Metal oxides act as a major type of heterogeneous catalysts; their catalytic performance is intimately linked with size, shape, and crystalline phase at the nanometer level. The effect of particle size has been well documented in the past three decades, but the effect of particle has been addressed only recently. Here we demonstrate that the redox and acidic-basic properties of oxides are largely dependent on their shapes by taking rod-shaped Co3O4, Fe2O3, CeO2, and La2O3 as examples. The catalytic activities of these nanostructured oxides are governed by the chemical nature of the exposed crystal planes. For instance, the dominant exposure of {110} planes which are rich in active Co3+ on Co3O4 nanorods provided a much higher activity towards CO oxidation than the nanoparticles that mainly exposed the {111} planes. The simultaneous exposure of iron and oxygen ions on the {110} surfaces of Fe2O3 nanorods has enhanced the adsorption and activation of NO and ammonia and consequently promoted the efficiency of DeNOx process. Meanwhile, crystalline control of Fe2O3 nanorods also plays an essential role in their catalytic properties. In addition, the exposed crystal facets of these rod-shaped oxides mediated their interactions with metal particles/clusters, and consequently the overall reaction performance. In this context, Au nanoparticles (~3 nm) anchored on CeO2 nanorods exhibited outstanding stability under water-gas shift conditions owing to the strong bonding of gold particle on the rod-shaped CeO2 support. The formed gold-ceria interface was resistant towards sintering even at high temperatures. Cu nanoparticles dispersed on CeO2, La2O3, and Fe2O3 nanorods also showed interesting catalytic features. In short, shape control of metal oxides allows preferential exposure of reactive crystal facets, and thus provides a new strategy for the design of highly efficient nano catalysts.

Rod-shaped metal oxides: Structural control and catalytic properties

249th National Meeting (2015)

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