To improve the long term catalytic stability without catalytic deactivation during ethanol steam reforming (ESR), this study considered two main areas; the role of the redox promoter of the Mn component in a Ni-based catalyst and the stability of the core@shell structure. Five different core@shell 30Ni(x)Mn(y)@70SiO(2) catalysts were prepared and applied to the ESR reaction. The hydrogen selectivity was highest on the core@shell-structured 30Ni(8.5)Mn(1.5)@70SiO(2) catalyst compared to those of the other catalysts. During ESR, the amount of evolved CO gas, which is related directly to catalyst deterioration, was large over the 30Ni@70SiO(2) catalyst, but it was relatively low on the 30Ni(x)Mn(y)@70SiO(2) catalysts. The carbon types deposited on the catalyst surface after the ESR reactions varied. Carbon nanotubes were produced on the 30Ni@70SiO(2) catalyst, whereas carbon lumps were produced predominantly over the 30Ni(x)Mn(y)@70SiO(2) catalysts. In particular, the amounts of carbon deposited were smallest over the 30Ni(8.5)Mn(1.5)@70SiO(2) catalyst. An ESR model over the core@shell-structured 30Ni(x)Mn(y)@70SiO(2) catalysts was suggested from the results of CH4-, CO- and H2O-TPD. CH4 and CO molecules, as intermediates, were adsorbed predominantly on the surface of Ni sites, but water molecules were adsorbed easily on the surface of the Mn sites, leading to a CO to CO2 transformation through a water gas shift (WGS). (C) 2015 Elsevier B.V. All rights reserved.