A key to the storage stability of Au/TiO2catalyst

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.