Three-Dimensional Hierarchical Seaweed-Derived Carbonaceous Network with Designed g-C₃N₄ Nanosheets: Preparation and Mechanism Insight for 4-Nitrophenol Photoreduction

Abstract

The development of g-C3N4-based photocatalysts with abundant active sites is of great significance for photocatalytic reactions. Herein, a smart and robust strategy was presented to fabricate three-dimensional (3D) g-C3N4 nanosheet-coated alginate-based hierarchical porous carbon (g-C3N4@HPC), including coating melamine on calcium alginate (CA) hydrogel beads, freeze-drying hydrogel beads as well as pyrolysis at high temperatures. The resulting photocatalyst possessed a significantly high surface area and a large amount of interconnected macropores compared with porous carbon without the melamine coating. The unique structural features could effectively inhibit the curling and agglomeration of g-C3N4 nanosheets, provide abundant photocatalytic active sites, and promote mass diffusion. Therefore, the g-C3N4@HPC composite exhibited remarkable photocatalytic activity and outstanding stability toward the photoreduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 under natural sunlight and simulated visible-light irradiation (λ > 420 nm) using a 300 W xenon lamp. Moreover, the mechanism toward the photocatalytic reaction was extensively studied by quenching experiments and electron spin resonance (ESR) experiments. The results showed that active hydrogen species were able to be achieved by following a dual-channel pathway in the NaBH4 system, which included photocatalytic reduction of H+ ions and photocatalytic oxidation of BH4 – ions. This work not only opens up a new way to design efficient photocatalysts for various reactions but also provides a reference for an in-depth study of the photoreduction mechanism.

Efficient Activation of Peroxymonosulfate by V-Doped Graphitic Carbon Nitride for Organic Contamination Remediation

“…The chemical structures of the materials were investigated by XRD patterns. As shown in Figure 2, the g-C3N4 shows two distinct peaks at 12.8 and 27.6°, corresponding to the extended distance of the interplanar repeat unit in the (1 0 0) diffraction plane and the stacking of the π-π conjugated aromatic rings in the (0 0 2) diffraction plane, which is in accordance with previous studies [29,37,38]. The peak related to the (0 0 2) facets of g-C3N4 is clearly noticed in V-doped g-C3N4.…”

“…The C 1s spectrum in Figure 4b exhibits two characteristic peaks at 288.5 and 284.8 eV, ascribing to the sp2 hybridized carbon (N−C=N) and graphitic carbons (C=C), respectively [38,42]. The N 1s spectrum in Figure 4c shows two peaks at binding energies of 398.9 and 400.5 eV, which are ascribed to the hybridized aromatic N atoms bound to C atoms in the triazine units (C−N=C) and tertiary nitrogen (N-(C) 3 , respectively [37,38,43]. Furthermore, two major peaks at binding energies of 517.2 and 524.4 eV are observed from the V 2p spectrum (Figure 4d), which are belonged to the V 2p 3/2 and V 2p 1/2 of V-O bond of V 5+ species, respectively [34].…”

“…The valence states of the V-doped g-C3N4 sample were further identified b XPS survey spectra (Figure 4a) prove the coexistence of N, C, and V elements i C3N4-0.5 sample. The C 1s spectrum in Figure 4b exhibits two characteristic pea and 284.8 eV, ascribing to the sp2 hybridized carbon (N−C=N) and graphit (C=C), respectively [38,42]. The N 1s spectrum in Figure 4c shows two peaks energies of 398.9 and 400.5 eV, which are ascribed to the hybridized aromati bound to C atoms in the triazine units (C−N=C) and tertiary nitrogen (N-(C)3, re [37,38,43].…”

Recent Advances in g-C3N4-Based Materials and Their Application in Energy and Environmental Sustainability

“…In addition, some unique g-C 3 N 4 -based structures, like the “seaweed” network, spiral rod, and hollow fusiform, have also been reported [ 55 , 56 , 57 , 58 , 59 ], and a superior photocatalytic activity to bulk samples was observed for higher specific surface areas. Among these morphologies of g-C 3 N 4 , 1D nanoribbons, with a large specific surface area, more active sites, a short diffusion distance, and preferential directions for photo-generated electron-hole carriers, effectively accelerate the catalytic performance of g-C 3 N 4 .…”

Cu-Based Catalysts Supported on H3PO4-Activated Coffee Biochar for Selective Reduction of Nitroaromatics

“…Different nitroaromatics could be smoothly reduced with good to excellent yield using the present Cu/PBCR-600 catalyst, as shown in Table and Figure S10. 4-Nitrophenol, as a kind of toxic and hard-degradable organic compounds, − could be smoothly converted to 4-aminophenol with 98.5% yield over Cu/PBCR-600 (Table , entry 1). Figure S10a,b traces the reduction of 4-nitrophenol.…”