Thermodynamically Metal Atom Trapping in Van der Waals Layers Enabling Multifunctional 3D Carbon Network

The construction of 3D graphitic structures can lead to many important scientific study and nanotechnology applications, but its widespread use can be limited by the narrow van der Waals gap (vdW; <0.35 nm). Here, this study reports the use of natural adsorbent organisms to engineer the expanded graphitic structure. It shows that, in chitosan, the abundant amino (^-NH₂) and hydroxyl (^-OH) groups can act as metal ions “pitfalls” for the growth of catalytic transition-metal crystals under thermally reductive conditions. In situ transmission electron microscopy study reveals the “liquidized” migration process of Ni carbide crystal that catalyzes the graphitization of 3D carbon network and enables the expansion of vdW gaps. A correlation between the thermodynamically trapped metal atoms and the expansion of vdW gaps is established by expanding the study to both Co and Cu. The findings provide insights into new strategy to be explored for engineering 3D carbon-based materials and show significant potential in energy storage and catalysis technologies.