How MoS2 assisted sulfur vacancies featured Cu2S in hollow Cu2S@MoS2 nanoboxes to activate H2O2 for efficient sulfadiazine degradation?

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This work synthesized a series of hollow Cu2S@MoS2-x nanoboxes by using Cu2O nanocubes as precursor. Electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy (XAS) analysis identified the existence of Sv in Cu2S@MoS2-x. Sulfadiazine (SDZ), a typical antibiotic, was selected as the target contaminant to evaluate the catalytic activity of Cu2S@MoS2-x via H2O2 activation. With adding 0.2 g/L Cu2S@MoS2-2 and 5 mM H2O2, 95.9% of SDZ (20 μM) was removed in 60 min and the reaction rate constant obtained by Cu2S@MoS2-2 (0.239 min−1) was improved by 4 times and 10 times in contrast with Cu2S (0.0622 min−1) and MoS2 (0.0219 min−1). EPR analysis and radical scavenger tests confirmed •OH and 1O2 as the dominated reactive oxygen species (ROS). In Cu2S@MoS2-2 activated H2O2 system, the yield of 1O2 was 6.12 × 10-14 mol/L, more than 8 times that in Cu2S/H2O2 system (0.73 × 10-14 mol/L). Density functional theory (DFT) calculation revealed that the Cu atoms exposed by the formation of Sv on Cu2S@MoS2-2 were the preferred adsorption sites for O2, which further achieved the conversion of O2 to •O2−. In the activation process, Cu2S mainly produced •OH through sulfur-enhanced Fenton process, while MoS2 shell accounted for the O2 production. Thereafter, the obtained O2 acquired electrons from the Cu atoms exposed by Sv to produce •O2−, followed by the generation of 1O2. The cooperation between MoS2 and Cu2S resulted in the superior catalytic activity. The excellent recyclability, stability, and adaptability demonstrated Cu2S@MoS2-2 as a reliable candidate for activating H2O2 toward refractory organics degradation.