Surface Of g-C3N4 Research Articles

G-C3N4/Ag@AgCl with Z-scheme heterojunction and Ag electron bridge for enhanced photocatalytic degradation of tetracycline wastewater.

Building Z-scheme heterojunctions with an electron bridge is a favored function for increasing photocatalytic activity. A facile approach for preparing g-C3N4/Ag@AgCl ternary heterojunctions by co-precipitation and photoreduction was established in this work. First, via co-precipitation, AgCl was modified on the surface of g-C3N4 to create a broad contact area between AgCl and g-C3N4. The AgCl is then reduced to Ag via an in-situ photoreduction technique, resulting in the formation of a ternary composite. The experimental results showed that when g-C3N4 modified 25% of the Ag@AgCl, that is, g-C3N4/Ag@AgCl-25 had the best photocatalytic performance, 94.9% of TC was degraded within 240 min, and the reaction rate to TC was 0.1214 min-1, which was 4.49 times and 8.12 times higher than that of g-C3N4 and Ag/AgCl, respectively. The excellent photocatalytic performance of g-C3N4/Ag@AgCl is attributed to the LSPR effect of Ag NPs and O-doping g-C3N4, which broadens the absorbance performance of g-C3N4, the establishment of Z-type heterojunctions between AgCl NPs and g-C3N4 NSs and Ag NPs as an electron transport bridge accelerate the photogenerated electrons transfer between AgCl and g-C3N4.

Nanoflower-like graphitic carbon nitride aerogel: Artful cyanuric acid-controlled synthesis and enhanced photocatalytic hydrogen evolution activity

The previously reported studies on cyanuric acid-assembly strategy usually ignores the promoting function of cyanuric acid in the production of g-C3N4, limiting the development of molecular assembly strategies. In this study, a cyanuric acid-controlled synthesis strategy involving the pre-assembly of cyanuric acid with melamine and subsequent one-step calcination was developed to produce a three-dimensional (3D) nanoflower-like graphitic carbon nitride (g-C3N4) aerogel. Some cyanuric acid molecules underwent a polycondensation reaction with melamine during the pre-assembly process and finally polymerized into the g-C3N4 structure during subsequent calcination. Meanwhile, the remaining cyanuric acid molecules assembled with melamine via hydrogen-bond interactions and underwent incomplete decomposition during subsequent calcination, which not only promoted the production of 3D nanoflower-like aerogel structures, but also introduced the carbonyl (CO) and hydroxyl (–OH) groups onto the g-C3N4 surface, resulting in the successful generation of a 3D nanoflower-like oxygen-modified g-C3N4 aerogel. Moreover, the fabricated g-C3N4 aerogel exhibited a greatly enhanced H2 production rate (1573 μmol h−1 g−1), which is ∼ 6.6 times higher than that of bulk g-C3N4 (239 μmol h−1 g−1) owing to the synergistic promotion function of ultrathin nanoflower-like aerogel and oxygen modification structures. This strategy provides a theoretical basis for the development of highly efficient g-C3N4 photocatalysts via molecular assembly.

Facile synthesis of multi-layer Co(OH)2/CeO2-g-C3N4 ternary synergistic heterostructure for efficient photocatalytic oxidation of NO under visible light

In this work, we report a one-step synthesis of ternary Z-scheme Co(OH)2/CeO2-g-C3N4 (CoCe-CN) heterostructure via hydrothermal method. Owing to the modification of Co(OH)2 and CeO2, the existence of Co(OH)2 as an electron acceptor-donor center between CeO2 and g-C3N4 accelerates the electron transfer and provides extra OH- reaction pathway for photocatalytic oxidation of NO. As a result, 50CoCe-CN (Co and Ce accounting for 25% mass ratio separately) achieved a 53.5% conversion efficiency of NO at 600 ppb concentration, which is 1.82 times that of g-C3N4 under visible light. The results of the DFT analysis and element distribution of cobalt and ceria provide convincing evidence supporting the existence of a novel multi-layer structure in the CoCe-CN photocatalyst. This structure involves the loading of CeO2 and Co(OH)2 on the g-C3N4 surface, and Co(OH)2 as a co-catalyst introduced between CeO2 and g-C3N4 realizes the synergy between CeO2 and Co(OH)2 which further improve the photocatalytic properties. The higher photocatalytic efficiencies observed in the CoCe-CN photocatalysts compared to those containing only cobalt (Co-CN) or ceria (Ce-CN) provide further evidence of the synergistic effect of these two elements. This work demonstrates a more efficient and effective ternary photocatalytic system, with greater practical potential for photocatalytic oxidation of NO.

Well-structured V2C MXenes coupled g-C3N4 2D/2D nanohybrids for proficient charge separation with the role of triethanolamine (TEOA) as a protective barrier of g-C3N4 for stimulating photocatalytic H2 production

Vanadium-carbide (V2C) MXenes have received scientific attention for their thinner structure, multiple oxidation states, and excellent conductivity, which can effectively serve as electron-sinking sites to suppress the backward recombination of electrons and holes. Herein, well-structured V2C/g-C3N4 nanohybrids were designed to promote photocatalytic hydrogen production. Stronger interfacial contact between 2D/2D V2C/g-C3N4 proffers 4.23-fold more H2 yield than pristine g-C3N4 with a maximal rate of 360 μmol g−1 h−1. The loading of V2C improves the light absorption capability and facilitates the charge transfer for photo-redox reaction. However, h+ accumulation fosters the degradation kinetics over consecutive cycles, which drives the homolytic cleavage of the g-C3N4 by hydroxyl radical (• OH). The tremendous decline in the photostability test over methanol-containing sacrificial reagents is consistent with the reduction of g-C3N4 functional units, corroborating the structural breaking. Employing TEOA as a hole scavenger slows the homolytic decomposition of g-C3N4, which could act as a binding ligand in protecting the g-C3N4 surface. Stronger intermolecular forces between the heterogeneous molecules with excellent scavenging activity effectively trap accumulated h+ and slow down the degradation kinetics. The findings of this work not only contribute to the scientific understanding of vanadium-based MXenes in photocatalytic hydrogen production but also lay the foundation for understanding the mechanistic structure of g-C3N4.

A differential strategy to enhance the anti-interference ability of molecularly imprinted electrochemiluminescence sensor with a semi-logarithmic calibration curve

The non-specific adsorption behaviors of various interferents on the surface of a molecularly imprinted polymer (MIP) are adverse for the selectivity of an MIP-based sensor, which can be overcome via a differential strategy by using the differential signal between MIP- and non-imprinted polymer (NIP)-based sensors. However, the normal differential mode is not suitable for the MIP-based sensors with non-linear calibration curves. Herein, an improved differential strategy is reported for an MIP-based sensor with a semi-logarithmic calibration curve, demonstrated by an electrochemiluminescence (ECL) sensor for dopamine (DA). Glassy carbon electrode (GCE) was modified by the mixture of g-C3N4, TiO2 nanoparticles (NPs) and carbon nanotubes (CNTs). MIP membrane for DA was fabricated on the surface of g-C3N4/TiO2NPs/CNTs/GCE using chitosan for film-forming, obtained MIP@GCE. To enhance the anti-interference ability of the MIP-based DA sensor, the difference between exponential functions ECL intensities of MIP@GCE and NIP@GCE is used as the analytical signal in the improved differential strategy. The differential signal was increased linearly with increasing DA concentration ranging from 10 pM to 0.10 μM, with the detection limit of 5.6 pM. The interference level of Cu2+ on DA determination in the improved differential mode is only 9.7% of that in the normal MIP mode. The improved differential strategy can be used in other MIP-based sensors with semi-logarithmic calibration curves.

Fabrication of g-C3N4@porphyrin nanorods hybrid material via CTAB surfactant-assisted self-assembly for photocatalytic degradation of Cr(VI) and methylene blue

Photocatalysts are an attractive solution for pollutant degradation under sunlight irradiation. One approach that has been proposed to enhance their activity is to combine two semiconductors, which can broaden the photon energy harvesting regions and improve charge separation. Herein, a facile approach to fabricating a g-C3N4@porphyrin nanorods hybrid material is presented using CTAB surfactant-assisted self-assembly of monomeric porphyrin molecules and g-C3N4 nanomaterials. Using different technical methods, the hybrid material was studied, and it was found that the porphyrin nanorods on the surface of g-C3N4 were all in the same place. The photocatalytic performance of the hybrid material was evaluated by investigating its behavior for the photo-oxidation and -degradation of Cr+6 ions and methylene blue organic dye under simulated sunlight irradiation. High photocatalytic performance towards these two pollutants was exhibited by the hybrid material with a removal percentage of nearly 100% after 100 min of reaction time under the simulated sunlight spectrum. Also, a possible photocatalytic mechanism of the C3N4@porphyrin nanorods photocatalyst was proposed. This mechanism involved the efficient separation and transfer of photo-induced electrons and holes on the surface of the hybrid material. This work offers a simple and efficient method for creating high-performance photocatalysts, and we have made progress in our understanding of their photocatalytic mechanisms. The findings have important implications for wastewater treatment and solar energy conversion. The use of this hybrid material may contribute to addressing environmental challenges and assist in building sustainable energy systems.

Anticorrosive coatings made from polydopamine modified graphitic C3N4 composites with synergistic anticorrosion effects

Since uniform dispersion and robust interfacial compatibility of nanofiller with epoxy resin are the most critical parameters to improve the corrosion protection property, a new effective anticorrosion nanofiller [polydopamine (PDA)@g-C3N4-CeO2] is designed by stacking PDA modified g-C3N4 and nano-CeO2 with the help of a silane coupling agent. The structure and morphology of PDA@g-C3N4-CeO2 are characterized by FTIR, XRD, XPS, SEM, and TEM. Furthermore, the PDA@g-C3N4-CeO2 nanofiller is loaded within waterborne epoxy coating (WEC) and the corrosion resistance of the prepared nanocomposite coating is studied. It can be inferred from the dispersion test that g-C3N4 modified by PDA and nano-CeO2 exhibits excellent dispersion and compatibility in de-ionized water. The Electrochemical impedance spectroscope (EIS) results indicate that nanocomposite coating with PDA@g-C3N4-CeO2 exhibits the best corrosion resistance, and its low-frequency impedance (Zf=0.01Hz) is 1.78 × 109 Ω cm2, which is two orders of magnitude higher than that of pure WEC (4.27 × 107 Ω cm2). In the salt spray test, PDA@g-C3N4-CeO2/WEC also showed excellent long-term corrosion resistance with few corrosion products even after 600 h, which was consistent with the results of the EIS test. In addition, PDA@g-C3N4-CeO2/WEC also reflects the most fantastic adhesion strength (14.22 MPa), which is improved by 45.40% than that of pure WEC (9.78 MPa). Generally, the excellent protection properties of PDA@g-C3N4-CeO2/WEC are attributed to the presence of PDA and KH-550 modified nano-CeO2 on the surface of g-C3N4, which increase the compatibility and surface interactions between nanofillers and epoxy resin.

Insight into the role of Ni atoms at the interface of g-C3N4/CdS in photocatalytic H2 evolution

Highly efficient interface charge carrier transfer and separation is a primary factor in guaranteeing the performance of hetero photocatalysts. Here, we construct a high-performance g-C3N4/CdS heterostructure by insetting highly dispersed Ni atoms between g-C3N4 nanosheets and CdS nanoparticles, and the obtained CNN/Ni500/CdS-2.4 displays the highest H2 evolution rate of 9.5 mmol/g/h without the addition of extra co-catalyst, which is about 4.3 times to that of CNN/CdS heterostructure without Ni atom addition. It is found that the significantly enhanced H2 evolution ability can be ascribed to the dual function of Ni atoms in linking hetero interfaces and facilitating charge transport. The introduced Ni atoms disperse uniformly on the surface of g-C3N4 and thus contributing to the large area uniform and intimately deposition of CdS nanoparticles, which provides sufficient surface-active sites for the photocatalytic reaction. At the same time, due to the good the conductivity, the introduction of Ni atoms dramatically facilitates the rapid transfer of charge carriers between g-C3N4 and CdS and thus accelerating the generation of hydrogen. This work demonstrates the great potential of trace amount of highly dispersed metals on improving the quality of heterojunctions and promoting the photocatalytic ability of heterostructures.

Study on CuO/g–C3N4 S–Scheme heterojunction for enhanced visible-light-driven photocatalytic degradation of xanthate

Xanthate wastewater is a serious threat to the surrounding environment of mining sites, and it is important to use visible light photocatalytic technology to remove xanthatefrom wastewater. In this paper, a simple hydrothermal calcination synthesis route was used to grow submicron-sized CuO onto the surface of g-C3N4 for the degradation of xanthate in mineral processing wastewater. The results showed that the CuO/g–C3N4–0.4 composite catalyst degraded xanthate with an efficiency of 83.2% in 120 min, which was 6.2 times higher than that of pure g-C3N4. The catalyst materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It was found that the excellent photocatalytic performance of the composite was attributed to the construction of S-scheme CuO/g–C3N4–Xheterojunction, which not only broadened the light absorption range but also retained the strong redox ability of holes and electrons to participate in the reaction while efficiently separating the photoinduced carriers. Based on the results of active substance capture, an S-scheme charge transfer model was proposed and the photodegradation mechanism of xanthate was reasonably elucidated.

Fast g-C3N4 sonocoated activated carbon for enhanced solar photocatalytic oxidation of organic pollutants through Adsorb & Shuttle process

To solve low mass transfer in photocatalytic technology for water treatment, the combination of photoactive nanoparticles with highly adsorptive materials has been regarded as a successful approach. The optimization of photoactive particle coating in terms of dispersion on the surface of adsorbing support is the main key to reach a maximum synergism for pollutants removal. This study discusses the coating of as-prepared biomass based activated carbon by g-C3N4 using three routes, namely ball milling (AC-CN@BM), physical stirring (AC-CN@Phy) and ultrasonic assisted coating (AC-CN@US). The coating mechanisms by different processes were discussed using different characterization techniques. Ball milling based coating provides good g-C3N4 dispersion on the surface of AC, however, a partial degradation of g-C3N4 structure and a lower surface area were confirmed by FTIR, XRD and BET analysis. Physically designed sample shows a significant agglomeration of particles on the surface of AC. However, ultrasonic coating provides excellent distribution of g-C3N4 and high surface of the composite. In terms of photoactivity, AC-CN@BM exhibits the lowest adsorption and photocatalytic activity under solar light for the removal of ciprofloxacin. AC-CN@Phy showed medium performance, but less physical stability of g-C3N4 particles on AC, leading to their partial release. AC-CN@US showed the highest efficiency and stability after using; suggesting the good combination between g-C3N4 and AC, which in turn maximizes the removal of ciprofloxacin via Adsorb & shuttle process. The overall costs of composite, including the starting elements and the coating ultrasonic process are relatively low and green as compared to commonly reported routes.

A greener approach to synthesize magnetically separable and photocatalytic recyclable g-C3N4-Fe3O4 nanomaterial for removing toxic organic dyes from water

A greener and eco-friendly approach was developed to prepare magnetic g-C3N4-Fe3O4 nanocomposite adsorbent. Here, first g-C3N4 was prepared from melamine by using simple thermal treatment method. Then magnetic Fe3O4 nanoparticles were introduced on 2D surface of g-C3N4 using guava leaf extract. The formation, functionality, morphologies, surface area, magnetic power and bonding of the prepared material were analysed by XRD, FTIR, FESEM, TEM, BET, VSM and XPS analytical techniques. The formation of Fe3O4 phase on g-C3N4 surface was confirmed by XRD analysis. TEM images confirmed the formation of fine NPs on 2D g-C3N4 sheet. The surface area was found to be 92.32 m2/g with BJH average pore size distribution of 4 nm.The saturation magnetization value of g-C3N4-Fe3O4 was 15.12 emu/g. This shows superior magnetic property of the prepared material and thus can easily be separated from the treated water using external magnet. The prepared material was used for the removal of commonly used toxic Congo red (CR) and Methylene blue (MB) dyes from water using batch adsorption method. The adsorption of CR and MB on the surface of adsorbent was pH dependent. The maximum adsorption capacity of CR was found to be 194 mg/g at pH=6 and MB was found to be 149 mg/g at pH=8. The CR and MB adsorption process follows Pseudo- second-order kinetic and Langmuir isotherm models. The adsorbed CR and MB were recovered from the surface of adsorbent using chemical free photocatalytic irradiation process under visible light. The regenerated adsorbent was also reused for the further adsorption study and showed significant adsorption efficiency. This novel material can be considered as a promising adsorbent for CR and MB dyes with high adsorption efficiency, high stability, eco-friendly synthesis and easy to separate from the treated water with good reusability power.

Theoretical verification on adsorptive removal of caffeine by carbon and nitrogen-based surfaces: Role of charge transfer, π electron occupancy, and temperature

Eliminating an emerging water pollutant, caffeine molecules, from an aqueous solution using carbon and nitrogen-based adsorbents is of significant interest to public health. These adsorbents have been shown to have decent adsorption capacity toward caffeine due to their surface functionality. Therefore, screening various carbon and nitrogen-based surfaces can be a better option for high-performance adsorbents to remove caffeine efficiently from wastewater. Herein, we present combined first principles and molecular dynamics quantification of the adsorption enthalpies of caffeine molecules on the possible active sites of carbon and nitrogen-based adsorbents (graphene, phagraphene, graphdiyne, single-wall carbon nanotube, fullerene, and graphitic carbon nitride) with the incorporation of Van der Waals interactions. From the DFT calculations, N-doped carbon surfaces show the highest adsorption energies of single and dimer CAF compared to pristine carbon-based adsorbents. A charge density difference and Bader charge analysis display that high charge transfer occurs between the caffeine's oxygen and the surface's nitrogen atoms. An abundance of π-electrons from the nitrogen atoms, composed of large electron clouds of aromatic rings on the graphitic carbon surface, tends to favor extensive π-π interactions with the caffeine molecule. The high value of pz electron occupancy (1.445) of N in the hexagonal ring of the graphitic surface transfers additional charge transfer, which leads to strong adsorption energy of CAF than pristine surfaces. Also, the g-C3N4 surface adsorbs the CAF molecule with higher adsorption than other N-doped carbon surfaces due to the high pz_eo (1.5448) of N atoms on the surface. At 310 K, the water molecules' kinetics aids the single and dimer caffeine molecules to adsorb with the highest adsorption energies on the active sites of g-C3N4 surfaces than graphene adsorbent.

Synergistic role of Cu-C and Cu-N dual bonding of nanostructured g-C3N4/Cu2SnS3 photocatalysts for efficient CO2 conversion to CO

Herein, a 2D/0D g-C3N4/Cu2SnS3 heterostructure is successfully constructed via the facile calcination method, and its application to photocatalytic CO2 conversion is demonstrated for the first time. The fabricated g-C3N4/Cu2SnS3 nanocomposite is featured with its unique Cu-C and Cu-N dual chemical bond at the interface. The engineered g-C3N4/Cu2SnS3 nanocomposites record a superior CO production rate of 18.2 μmol∙g−1∙h−1 with an apparent quantum yield of 2.2% at 500 nm of light illumination, which is the highest among g-C3N4/ternary metal sulfide photocatalysts to the best of our knowledge. This notable improvement is attributed to the effective incorporation of Cu2SnS3 nanoparicles onto the surfaces of ultra-thin g-C3N4 and, the formation of Cu-N and Cu-C dual bonds at the interface. This helps not only the activation of interface defect-mediated Z-scheme conduction but also supplies highly reactive Cu sites in the Cu2SnS3 nanoparticles for efficient photocatalytic CO2 conversion.

Rational construction of α-Fe2O3/g-C3N4 heterojunction for effective photo-Fenton-like degradation of tetracycline

A novel α-Fe2O3/g-C3N4 composite was successfully designed by loading α-Fe2O3 hexagonal flakes on the spherical surface of g-C3N4 to enhance visible light absorption and manipulate the directed transfer of electrons and holes. The results of UV–vis DRS, XPS valence band, and Mott-Schottky calculations indicated that the g-C3N4 microspheres obtained after morphology modulation have improved absorption of visible light and the band gap structure has been changed. The catalyst achieved 90.7% removal of tetracycline in 120 min under visible light irradiation and hydrogen peroxide, which was 58.2 and 37.6% higher relative to the photocatalytic and Fenton-like systems alone, respectively. It was shown that the significantly enhanced catalytic activity was attributed to the synergistic effect of α-Fe2O3 and g-C3N4. In addition, the possible degradation pathways of tetracycline were investigated by HPLC-MS to identify intermediates. This work provided insight into the construction of Z-scheme heterojunction photo-Fenton catalysts for environmental remediation.

Solvent-freely polymerizing catechol and paraformaldehyde to nitrogen-rich carbon for high-volumetric-performance supercapacitor

Fabrication of nitrogen functionalized carbon with high nitrogen content (over 10 atom%) by a route with simplified and solvent-free procedures would be both economically and environmentally scalable. We demonstrate here a simple solvent-free route towards synthesizing porous carbon doped by nitrogen functionalties (21.7 atom%) involving solid state catalytic polymerization of catechol and paraformaldehyde with g-C3N4 as catalyst. Upon high-temperature treatment, the vaporized catechol and paraformaldehyde would be in situ polymerized on the surface of g-C3N4 forming the composite of g-C3N4@resin. During the following carbonization process, the resin was carbonized to carbon skeleton, while the g-C3N4 would be decomposed in situ doping the carbon skeleton. In our design, the avoidance of solvents in the whole synthesis procedure and the usage of g-C3N4 in the preparation not only reduces the waste production, but also introduces high nitrogen species (21.7 atom%). As electrode for supercapacitor, the resultant SFC based electrode achieves a large specific capacitance of 391F cm−3@1.0 A/g and high energy density of 34.5 Wh/L@1370 W/L, suggesting a potential as electrode for energy storage. And more, the developed method offers a promising and alternative route for the fabrication of new materials in manner of green and environmentally friendly.

Design and synthesis of Bi-doped NiAl-LDH/g-C3N4 heterostructure; a novel 2D/2D system for simultaneous enhanced photocatalytic degradation and fluorescence sensing of ciprofloxacin

2D systems enable new opportunities for the development of photocatalysts. Layered double hydroxides (LDHs) indicate a wide range of applications due to their tunable functional properties. Regarding the intrinsic catalytic performance and excellent electronic structure of LDHs, and physicochemical stability of g-C3N4, we innovatively propose and investigate a novel Bi-doped NiAl-LDH/g-C3N4 2D/2D heterostructure system toward visible-light-driven photocatalytic degradation and fluorescence sensing of ciprofloxacin (Cipro). Based on the electrostatic self-assembly method, LDH nanosheets were grown on the g-C3N4 surface. SEM and TEM images confirmed that the LDH nanosheets were successfully loaded on the carbon nitride’s smooth surface. The most efficient composite (40%-g-C3N4/LDH) displayed 86% Cipro removal efficiency over 180 min under visible light irradiation. The main reason for the aforementioned improvement in catalytic activity was due to the intimate face-to-face contact in heterojunction between two semiconductors and increased flow of charge-carrier to the surface. As an auxiliary agent, bismuth-containing LDH can trap electrons and thus reduce carrier pairs recombination. Additionally, the prepared composite displayed excellent fluorescence sensitivity toward Cipro with a low detection limit of 3.7 nM. Our approach will provide a new perspective on designing 2D/2D heterojunctions between LDH and other two-dimensional semiconductors toward simultaneous photodegradation and detection of antibiotics.

Facile Preparation of Humins-loaded Graphitic Carbon Nitride with Improved Catalytic Activity on the Thermal Decomposition of Ammonium Perchlorate

Novel g-C3N4/humins (denoted as CNH) composite was synthesized through a simple two-step method. The results indicated that humins nanoparticles with sizes ≤ 200 nm were successfully loaded on the surface of g-C3N4 (CN). The catalytic effect of the as-prepared composite on the thermal decomposition of ammonium perchlorate (AP) was investigated by means of thermogravimetric and differential thermal analyses (TG-DTA). Compared with pure CN, CNH was proved to catalyze the thermal decomposition of AP more effectively. Specifically, the high temperature decomposition step of AP was decreased by 80.9 ◦C, with an increase of the total heat release to 1320 Jg−1. Besides, thepossible catalytic mechanism of AP decomposition was discussed.

Fabrication ternary dual electron transfer Ag2MoO4/SrWO4/g-C3N4 heterojunction photocatalyst for the highly efficient visible-light-driven degradation of tetracycline

The construction of new electron transfer channels is essential to improve the photocatalyst activity. Herein, a novel Ag2MoO4/SrWO4/g-C3N4 photocatalyst with dual electron transfer channels was constructed by one-step precipitation method. The obtained photocatalysts were characterized using XRD, SEM, FT-IR, TEM, Uv-vis and PL. Under visible light, the photocatalyst was evaluated for its ability to degrade tetracycline (TC). The characterization results presented that the olive sphere-like SrWO4 and the nanosphere-like Ag2MoO4 were uniformly dispersed on the surface and pores of g-C3N4, forming a heterostructure and thereby heterojunctions, which promoted the internal electron transfer. The degradation experiments showed that the Ag2MoO4/SrWO4/g-C3N4 improved degradation efficiency of TC under visible light relative to monomeric and binary materials. In addition, the 20AMO/8SW/CN maintained 92.19 % degradation of TC after four cycles of experiments, showing excellent reusability. During the photocatalytic process, ·O2-, h+, and ·OH promoted the degradation of TC. Combining with the energy band structure analysis, it was found that a novel dual electron transfer channel had been constructed among Ag2MoO4, SrWO4 and g-C3N4, which markedly enhanced photocatalytic efficiency. The work provides a potential approach for developing efficient and stable photocatalysts.

Facile synthesis of ultrathin g-C3N4 nanosheets modified with N-doped carbon dots: Enhanced photocatalytic hydrogen production activity and mechanism insight

In this study, nitrogen-doped carbon dots (NCDs) modified ultrathin carbon nitride (g-C3N4) nanosheets were synthesized by a simple secondary calcination method, which realizes efficient photocatalytic hydrogen production. The secondary calcination process can not only thermally exfoliate g-C3N4 into ultrathin nanosheets, but also uniformly anchor NCDs (∼3 nm) on the surface of g-C3N4. The photocatalytic results manifested that a very small amount of NCDs (0.5 wt%) loading on g-C3N4 could achieve a high photocatalytic hydrogen production rate (5.21 mmol g−1 h−1). The reasons for the enhanced photocatalytic activity were analyzed. The ultrathin g-C3N4 nanosheets facilitated the migration of photogenerated carriers. Moreover, NCDs/g-C3N4 exhibited enhanced visible light absorption owing to the up-conversion fluorescence effect of NCDs and the narrow band gap caused by the decoration of NCDs. Furthermore, NCDs as electron acceptors can promote carrier separation. This combination strategy provides a basis for the synthesis of inexpensive, metal-free, and efficient carbon-based photocatalysts.

Enhanced electron channel via the interfacial heterotropic electric field in dual S-scheme g-C3N4/WO3/ZnS photocatalyst for year-round antibiotic degradation under sunlight

Widespread and persistent presence of antibiotic contaminants in natural aquatic environments has aroused all mankind concern due to their potential threat to human health. Photocatalysis represents a promising means to remediate polluted waters with the simple assistance of solar energy. In this context, the feasibility of treating antibiotic contaminated water with g-C3N4/WO3/ZnS dual S-scheme heterojunction driven by interfacial heterotropic electric field was investigated under year-round climate conditions. The optimum composite (5-CWZ) could degrade >85% of tetracycline within 1 h of summer sunlight and 1.5 h of winter sunlight irradiation. The results of electron spin resonance (ESR), chemical trapping experiment, High performance liquid chromatography mass spectrometry (HPLC-MS), ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) calculation reflected that in-situ anchoring of WO3 and ZnS on the surface of g-C3N4 facilitates the formation of interfacial heterotropic electric field which were effective towards low-resistance charge carrier channelization, resulting sufficient •O2–, h+, •OH species evolving for attacking the active atoms of contaminants with high Fukui index. Furthermore, the retention of superior photocatalytic properties in complex actual water matrices together with the non-toxicity of both 5-CWZ photocatalyst and treated TC solution proved by Pisum sativum bud radicle elongation and bacterial (E. coli and B. subtilis) cultivation further demonstrated the feasibility of the 5-CWZ to treat antibiotics in real water under irradiation of solar light.