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The advancement of heteroatom-doped photocatalysts represents a promising approach to enhancing the efficiency of photocatalytic hydrogen production. Nonetheless, current doping methods often use toxic and complex processes, along with environmentally harmful materials. For example, traditional sodium dihydrogen phosphate dopants emit toxic fumes at high temperatures. Thus, there is an urgent need to investigate sustainable and direct doping techniques. This study presents the synthesis of phosphorus-doped graphite carbon nitride (P-g-C₃N${}_4)$ through a solvent pre-mixing assisted calcination process, utilizing nontoxic ammonium dihydrogen phosphate as the dopant, the optimal photocatalytic performance was observed at a phosphorus doping concentration of 5wt.%, resulting in a hydrogen production rate of 268$\mu$mol/g/h. Notably, the foaming effect resulting from the thermal decomposition of ammonium dihydrogen phosphate significantly enhances the specific surface area of P-g-C₃N₄, and exhibits superior light absorption capabilities and enhanced photocatalytic activity. The catalyst prepared in this research is both cost-effective and environmentally sustainable, positioning it as a promising candidate for applications in photocatalytic hydrogen production. It provides a new method for the development of clean energy and the solution of environmental pollution problems.

In this study, K₂Ti₆O${}_{13}$ (KTO) nanowires were doped with carbon (CKTO) via a novel solid-phase approach at 800^∘C for the first time using ethanol, KF, and TiO₂. In addition to the lower sintering temperature, a shorter insulation period was achieved compared to the conventional solid-phase method. Furthermore, by combining and calcining CKTO and g-C₃N₄, a CKTO/g-C₃N₄ heterojunction composite was produced. The rate at which CKTO/g-C₃N₄ photocatalytically degraded methylene blue was higher than those of pure CKTO and g-C₃N₄. Our study indicates that adding g-C₃N₄ enhances photocatalytic performance by reducing the recombination rate of photogenerated electron–hole pairs and narrowing the bandgap of the CKTO/g-C₃N₄ heterostructure. This paper presents a novel method for creating KTO composites in an eco-friendly and productive manner for the photocatalytic degradation of organic colors.

Co₃O₄ decorated flower-like g-C₃N₄ hybrid nanocatalysts were successfully synthesized and prepared via a facial hydrothermal method. The composition and morphology of the as-synthesized Co₃O₄/g-C₃N₄ nanocatalysts were characterized by the techniques of XRD, FT-IR, SEM, TEM, XPS and N₂-sorption. The analysis results indicated that the as-synthesized samples possess the flower-like structure, which consisted of g-C₃N₄ nanosheets and Co₃O₄ nanoparticles with the size about 25nm. The as-prepared Co₃O₄/g-C₃N₄ catalysts possess high catalytic activity and excellent stability for carbon monoxide (CO) oxidation. The total conversion of Co can be kept for more than 48h under the reaction temperature of 120${}^{\circ }$C.

Durability is a key factor to determine the service life of organic coating. The addition of nanomaterials can improve the mechanical properties and compactness of the organic coatings. As a kind of nanomaterial, g-C₃N₄ has lamellar structure and can be excited by visible light. At the same time, its cost is low. So it can be selected as a filler to prepare organic coating. The lamellar structure of g-C₃N₄ is favorable for its dispersion in organic coatings. Stearic acid is an environmentally friendly material with low surface energy. It can improve the hydrophobicity of the coating. In this research, porous g-C₃N₄ nanosheets were used as filler and stearic acid was used as surface modifier to prepare waterborne acrylic resin-based organic composite coating. The chemical reagent durability, electrochemical durability and mechanical properties of the composite coating were tested. At the same time, the photocatalytic degradation performance of the coating surface was also tested. The results showed that g-C₃N₄ as filler and stearic acid could effectively improve the durability of the waterborne acrylic resin coating. Meanwhile, the coating surface has obvious visible light-activated photocatalytic performance due to the addition of g-C₃N₄.

A heterostructural composite composed of g-C₃N₄ and Bi₂O₃ was achieved by the one-pot and thermal-induced polycondensation method using melamine and Bi(NO${}_3{)}_3$ as precursor at 550${}^{\circ }$C under air atmosphere. The crystalline phase, components and morphologies of the as-prepared composites were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Besides, the photocatalytic activity of composites was evaluated by degrading RhB aqueous solution at room temperature under visible light irradiation. Compared with bulk g-C₃N₄, the photocatalytic efficiency of the 0.5% Bi₂O₃/g-C₃N₄ (Bi–CN) was increased by up to four times. The introduction of Bi₂O₃ enhances not only the light absorption ability, but also the separation of photogenerated electron–hole pairs.

A novel heterojunction photocatalyst consisting of three-dimensional (3D) flower-like MgAl LDH and acidified g-C₃N₄ (CN-H) was first developed by a simple facile coating method. The obtained MgAl LDH/CN-H samples were thoroughly characterized by powder X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and Brunauer–Emmett–Teller (BET) analyzer. The detailed results demonstrated that g-C₃N₄ could transform from a generally two-dimensional layered structure into special cavity-like structure after acid treatment. CN-H increased specific surface to expose more active reaction sites in comparison to pristine g-C₃N₄. MgAl LDH and CN-H with matched band gaps were tightly bonded to form heterojunction structure by strong electrostatic intercalation. The combination could obviously boost the separation of photogenerated carriers. The as-prepared MgAl LDH/CN-H exhibited high photocatalytic performance in the degrading on typical antibiotic tetracycline hydrochloride (TC$\cdot$HCl), of which degradation rate was 6.5 and even 22 times higher than that of MgAl LDH and pristine g-C₃N₄, respectively. The synthesis of MgAl LDH/CN-H heterojunction photocatalyst could have some positive suggestions for the rational construction of new photocatalysts and also has great application prospect in the degradation of environmental pollutants.

In this work, a highly efficient p-type Cu₃P/$n$-type g-C₃N₄ heterojunction photocatalyst was synthesized in situ. XRD, UV–Vis, N₂ adsorption, TEM, XPS, PL, and EIS are used to characterize the as-prepared catalysts. The results show that Cu₃P nanoparticles are highly dispersed onto the g-C₃N₄ surface, which obviously promotes the separation rate of electrons and holes. The charge transfer between Cu₃P and g-C₃N₄ follows the “Z-scheme” mechanism. The as-prepared Cu₃P/g-C₃N₄ heterojunction photocatalyst displays the ammonium ion production rate of 7.5mgL${}^{-1}$h${}^{-1}$g${}_{\mathrm{\text{cat}}}^{-1}$, which is 28.8 times higher than that of neat g-C₃N₄, as well as good catalytic stability. The possible reaction mechanism is proposed.

The present study describes a novel method to improve the dispersibility of silicon nitride powders in aqueous media. Specifically, a new Si₃N₄@g-C₃N₄ core–shell composite material was synthesized via annealing the mixture of silicon nitride and melamine under a nitrogen atmosphere using heating method. The effects of various initial mass ratios of Si₃N₄ and melamine on the structure and dispersibility of the composite were systematically investigated. The results of X-ray photoelectron spectroscopy and transmission electron microscope demonstrated that as-obtained Si₃N₄@g-C₃N₄ composite powders possess the core–shell structure, whereas the zeta potential and sedimentation analysis showed that they exhibit good dispersion in aqueous media. Furthermore, the colloidal dispersion of the composite powders is most stable when the initial mass ratio of Si₃N₄ and melamine is 100:3. The coated g-C₃N₄ could be completely removed in a cryogenic nitrogen atmosphere. The proposed process is expected to provide novel avenues for the study of dispersion of other inorganic powders.

Graphitic carbon nitride with nitrogen vacancies was successfully synthesized by the three-step method for the calcination of melamine, following urea-assisted hydrothermal and jacjoin calcination approach. The structural, surface, optical and electric properties were characterized by XRD, FT-IR, SEM, TEM, UV–Vis DRS, PL, N₂ physical adsorption/desorption and electrochemical methods, which proved that this strategy of modifying g-C₃N₄ by nitrogen vacancies not only increased the specific surface area, exposed more active sites, but also inhibited the recombination of photogenerated carriers on the surface of photocatalysts, resulting in the enhancement of photocatalytic and electrocatalytic performances. The photocatalytic activities were measured under visible light irradiation ($\lambda >420$nm), and their degradation efficiencies could be achieved for 99.8%, 55%, 100% and 99.7% corresponding to that of rhodamine B, acid orange II, methyl orange and methylene blue, respectively. The trapping experiments demonstrated that $•{\mathrm{\text{O}}}_2^{-}$ played an important role in the degradation process. In addition, being an active electrocatalyst, nitrogen-deficient g-C₃N₄ showed a lower Tafel slope, smaller overpotential and the more effective electrochemical surface area compared with that of bare g-C₃N₄ in neutral media. This work underlines the importance of defect engineering to promote catalytic performance, which can provide a simple and efficient way for modifying g-C₃N₄ and other N-based catalysts.

The WSe₂/g-C₃N₄ (graphite carbon nitride) composite with photocatalytic properties was synthesized using a hydrothermal method. This synthesis pathway can be characterized by being simple, inexpensive and nonpolluting, integrating the concept of green chemistry. The WSe₂/g-C₃N₄ composite could effectively degrade methyl orange solution under visible light irradiation. The decolorization experiment of methyl orange solution shows that the degradation rate of the 30wt.% WSe₂/g-C₃N₄ composite can reach 98.7% after 100min of illumination, while the degradation rate of pure g-C₃N₄ was only 87.6% under the same conditions. This can be attributed to the fact that the combination of WSe₂ and g-C₃N₄ nanosheets can increase the number of active binding sites, increasing the rate of charge separation and transport ability, decreasing the recombination rate of the photogenerated electron–hole pairs. Therefore, the WSe₂/g-C₃N₄ composite will have potential development as a new material with low cost, easy synthesis and excellent performance in photocatalytic degradation of water pollution.

Porous hybrid nanosheets of g-C₃N₄/$\beta$-Ni(OH)₂(CN/$\beta$-NiOH) were constructed via gas bubble method in the NiCl${}_2\cdot 6$H₂O-NH₃$\cdot$H₂O-C₂H₅OH-CN system at 140^∘C for 6h. The resulting CN(5.3wt.%)/$\beta$-NiOH nanosheets show a porous texture and a large interface contact area, which facilitates the electrolyte ion diffusion during reversible insertion/deinsertion processes. The fabricated CN(5.3wt.%)/$\beta$-NiOH hybrid-based electrode displays an enhanced specific capacitance of 887Fg${}^{-1}$ at a current density of 0.5Ag${}^{-1}$ when compared with single phase $\beta$-NiOH (480Fg${}^{-1}$). Using CN(5.3wt.%)/$\beta$-NiOH porous nanosheets and activated carbon (AC) as cathode and anode, an asymmetric supercapacitor (ASC) was assembled and the energy density achieves 28.3Whkg${}^{-1}$ and 10.9Whkg${}^{-1}$ at a power density of 798.4Wkg${}^{-1}$ and 7991.9Wkg${}^{-1}$, respectively.

Large specific surface area porous g-C₃N₄ nanosheets were prepared by utilizing acetaldehyde-mediated melamine. The synthetic processes adopted two-step thermal treatments which are in N₂ and then in an air atmosphere. The introduced acetaldehyde made melamine condensation incompletely and generated body defects in g-C₃N₄ when heated in N₂. Further heating in air realized pores formation at sites of body defects, thus increase the specific surface area of g-C₃N₄. Notably, the introduction of acetaldehyde is beneficial to generate high concentration defects, which are active sites for thermal oxidative etching, and increase the yield of g-C₃N₄ by inhibiting the sublimation of melamine. The photocatalytic performance of obtained g-C₃N₄ was evaluated by the degradation of 2-propanol under visible light irradiation ($\lambda >420$nm). The porous g-C₃N₄ exhibits excellent photocatalytic performance than bulk g-C₃N₄. The addition of trace acetaldehyde significantly increased the specific surface area and enhanced photocatalytic activity, providing a new idea for the development of simple, low-cost and high active g-C₃N₄ photocatalyst.

The treatment of phenol-containing wastewater is a hot topic in the field of environmental chemistry. In this work, the hydroxyl grafted graphite phase carbon nitride (g-C₃${\text{N}}_4)$ was prepared by alkaline hydrothermal (AH) treatment, and its degradation of phenol under visible light was investigated. XRD, UV-Vis, FT-IR, XPS, N₂ adsorption, PL, ESR, TPD and EIS were used to characterize the as-prepared catalysts. The results showed that the hydroxyl group grafting does not influence the crystal structure, optical property and specific surface area of catalyst. Compared with the hydroxyl group modified g-C₃N₄ prepared by H₂O₂ method, the alkali hydrothermal treatment can graft more hydroxyl groups onto the g-C₃N₄ surface, leading to the higher electron–hole separation efficiency. The as-prepared catalyst using this method had more surface negative charges and stronger adsorption capacity for the reaction substrate phenol. The g-C₃N₄ prepared by this alkali hydrothermal treatment displayed the phenol degradation rate constant of 0.22h${}^{-1}$, which is 3.72 and 2.06 times higher than that of neat and H₂O₂ treated g-C₃N₄, as well as excellent catalytic stability and structural stability. The possible reaction mechanism was proposed.

The presence of the antibiotics in the wastewater has posed a huge risk to aquatic life and human health. It is a great significance to develop an effective technology to treat the antibiotics-containing wastewater. In this study, a series of g-C₃N₄/NH₂-MIL-88B(Fe) composite photocatalysts are synthesized through a simple one-step method. The structure and optical properties of prepared photocatalysts are detected by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis absorption spectra (UV–Vis DRS), photoluminescence (PL) spectroscopy and transient photocurrent techniques, respectively. FESEM and TEM show that MOF is uniformly dispersed in petaloid g-C₃N₄. The uniform dispersion of Fe-MOFs in the heterojunction composites increases the specific surface area ($S_{\mathrm{\text{BET}}})$ of g-C₃N₄, which results in a great adsorption property for the nanocomposite. The capture experiment shows that $•$${\text{O}}_2^{-}$ and ${\text{h}}^{+}$ are the main active substances in ciprofloxacin (CIP) degradation. These prepared composite photocatalysts exhibit excellent CIP photodegradation activity under visibly light irradiation with an apparent rate constant of 0.0127${\text{min}}^{-1}$ (3.74 times as the rate of single component). The remarkable catalytic performance can be ascribed to the fact that the g-C₃N₄/NH₂-MIL-88B(Fe) heterojunction inhibits the recombination of photoinduced electron–hole pairs and improved the visible light absorption.

Layered g-C₃N₄ was obtained through secondary calcination, and the MoS₂–Ag/g-C₃N₄ catalyst was prepared via hydrothermal and light deposition methods. XRD, SEM and TEM results proved that the MoS₂–Ag/g-C₃N₄ sandwich biscuit structure was successfully obtained, and the sharper diffraction peak of MoS₂–Ag/g-C₃N₄ than g-C₃N₄ or MoS₂ is attributed to the synergistic crystallinity effect. SPR effect of Ag increases the electron transport time, which effectively prolonging the survival time of electron–hole pairs. Compared the degradation performance of 10mg/L rhodamine B (RhB) with different ratios of materials, 10wt.% MoS₂–Ag/g-C₃N₄ has the highest degradation property. The degradation rate remains at 87.2% under the best condition after four cycles proved that the MoS₂–Ag/g-C₃N₄ composite possesses good stability.

Constructing heterojunction photocatalyst is an effective method to enhance the separation of photogenerated electron and hole, which significantly improves ability of visible light response. In this study, calcination methods have been proposed to prepare highly efficient magnetic ternary photocatalyst g-C₃N₄/TiO₂-MnFe₂O₄ halloysite. It showed an enhanced photocatalytic degradation for dyes (crystal violet) and nonsteroidal anti-inflammatory drugs (acetaminophen) under vision light irradiation. Compared to pure g-C₃N₄, TiO₂, MnFe₂O₄ halloysite and binary g-C₃N₄-MnFe₂O₄ halloysite, the optimized ternary g-C₃N₄/TiO₂-MnFe₂O₄ halloysite displayed enhanced photodegradation efficiency with 91.1% removal of crystal violet (10ppm) in 90min under visible light irradiation, the optimized ternary g-C₃N₄/TiO₂-MnFe₂O₄ halloysite composite showed significantly enhanced photocatalytic activity with more than 79.1% removal of acetaminophen (10ppm) within 90min under visible light. The photocatalytic mechanism was identified through the free radical quenching experiment. The heterojunction photocatalyst could be easily recovered by an extra magnetic field and reused several times without any obvious deterioration in catalytic activity. Besides, the ternary heterojunction also exhibited antibacterial ability against Escherichia coli. The superior photocatalytic performance of composite should be mainly attributed to both the improvement of light harvesting as well as the enhanced separation and transfer efficiency. It is expected that this novel ternary visible-light responding composite would be a promising candidate material for organic pollutants degradation and bacteria inactivation.

Preventing the high recombination rate of carriers in graphite-carbon nitride (GCN) is essential for hydrogen production. In this work, we break the original symmetry of GCN by embedding benzene ring for enhanced visible-light absorption and carriers transfer efficiency. The new catalyst was prepared by a condensation reaction using dicyandiamide and 5-amino-2,4,6-triiodoisophthalic acid as precursors. It shows photocatalytic hydrogen evolution rate of 690.74$\mu$molg${}^{-1}$h${}^{-1}$, 9.3 times enhancement than the original GCN. This work provides a new strategy for designing efficient two-dimensional photocatalytic materials for water splitting.

Graphitic carbon nitride (g-C₃N₄)-based materials are considered promising catalysts for organic waste photodegradation due to their excellent photocatalytic activity and stability. Herein, a ternary thin layer system based on g-C₃N₄ was prepared by hexagonal boron nitride (h-BN) deposition followed by liquid phase ultrasonic stripping and Ag deposition (marked as Ag-BCN), which increased the specific surface area of g-C₃N₄, expanded the corresponding range of the visible-near-infrared spectrum of g-C₃N₄ and promoted the photo-generated electron–hole pair separation in g-C₃N₄ to improve the photocatalytic efficiency of pure g-C₃N₄. The results showed that after deposition of h-BN and Ag into bulk g-C₃N₄ and liquid phase ultrasonic stripping, the efficiency of photocatalytic degradation of tannic acid (TA) was enhanced. The efficiency of photocatalytic degradation of TA by Ag-BCN-2 was 84.3% at 90 min, which was 1.6 times the efficiency of bulk g-C₃N₄.

In this work, potassium ion-hydroxyl double modified graphite phase carbon nitride (KCN–OH) was synthesized in one step by alkali hydrothermal (AH) method. The as-prepared catalysts were characterized by XRD, FT-IR, UV–Vis, N₂ adsorption, SEM, XPS, PL, ESR, TPD and EIS. The introduction of potassium ion causes the reduced crystal size, increased specific surface area and promoted electron–hole separation efficiency of as-prepared catalyst. The hydroxyl group not only further improves the electron–hole separation efficiency but, as the electron donor group, can also make stronger interaction between catalyst and acidic phenolic compounds. The photocatalytic degradation of phenol was investigated under visible light. The results show that the phenol degradation rate constant of KCN–OH is 0.22 h${}^{-1}$ under visible light, which is over 3.7 and 2.0 times higher than that of neat g-C₃N₄ and single hydroxyl-modified g-C₃N₄. KCN–OH also displays outstanding catalytic and structural stability. The possible reaction mechanism is discussed in this paper.

ZnO/g-C₃N₄ photocatalysts were prepared by adopting room-temperature solid-phase grinding with Zn(CH₃COO)₂, NaOH, and g-C₃N₄ powders. ZnO grains with flower-like architectures were loaded on g-C₃N₄ thin flakes. The as-synthesized ZnO/g-C₃N₄ composite displayed highly visible photocatalytic activity during the degradation of methylene blue (MB).