Europium barium titanate perovskite nano-photocatalysts: Mechanistic analysis of a chloro-dialkyl sulfide decomposition/detoxification

Mixed europium-barium titanate perovskites, EuxBa1-xTiO3, were investigated as nanocatalysts for the photodetoxification of a mustard gas surrogate, 2-chloroethylethyl sulfide, CEES. EuxBa1-xTiO3 nanoparticles were prepared using an enhanced sol-gel method, resulting in 10-25 nm particles. A lanthanide valence and nanostructure was altered by applying a heat treatment in either oxidizing or reducing atmospheres. The results demonstrated a high adsorption capacity and improved catalytic decomposition activity in comparison to a set of previously explored transition metal oxide photocatalysts, including barium titanate. Analysis of the decomposition products indicated hydrolysis as the predominant reactive detoxification mechanism in the dark. Upon light irradiation, radicals were formed and contributed to the degradation and oxidation of CEES, especially in the sample rich in Eu(III) and oxygen, with a more developed porosity. The results suggested photogenerated electrons and holes, influenced by the presence of Eu, contributed to the free radical formation and oxidation reactions, respectively, increasing both the weight uptake and efficiency of catalytic decomposition.