Reduced polyoxomolybdate immobilized on reduced graphene oxide for rapid catalytic decontamination of a sulfur mustard simulant

Keggin-type polyoxometalates (POMs) were immobilized on poly(diallyldimethylammonium chloride) (PDDA) functionalized reduced graphene oxide (rGO) by a facile and broad-spectrum hydrothermal method. The prepared POMs@PDDA-rGO composites (POM = H₃PMo₁₂O₄₀, H₃PW₁₂O₄₀, H₅PMo₁₀V₂O₄₀) have been thoroughly characterized using a series of techniques. The three composites can catalyze the oxidative decontamination of a sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES) in the order of PMo₁₂@PDDA-rGO > PMo₁₀V₂@PDDA-rGO > PW₁₂@PDDA-rGO. Notably, under ambient conditions PMo₁₂@PDDA-rGO can convert 99% of CEES within 30 min in the presence of nearly stoichiometric aqueous H₂O₂(3 wt%) and its catalytic activity is significantly higher than that of homogeneous H₃PMo₁₂O₄₀. XPS spectral analysis and control experiments indicate that the Mo center of POM is reduced from +6 to +5 during the hydrothermal process, and the excellent catalytic performance is related to the reduction of Mo. Moreover, the PMo₁₂@PDDA-rGO composite is stable during the decontamination process and it can be used for at least five cycles without loss of activity.