Insights into the enhanced adsorption/photocatalysis mechanism of a Bi4O5Br2/g-C3N4 nanosheet

The composite Bi4O5Br2/g-C3N4 nanosheet was fabricated by facile precipitation method for the first time. The results of XRD, XPS and FT-IR confirmed the successful construction of heterojunctions. Bi4O5Br2/g-C3N4 displayed better adsorptive and photocatalytic activity for removal of rhodamine B (RhB) and tetracycline hydrochloride (TC) with good stability. Zeta potential and BET analysis suggested that the enhancement of Lewis base sites and large surface area were the reason for the improvement of adsorptive mechanism. On the side of photocatalysis, the better charge separation and visible light utilization in Bi4O5Br2/g-C3N4 were confirmed by transient photocurrent response, PL spectrum and UV-vis DRS. Moreover, active species trapping experiments and ESR tests indicated that h(+) and center dot O-2(-) were the main radicals in the photocatalytic system. As the formation of type II heterojunction, band structures were optimized by valence band (VB) and conduct band (CB) offset, which was depth calculated. Due to this optimization and more activity sites generated in the photocatalyst surface, a slight improvement of the center dot O-2(-) generation was displayed by quantification test. This work might provide some guidance for synergy of adsorption and the photocatalytic degradation mechanism, and rational construction of type II heterojunctions to solve ever-increasing environmental problems. (C) 2019 Elsevier B.V. All rights reserved.