Effect of synthesis time on morphology of CeO₂ nanoparticles and Au/CeO₂ and their activity in oxidative steam reforming of methanol

Ceria (CeO₂) supports, synthesized by hydrothermal treatment with different synthesis time (CeO₂-X h, where X is the synthesis time in h) in the presence of the surfactant cetyltrimethyl ammonium bromide, were used as supports for gold (Au) catalysts. The synthesis time significantly affects the morphological structure and crystallite size of CeO₂, where CeO₂-2 h has the smallest crystallite size with coexisting nanorods and nanoparticles. Transmission electron microscopy analysis confirms the morphology of CeO₂ with distinctive (110), (100) and (111) planes, in agreement with interplanar spacings of 0.19, 0.27 and 0.31, respectively. However, the morphology of CeO₂-8 h and CeO₂-48 h is mainly a truncated octahedral with crystal planes (111) and (100) accompanied by an interplanar spacing of 0.31 and 0.27 nm, respectively. The CeO₂-X h supports and those with a 3 wt% Au loading (Au/CeO₂-X h) were investigated in the oxidative steam reforming of methanol at temperatures between 200 and 400 °C. The Au/CeO₂-2 h gave the highest methanol conversion level and hydrogen yield at a low temperature of 250 °C. This superior catalytic performance results from the good interaction between the metal and support and the well-distributed Au species on the CeO₂ support.