Fabrication of microfibrillated cellulose from biomass by use of carbon nitride with high nitrogen/carbon ratio.

Microfibrillated cellulose (MFC) as an attractive green bio-based material has attracted widespread attention in recent years due to its non-toxicity, degradability, excellent performance, and high aspect ratio. In this study, the g-C3N5 with a high nitrogen/carbon ratio was prepared as a catalyst through the self-polymerization of a nitrogen-rich precursor. The triazole groups at the edges of g-C3N5 were proven to exhibit strong adsorption to biomass and strong alkalinity. In a low-acidic aqueous system with g-C3N5, MFC with diameters of 100-200 nm and lengths up to 100 µm was fabricated from various biomasses within 5 min under microwave radiation. The ultimate yield of the MFC produced from viscose reached 90 %. Young's modulus of the MFC reaches 3.7 GPa. This work provides a particular method with high efficiency to prepare MFC with excellent properties from biomass by chemical method.

Mediating peroxymonosulfate activation path in Fenton-like reaction via doping different metal atoms into g-C3N5.

Peroxymonosulfate (PMS) could be activated by either radical path or non-radical path, how to rationally mediate these two routines was an important unresolved issue. This work has introduced a simple way to address this problem via metal atom doping. It was found that Fe-doped nitrogen-rich graphitic carbon nitride (Fe-C3N5) exhibited high activity towards PMS activation for tetracycline degradation, and the degradation rate was 3.14 times higher than that of Co-doped nitrogen-rich graphitic carbon nitride (Co-C3N5). Radical trapping experiment revealed the contributions of reactive species over two catalysts were different. Electron paramagnetic resonance analysis further uncovered the non-radical activation path played a dominated role on Fe-C3N5 surface, while the radical activation path was the main routine on Co-C3N5 surface. Density functional theory calculations, X-ray photoelectron spectroscopy analysis, and electrochemical experiments provided convincing evidence to support these views. This study supplied a novel method to mediate PMS activation path via changing the doped metal atom in g-C3N5 skeleton, and it allowed us to better optimize the PMS activation efficiency.

Efficient photocatalytic hydrogen peroxide production over S-scheme In2S3/molten salt modified C3N5 heterojunction.

Graphitic phase carbon nitride (g-C3N5), as a novel n-type metal-free material, is employed as a visible light-receptive catalyst because of its narrow band gap and abundant nitrogen. To overcome the low carrier mobility efficiency of g-C3N5, its modification by K ions was adopted. In addition, In2S3 was selected to couple with modified g-C3N5 to overcome the recombination of photogenerated e-/h+. As a novel photocatalytic material, it was proven to possess a high visible light absorption capacity and a strong H2O2 production ability (up to 3.89 mmol⋅L-1 in 2 h). Moreover, a S-scheme heterojunction structure was successfully constructed between the two materials, which was tested and confirmed to be successful in raising the photogenerated e-/h+ separation efficiency. Ultimately, the primary processes of photocatalytic H2O2 production were summarized by superoxide radical and rotating disc electron measurements. This research provides a fresh perspective for the synthesis of C3N5-based S-scheme heterojunction photocatalysts for producing H2O2.

Simultaneous Efficient Photocatalytic Hydrogen Evolution and Degradation of Dye Wastewater without Cocatalysts and Sacrificial Agents Based on g-C3N5 and Hybridized Ni-MOF Derivative-CdS-DETA.

Inspired by energy conversion and waste reuse, hybridized Ni-MOF derivative-CdS-DETA/g-C3N5, a type-II heterojunction photocatalyst, is synthesized by a hydrothermal method for simultaneous and highly efficient photocatalytic degradation and hydrogen evolution in dye wastewater. Without the addition of cocatalysts and sacrificial agents, the optimal MOF-CD(2)/CN5 (i.e. Ni-MOF derivative-CdS-DETA (20 wt.%)/g-C3N5) exhibit good bifunctional catalytic activity, with a H2 evolution rate of 2974.4 µmol g-1 h-1 during the degradation of rhodamine B (RhB), and a removal rate of 99.97% for RhB. In the process of H2-evolution-only, triethanolamine is used as a sacrificial agent, exhibiting a high H2 evolution rate (19663.1 µmol g-1 h-1) in the absence of a cocatalyst, and outperforming most similar related materials (such as MOF/g-C3N5, MOF-CdS, CdS/g-C3N5). With the help of type-II heterojunction, holes are scavenged for the oxidative degradation of RhB, and electrons are used in the decomposition of water for H2 evolution during illumination. This work opens a new path for photocatalysts with dual functions of simultaneous efficient degradation and hydrogen evolution.

All-solid-state Z-scheme ZnFe-LDH/rGO/g-C3N5 heterojunction for enhanced sonophotocatalytic degradation of ciprofloxacin: Performance and mechanistic insights.

The fabrication of all-solid-state Z-scheme sonophotocatalysts is vital for improving the transfer rate of photogenerated electrons to remove antibiotics present in wastewater. Herein, a novel indirect Z-scheme ZnFe-layered double hydroxide (LDH)/reduced graphene oxide (rGO)/graphitic carbon nitride (g-C3N5) heterojunction was synthesized using a simple strategy. The ZnFe-LDH/rGO/g-C3N5 (ZF@rGCN) ternary composites were systematically characterized using different techniques. Results revealed that the 15%ZF@rGCN catalyst achieved a ciprofloxacin (CIP) degradation efficiency of 95% via the synergistic effect of sonocatalysis and photocatalysis. The improved sonophotocatalytic performance of the ZF@rGCN heterojunction was attributed to an increase in the number of active sites, a Z-scheme charge-transfer channel in ZF@rGCN, and an extended visible light response range. The introduction of rGO further enhanced the charge-transfer rate and preserved the reductive and oxidative sites of the ZF@rGCN system, thereby affording additional reactive species to participate in CIP removal. In addition, owing to its unique properties, rGO possibly increased the absorption of incident light and served as an electronic bridge in the as-formed ZF@rGCN catalyst. Finally, the possible CIP degradation pathways and the sonophotocatalytic Z-scheme charge-migration route of ZF@rGCN were proposed. This study presents a new approach for fabricating highly efficient Z-scheme sonophotocatalysts for environmental remediation.

First-principles study of Li-doped planar g-C3N5 as reversible H2 storage material.

Under the background of energy crisis, hydrogen owns the advantage of high combustion and shows considerable environment friendliness; however, to fully utilize this novel resource, the major hurdle lies in its delivery and storage. The development of the in-depth yet systematical methodology for two-dimensional (2D) storage media evaluation still remains to be challenging for computational scientists. In this study, we tried our proposed evaluation protocol on a 2D material, g-C3N5, and its hydrogen storage performance was characterized; and with addition of Li atoms, the changes of its electronical and structural properties were detected. First-principles simulations were conducted to verify its thermodynamics stability; and, its hydrogen adsorption capacity was investigated qualitatively. We found that the charges of the added Li atoms were transferred to the adjacent nitrogen atoms from g-C3N5, with the formation of chemical interactions. Thus, the isolated metallic sites tend to show considerable electropositivity, and can easily polarize the adsorbed hydrogen molecules, and the electrostatic interactions can be enhanced correspondingly. The maximum storage capacity of each primitive cell can be as high as 20 hydrogen molecules with a gravimetric capacity of 8.65 wt%, which surpasses the 5.5 wt% target set by the U.S. Department of Energy. The average adsorption energy is ranged from -0.22 to -0.13 eV. We conclude that the complex 2D material, Li-decorated g-C3N5 (Li@C3N5), can serve as a promising media for hydrogen storage. This methodology provided in this study is fundamental yet instructive for future 2D hydrogen storage materials development.

Photocatalytic degradation of chlorpyrifos using Ag nanoparticles-doped g-C3N5 decorated with dendritic CdS.

In this work, g-C3N5/CdS dendrite/AgNPs nanocomposite was synthesized using a mixed method consisting of hydrothermal, ultrasonic and chemistry reduction with sodium borohydride. The characterization of the as-prepared nanocomposite was done using infrared spectroscopy, X-ray, scanning electron microscopy, transmission electron microscopy, BET, and DRS methods was performed. The DRS results showed that the g-C3N5/CdS dendrite/AgNPs nanocomposite nanocomposite has a band gap of 1.08 eV. This band gap indicates the good capability of this nanocomposite as a photocatalyst. Accordingly, the photocatalytic degradation of chlorpyrifos (CPS) in was performed in an aqueous solution of the synthesized nanocomposite. The results showed that almost 95.3% of this poison, a concentration of 50 mg L-1 was degraded in the presence of 0.05 g L-1 of nanocomposite at pH = 5 in a 60 min. Hydroxide radicals and holes play a significant role in the photocatalytic process. The reusability of the nanocomposite with excellent performance in the degradation of photocatalytic toxins caused by the reduction in the electron-hole recombination and the high surface area of the nanocomposite are among the unique features of this work.

Heterojunction photocatalyst FeS2/g-C3N5 for activating sulfites to degrade tetracycline: A stable degradation system based on heterogeneous processes.

The UV/sulfite system is a promising source of •SO4- and/or •OH, but its application is largely limited by the use of UV light due to its high cost and high energy consumption. Graphite carbon nitride (g-C3N5), as a new photocatalytic material, has better visible light absorption capacity and narrower band gap than g-C3N4, which is expected to activate sulfite under visible light to solve this problem. Herein, a novel FeS2/CN heterojunction material based on g-C3N5 was constructed by hydrothermal in-situ synthesis method and successfully activated sulfite, which was confirmed by tetracycline degradation experiments in water. Under optimized conditions, the degradation rate of TC in 1 h reached 96%. The experimental results revealed that the FeS2/CN heterostructure enhances the absorption of visible light and inhibits the recombination of carriers, enabling more electrons and holes to be utilized. Holes play a major role in the degradation reaction, promote the sulfite chain reaction, and effectively regulate the cycle of Fe2+ and Fe3+ in the solution. Iron ion leaching is negligible and the degradation reaction remains stable at pH 5-9.

Liquid exfoliation of bulk g-C3N5 to nanosheets for improved photocatalytic antibacterial activity.

Liquid exfoliation of bulk g-C3N5 was applied to synthesize g-C3N5 nanosheets. In order to characterize the samples, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectra (XPS), UV-Vis absorption spectra (UV-Vis), and photoluminescence spectra (PL) were examined. g-C3N5 nanosheets exhibited enhanced performance in the inactivation of Escherichia coli (E. coli) with visible light irradiation relative to bulk g-C3N5 and promoted complete inactivation of E. coli within 120 min. h+ and •O2- were the principal reactive species in the antibacterial process. In the early stages, SOD and CAT played a defensive role in resisting oxidative damage of active species. With the prolonged light exposure time, the antioxidant protection system was overwhelmed leading to the destruction of the cell membrane. The leakage of cell contents such as K+, protein, and DNA caused bacterial apoptosis ultimately. The enhanced photocatalytic antibacterial performance of g-C3N5 nanosheets is ascribed to the stronger redox property by the upward shift of CB and downward shift of VB compared with bulk g-C3N5. On the other hand, larger specific surface area and better separation efficiency of photoinduced carriers are helpful to the improved photocatalytic performance. This study systematically revealed the inactivation process toward E. coli and expanded the application range of g-C3N5-based materials with abundant solar energy.

Efficiently photocatalysis activation of peroxydisulfate by Fe-doped g-C3N5 for pharmaceuticals and personal care products degradation.

Peroxydisulfate (PDS) based advanced oxidation processes (AOPs) are widely used for the degradation of pharmaceutical and personal care products (PPCP) in wastewater treatment. In this study, a Fe-doped g-C3N5 (Fe@g-C3N5) was synthesized as a photocatalyst for catalyzing the PDS-based AOPs to degrade tetracycline hydrochloride (TH) at pH 3 and Naproxen (NPX) at pH 7. The photocatalytic performance of Fe@g-C3N5 was 19% and 67% higher than g-C3N5 and g-C3N4 for degradation of TH at pH 3, respectively, while it was 21% and 35% at pH 7. The Fe:N ratio in Fe@g-C3N5, was calculated as 1:3.79, indicating that the doped Fe atom formed a FeN4 structure with an adjacent two-layer graphite structure of g-C3N5, which improved the charge separation capacity of g-C3N5 and act as a new reaction center that can efficiently combine and catalyze the PDS to radicals. Although the intrinsic photo-degradation performance is weak, the photocatalytic performance of Fe@g-C3N5 has great room for the improvement and application in wastewater treatment.

Photoelectrochemical determination of cardiac troponin I based on rod-like g-C3N5@MnO2 heterostructure.

Rod-like graphite carbon nitride@MnO2 (R-g-C3N5@MnO2) heterostructure was prepared by in situ self-anchored growth of MnO2 nanosheet on the surface of R-g-C3N5. The synthesized R-g-C3N5@MnO2 heterostructure as photoactive material exhibited excellent photoelectrochemical (PEC) performance, and the prepared heterostructure-aptamer probe displayed sensitive PEC response to cTnI. Therefore, the PEC method was developed to detect cTnI based on the R-g-C3N5@MnO2 heterostructure. It was found that the linear response to cTnI was in the range 0.001-30 ng/mL under optimized conditions, and the detection limit of the proposed sensor was 0.3 pg/mL. The PEC method displays stable photocurrent response up to 8 cycles and exhibited outstanding selectivity and sensitivity. The PEC method was successfully applied to detect cTnI in serum samples. The recoveries of cTnI detection in serums reach 95.5-104%, and the relative standard deviations range from 3.20 to 4.45%.

Construction of a 2D/2D g-C3N5/NiCr-LDH Heterostructure to Boost the Green Ammonia Production Rate under Visible Light Illumination.

Photocatalytic N2 fixation has emerged as one of the most useful ways to produce NH3, a useful asset for chemical industries and a carbon-free energy source. Recently, significant progress has been made toward designing efficient photocatalysts to achieve this objective. Here, we introduce a highly active type-II heterojunction fabricated via integrating two-dimensional (2D) nanosheets of exfoliated g-C3N5 with nickel-chromium layered double hydroxide (NiCr-LDH). With an optimized loading of NiCr-LDH on exfoliated g-C3N5, excellent performance is realized for green ammonia synthesis under ambient conditions without any noble metal cocatalyst(s). Indeed, the g-C3N5/NiCr-LDH heterostructure with 2 wt % of NiCr-LDH (CN-NCL-2) exhibits an ammonia yield of about 2.523 mmol/g/h, which is about 7.51 and 2.86 times higher than that of solo catalysts, i.e., NiCr-LDH (NC-L) and exfoliated g-C3N5 (CN-5), respectively, where methanol is used as a sacrificial agent. The enhancement of NH3 evolution by the g-C3N5/NiCr-LDH heterostructure can be attributed to the efficient charge transfer, a key factor to the photocatalytic N2 fixation rate enhancement. Additionally, N2 vacancies present in the system help adsorb N2 on the surface, which improves the ammonia production rate further. The best-performing heterostructure also shows long-term stability with the NH3 production rate remaining nearly constant over 20 h, demonstrating the excellent robustness of the photocatalyst.

Regulating directional transfer of electrons on polymeric g-C3N5 for highly efficient photocatalytic H2O2 production.

Graphite carbon nitride (g-C3N5) has been widely used in various photocatalytic reactions due to its higher thermodynamic stability and better electronic properties compared to g-C3N4. However, it is still challenging to endow g-C3N5 with high performance on photocatalytic hydrogen peroxide (H2O2) production. Herein, potassium and iodine are co-doped into g-C3N5 (g-C3N5-K, I) for photocatalytic production of H2O2 with high efficiency. As expected, the photocatalytic H2O2 production rate over the g-C3N5-K, I (2933.4 µM h-1) reaches to 84.22 times as that of g-C3N5. The excellent photocatalytic H2O2 production activity is mainly ascribed to the co-doping of K and I, which significantly improves the capacity of oxygen (O2) adsorption, selectivity of two-electrons oxygen reduction reaction (2e- ORR) and separation efficiency of charge carriers. The density functional theory (DFT) calculations reveal that O2 molecules are more conducive to being adsorbed on g-C3N5-K, I. Besides, the result of excited states further indicates that photo-generated electrons can be directionally driven to the adsorbed O2 molecules, which are effectively activated to form H2O2. The findings will contribute to new insights in designing and synthesizing g-C3N5 based photocatalysts for the H2O2 production.

Facile synthesis of broom stick like FeOCl/g-C3N5 nanocomposite as novel Z-scheme photocatalysts for rapid degradation of pollutants.

A simple and cost-effective route has been utilized for the preparation of a novel lamellar structured FeOCl/g-C3N5 nanocomposite as Z-scheme photocatalyst. The preparation method was performed under the ambient temperature conditions without any hazardous chemicals. Various characterization techniques, namely XRD, FESEM, TEM, FT-IR, UV-Vis, DRS, and PL were carried out to analyse the nanocomposite for confirmation of FeOCl/g-C3N5 nanocomposite. To evaluate its and visible light degradation performances tetracycline (T-C) was used as target pollutant. Among the optimum loading for the g-C3N5 incorporated FeOCl binary nanocomposites, the g-C3N5/FeOCl exhibited a superlative degradation performance toward the T-C antibiotic pollutant. The results confirmed that 95% of T-C was degraded within 40 min under photodegradation mechanism. The improved photodegradation performance in degradation of T-C was mainly due to the reduction in electron-hole recombination, broadening in the light absorption by g-C3N5 incorporation, which leads to shortening the degradation time. Furthermore, the hydroxyl and superoxide radicals played a major role in the photodegradation process and the possible mechanism was elucidated and proposed. The present work implies a novel, sustainable, and efficient Z-scheme system that may deliver a convenient method for environment remediation.

Novel S-scheme 2D/2D Bi4O5Br2 nanoplatelets/g-C3N5 heterojunctions with enhanced photocatalytic activity towards organic pollutants removal.

Removal of organic pollutants and pharma products in waste water using semiconductor photocatalysts has gained huge interest among recent days. However, low visible light absorption, recombination rate of charge carriers and less availability of reaction sites are still major obstacles for the photocatalysis process. Herein, an in situ-forming Bi4O5Br2 nanosheets decorated on the surface g-C3N5 were prepared via simple hydrothermal method under ambient temperature. The basic pH condition plays a vital role in growing for Bi4O5Br2 nanosheets. Various characterization studies such as TEM, SEM, PL and UV-DRS studies confirmed the formation of close contact between the Bi4O5Br2 and g-C3N5 nanosheets. The construction of Bi4O5Br2 nanoplatelets/g-C3N5 nanocomposite increases the surface-active sites and improving the separation efficiencies of excitons, which is greatly influenced in the degradation of ciprofloxacin and bisphenol-A pollutants. Meanwhile, the flow of electrons from the layered structured graphite carbon of g-C3N5 which enables excellent electrical contact in the heterojunction. Besides, the main free radicals were determined as e- and •O2-, and production level of free radicals were confirmed by radical trapping experiments. The possible degradation mechanism was proposed and discussed. Finally, this work provides a unique approach to in-situ preparation of heterojunction photocatalysts and demonstrates the prepared Bi4O5Br2 nanoplatelets/g-C3N5 photocatalysts have great potential in the waste water management.

Influence of Phosphorus Doping on Triazole-Based g-C3N5 Nanosheets for Enhanced Photoelectrochemical and Photocatalytic Performance.

Triazole-based g-C3N5, a potential catalyst, has received little attention over the years. We prepared phosphorus-doped g-C3N5 with one triazole and two triazine units for the first time to investigate its photoelectrochemical (PEC) and photocatalytic properties. The doping states and crystalline structures of the samples were determined using X-ray techniques, namely, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption fine structure analysis. Our results suggested that the phosphorus was substituted into carbon sites form P-N/P═N bonds with four coordination, which contribute P 2p level donor states in the band gap to enhance light absorption and reduce charge separation. Therefore, P-doped g-C3N5 exhibited higher PEC current density and better photocatalytic efficiency toward the degradation of rhodamine B dye or tetracycline under light irradiation compared to the undoped g-C3N5 sample. However, excess phosphorus doping resulted in the formation of impurities and disrupted the triazine and triazole units, reducing the PEC and photocatalytic efficiency. In summary, P-doped g-C3N5 was successfully prepared in the present study and represents a promising, facile, and effective catalyst for energy applications and environmental remediation.

Photoinduced Charge Separation via the Double-Electron Transfer Mechanism in Nitrogen Vacancies g-C3N5/BiOBr for the Photoelectrochemical Nitrogen Reduction.

Due to the harsh reaction conditions, high energy consumption, and numerous carbon emissions of the traditional Haber-Bosch method, the fixation of nitrogen under environmentally friendly and milder conditions is of great importance. Recently, photoelectrochemical (PEC) strategies have attracted extensive attention, where the catalysts with the advantages of cost-effectiveness and improved efficiency are critical for the nitrogen reduction reaction (NRR). Herein, we synthesized nitrogen vacancies that contained g-C3N5 (NV-g-C3N5) and combined with BiOBr to construct the p-n heterostructure NV-g-C3N5/BiOBr, in which the double-electron transfer mechanism was constructed. In one side, the nitrogen vacancies store the electrons coming from the g-C3N5 and provide for the nitrogen activation when needed; in addition, NV-g-C3N5/BiOBr further separates photoinduced electrons and holes because of the matched "Z"-shaped energy band structure. The double-electron transfer mechanism effectively retards the recombination of charge carriers and ensures the support of high-quality electrons, which results in excellent PEC NRR performance without the addition of noble metals. Although yields and durability are insufficient, the described double-electron transfer mechanism manifests the potential of the non-noble metal material in the PEC NRR, providing a foundation for the design of a more affordable and efficient photocathode in nitrogen reduction.