Unexpectedly sample S Bi Cl xA
Unexpectedly, sample S6 (Bi:Cl = 6:1, calcined at 300 °C) revealed a mixture of Bi12O17Cl2, β-Bi2O3, and Bi3O4Cl (JCPDS No. 36-0760) instead of the expected pure Bi12O17Cl2. To further investigate the effects of the amount of chloride ions on the composition of products, a series of supplementary experiments were conducted with increasing chloride SRPIN340 contents. As presented in Fig. S10 (Supporting information), the samples with initial Bi:Cl atomic ratios of 5:1 and 4:1 can be identified as the mixed phases of Bi12O17Cl2 and Bi3O4Cl. The sample with an initial atomic ratio of Bi:Cl = 3:1 can be identified as the mixed phase of Bi3O4Cl and Bi4O5Cl2 (JCPDS No. 41-0658), the sample with an initial atomic ratio of Bi:Cl = 2:1 can be recognized as the mixed phase of Bi3O4Cl, Bi4O5Cl2 and BiOCl (JCPDS No. 82-0485), and the sample with an initial atomic ratio of Bi:Cl = 1:1 can be identified as pure BiOCl. The results suggest that, except for BiOCl, other single-phase bismuth oxychlorides are not easily obtained under the current conditions (calcined at 300 °C), and that the compositions of the products are significantly influenced by the amount of chloride ions added and the temperature of the heat treatment. Therefore, a subsequent study should focus on the addition of a small amount of chloride ions (Cl:Bi < 6), i.e., the mixed phase of Bi12O17Cl2 and β-Bi2O3 samples. The reason for the formation of Bi12O17Cl2 instead of other bismuth oxychlorides or their mixtures in low Cl− concentration is not clear now and needs further investigation. It is likely to be associated with bismuth is obviously in excess in the system and Bi12O17Cl2 has smaller formation enthalpy among bismuth oxychlorides . This assumption may be further confirmed in another study on synthesis of bismuth oxychlorides using Bi2O3 and BiOCl as starting materials, which found that pure Bi12O17Cl2 can be obtained at a relatively lower temperature (350–400 °C) than other bismuth oxychlorides . In addition, according to XRD and XPS analyses, compound leaf is hard to detect that any Cl was doped into β-Bi2O3 matrix, which may be attributed to the lower calcination temperature.