Highly recyclable and efficient piezocatalyst of Nafion decorated MoS2 with hierarchical structure for organic pollutants degradation

The piezocatalytic effect is a promising approach for the efficient degradation of organic pollutants. However, directly dispersing such catalysts in aqueous media introduces other issues including media purification (since it constitutes a secondary pollutant), and catalyst recyclability. In this work, a highly recyclable hierarchical composite material, MoS2 decorated onto carbon felt with further coated by Nafion (Nf-MSCF), was demonstrated to be an efficient piezocatalyst for organic pollutants degradation. The hierarchical Nf-MSCF catalyst structure designed in this way exhibited strong piezocatalytic performance as well as stability and durability. It achieved a high efficiency of removing 98% of Rhodamine B (RhB) pollutants in water after 4 min under ultrasound and this efficiency was maintained even after 300 min of ultrasound. Such excellent properties were attributed to the combined effects of high piezocatalytic activity of MoS2 nanosheets, high specific surface area of carbon felt, and improved cation adsorption as well as stability resulting from surface modification by the Nafion layer. The reactive oxygen species generated was verified and analyzed by electron spin resonance measurements and radical trapping experiments. The Zeta potentials were measured to confirm the more negatively charged surface brought about by Nafion modification. Finally, combining COMSOL Multiphysics simulation and piezoelectric voltage measurement with energy band theory, the possible piezocatalytic mechanism of the structure was proposed. This work provides a facile strategy to prepare recyclable and high efficiency piezocatalysts, and further promotes the practical applications of piezocatalysis.