EXAFS observation of the Sr and Fe site structural environment in SrO and Fe2O3-coated SrO nanoparticles used as carbon tetrachloride destructive adsorbents

The Sr and Fe sites structural environment in uncoated SrO and Fe2O3-coated SrO nanoparticles used as destructive adsorbents in the CCl4 decomposition have been investigated for the first time by extended X-ray absorption fine structure (EXAFS). It was found that the local structure of the Sr ions depends on the synthetic procedure used to prepare the nanoparticles. The short-range order exhibited by the sol-gel prepared SrO particles (AP-SrO) and the conventionally prepared (CP-SrO) particles is not as high as that of the commercial strontium oxide. The Sr local structure observed for the non-Fe2O3-coated samples after CCl4 decomposition shows that the Sr environment is only made of Cl ions for the AP sample and made of both Cl and O ions for the CP sample, indicating that the AP-SrO sample was more reactive with CCl4. The enhancement of the reactivity toward the CCl4 decomposition by the iron oxide coating was evidenced from the EXAFS investigation of both the Sr and the Fe local structure after CCl4 decomposition on Fe2O3-coated CP-SrO and Fe2O3-coated AP-SrO. It was found that the SrO inner layers are involved in the reaction since only Cl ions were detected as Sr neighbors and that no Cl ions were detected in the iron environment of this sample, suggesting that the iron oxide coating the sample surface is continuously renewed during the reaction.