Efficient removal of 2-chloroethyl ethyl sulfide in solution under solar light by magnesium oxide-decorated polymeric carbon nitride photocatalysts and mechanism investigation

Removing hazardous chemicals such as chemical warfare agents is crucial for the environment, defense, and public security. Herein, magnesium oxide-decorated carbon nitride photocatalysts (CN/MgO) were fabricated for detoxification of 2-chloroethyl ethyl sulfide (CEES) in solutions under the irradiation of a solar simulator. CN/MgO samples were prepared via thermal exfoliation followed by precipitation. The surface enhancements of as-prepared photocatalyst, such as high specific surface area, rich-nitrogen defects, and oxygen dopants, improved adsorption capacity, reaction active sites, and localized charge distribution. CN/MgO catalyst showed high performance of detoxification of CEES in solutions (99% of 200 parts per million volume (ppmv) hydroxylethyl ethyl sulfide, a hydrolysis product of CEES, within 120 min). In addition, the detoxification in chloroform solution was conducted to elucidate the hydrolysis effect in the solution phase. Density functional theory calculations revealed that a built-in electric field at the heterostructure interface could facilitate spatial separation of photo-excited electron-hole pairs. Scavenger tests proved that superoxide radicals contributed to good photo-oxidation reactivity. The reaction mechanism was suggested using the results with GC-MS, XPS, FTIR, and XRD. The as-prepared photocatalyst could function under ambient conditions without adding any base or acid. The detoxification exhibited good selectivity to transfer CEES to sulfoxide, avoiding over-oxidation to generate toxic sulfone.