Crystallinity-electrical transport relationships in upcycled graphene via catalyst-controlled aspect ratio engineering

Official URL: https://dx.doi.org/10.1002/adfm.77116

Electrical transport–structure relationships in graphene networks remain unclear, particularly in upcycled systems with tunable crystallinity and morphology. Here, we report a catalyst-controlled upcycling strategy that converts post-consumer polycarbonate (PC) waste into graphene nanosheets (GNS) with tunable crystallographic architecture and network-forming characteristics. Using Fe, Co, and Ni catalysts, thermo-catalytic carbonization enables systematic control over stacking thickness, in-plane crystallite size, and effective crystallographic aspect ratio. Despite possessing higher crystallinity and thicker stacked domains (Fe: L_c = 3.6 nm, ∼10 layers), Fe-derived graphene shows the lowest electrical conductivity, whereas Ni-derived graphene, composed of thinner few-layer nanosheets (L_c = 1.1 nm, ∼4 layers), exhibits the highest conductivity (0.63 S cm−1). This behavior highlights that macroscopic electrical transport depends on catalyst-induced nanosheet architecture and network-forming ability beyond crystallinity alone. Accordingly, the effective crystallographic aspect ratio is used as a structural descriptor to rationalize the conductivity trend among the catalyst-derived GNS samples. When incorporated at low loading (1 wt.%) into polypropylene, highly crystalline Fe-derived graphene enables efficient stress transfer, increasing flexural strength and modulus by 28.8% and 38.6%, respectively, highlighting the distinct roles of graphene architecture in electrical versus mechanical functionality. Life cycle assessment shows an approximately 99% lower cradle-to-gate global warming potential than conventional graphene production.