Synthesis of heterostructure composite (g-C3N4/phosphomolybdic acid) for synergistic piezo/photo-catalytic degradation of CR dye and S. aureus bacteria

In photocatalysis systems, piezocatalytic effect is widely utilized to achieve efficient separation of photo-produced carriers for powerfully decomposing organic contaminants and bacteria under both mechanical vibrations and visible illumination. Herein, an efficient heterogeneous composite of phosphomolybdic acid (PMA)-immobilized onto g-C3N4 has been constructed via ionothermal and impregnation methods. After characterization, the g-C3N4/PMA hybrid has been applied for piezophotocatalytic degradation of Congo red dye (CR) and bacterial inactivation of staphylococcus aureus (S. aureus) under visible-light illumination and ultrasonication. Compared with the photocatalysis, the g-C3N4/PMA hybrid exhibited improved piezophotocatalytic degradation of CR, reaching 99 % within only 60 min, indicating the piezoelectric polarization promotes considerably photocatalytic activity. Also, high bacterial inactivation performance (>94.0 %) has been obtained compared with pristine g-C3N4 and PMA samples after 180 min of visible-illumination/ultrasonication. These improved outcomes were due to the synergistic impact between high reversible redox capabilities of PMA with the controllable electronic structured of g-C3N4, and piezoelectric polarization, which acts as a driving force to prevent the recombination of generated charges, leading to an efficient separation rate and transfer of the photogenerated electrons-holes, and thus boosting degradation and bacterial inactivation efficiencies. The recommended mechanisms for piezophotocatalytic degradation of both CR dye and S. aureus bacteria have been clarified and supported by trapping experiments, which confirmed the significant roles of O-center dot(2)- and electrons. The reusability investigations demonstrated the high stability performance of g-C3N4/PMA hybrid during five sequential piezophotocatalytic cycles.