▎ 摘　　要

Nanomaterials comprising earth-abundant elements show great potential as substitutes for scarce, expensive materials in energy conversions, but degradation and contamination issues in working environments severely limit their practical applications. Here we report a facile and scalable strategy to synthesize ultrathin-graphenecoated cobalt nanoparticles which are achieved by the application of an electrical current pulse to a carbon-based substrate and by generating a transient high temperature of up to 1500 K in 50 ms to induce the nanoparticle growth and graphene coating. Thickness of the graphene shell is effectively controlled to be under three atomic layers, favorable for charge transfer and electrocatalytic applications. Our one-step synthetic strategy provides a universal, scalable and cost-effective approach for the fast synthesis of metal-carbon core-shell nanoarchitectures for energy conversion applications.