main potential regions: (1) Above 0.5 V, oxidation processes corresponding to the formation of adsorbed oxygen, ‘oxide region’, (2) the small region where little current is observed, the ‘double layer region’, and (3) the region below 0.2 V, where two couples of reversible hydrogen adsorption/desorption processes are observed, ‘H region’ [ 40 , 41 ].…”

Nanoscale electrochemical movies and synchronous topographical mapping of electrocatalytic materials

“…In SECM, care must also be taken to ensure the tip activity is robust, which is non-trivial, given the high rates of mass transport to nanoscale electrodes. 22,23 By contrast, in droplet cell-based SEPM techniques such as scanning electrochemical cell microscopy (SECCM), the electrochemical properties of a surface are probed directly and locally with integrated probe positional feedback. 24,25 In SECCM, electrochemical measurements are performed within a confined area of a surface, defined by the dimensions of a droplet (meniscus) formed at the end of a pulled glass capillary, with probe (tip) diameters typically in the hundreds of nm [26][27][28][29] to µm 30,31 range.…”