Enhanced metal-free photocatalyst performance by synergistic Coupling of internal magnetic field and piezoelectric field

Graphitic carbon nitride (g-C3N4) is a promising metal-free photocatalyst; however, its high carrier recombination rate and insufficient redox capacity limit its degradation effect on antibiotics. In order to overcome these shortcomings, the photocatalytic activity is improved by regulating the spin polarization state, constructing the internal electric field, and applying the external piezoelectric field. In this paper, the chlorine-doped and nitrogen-deficient porous carbon nitride composite carbon quantum dots (N-v-Cl/UPCN@CQD) has been synthesized successfully. The doping position of chlorine and spin polarization properties are verified by DFT calculation. The key intermediates *O-2(-) and *OOH for the synthesis of reactive oxygen species were detected by in-situ infrared testing, which promotes the production of center dot O-2(-) and H2O2. The degradation rate constant of N-v-Cl/UPCN@CQD for removal of tetracycline is 8.45 times higher than that of g-C3N4. The active oxygen production and degradation efficiency of piezoelectric photocatalysis under the synergistic effect of intense stirring and vis-light irradiation are much higher than those of photocatalysis and piezoelectric catalysis, and the conversion of H2O2 to center dot OH is promoted by piezoelectric field. This paper provides a reliable way to improve the performance of piezoelectric photocatalysts by adjusting their energy band, electronic structure and piezoelectric force.