Electrochemical characteristics of nanostructured platinum electrodes – a cyclic voltammetry study

Abstract

Platinum surfaces play a decisive role in catalysis in sensors, fuel cells, solar cells and other applications like neuronal stimulation and recording. Technical advances in nanotechnology contributed tremendously to the progress in these fields. A fundamental understanding of the chemical and physical interactions between the nanostructured surfaces and electrolytes is essential, but was barely investigated up to now. In this article, we present a wet-chemical process for the deposition of nanostructures on polycrystalline platinum surfaces. The electrochemically active surface area was increased by a factor of over 1000 times with respect to the geometrical surface. The influence of the nanostructures was examined in different acidic, alkaline, and neutral electrolytes. Comparing cyclic voltammograms of nanostructured and planar polycrystalline platinum revealed new insights into the microenvironment at the electrode-electrolyte interface. The characteristic features of the cyclic voltammograms were altered in their shape and strongly shifted with respect to the applied potential. In neutral buffered and unbuffered electrolytes the water window was expanded from 1.4 V to more than 2 V. The shifts were interpreted as local pH-changes and exhausted buffer capacity in direct proximity of the electrode surface due to the strong release and binding of protons, respectively. These polarized electrodes induce significant changes in the electrochemical potential of the electrolyte due to the high roughness of their surface. The electrochemical phenomena and the observed voltage shifts are crucial for the understanding of the basic mechanism at nanostructured electrodes and mandatory for designing fuel cells, sensors and many other devices.

Elucidating the alkaline oxygen evolution reaction mechanism on platinum

“…As the potential applied to the WE becomes more anodic, the local increase of hydroxyl concentration (within the inner Helmholtz layer, IHL) becomes more pronounced. At the same time the high positive potential at the electrode surface lowers the Pt/ OH À surface binding energy whilst the high pH value (13.9) decreases the electrochemical potential of the electrolyte, 46 thereby favoring the activation of the Pt surface via hydroxyl adsorption followed by the electron transfer and the consequent formation of the Pt d -OH ads species. [47][48][49] The nal surface coupling and deprotonation of the adsorbed OH À leads to the evolution of oxygen.…”

pH dependent kinetic insights of electrocatalytic arsenite oxidation reactions at Pt surface

“…While the scan was reversed, these oxide species were reduced, and as a consequence, reductive waves are seen(Fig. 3)to appear between 0.4 and −0.02 V[23]. Several voltammetric data attained by averaging the results from three different experiments performed at pH values of 3, 5, 7, and 9…”

Platinum oxidation in alkaline electrolyte under potentiostatic conditions

“…A CHI 660D potentiostat (CH Instruments) was used in the experiments. The real surface area, used for current density calculation, was determined by integration of voltammetric currents due to desorption of underpotential deposited (UPD) adsorbed hydrogen [25][26][27] recorded with negative potential limit of − 800 mV (typically adopted surface coverage with adsorbed hydrogen of 0.77 [27] although the value of unity is also considered [26]) and with assumed specific charge density of 210 μC cm −2 for full coverage with adsorbed hydrogen [26][27][28]. Fig.…”