Boosting the catalytic activity and stability of FePt nanoparrticles by innovative in situ electron tomography (CATOM). 01/05/2021 - 30/04/2022

Abstract

Bimetallic MPt (M: Fe, Co, Ni) nanoparticles (NPs) displaying anisotropic morphologies are of great interest for the electrocatalytic oxygen reduction reaction (ORR). Unfortunately, MPt alloys in their native A1 phase rapidly degrade in acidic media and therefore severely restrict fuel cell applications. High temperature thermal annealing of CoPt and FePt NPs to achieve its chemically ordered L10 phase is crucially required to achieve an acid-stable catalyst and boost ORR activity to make fuel cells a financially viable technology. In CATOM, my goal is to establish a controlled route to thermally induce the L10 phase whilst protecting the catalyst morphology, achieving ORR performance and acid-stability within the same NP. I will gain the necessary insights to reach this ambitious goal by exploiting advanced electron microscopy (EM) techniques. Due to the complex NP morphologies, these investigations must be performed in 3D. I will therefore develop innovative quantitative electron tomography techniques to track atom-level dynamics and morphology evolution during the annealing process on the single particle level. Moreover, combining in situ gas cell annealing data with computational simulations will enable me to follow the 3D structure evolution of MPt alloys under realistic industrial conditions with atomic resolution. Finally, the direct comparison of A1 and L10 stability of faceted NPs during electrochemical cycling using a liquid cell holder will allow me to compare activation and degradation processes between the phases and to couple catalyst evolution with its ORR performance. These innovative experiments could not be obtained so far because of a lack of 3D characterization tools suitable to track NP evolution under realistic conditions. The outcome of my program will fundamentally advance in situ EM characterization techniques and direct future catalyst design to prepare highly active and acid-stable ORR catalysts critically needed for fuel cell development.

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