Bimetallic Exsolved Heterostructures of Controlled Composition with Tunable Catalytic Properties.
basic_science · Level V
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- Also identified by DOI 10.1021/acsnano.1c11111.
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Abstract
In this paper, we show how the composition of bimetallic Fe-Ni exsolution can be controlled by the nature and concentration of oxygen vacancies in the parental matrix and how this is used to modify the performance of CO<sub>2</sub>-assisted ethane conversion. Mesoporous A-site-deficient La<sub>0.4</sub>Sr<sub>0.6-α</sub>Ti<sub>0.6</sub>Fe<sub>0.35</sub>Ni<sub>0.05</sub>O<sub>3±δ</sub> (0 ≤ α ≤ 0.2) perovskites with substantial specific surface area (>40 m<sup>2</sup>/g) enabled fast exsolution kinetics (<i>T</i> < 500 °C, <i>t</i> < 1 h) of bimetallic Fe-Ni nanoparticles of increasing size (3-10 nm). Through the application of a multitechnique approach we found that the A-site deficiency determined the concentration of oxygen vacancies associated with iron, which controlled the Fe reduction. Instead of homogeneous bimetallic nanoparticles, the increasing Fe fraction from 37 to 57% led to the emergence of bimodal Fe/Ni<sub>3</sub>Fe systems. Catalytic tests showed superior stability of our catalysts with respect to commercial Ni/Al<sub>2</sub>O<sub>3</sub>. Ethane reforming was found to be the favored pathway, but an increase in selectivity toward ethane dehydrogenation occurred for the systems with a low metallic Fe fraction. The chance to control the reduction and growth processes of bimetallic exsolution offers interesting prospects for the design of advanced catalysts based on bimodal nanoparticle heterostructures.