Switching Oxygen Reduction Pathway by Exfoliating Graphitic Carbon Nitride for Enhanced Photocatalytic Phenol Degradation

Abstract

The selectivity of molecular oxygen activation on the exfoliated graphitic carbon nitride (g-C 3 N 4 ) and its influence on the photocatalytic phenol degradation process were demonstrated. Compared with bulk g-C 3 N 4 , the exfoliated nanosheet yielded a 3-fold enhancement in photocatalytic phenol degradation. ROS trapping experiments demonstrated that although the direct hole oxidation was mainly responsible for phenol photodegradation on both g-C 3 N 4 catalysts, molecular oxygen activation processes on their surface greatly influenced the whole phenol degradation efficiency. Reactive oxygen species and Raman spectroscopy measurements revealed that oxygen was preferentially reduced to ·O 2 − by one-electron transfer on bulk g-C 3 N 4 , while on g-C 3 N 4 nanosheet the production of H 2 O 2 via a two-electron transfer process was favored due to the rapid formation of surface-stabilized 1,4-endoperoxide. The latter process not only promotes the separation of photogenerated electron−hole pairs but also greatly facilitates reactive oxygen species formation and subsequently enhances phenol degradation.

Toward High Performance 2D/2D Hybrid Photocatalyst by Electrostatic Assembly of Rationally Modified Carbon Nitride on Reduced Graphene Oxide

“…Noticeably, the exfoliation process caused an obvious blue shift to 415 nm, accompanying by the bandgap broadening to 2.99 eV, which is consistent with literatures91011. It was reported that the conduction band (CB) and valence band (VB) edges shifted in opposite direction after exfoliation due to the quantum effect45. Fortunately, the molecular grafting of remarkably altered the electronic structure so that the absorption edge onset of CNX is extended to ~600 nm1418.…”

“…The well-contacted RGO acted as an electron reservoir and transferred abundant photogenerated electrons to O 2 , favoring a two-electron process to H 2 O 2 45. It was found that the degradation rate in the presence of catalase was similar to that of t -BuOH.…”

Carbon dots decorated graphitic carbon nitride as an efficient metal-free photocatalyst for phenol degradation

“…Since the photogenerated holes in the valance band of g-C 3 N 4 (E VB = +1.40 V, vs. NHE) are incapable of oxidizing hydroxyl groups into • OH radicals (E ( • OH/OH − ) = +1.99 V, vs. NHE) due to the more negative valance band potential [42], it is believed that the observed • OH radicals were generated from the • O 2 − radicals by photochemical reaction. Time-dependent ESR signals were also measured under the same conditions, where the intensity of the ESR signal could imply the concentration of ROS generated in each catalyst suspension.…”

Peroxymonosulfate enhanced visible light photocatalytic degradation bisphenol A by single-atom dispersed Ag mesoporous g-C3N4 hybrid

“…Graphitic carbon nitride (g-C 3 N 4 ), as a metal-free polymeric semiconductor, has shown huge potential in the field of photocatalytic H 2 evolution [1][2][3], CO 2 reduction [4,5], contamination elimination [6,7], and H 2 O 2 synthesis [8][9][10]. With an optical band gap of 2.70 eV, g-C 3 N 4 has shown a response to visible light up to 460 nm.…”