Highly Stable Bimetal Ni–Co on Alumina-Covered Spinel Oxide Derived from High Entropy Oxide for CO2 Methanation

Inhibiting the sintering of supported metal catalysts for CO2 methanation is still a great challenge, especially at high temperature. Herein, the novel catalyst was prepared by using high entropy spinel oxide (Co0.2Ni0.2Mg0.2Zn0.2Mn0.2)Al2O4 (HEO) as precursor, which was reduced in a hydrogen atmosphere to obtain Ni–Co alloys supported on Al2O3-covered (Mg0.2Zn0.2Mn0.2)Al1.2O2.4 spinel oxide with a core–shell structure. This catalyst exhibited excellent stability at 550 °C for 320 h. Characterization results showed that the formation of the core–shell structure due to uniform element dispersion of the HEO precursor led to a larger interface, closer contact, and stronger interaction between the core and shell, which ensured the stability of the shell Al2O3 and further stabilized Ni–Co alloys. However, the catalyst derived from the mixed spinel oxide precursor was unable to achieve the core–shell structure support due to uneven element dispersion, which exhibited inferior stability. This study has successful extended the application of high entropy oxides.