Boosting piezocatalytic activity of graphitic carbon nitride for degrading antibiotics through morphologic regulation and chlorine doping

Graphitic carbon nitride (GCN) has been demonstrated to be a potential piezocatalyst in environmental remediation. The common piezoelectric materials synthesized by GCN are often designed to have a larger specific surface area to increase the adsorption and degradation performance of environmental pollutants. However, these process will also decrease the particle size of two-dimensional GCN, which thus affect the in-plane polarization intensity and inhibit the piezoelectric catalytic performance. Herein, we proposed an NH4Cl assistant synthesis to obtain ultrathin Cl-doped GCN (Cl-GCN) with large surface area and developed porosity. The introduced Cl with strong electronegativity can better change the electron cloud density distribution in GCN. From the experiment measurements and the theoretical calculation, Cl dopant in GCN skeleton resulted in partially destroyed crystal symmetry, and increased the structural polarity. As a result, the Cl-GCN simultaneously possessing large surface area and high piezoelectric polarization contributed enhanced piezocatalytic activity for degradation of antibiotics compared to the pristine GCN. Within 30 min, the degradation efficiency of tetracycline hydrochloride (TC-HCl) reached to ca. 94%. Besides, the effects of antibiotic concentration as well as the piezocatalytic durability for eliminating different antibiotics were investigated. Finally, based on determinations of mainly active species and the intermediate products during the piezocatalytic process, a plausible piezocatalytic degradation mechanism was proposed. This study implies that enhancing the piezoelectric polarization of piezocatalyst by heteroatomic doping and meanwhile improving its surface area are promising strategies to promoting piezocatalytic performance both for environmental application and for clean energy production.