Exploring Methane Dry Reforming Using Thermally Switchable High-Entropy Perovskite Oxide and an <i>In Situ</i> -Produced Molecular Nanocomposite

We report here the sol–gel synthesis of Ln(Mn0.2Fe0.2Co0.2Ni0.2Cu0.2)O3 (Ln= La, Ce, Pr, Nd, Sm, and Gd) high-entropy perovskite oxide (HEPO) materials that have subsequently been tested for the dry reforming of methane (DRM) reaction. Among the six lanthanide-based HEPOs, the pure-phase La(Mn0.2Fe0.2Co0.2Ni0.2Cu0.2)O3 catalyst has shown the highest catalytic activity, with 86% methane conversion and 90% CO2 conversion for a 100 h DRM reaction with H2/CO ∼ 1. Same catalyst synthesized by solution combustion synthesis route results in much lower activity behavior. The pristine HEPO phase of the catalyst decomposes in the DRM environment and can be regenerated from the individual oxide phases by in situ thermal treatment close to the phase formation temperature, without compromising the DRM activity. This outcome indicates an unusual reversible thermal switching between the pristine HEPO phase of the catalyst and the fragmented phases formed during DRM and highlights the need for further research into the function of the decomposed phases that are produced in situ. We have explored the structure–property correlation in the framework of an in situ generated nanocomposite at the molecular level of the promising HEPO catalyst.