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

Abstract

A novel g-C N photocatalyst (RCNO) with abundant nitrogen vacancies and oxygen-containing electron-withdrawing groups was prepared. Oxygen was gradually introduced into the g-C N structure by a hydrothermal hydrolysis/condensation process, and nitrogen vacancies were produced with H reduction. The presence of nitrogen vacancies reduced the conduction band energy of g-C N from -0.75 to -0.5 eV and introduced plenty of defect levels in the band gap (just below the conductive band with a width of 0.45 eV). The oxygenation of g-C N induced the formation of oxygen-containing functional groups, such as C=O and C-O, as well as effectively enhancing the separation efficiency of photogenerated carriers and reducing the valence band energy from 2.05 to 2.30 eV. Therefore, the photocatalytic activity and photocurrent responses of RCNO were about nine and eight times higher than that of g-C N , respectively.

Oxygen Doping in Graphitic Carbon Nitride for Enhanced Photocatalytic Hydrogen Evolution

“…In order to further study the chemical structure of all samples, the high‐resolution deconvolution of O 1s , N 1s and C 1s XPS spectra were carried out (Figure and Figure S5). Three peaks centered at 531.3 eV, 532.1 eV and 533.1 eV are observed in all samples, corresponding to N−C−O (O1), adsorbed H 2 O (O2) and C−O−C species (O3), respectively (Table S3) . The contents of the O species increased significantly in modified CNx, in which N−C−O is the dominant functionality.…”

Defects Engineering Leads to Enhanced Photocatalytic H2 Evolution on Graphitic Carbon Nitride–Covalent Organic Framework Nanosheet Composite

“…Room‐temperature electron paramagnetic resonance (EPR), which has been supposed to be an effective approach of investigating the defects in CNS, [ 40,55–59 ] was then employed to probe the CNS‐ x . For all CNS‐ x , the peak with a g value of 2.0029 is observed ( Figure a).…”

“…This is ascribed to the unpaired electrons of sp 2 carbon atoms in the delocalized π‐conjugated aromatic rings. [ 55–59 ] The intensity of the peak is hardly affected when the exfoliation temperature is ≈550 °C (Figure S2, Supporting Information). However, CNS prepared at higher exfoliation temperatures exhibited obviously weaker EPR peak intensity than the bulk CN, indicating the decrease of the surface defect density on CNS prepared at higher exfoliation temperature.…”

Two‐photon Absorption in a Defect‐engineered Carbon Nitride Polymer Drives Red‐light Photocatalysis

“…As shown in Table 2, the overall C/N ratio of the PCN samples slightly increased as the calcination temperature increased, which suggests the presence of nitrogen vacancies. [30] To further analyze the surface composition and chemical states of PCN photocatalysts, XPS was employed. XPS spectra of the N 1s, C 1s and O 1s core levels of PCN-550, PCN-600, PCN-650 and Table S1.…”