One weight percent Pt impregnated on activated carbon (Pt/AC) and alumina supports (Pt/Al2O3) have been tested for decalin dehydrogenation for the production of clean H-2. CO pulse chemisorption results indicate nearly same Pt dispersion in both Pt/AC and Pt/Al2O3 catalysts. The comparison of activity between Pt/AC and Pt/Al2O3 catalysts revealed superior decalin dehydrogenation activity over Pt/AC both in terms of turn over frequency as well as the yield towards H-2 production which is due to the spill over of H-2 on Pt/AC. The Pt dispersion in Pt/Al2O3 is lost due to the phase transformation of support (boehmite phase of alumina to gamma phase) during reduction treatment and this is the main reason for the loss of decalin dehydrogenation activity. It is concluded that spill over hydrogen is also an important aspect in addition to Pt dispersion for getting higher H-2 yield from decalin dehydrogenation. (C) 2012 Elsevier B.V. All rights reserved.