In Situ Liquid Cell TEM Study of Morphological Evolution and Degradation of Pt–Fe Nanocatalysts During Potential Cycling

Abstract

Nanocatalyst degradation is a serious limiting factor for the commercialization of proton exchange membrane fuel cells. Although the degradation has been extensively studied in the past through various ex situ electrochemical methods, employing an in situ technique can greatly improve our understanding of the mechanisms involved during the electrochemical cycling. In this work, we have employed an in situ liquid cell inside a TEM for a simultaneous investigation of the structural evolution and electrochemical response of Pt–Fe nanocatalysts. We demonstrate that the coarsening processes of these nanocatalyst particles, including the nucleation and growth, are not uniform, both in space and in time scale. The growth rate is found to be both site- and potential-dependent. Furthermore, these particles were found to exhibit considerably different behaviors when attached to an electrode as opposed to when isolated in the electrolyte. With Pt–Fe nanoalloy system as a candidate material, this work demonstrates that the in situ structural characterization of nanocatalysts under electrochemical bias and inside the native electrolyte environment provides much deeper insight into the catalyst degradation mechanisms as compared to the routine ex situ electrochemical studies.

Surface Segregation of Fe in Pt–Fe Alloy Nanoparticles: Its Precedence and Effect on the Ordered‐Phase Evolution during Thermal Annealing

“…This crucial question needs to be addressed. Recently, we have performed an in situ potential cycling of disordered Pt–Fe nanoparticles inside a TEM . In the future, by coupling this setup with the EELS technique, we look forward to gaining more insights into the surface tunability of the VD procedure.…”

Perovskite Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

“…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]. The latter should be supported by rigorous electroanalytical analysis of the measured currents.…”

In Situ Transmission Electron Microscopy on Energy‐Related Catalysis

“…Zhu et al investigated structural evolutions of Pt-Fe nanoalloy while recording CV curves. [113] Commercial electrochemical liquid cell holder, which features microfluidic and electrical circuitry for introducing liquid flow and applying electrical bias, was utilized for this work. 0.1 m HClO 4 was the electrolyte for this operando studies, showing particle growth over cycles.…”