Boosting O2 activation by internal electric field regulation in vacancy-enhanced S-scheme heterojunction for efficient degradation of bisphenol A

Abstract

The photocatalytic molecular oxygen (O2) activation is hindered by the weak O2 adsorption capacity and obstacles to electron transfer. Herein, a vacancy-enhanced BiOI/g-C3N4 S-scheme heterojunction was designed to enhance the O2 adsorption capacity and accelerate electron transfer in water treatment. The density functional theory calculation (DFT), in-situ irradiation X-ray photoelectron spectroscopy (XPS) spectra and experiments demonstrate that the S-scheme charge transfer mechanism. And the introduction of N vacancies in g-C3N4 can adjust the electronic structure, strengthen the internal electric field in S-scheme heterojunction, thereby broadening the light response range and further improving the separation rate of photoinduced electron-hole pairs. Besides, the presence of N vacancies can function as the active sites for the adsorption of O2 and facilitate the capture of electrons, promoting the generation of superoxide radicals (•O2−). Thanks to the synergistic effect of the S-type charge transfer route with N vacancies in g-C3N4, degradation rate of bisphenol A (BPA) for BCN-680 increases to 0.0433 min−1, which is 1.86 and 10.56 times higher than BiOI and CN-680. This work presents a valuable method for O2 activation through designing the S-scheme heterojunction with abundant active sites by vacancy construction.