Crystallinity–Electrical Transport Relationships in Upcycled Graphene via Catalyst‐Controlled Aspect Ratio Engineering

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.