Bimetallic Exsolved Heterostructures of Controlled Composition with Tunable Catalytic Properties.

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 2 -assisted ethane conversion. Mesoporous A-site-deficient La 0.4 Sr 0.6-α Ti 0.6 Fe 0.35 Ni 0.05 O 3±δ (0 ≤ α ≤ 0.2) perovskites with substantial specific surface area (>40 m 2 /g) enabled fast exsolution kinetics ( T < 500 °C, t < 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 3 Fe systems. Catalytic tests showed superior stability of our catalysts with respect to commercial Ni/Al 2 O 3 . 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.