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-assisted ethane conversion. Mesoporous A-site-deficient LaSrTiFeNiO (0 ≤ α ≤ 0.2) perovskites with substantial specific surface area (>40 m/g) enabled fast exsolution kinetics ( < 500 °C, < 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/NiFe systems. Catalytic tests showed superior stability of our catalysts with respect to commercial Ni/AlO. 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.