Modulating interface internal electric field for efficient charge separation in Co3O4/M-TiO2 p-n junction

Abstract

The practical application of photocatalysis in water purification is restricted by the high electron-hole recombination efficiency. Herein, a Co3O4/M-TiO2 p-n composite catalyst with internal electric field (IEF) modulation was constructed. Because of the large number of oxygen vacancies (OVs) within Co3O4/M-TiO2, which could redistribute extra electrons to adjacent Co sites through the strong electron absorption effect of Co. Consequently, the charge distribution at the interface of Co3O4/M-TiO2 have been changed, forming positive and negative charge regions on M-TiO2 and Co3O4, respectively. Compared with Co3O4/P25, the amount of OVs in Co3O4/M-TiO2 is significantly increased, making the charge distribution at the interface more uneven and resulting in a significantly increased IEF intensity of Co3O4/M-TiO2 by 1.9 times. A series of photoelectric chemical experiments showed that driven by powerful IEF, the photogenerated electron-hole separation efficiency of Co3O4/M-TiO2 is significantly improved. In the photocatalysis-peroxymonosulfate (PMS) oxidation coupling system, Co3O4/M-TiO2 achieved high efficiency degradation of tetracycline hydrochloride (93.6 %) within 30 min, and a synergistic degradation mechanism of photocatalysis and PMS oxidation was proposed. This study provides a novel perspective on the construction of heterojunctions possessing strong internal electric fields.