Genesis of an Fe5C2@Fe3O4 core/shell structure during CO carburization of metallic iron nanoparticles

• a time- and space-resolved iron carbide-oxide Fe 5 C 2 @Fe 3 O 4 core–shell structure. • NAP-XPS and ETEM uncovering of phase transformation of a metallic iron catalyst exposed to carbon monoxide . • role of iron carbides in FTS chain growth and Fe 3 O 4 overlayer in the water–gas shift reaction. High resolution structure models of the spatial distribution of iron carbide cores with decorated oxide species are critical to the understanding and definition of active species for Fischer-Tropsch Synthesis and the water–gas shift reaction. In situ tools such as NAP-XPS and ETEM facilitated a layered uncovering of the dynamic phase transformation of a metallic iron catalyst exposed to carbon monoxide, leading to a time- and space-resolved iron carbide-oxide core–shell model, which can unravel the role of iron carbides in FTS chain growth and of an Fe 3 O 4 overlayer in the water–gas shift reaction, respectively. Such definitive knowledge on Fe 5 C 2 @Fe 3 O 4 core–shell structure can potentially boost iron catalyst stability and realize CO 2 selectivity mitigation.