Fluid Mechanical and Visible-Light-Driven Piezophotocatalysis in MoS₂/Carbon-Rich Carbon Nitride Heterostructures for Enhanced Green Energy Production and Environmental Remediation

Molybdenum disulfide (MoS₂)/carbon-rich carbon nitride (TCN) heterostructure, a piezophotocatalyst sensitive to fluid mechanical energy and visible light, has been developed for green energy production and environmental remediation. The optimized MoS₂/TCN heterostructure exhibits an absorption edge at 520 nm, identical to that of TCN but significantly red-shifted compared with conventional carbon nitride. Piezopotential measurements via piezoelectric force microscopy demonstrate that the MoS₂/TCN heterostructure generates a much higher piezopotential response than TCN under the same applied voltage. This heterostructure exhibits substantial improvements in photocatalytic performance for both the hydrogen evolution reaction (HER) and the degradation of tetracycline (TC) under visible light. Additionally, its photocatalytic activity is further enhanced by vortex-induced fluid motion. Compared to TCN, the piezophotocatalytic activity of the optimized MoS₂/TCN heterostructure increases the HER rate from 1.8 to 3.62 mmol g^-1 h^-1 and the TC degradation rates from 57.8 to 85.1% and 73.2 to 98.8% in 15 and 60 min, respectively. MoS₂ nanosheets act as piezoelectric generators, triggered by fluid flow, to induce a macroscopic piezopotential, aiding in the collection of visible-light-generated electrons and holes on the TCN surface to enhance catalytic activity. This work highlights that the shearing forces from fluid flow, essential for wastewater discharge, piezoelectrically amplify the photocatalytic efficiency of the MoS₂/TCN heterostructure.