CuS@MoS2 p n heterojunction photocatalyst integrating photothermal and piezoelectric enhancement effects for tetracycline degradation

Photocatalysis is an environmentally friendly and low-cost technology for the degradation of pollutants. In addition to the construction of heterojunction which may decrease the recombination of charge carriers and extend the photo-response range, the utilization of piezoelectricity and photothermal conversion also provides the promising routes to improve the photocatalytic performance. Herein, a CuS@MoS2 heterostructure was developed to simultaneously meet the needs of these enhancement mechanisms. The formation of pn heterojunction was confirmed and the associated energy band diagram was constructed with band gaps of CuS and MoS2 as 1.56 and 1.80 eV, respectively. For the degradation of tetracycline, it was demonstrated that the inherent piezoelectric property of MoS2 surface enhanced the piezocatalytic activity by inducing an electric field to aid charge separation. The heat generated by illumination raised the photocatalytic reaction rate by supplying extra energy to carriers. The CuS@MoS2 heterostructure exhibited significantly better catalytic performance than the individual CuS or MoS2 due to the formation of pn heterojunction. Furthermore, the combination of piezoelectricity and photothermal conversion also led to a significant synergistic effect, achieving a degradation efficiency of over 95% within 30 min. As compared to the conditions under ultrasonic vibration, visible light irradiation and visiblenearinfrared light irradiation alone, the combination of visiblenearinfrared irradiation and ultrasonic vibration could lead to 96, 205 and 81% enhancement. This work provides valuable insights into the design of novel heterojunction photocatalysts integrating the piezoelectric and photothermal enhancement effects.