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

Abstract

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.

Perovskite Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

“…Due to the limitation by the available signal, synchrotron-based experiments will be crucial for monitoring chemical and structural changes of the catalyst. Furthermore, surface-enhanced vibrational spectroscopy has also been used to track the formation of surface states with relevance to the ORR [210,211]. Changes in the morphology of a fuel cell material have been resolved by transmission electron microcopy (TEM) using a commercial liquid cell [212] but several challenges need to be overcome to provide the resolution required for catalytic insight [213].…”

Co‐adsorption of Cations as the Cause of the Apparent pH Dependence of Hydrogen Adsorption on a Stepped Platinum Single‐Crystal Electrode

“…An ionic strength effect would be expected if the adsorbates on the step carry a residual charge [6] . There is either a slight pH or an anion (ClO 4 − ) effect on the OH adsorption-desorption feature on terraces, which may be due to the interaction of perchlorate with the OH adlayer [8] . Figure 1b shows the voltammetric profiles of the Pt(553) electrode recorded in 0.1 M HClO 4 (pH=1) electrolytes containing 0.01 M Li + , Na + , K + and 0.001 M Cs + , respectively.…”

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

“…Much qualitative information of surface species can be extracted from CV combined with in situ surface technics such as Fourier Transformation Infrared Spectroscopy (FTIR), [10,11] Raman spectroscopy, [12] scanning tunneling microscopy (STM), [7,9] and surface X-ray scattering. Much qualitative information of surface species can be extracted from CV combined with in situ surface technics such as Fourier Transformation Infrared Spectroscopy (FTIR), [10,11] Raman spectroscopy, [12] scanning tunneling microscopy (STM), [7,9] and surface X-ray scattering.…”

“…[14,15] To well understand the behavior of Pt polycrystal, Pt(111) electrode was used as a model electrode due to its most thermodynamically stability among all the facets of Pt crystal. [7,12] Two typical CVs of Pt(111) with different upper potentials in HClO 4 electrolyte are shown in Figure 1. Feliu group investigated the influences of potential scan rate, temperature, upper limit potential, electrolyte, and pH on the CV shapes at Pt(111) electrode and proposed kinetics models to illustrate the mechanisms underlying the observed CV curves.…”

“…Feliu group investigated the influences of potential scan rate, temperature, upper limit potential, electrolyte, and pH on the CV shapes at Pt(111) electrode and proposed kinetics models to illustrate the mechanisms underlying the observed CV curves. [7,12,15,[27][28][29] Rinaldo et al proposed a series of elementary reactions and applied the Butler-Volmer equations to simulate the CVs between 0.65 and 1.15 V. [30] However, a small cathodic peak around 1.05 V cannot be simulated at high scan rates, indicating that the proposed kinetics model should have room to be improved. [7,12] Two typical CVs of Pt(111) with different upper potentials in HClO 4 electrolyte are shown in Figure 1.…”