The biomorphic CuO/CeO2/Al2O3 was used as a catalyst in methanol steam reforming ( SRMe), and the reaction mechanism was studied. It was found that the oxidation states of Cu in the biomorphic sample would vary with the reaction temperature and they also affected the rate of the reaction. Below 200 degrees C, SRMe would not occur, and the X-ray diffractometry study indicated that the CuO/CeO2/Al2O3 sample remained unchanged. Above 200 degrees C, the SRMe occurred when CuO started to be reduced to Cu. As the reaction temperature increased, Cu reacted with CO2 and led to the formation of Cu2O during the reversed water gas shift reaction. Above 250 degrees C, the conversion of MeOH to CO2 and H-2 reached to a saturation of 95% even if the amount of metallic Cu was reduced to half of its original portion. This confirmed that both Cu and Cu2O were active components for promoting SRMe. (c) 2012 Elsevier B.V. All rights reserved.