The catalytic activity of cobalt in the production of hydrogen via ethanol steam reforming has been investigated in its relation to the crystalline structure of metallic cobalt. At a reaction temperature of 350 degrees C, the specific hydrogen production rates show that hexagonal close-packed (hcp) cobalt possesses higher activity than face-centered cubic (fcc) cobalt. However, at typical reaction temperatures (400-500 degrees C) for ethanol steam reforming, hcp cobalt is transformed to less active fcc cobalt, as confirmed by in situ X-ray diffractometry (XRD). The addition of CeO2 promoter (10 wt.%) stabilizes the hcp cobalt structure at reforming temperatures up to 600 degrees C. Moreover. during the pre-reduction process, CeO2 promoter prevents sintering during the transformation Of Co3O4 to hcp cobalt. Both reforming experiments and in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the surface reactions were modified by CeO2 promoter on 10% Ce-Co (hcp) to give a lower CO selectivity and a higher H-2 yield as compared with the unpromoted hcp Co. (C) 2008 Elsevier B.V. All rights reserved.