Issue 5, 2022

Unraveling the evolution of exsolved Fe–Ni alloy nanoparticles in Ni-doped La0.3Ca0.7Fe0.7Cr0.3O3−δ and their role in enhancing CO2–CO electrocatalysis

Abstract

The growth and phase evolution characteristics of exsolved metal nanoparticles (NPs) in a Ni-doped La0.3Ca0.70Fe0.7Cr0.3O3−δ (LCFCrN) perovskite is investigated in H2–N2 and CO–CO2 environments. Exsolution kinetics are rapid in H2–N2 while those in CO–CO2 atmospheres are sluggish, possibly due to a combination of pO2 difference in excess of three orders of magnitude as compared to that in H2–N2, and a different reaction pathway in the two atmospheres. NPs grown in H2–N2 exhibit a compositional and structural progression from an initially Ni-rich phase to an Fe-rich phase at short and long heat treatment durations, respectively. Once the subsurface Ni depletes, the NPs seem to coarsen via a combination of addition of Fe from the parent perovskite and Ostwald ripening. For longer heat treatment durations, CaO particles are observed to be appended to the Fe–Ni NPs. Exsolution also occurred in CO2–CO atmospheres exhibiting similar trends, although the composition of the NPs was Ni-rich even after a 25 h reduction treatment in 70 : 30 CO : CO2 at 800 °C, indicating that the NPs are resistant to coarsening and stable for use in highly reducing CO–CO2 environments. In reversible solid oxide cells (RSOC) applications, the CO oxidation kinetics are typically sluggish on single phase perovskite electrodes. However, for Fe–Ni alloy NP-decorated LCFCrN (Fe–Ni@LCFCrN), the NPs are shown to enhance the CO oxidation kinetics (by ca. 75%) and the CO2 reduction reaction (CO2-RR) kinetics (by ca. 15%) as compared to the parent material, LCFCr. This makes the Fe–Ni@LCFCrN catalyst equally active for both reactions, hence significantly enhancing its potential for use in reversible solid oxide cell applications.

Graphical abstract: Unraveling the evolution of exsolved Fe–Ni alloy nanoparticles in Ni-doped La0.3Ca0.7Fe0.7Cr0.3O3−δ and their role in enhancing CO2–CO electrocatalysis

Supplementary files

Article information

Article type
Paper
Submitted
02 Sept. 2021
Accepted
10 Okt. 2021
First published
13 Okt. 2021

J. Mater. Chem. A, 2022,10, 2280-2294

Unraveling the evolution of exsolved Fe–Ni alloy nanoparticles in Ni-doped La0.3Ca0.7Fe0.7Cr0.3O3−δ and their role in enhancing CO2–CO electrocatalysis

H. M. Ansari, A. S. Bass, N. Ahmad and V. I. Birss, J. Mater. Chem. A, 2022, 10, 2280 DOI: 10.1039/D1TA07552G

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