Carbon-supported Ni nanoparticles in CO2 methanation: role of a superficial NiO shell observed by in situ TEM

Abstract

CO₂ methanation offers a pathway to produce a carbon-neutral methane fuel. Although a number of research efforts have been conducted on this topic, a greater understanding of the mechanism of the reaction, which is still under debate, is needed. Here, using in situ transmission electron microscopy, we provide direct insights into the dynamics of a metallic nickel catalyst supported on activated carbon during CO₂ methanation. The keys to the high performance of the catalyst are the in situ formation and dynamic behavior of a Ni@NiO core@shell nanostructure. Based on the detailed electron microscopy investigation, the mechanism of such nanostructure formation during methanation is proposed. Our studies revealed that the deactivation of the catalyst is not due to the accumulation of carbon coke over nickel nanoparticles, but an increase in the size of the nickel nanoparticles that is responsible for the deactivation of the catalyst over time.

Keywords: CO₂ valorization; Hydrogenation; in situ TEM; Carbon catalysts; Core–shell nanoparticles; Microstructure.