Single Crystal Electrochemistry as an In Situ Analytical Characterization Tool

Deconvolution of the Voltammetric Features of a Pt(100) Single-Crystal Electrode

The Pt(100) single-crystal electrode shows four voltammetric features in acid electrolytes, but the precise corresponding surface phenomena remain unresolved. Herein, a deconvolution of the classical "hydrogen region" from the "hydroxyl and anion region" is attempted by the comparison of voltammetric behavior of Pt(100) and GMLPt(100) electrodes. A systematic study performed on Pt(s)-[n(100) × (111)] and Pt(s)-[n(100) × (110)] electrodes reveals that the feature at EPI = 0.30 VRHE corresponds to pure hydrogen adsorption taking place at (111) step sites vicinal to (100) domains, while the peak at EPII = 0.36 VRHE actually involves hydroxyl replacing hydrogen at (100) domains. An analysis examined for H2SO4, HClO4, CH3SO3H, and HF demonstrates that the specific (H)SO4- adsorption commences at EPIII = 0.40 VRHE and effectively suppresses the formation of hydroxyl at the (100) terrace at higher potentials 0.40 < EPIV < 0.75 VRHE. Non-specifically adsorbing anions (ClO4-, CH3SO3- and F-) would only interact with the hydroxyl phase formed on the Pt(100) terrace in both potential regions.

Nanoscale morphological evolution of monocrystalline Pt surfaces during cathodic corrosion

Cathodic corrosion is a relatively unexplored but highly enigmatic electrochemical phenomenon that transforms, roughens, and dissolves metal surfaces under cathodic polarization. We show how cathodic corrosion of a platinum spherical single-crystal electrode in an aqueous alkaline electrolyte leads initially to the formation of etch pits that reflect the local symmetry of the surface and subsequently develop into a growth regime in which self-similar diffusion-limited patterns emerge. These are unique observations that may eventually open the door to controlled surface patterning and nanoparticle preparation.

This paper studies the cathodic corrosion of a spherical single crystal of platinum in an aqueous alkaline electrolyte, to map out the detailed facet dependence of the corrosion structures forming during this still largely unexplored electrochemical phenomenon. We find that anisotropic corrosion of the platinum electrode takes place in different stages. Initially, corrosion etch pits are formed, which reflect the local symmetry of the surface: square pits on (100) facets, triangular pits on (111) facets, and rectangular pits on (110) facets. We hypothesize that these etch pits are formed through a ternary metal hydride corrosion intermediate. In contrast to anodic corrosion, the (111) facet corrodes the fastest, and the (110) facet corrodes the slowest. For cathodic corrosion on the (100) facet and on higher-index surfaces close to the (100) plane, the etch pit destabilizes in a second growth stage, by etching faster in the (111) direction, leading to arms in the etch pit, yielding a concave octagon-shaped pit. In a third growth stage, these arms develop side arms, leading to a structure that strongly resembles a self-similar diffusion-limited growth pattern, with strongly preferred growth directions.

Advances and challenges for experiment and theory for multi-electron multi-proton transfer at electrified solid–liquid interfaces

Understanding microscopic mechanism of multi-electron multi-proton transfer reactions at complexed systems is important for advancing electrochemistry-oriented science in the 21st century.