For the highly productive nanocatalyst synthesis, ensuring the formation and stabilization of active nanoparticles with enlarged surface areas by increasing their metal loading and dispersion have been major issues. Herein, we report a facile method based on a simple melt-infiltration process for creating extremely productive Fe5C2 nanoparticles (similar to 14 nm) incorporated into graphene flakes (Fe5C2/G) with a stable and high Fe load (similar to 35 wt%). They showed extremely high C5+ hydrocarbon productivity (4.41 g(C5+HC) g(cat)(-1) h(-1)), CO conversion (91.8%), and Fe time yield (6.5 x 10(-4) mol(CO) g(Fe)(-1) s(-1)) as well as good thermal stability in CO hydrogenation reactions under harsh conditions. (C) 2019 Elsevier Inc. All rights reserved.