In Situ Electrochemical AFM Imaging of a Pt Electrode in Sulfuric Acid under Potential Cycling Conditions

Abstract

Understanding the electrochemical behavior of Pt at the solid/liquid interface is of significant importance for the development of efficient electrochemical devices, such as fuel cells and water electrolyzers. In this work, the evolution of the surface morphology of a polycrystalline platinum under potential cycling conditions was investigated by in situ electrochemical atomic force microscopy (EC-AFM). After 50 cycles between 0.05 and 1.8 V in 0.1 M HSO, the Pt surface is coarsened and nanoparticles of several nanometers appear on the surface. The critical upper and lower potentials for the formation of nanoparticles are found to be 1.8 and 0.8 V, respectively. The in situ AFM observation coupled with Cyclic Voltammerty reveals the periodic disappearance and reappearance of the nanoparticles, based on which the formation of nanoparticles is attributed to the deposition of dissolved Pt from solution, and a model for the nanoparticle formation is proposed. While the formation of a thick oxide layer is a prerequisite, the reduction process is found to have a strong influence on Pt nanoparticle formation as well. This investigation provides a visualization of the Pt electrode surface under electrochemical control in a large potential window, enabling a broader understanding of the Pt electrode roughening mechanisms.

Thermodynamics of the formation of surface PtO2 stripes on Pt(111) in the absence of subsurface oxygen

“…Pt from the platinum oxide may also dissolve into the electrolyte during the reductive scan, leading to platinum corrosion; however, this Pt dissolution is expected to be more dominant when a thicker oxide is formed. 6,32 When comparing the stripe model and our corresponding results to the electrochemical place-exchange studies, we find that oxide chains are plausible products of Pt(111) oxidation under electrochemical conditions, compatible with X-ray diffraction analysis by Drnec et al 4 Although the structures we studied exhibit long-range order, which runs contrary to the conclusions of Drnec et al, the observation of disordered and isolated spokewheels by Van Spronsen et al in early Pt(111) oxidation is consistent with both our dilated stripe structures and findings by Drnec et al 4,17 Pt atoms are suspended by more than one oxygen atom; in fact, two oxygen atoms per Pt atom are adsorbed above surface platinum atoms. This agrees with electron distributions found by Drnec et al, 4 yet contradicts their assumed place exchange model in which one O atom displaces one Pt atom and is incorporated into the surface.…”

Nanoscale Electrochemical Mapping

“…The roughening up to 1.5 V previously observed was not seen (possibly due to the polycrystalline nature of the sample, as well as the reduced resolution of the AFM), but the surface was instead roughened above 1.8 V through the formation of PtNPs. 143 A combined ultrahigh vacuum (UHV)-electrochemistry set-up has been developed that…”

Unsupported Pt nanoparticles: Synthesis, Deactivation, and Hydrogen Electrocatalysis in Unpurified Electrolytes

“…The propensity of Pt electrocatalysts to deactivate under reaction conditions makes these key measurements considerably more challeng-ing. [36][37][38] Whereas prior studies have generally addressed this challenge by maintaining scrupulously clean experimental conditions, [31][32][33] routine measurements of novel electrocatalysts (and associated comparisons to Pt) are often carried out in unpurified, reagent-grade electrolytes. This motivates the question of whether control experiments using Pt electrodes can be properly executed.…”