Hydrogen-Induced Defective Crystalline Carbon Nitride with Enhanced Bidirectional Charge Migration for Persulfate Photoactivation

Abstract

A feasible way to overcome the moderate photoactivity of carbon nitride is by decreasing the carrier diffusion distance and increasing the intralayer active sites by synthesizing defective crystalline carbon nitride. However, the additive-free synthesis of this type of structure remains a great challenge, due to the trade-off between crystallinity control and defect modulation. Herein, we demonstrate the hydrogen-assisted synthesis of ultrathin carbon nitride nanosheets with efficient exciton dissociation and fast electron transfer. Experimental and theoretical investigations indicate that hydrogen not only facilitates intermolecular cross-linking for crystallization but also generates abundant nitrogen vacancies among non-hydrogen-bonded tri-s-triazine units for charge transportation. The simultaneous modulation of interlayer and intralayer interactions contributes to the efficient bidirectional charge transfer during photocatalytic reactions. The synergy of defective crystalline carbon nitride and persulfate oxidants results in a striking performance for contaminant degradation, with 9.2-and 18.4-times higher activity than separate photocatalysis and persulfate photoactivated by bulk g-C 3 N 4 , respectively. This work not only provides a facile approach to synthesizing defective crystalline carbon nitride without employing any extrinsic additives but also opens up a new avenue to improve the efficiency of metal-free photocatalysts by bidirectional charge modulation.

Synergistic Effects of the Ni3B Cocatalyst and N Vacancy on g-C3N4 for Effectively Enhanced Photocatalytic N2 Fixation

“…As illustrated in the C 1s spectrum of CN (Figure 3d), the three peaks were observed at the binding energies of 284.80, 286.41, and 288.11 eV, which could be ascribed to C−C bonds, C−NH x (x = 1 and 2) on the edges of tri-s-triazine units, and sp 2 -hybridized carbon in N�C−N bonds, respectively. 40,49 The peak area of the C−NH x component in V N -CN at 286.48 eV is significantly intensified compared with that of CN, deriving from the loss of lattice N atoms. 50 The N 1s XPS spectrum of CN (Figure 3e) displays three peaks at 398.39, 399.43, and 400.73 eV, which correspond to C−N�C, N−(C) 3 , and C−NH, respectively.…”

Polymeric Carbon Nitride Nanosheets as a Metal‐Free Heterogeneous Catalyst for Highly Efficient Methanolysis of Polycarbonates

“…The peaks at 398 eV, 400 eV, and 401 eV are attributed to the sp 2 -bonded nitrogen in CÀ N=C, the nitrogen in tertiary N-(C) 3 groups, and NH x groups in the heptazine framework. [50] After thermal exfoliation, the specific surface area increased, exposing more edge NH x active sites, and the content of NH x groups increased to 15.2 % in PCNS from an initial 9.1 % in BPCN. Based on the reduction in total alkalinity after stripping and the results of the catalytic reactions, it is presumed that the NH x groups are probably the main basic active site.…”

“…The N 1s XPS results of BPCN and PCNS are depicted in Figure 4a. The peaks at 398 eV, 400 eV, and 401 eV are attributed to the sp 2 ‐bonded nitrogen in C−N=C, the nitrogen in tertiary N‐(C) 3 groups, and NH x groups in the heptazine framework [50] . After thermal exfoliation, the specific surface area increased, exposing more edge NH x active sites, and the content of NH x groups increased to 15.2 % in PCNS from an initial 9.1 % in BPCN.…”

Cyano-modified poly(triazine imide) with extended π-conjugation for photocatalytic biological cofactor regeneration

“…Furthermore, π–π interactions between crystalline carbon nitride and NADH can be finely tuned by modifying the π-conjugation property. When the surface defects are introduced, such as missing atoms, 32 impurities 33,34 or functionalization, 35,36 additional electronic states could be generated that interact with the existing π-conjugated planes, further enhancing the conjugation of the crystalline carbon nitride. 37 Typically, cyano (–CN) is a functional group with strong electronegativity that can influence the electron distribution in carbon nitride through the electron-attracting effect, further extending the π conjugation plane.…”

“…37 Typically, cyano (–CN) is a functional group with strong electronegativity that can influence the electron distribution in carbon nitride through the electron-attracting effect, further extending the π conjugation plane. 32,38 However, we still lack sufficient understanding of the rational construction and the utilization of non-covalent interactions to develop more efficient and biocompatible photo-enzyme coupling systems (Table S1†).…”