One-step fabrication of porous oxygen-doped g-C₃N₄with feeble nitrogen vacancies for enhanced photocatalytic performance

Abstract

Porous oxygen-doped graphitic carbon nitride (g-CN) with feeble nitrogen vacancies was fabricated through thermal polycondensation of melamine with an appropriate amount of polyvinylpyrrolidone. After optimization, the bandgap of g-CN can be narrowed by 0.2 eV and the specific surface area expanded, which contribute to increasing the utilization of solar energy. Consequently, the optimized g-CN exhibits impressive enhancement in photocatalytic hydrogen evolution performance, by nearly 5 times compared with the pristine one under the irradiation of visible light.

Reduced Oxygenated g‐C3N4 with Abundant Nitrogen Vacancies for Visible‐Light Photocatalytic Applications

“…[29] Specifically,t he value of N (2C) /N (3C) in the RCN was only 0.2 lower than that of g-C 3 N 4 ,w hereasR CNO displayed av alue that was 1.00 lower;t his indicated that the pre-oxygenated treatment towards the g-C 3 N 4 prefers much the nitrogen vacancies formation during the H 2 reduction step, which was Table 2). The XPS spectra of O1s in g-C 3 N 4 andR CN showed a peak at the binding energy of 531.85 eV,w hich was attributed to the Oa toms in the NÀCÀOÀHm oiety.T he O1s peak in the RCNO sample was shifted to al ower binding energy of 531.36 eV,w hich corresponds to the formation of the C (3C) ÀNÀ Of unctionalg roup; [26] furthermore,anew peak appeared at 533.28 eV,w hich represented the Oa tom in C=Oo rC ÀO groups [30] and should be relatedt ot he release of the Na tom (i.e.,aNvacancy formation) followed by the oxidation of the freshly formed Ctermini.…”

“…This phenomenon implies that the interplanar spacing of the crystal decreased after oxidation, which intensifies the interaction between the g ‐C 3 N 4 crystal layers. This was attributed to the fact that the electronegativity of the O atom is greater than that of N and C atoms . The diffraction peak at 13.1° is the characteristic peak of crystal face (100) of the inplane repetition of tri‐ s ‐triazine units, which corresponds to a unit cell length along the c ‐axis of 0.68 nm .…”

“…The XPS spectra of O1s in g ‐C 3 N 4 and RCN showed a peak at the binding energy of 531.85 eV, which was attributed to the O atoms in the N−C−O−H moiety. The O1s peak in the RCNO sample was shifted to a lower binding energy of 531.36 eV, which corresponds to the formation of the C (3C) −N−O functional group; furthermore, a new peak appeared at 533.28 eV, which represented the O atom in C=O or C−O groups and should be related to the release of the N atom (i.e., a N vacancy formation) followed by the oxidation of the freshly formed C termini.…”

“…This was attributed to the fact that the electronegativity of the Oa tom is greater than that of Na nd Ca toms. [26] The diffraction peak at 13.18 is the characteristic peak of crystal face (100) of the inplane repetition of tri-s-triazine units, [25] which corresponds to au nit cell length along the c-axis of 0.68 nm. [27] Simultaneously, owing to ah ydrolysis/condensation process of g-C 3 N 4 ,anew peak emerged at 10.98 for CNO, [27] which disappeareda fter the conversion to RCNO.…”

Recovery Behavior of the Luminescence Peak from Graphitic Carbon Nitride as a Function of the Synthesis Temperature

“…A decrease of the PL intensity from g‐C 3 N 4 synthesized at high temperatures (>575 °C) is usually related to the formation of structure defects, which can capture charge carriers and cause the increased non‐radiative recombination rates and shorter lifetime of the carriers . Here, PL quenching presumably caused by in situ O‐doping of g‐C 3 N 4 facilitates charge separation …”