Elucidating the Mechanism of Iron-Catalyzed Graphitization: The First Observation of Homogeneous Solid-State Catalysis

Carbon is a critical material for existing and emerging energy applications and there is considerable global effort in generating sustainable carbons. A particularly promising area is iron-catalyzed graphitization, which is the conversion of organic matter to graphitic carbon nanostructures by an iron catalyst. In this paper, it is reported that iron-catalyzed graphitization occurs via a new type of mechanism that is called homogeneous solid-state catalysis. Dark field in situ transmission electron microscopy is used to demonstrate that crystalline iron nanoparticles "burrow" through amorphous carbon to generate multiwalled graphitic nanotubes. The process is remarkably fast, particularly given the solid phase of the catalyst, and in situ synchrotron X-ray diffraction is used to demonstrate that graphitization is complete within a few minutes. Catalytic graphitization is a simple and flexible route to graphitic carbons from biomass or organic precursors. Here, it is shown that the mechanism of graphitization involves a new type of catalysis where all components are in the solid state. This has broad implications in the important world of carbon but also more widely in materials science. image