Atomic-Level Observation of Electrochemical Platinum Dissolution and Redeposition

Abstract

An understanding of electrochemical dynamics at solid−liquid interfaces is essential to develop advanced batteries and fuel cells and so on. For example, an atomic-level understanding of electrochemical Pt dissolution and redeposition behavior is crucial for optimizing the material design and operating conditions of polymer electrolyte fuel cells (PEFCs). This understanding enables the prevention of the degradation of Pt nanoparticles used as electrocatalysts. However, the mechanisms of Pt dissolution and redeposition are still not fully understood due to the lack of spatial resolution available with current observation techniques. Here, we have revealed for the first time atomic-level electrochemical Pt dissolution and redeposition behavior using in-house-developed observation techniques. We achieved atomic-level observations of closed-cell type liquid electrochemical transmission electron microscopy (TEM) by combining in-housedeveloped microelectromechanical system (MEMS) chips as an electrochemical cell, an aberration-corrected TEM apparatus, and an energy filter. Furthermore, accurate and stable potential control was achieved using an in-house-developed reversible hydrogen electrode (RHE) with a liquid junction connected to the outside of a TEM specimen holder. Our observation results confirmed that Pt dissolves from surface step edges layer-by-layer, as previously predicted by the density functional theory (DFT). The observation techniques developed are also applicable to other research fields concerning electrochemistry.

Applications of in situ electron microscopy in oxygen electrocatalysis

“…Consequently, it is generally not possible to achieve atomic resolution in LC-(S)TEM, except in a few cases where graphene is used as the cell window material and the liquid layer is very thin [40][41][42] . Furthermore, the radiolysis of water caused by the electron beam irradiation produces various [71] , (B) an in situ electrochemical liquid cell placed in the optical path of TEM, and (C) an electrochemical microchip with micro-fabricated counter electrode (CE), working electrode (WE) and reference electrode (RE). The WE is made of glassy carbon, while the CE and RE are both made of Pt.…”

“…While IL-electron microscopy can provide high-resolution images of the initial and final states of a specimen, it is more desirable to observe the evolution of a specimen in its native states in real time during a dynamic process, such as an electrochemical reaction. For this purpose, in situ LC-(S)TEM techniques have been developed and widely used in a variety of fields, including nanomaterial nucleation and growth, corrosion science, biomolecular structure studies, bubble dynamics, radiation effects and electrochemistry [36,71] . Although liquid-phase imaging can be carried out in an open or closed cell configuration, we mainly focus on the closed cell method, where the liquid solution surrounding the samples is confined using ultrathin windows made of SiN x or graphene-based materials.…”

“…Figure2. Schematic illustrations of (A) a commercial in situ electrochemical LC-(S)TEM sample holder[71] , (B) an in situ electrochemical liquid cell placed in the optical path of TEM, and (C) an electrochemical microchip with micro-fabricated counter electrode (CE), working electrode (WE) and reference electrode (RE). The WE is made of glassy carbon, while the CE and RE are both made of Pt.…”

Challenges and Opportunities in Understanding Proton Exchange Membrane Fuel Cell Materials Degradation Using In‐Situ Electrochemical Liquid Cell Transmission Electron Microscopy

“…[111] Irradiation by the imaging electron beam creates a wide range of sample responses that, depending on the target being irradiated and the incident energy, can provide one with the basic imaging and spectroscopic signals collected on detectors, but can also cause displacement of lattice atoms, ionizing/exciting effects, and cause driving, interfering, or hindering intrinsic physico-chemical reactions of the system. Beam-sample interactions involve both elastic [107] Copyright 2019, ACS Publications.…”

“…Figure 3. a) Schematic representation of the EC-LCTEM chip with the electrodes on it, b) the expanded view of the electrodes, and c) the schematic representation of the electrochemical experiment setup with the liquid junction used by Nagashima et al Adapted with permission [107]. Copyright 2019, ACS Publications.…”