Graphitic carbon nitride embedded with graphene materials towards photocatalysis of bisphenol A: The role of graphene and mediation of superoxide and singlet oxygen

Composite photocatalysts comprising graphitic carbon nitride (g-C 3 N 4 ) and graphene materials were synthesized and evaluated in the photocatalysis of bisphenol A (BPA) with a focus on elucidating the reaction mechanism. Embedding reduced graphene oxide (rGO) to g-C 3 N 4 significantly accelerated the photocatalysis rate of BPA by three folds under visible light irradiation at neutral pH. We showed that rGO synthesized in intimate contact with g-C 3 N 4 increased the surface areas and electrical conductivity of the g-C 3 N 4 composites and promoted the electron-hole pair separation. The BPA photodegradation mechanism involved selective oxidants as superoxide (O 2 •− ) and singlet oxygen ( 1 O 2 ) that were formed through one-electron reduction of O 2 and the unique oxidation of O 2 •− by photogenerated hole (h + ), respectively. The synthesized photocatalyst exhibited superior visible light photoreactivity to that of N-doped P25 TiO 2 , good photo-stability and reuse potential, and was operative in complex wastewater. rGO embedded g-C 3 N 4 achieved good photomineralization of BPA at 80% in 4 h compared to 40% of bare g-C 3 N 4 . This study sheds light on the photocatalysis mechanism of BPA with a metal-free, promising rGO/g-C 3 N 4 photocatalyst. g-C 3 N 4 embedded with reduced graphene oxide facilitates electron-hole separation and photogeneration of superoxide and singlet oxygen towards mineralization of BPA. • rGO enhanced the photoreactivity of pure g-C 3 N 4 by promoting electrical conductivity and electron-hole separation. • The mechanism involved O 2 . •− and 1 O 2 that was formed through the oxidation of O 2 •− by h + . • rGO/g-C 3 N 4 exhibited superior photoreactivity to that of visible light N-doped TiO 2 . • rGO/g-C 3 N 4 achieved 80% of BPA photomineralization at neutral pH compared to 40% of pure g-C 3 N 4 .