Steam reforming of iso-octane toward hydrogen production over mono- and bi-metallic CueCo/ CeO 2 catalysts: Structure-activity correlations A.A. Al-Musa a , Z.S. Ioakeimidis b , M.S. Al-Saleh a , A. Al-Zahrany a , G.E. Marnellos b,c,* , M. Konsolakis d,** a National Center for Combustion and Plasma Technologies, Water and Energy Research Institute, King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, 11442, Riyadh, Saudi Arabia b School of Mechanical Engineering, University of Western Macedonia, Bakola & Sialvera, GR-50100, Kozani, Greece c Chemical Process & Energy Resources Institute, Centre for Research & Technology Hellas, 6th km, Charilaou e Thermi Rd., P.O. Box 60361, GR-57001, Thermi, Thessaloniki, Greece d School of Production Engineering and Management, Technical University of Crete, GR-73100, Chania, Crete, Greece article info Article history: Received 24 July 2014 Received in revised form 15 September 2014 Accepted 19 September 2014 Available online xxx Keywords: Iso-octane Steam reforming Hydrogen production Cu/CeO 2 Co/CeO 2 Bimetallic catalysts abstract Τhe feasibility of tailoring the iso-octane steam reforming activity of Cu/CeO 2 catalysts through the use of Co as a second active metal (Cu 20x Co x , where x ¼ 0, 5, 10, 15, 20 wt%), is investigated. Characterization studies, involving N 2 adsorptionedesorption at 196  C (BET), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Temperature Programmed Reduction (H 2 -TPR), were carried out to reveal the impact of the morphological, structural and surface properties of the catalysts on the reforming performance. The results showed that reforming activity was mono- tonically increased upon increasing cobalt loading. The Co/CeO 2 catalyst demonstrated the optimum performance with a H 2 yield of 70e80% in the 600e800  C temperature interval. The Co/CeO 2 catalyst exhibited also excellent stability at temperatures above 700  C, while Cu-based catalysts rapidly deactivated in long term stability tests. A close correlation be- tween surface/redox properties and steam reforming efficiency was established. The lower reducibility of Co/CeO 2 catalysts, associated with the formation of Co 3þ species, in Co 3 O 4 - like phase, can be accounted for the enhanced carbon tolerance of Co-based catalysts. Furthermore, the high concentration of surface oxygen species on Co/CeO 2 catalysts can be considered for their enhanced performance. On the other hand, the Cu-induced easier reducibility of bimetallic catalysts, in conjunction with carbon deposition and active phase sintering can be accounted for their inferior steam reforming performance. Irreversible * Corresponding author. Department of Mechanical Engineering, University of Western Macedonia, Bakola & Sialvera, GR-50100, Kozani, Greece. ** Corresponding author. School of Production Engineering and Management, Technical University of Crete, GR-73100, Chania, Crete, Greece. Tel.: þ30 28210 37682. E-mail addresses: gmarnellos@uowm.gr (G.E. Marnellos), mkonsol@science.tuc.gr (M. Konsolakis). URL: http://www.tuc.gr/konsolakis.html Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2014) 1 e14 Please cite this article in press as: Al-Musa AA, et al., Steam reforming of iso-octane toward hydrogen production over mono- and bi-metallic CueCo/CeO 2 catalysts: Structure-activity correlations, International Journal of Hydrogen Energy (2014), http:// dx.doi.org/10.1016/j.ijhydene.2014.09.107 http://dx.doi.org/10.1016/j.ijhydene.2014.09.107 0360-3199/Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.