The present study is focused on the influence of Pt loading on the reactivity of catalysts prepared supporting the metal on novel core-shell molybdenum substrates. The electrocatalytic activity and stability of nine Pt/X@MoO3/C catalysts (where X denotes the nature of Mo-phases in the core of the core- shell Mo-particle: MO2C, MoO2 and/or Mo-0) with three Pt loading (5, 20 and 30 wt% Pt) were tested for carbon monoxide and methanol electro -oxidation reactions. For both reactions, Pt loading appears to be a key factor, obtaining the best performance for those catalysts with higher Pt content. Furthermore, it is observed that the nature of X@MoO3/C samples plays an important role as promoter for CO and methanol oxidation. MoO3-shell catalyzes and homogenizes the potentiodynamic responses, while the reduced Mo-phase in the core produces an electronic effect which determines the catalytic activity and stability during the electro-oxidation processes investigated. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.