Kinetically induced irreversibility in electro-oxidation and reduction of Pt surface

The Melamine-Driven Solvation Effect Promotes Oxygen Reduction on a Platinum Catalyst: Machine Learning-Aided Free Energy Calculations

The modification of Pt surfaces with organic compounds like melamine enhances oxygen reduction reaction activity and catalyst durability. Through first-principles free energy calculations utilizing thermodynamic integration and finite-temperature molecular dynamics, enhanced by machine learning force fields for efficient sampling of nanosecond-scale interfacial water fluctuations and incorporating corrections to accurately reproduce first-principles free energies, we demonstrate that melamine destabilizes OH adsorbates, facilitating their removal and enhancing catalytic activity. Unlike alloys, where OH destabilization is driven by changes in electronic structure and surface strain, melamine disrupts hydrogen bonding between OH and interfacial water. Structural and vibrational analyses reveal that melamine alters the water solvation structure, which is evident in modified radial distribution functions and a blue shift in the O-H stretching vibrations. These findings indicate that manipulating interfacial solvation with organic compounds could be a promising approach to enhance catalytic activity without compromising durability.

Mechanistic Insights into Cyclic Voltammograms on Pt(111): Kinetics Simulations

A detailed understanding of the electrochemistry of platinum electrodes is of great importance for the electrochemical oxidation of fuels and electrochemical reduction of dioxygen in fuel cells. The Pt(111) facet is the most representative model mimicking Pt nanoparticles and polycrystals for fundamental studies. Herein, we propose a site-specific model accompanied with the typical elementary steps of the electrochemistry of Pt(111) in non-adsorbing electrolyte within the potential range between 0.05 and 1.15 V versus reversible hydrogen electrode. Simulations were conducted at different scanning rates based on the kinetics models. We reproduce all the anodic and cathodic peaks observed in the reported experimental curves. These results demonstrate the underlying mechanisms of the peak formation in different potential regions.

Toward full simulation of the electrochemical oxygen reduction reaction on Pt using first-principles and kinetic calculations

First-principles molecular dynamics gave the kinetic and redox parameters of the oxygen reduction reaction in a fuel cell using a bias control scheme, and gave the current–voltage relationship.

Intermediate stages of electrochemical oxidation of single-crystalline platinum revealed by in situ Raman spectroscopy

Understanding the atomistic details of how platinum surfaces are oxidized under electrochemical conditions is of importance for many electrochemical devices such as fuel cells and electrolysers. Here we use in situ shell-isolated nanoparticle-enhanced Raman spectroscopy to identify the intermediate stages of the electrochemical oxidation of Pt(111) and Pt(100) single crystals in perchloric acid. Density functional theory calculations were carried out to assist in assigning the experimental Raman bands by simulating the vibrational frequencies of possible intermediates and products. The perchlorate anion is suggested to interact with hydroxyl phase formed on the surface. Peroxo-like and superoxo-like two-dimensional (2D) surface oxides and amorphous 3D α-PtO₂ are sequentially formed during the anodic polarization. Our measurements elucidate the process of the electrochemical oxidation of platinum single crystals by providing evidence for the structure-sensitive formation of a 2D platinum-(su)peroxide phase. These results may contribute towards a fundamental understanding of the mechanism of degradation of platinum electrocatalysts.

Understanding degradation of platinum catalysts during oxygen reduction is vital for improving proton-exchange membrane fuel cells. Here, the authors identify intermediate stages in the oxidation of Pt(111) and Pt(100) in perchloric acid using in situ shell-isolated nanoparticle-enhanced Raman spectroscopy.