Copper oxide shape effect in CeO_{2/Cu_{2O catalysts for PROX reaction

Cubic and octahedral Cu2O nanocrystals were used as supports for ceria deposition. Ceria tended to deposit on the vertexes and edges of the nanocrystals more. Whisker type of ceria was deposited on Cu2O surface. The prepared CeO2/Cu2O composite materials were tested as catalysts for preferential oxidation (PROX) reaction of CO in the presence of abundant H2. As the amount of ceria became higher (e.g., 1 wt% vs. 10 wt%), CO conversion was higher. Cubic nanocrystals showed higher activity than octahedral nanocrystals, especially at lower temperature region. Also, the activity depended significantly on the oxidation state of copper oxide. When CeO2/Cu2O catalysts were oxidised first then used for PROX reaction, the activity was enhanced. Cu2O turned into CuO with a slight shape change after oxidation at 400oC. The activity degraded at higher reaction temperature because the copper oxide was reduced to metallic copper.