Strain-Driven Polarized Electric Field-Promoted Photocatalytic Activity in Borate-Based CsCdBO3 Bulk Materials

Piezoelectrically polarized electric field can provide a strong driving force for the separation of the photoinduced charge carriers that has attracted a wide attention in the field of photocatalysis. In this paper, a new type of piezoelectric borate material CsCdBO₃ exhibits a high efficiency for the degradation of typical organic pollutants under the synergistic effects of strain and light conditions. The oxidation rate constant of the synergistic effect is 0.653 min^-1, which is 3.77 times that of just under visible light irradiation. Further, the material shows a higher efficiency when treated both under the clockwise stirring direction and a high stirring speed. A characteristic piezoresponse hysteresis loop was detected using the piezoresponse force microscopy (PFM) approach. The strain-driven polarized electric field facilitates to promote the photoinduced electron-hole pair separation, thus enhancing the photocatalytic activity. The present work provides a new direction of the borate with a noncentrosymmetric structure in the environmental remediation.

Boosting photocatalytic chlorophenols remediation with addition of sulfite and mechanism investigation by in-situ DRIFTs

Sulfite is recently found to be promising in enhancing photocatalytic pollutants degradation, which is a byproduct from flue gas desulfuration process. Herein, 4-chlorophenol (4-CP) photodegradation was systematically investigated in a sulfite mediated system with g-C₃N₄ as photocatalyst. The degradation efficacy was improved by about 3 times with addition of 25 mM Na₂SO₃. The dominant responsible reactive oxygen species for chlorophenols remediation in the presence of sulfite included O₂^·-, SO₃^·-, and SO₄^·- as confirmed by radical quenching experiments and electron spin resonances technology. In-situ DRIFTs results indicated the improved cleavage of CCl and CH bonds with the simultaneous formation of CO and CC bonds when bisulfite was added. Degradation intermediates such as 4-chlorocatechol, hydroquinone, and muconic acid were detected by HPLC-MS. Furthermore, the photodegradation mechanisms of 4-CP were tentatively discussed . Other chlorophenols (phenol, 2-CP, 2,4-DCP, and their mixture) were also efficiently removed in the system, suggesting that sulfite could be universally applied in photocatalytic wastewater purification.