A key to the storage stability of Au/TiO2catalyst

Abstract

The effect of Au³⁺ percentage in Au/TiO₂ on its storage stability at room temperature was studied by varying the drying temperature and storage duration of a deposition–precipitation prepared Au/TiO₂ 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 H₂-TPR, TEM and TG measurements. Reduction of Au³⁺ ions and agglomeration of metallic Au particles were shown to be the main reasons for the deterioration of Au/TiO₂ during desiccator-storage. Correlating the percentage of Au³⁺ ions, determined by H₂-TPR, with the storage stability of Au/TiO₂ for CO oxidation at 273 K revealed that Au/TiO₂ samples with higher Au³⁺ percentages (>90%) were much more stable during the desiccator-storage than those with higher percentages of metallic Au. Residual water in fresh Au/TiO₂ before storage showed a promotional effect on gold reduction and agglomeration during storage. By maximizing the percentage of Au³⁺ ions and minimizing the residual water in the fresh sample, the deterioration of the Au/TiO₂ catalyst was successfully avoided during desiccator-storage of up to 150 days in dark. A possible mechanism of Au/TiO₂ deterioration during the desiccator-storage was also discussed.