3D atomic-scale imaging of mixed Co-Fe spinel oxide nanoparticles during oxygen evolution reaction

Abstract

The three-dimensional (3D) distribution of individual atoms on the surface of catalyst nanoparticles plays a vital role in their activity and stability. Optimising the performance of electrocatalysts requires atomic-scale information, but it is difficult to obtain. Here, we use atom probe tomography to elucidate the 3D structure of 10 nm sized Co2FeO4 and CoFe2O4 nanoparticles during oxygen evolution reaction (OER). We reveal nanoscale spinodal decomposition in pristine Co2FeO4. The interfaces of Co-rich and Fe-rich nanodomains of Co2FeO4 become trapping sites for hydroxyl groups, contributing to a higher OER activity compared to that of CoFe2O4. However, the activity of Co2FeO4 drops considerably due to concurrent irreversible transformation towards CoIVO2 and pronounced Fe dissolution. In contrast, there is negligible elemental redistribution for CoFe2O4 after OER, except for surface structural transformation towards (FeIII, CoIII)2O3. Overall, our study provides a unique 3D compositional distribution of mixed Co-Fe spinel oxides, which gives atomic-scale insights into active sites and the deactivation of electrocatalysts during OER.

Electrochemistry under confinement

“…226 A reliable method to experimentally overcome the problem of too many unknowns lies in the quickly developing field of correlated, complementary electrochemical and spectroscopic methods. [227][228][229] For these experiments, the knowledge gain from one method is used to interpret the signal of the other method. A very recent example for simplifying the interpretation of electrochemical data by fixing one of its parameters to a value, which is known via spectroscopic measurements in nanoemulsion electrochemistry, was presented by Dick and co-workers.…”

Porous spinel-type transition metal oxide nanostructures as emergent electrocatalysts for oxygen reduction reactions

“…, rich active sites, p-type conductivity, optical transparency, magnetic properties, semiconductivity, multiple valence states of their oxides, and redox properties). 21–28 For the production cost, spinel-type TMO nanocatalysts are easily prepared from inexpensive and Earth-abundant precursors. 29–31 Moreover, spinel-type TMO nanocatalysts are easily stored and handled during preparation, making the production cycle more cost-effective relative to state-of-the-art noble metal catalysts.…”

Recent Progress on Revealing 3D Structure of Electrocatalysts Using Advanced 3D Electron Tomography: A Mini Review

“…However, the characterization of nanocatalysts with complexity at all three dimensions in nanoscale or even atomic scale remains challenging yet crucial to understand the unique link between property and structure ( Spivey et al, 2014 ; Devivaraprasad et al, 2019 ; Hu et al, 2019 ; Li et al, 2021b ; Pal et al, 2021 ; Suter, 2021 ). X-ray computed tomography (XCT) and atom probe tomography (APT) have been applied to study some of the electrocatalysts in 3D ( Alrwashdeh et al, 2017 ; He et al, 2020 ; Xiang et al, 2022 ). Nevertheless, XCT is relatively low in spatial resolution, whereas APT is less capable of resolving crystal structures.…”