A type of Pd-ZnO catalyst doubly promoted by CNTs and Sc2O3 for methanol steam reforming (MSR) was developed, and displayed excellent activity and operation stability for the selective formation of H-2 and CO2. Over a Pd0.15Zn1Sc0.067-10%CNTs catalyst under the reaction conditions of 0.5 MPa and 548 K, the STY(H-2) can maintain stable at the level of 1.56 mol h(-1) g(-1) at 75 h after the reaction started, which was 1.7 times that of the corresponding (CNTs and Sc)-free counterpart Pd0.15Zn1. Characterization of the catalyst revealed that the highly conductive CNTs could promote hydrogen spillover from the PdZn/ZnO-sites to the CNTs adsorption-sites, and then combine to form H-2(a), followed by desorbing to H-2(g), which would help increase the rate of a series of surface dehydrogenation reactions in the MSR process. The pronounced modification action of Sc3+ may be due to the high solubility of Sc2O3 in ZnO lattice. Solution of a small amount of Sc2O3 in ZnO lattice resulted in the formation of Schottky defects in the form of cationic vacancies at the surface of ZnO, where the (PdZn)(0)-Pd2+ clusters can be better stabilized through the Pd2+ accommodated at the surface vacant cation-sites. This would be conducive to inhibiting the sintering of the catalytically active (PdZn)(0) nanoparticles, and thus, markedly prolonging the life of the catalyst. (c) 2013 Elsevier B.V. All rights reserved.