Low-frequency hydromechanical energy triggered piezocatalytic activity of MoS2 nanosheets for sustainable removal of Cr (VI)

Abstract

Piezocatalysis is an emerging technology where a piezoelectric material under mechanical stress in water produces reactive oxygen species (ROS) that are effectively utilized for environmental remediation applications. However, unavailability of high-power mechanical energy source like ultrasound in nature, restricts the wide-spread deployment of piezocatalysis for real-life applications. Herein, we demonstrate successful utilization of low-power hydromechanical energy for ROS generation and consequent reduction of Cr (VI) through MoS₂ nanosheets based piezocatalyst. MoS₂ nanosheets are grown on cotton fabric (MoS₂@CF) via facile solvothermal method and further characterized by XRD, XPS, FESEM and HRTEM techniques. With the application of mechanical force, the developed MoS₂ nanosheets based piezocatalyst exhibits high Cr (VI) reduction efficiency, achieving complete reduction of 100 ppm Cr (VI) in just 50 min. A piezocatalytic filter is designed with MoS₂@CF for mimicking piezocatalysis under real-life low-frequency water flow. The designed piezocatalytic filter demonstrates almost 99 % reduction of Cr (VI) in 9 hrs at a flow rate of 2 L/min. Piezocatalytic Cr (VI) reduction activity has been elucidated in light of mechanical stress induced band bending and the free carrier separation phenomena. The undertaken strategy highlights the great potential of piezocatalysis technology for harnessing low-power mechanical energy source in nature for wastewater treatment.