Manganese oxide octahedral molecular sieve (OMS-2) catalyst prepared by the reflux method was investigated for hydrogen generation via the water-gas shift reaction. Catalysts were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), The Brunauer-Emmett-Teller (BET) surface area and determination of average oxidation state (AOS). The OMS-2 catalyst showed very good catalytic activity for the water-gas shift reaction to generate hydrogen under laboratory conditions. An in situ study was conducted to monitor the structural changes in the catalyst during the water-gas shift reaction using synchrotron radiation-based time-resolved X-ray diffraction (TR-XRD). During the water-gas shift reaction, the mixed valent OMS-2 catalyst undergoes a structural transformation to form Mn2O3 and finally to form MnO. The study showed that OMS-2 catalysts can be used as inexpensive catalysts for hydrogen generation. (C) 2010 Elsevier B.V. All rights reserved.