Nickel nanoparticles encapsulated with multilayered graphene were fabricated through segregation of the dissolved carbon atoms from nickel. The catalyst, vividly described as "chainmail catalyst", was demonstrated to be promising for ethanol steam reforming (ESR) to produce H-2. Chainmail catalysts with different content of Ni were denoted as Ni@G(2), Ni@G(4), Ni@G(8) and Ni@G(12), respectively. Fresh and spent catalysts were characterized to analyze the role of graphene shell using various techniques (e.g., XRD, Raman, TEM). The graphene shell can protect the Ni core away from sintering, oxidation, or corrosion. ESR was investigated with a focus on the characterization of the catalysts, reaction conditions, and reaction mechanism. The ESR tests showed that the Ni@G(4) exhibited better activity, stability and lower byproducts with no deactivation phenomena for 4 h. During ESR, ethanol was preferentially adsorbed on the external surface of the chainmail catalyst by forming p-pi conjugated system. The spent catalyst could be separated easily by an external magnetic field due to the ferromagnetism of nickel core. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.