Carbon quantum dots modified MoS2 for high-efficiency and long-endurance persulfate activation: Enhanced electron transfer and piezoelectricity

Persulfate (PS) or peroxymonosulfate (PMS) activated sulfate radicals can significantly enhance advanced oxidation processes owing to their high oxidation potentials. However, highly efficient and continuous activation of PS or PMS has been limited owing to the sluggish redox cycle. Herein, a photo-piezoelectric synergistic catalyst, Carbon quantum dots modified MoS2 nanosheets (MoS2/C-dots), has been developed to boost the electron transfer for PMS activation, and achieved significant antibiotics degradation (85.06 % degradation under weak visible-light and simulated water flow within 10 min, which is 3.83 times higher than that with PMS). The advance of MoS2/C-dots fabrication is four-fold: a. the attached C-dots on MoS2 improved the asymmetry of MoS2 and enhanced its piezoelectricity, which accelerated the photogenerated e− and hole separation, and hence, improved its photo-photocatalytic activity; b. C-dots surface charge promotes the electron transfer to MoS2, and provides e− for PMS activation; c. C-dots may act as e− banks for continuous PMS activation, hence, improving the PMS activation endurance; d. the photo-piezocatalysts can synergistically utilize the abundant weak visible light and the natural mechanical energy such as tide and water flow for highly efficient water waste degradation and also exhibit good cycling stability. In addition, free radical trapping experiments were employed to reveal the PMS activation mechanism, and the results showed that h+, 1O2, SO4·−, and ·OH were the main active species and a possible reaction pathway has been proposed. This work provides a rational piezo-photocatalyst design strategy for high-efficiency PS or PMS activation.