A key to the storage stability of Au/TiO(2) catalyst.

The effect of Au(3+) percentage in Au/TiO(2) on its storage stability at room temperature was studied by varying the drying temperature and storage duration of a deposition-precipitation prepared Au/TiO(2) sample. Carefully-designed room temperature storage in a desiccator, in the dark to exclude any interference of light irradiation, was referenced to the freezing storage (255 K) in a refrigerator. The samples were characterized by well-calibrated H(2)-TPR, TEM and TG measurements. Reduction of Au(3+) ions and agglomeration of metallic Au particles were shown to be the main reasons for the deterioration of Au/TiO(2) during desiccator-storage. Correlating the percentage of Au(3+) ions, determined by H(2)-TPR, with the storage stability of Au/TiO(2) for CO oxidation at 273 K revealed that Au/TiO(2) samples with higher Au(3+) percentages (>90%) were much more stable during the desiccator-storage than those with higher percentages of metallic Au. Residual water in fresh Au/TiO(2) before storage showed a promotional effect on gold reduction and agglomeration during storage. By maximizing the percentage of Au(3+) ions and minimizing the residual water in the fresh sample, the deterioration of the Au/TiO(2) catalyst was successfully avoided during desiccator-storage of up to 150 days in dark. A possible mechanism of Au/TiO(2) deterioration during the desiccator-storage was also discussed.