In-situ Synthesis of g-C 3 N 4 with Nitrogen Vacancy and Cyano Group via One-pot Method for Enhanced Photocatalytic Activity

In-situ Synthesis of g-C 3 N 4 with Nitrogen Vacancy and Cyano Group via One-pot Method for Enhanced Photocatalytic Activity | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article In-situ Synthesis of g-C 3 N 4 with Nitrogen Vacancy and Cyano Group via One-pot Method for Enhanced Photocatalytic Activity Xiang BI, Li-Zhong WANG, Dong-Hua ZHAI, Lei WANG, Hui YANG, Gao-Hui DU This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5695645/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 05 Jun, 2025 Read the published version in Scientific Reports → Version 1 posted 12 You are reading this latest preprint version Abstract In-situ synthesis of g-C 3 N 4 containing nitrogen vacancies and cyano group via one-pot method using urea as the precursor. The structural, morphological or electrochemical properties of synthesized photocatalysts were characterized by XRD, BET analysis, TEM, FTIR, UV-DRS, PL, XPS and EPR. It was found that the nitrogen vacancy was successfully introduced into g-C 3 N 4 . Compared to pure g-C 3 N 4 , the (200) crystal plane in XRD of synthesized g-C 3 N 4 showed slight red-shift, and the BET surface areas had changed from 27.5 to 35.7 m 2 · g − 1 , which could provide more reaction center and active site. TEM confirmed that g-C 3 N 4 and V N -g-C 3 N 4 were porous materials, and FTIR, XPS as well as EPR could prove the presence of nitrogen vacancies and cyano group. The UV-Vis absorption edge of V N -g-C 3 N 4 demonstrated briefly red-shift, PL intensity and lifetime of carriers declined in comparison with pure g-C 3 N 4 . Electrochemical test results showed that enhanced charge separation efficiency and low recombination rate of charge carriers of V N -g-C 3 N 4 . The photocatalytic activity of the photocatalysts was researched by RhB degradation and ACT removal under visible light irradiation, the results showed the rate of RhB degradation on the V N -g-C 3 N 4 was 81%, which was 1.4-fold as high as that of g-C 3 N 4 in visible light. The degradation contribution from the active species were h + (67.3%) > 1 O 2 (63.0%)>•OH (49.4%) >•O 2 − (20.3%) > e − (20.1%) > H 2 O 2 (0.2%), and V N -g-C 3 N 4 exhibited excellent ACT removal rate,which was 1.6-fold higher than that of pure g-C 3 N 4 in visible light. This study provides an efficient photocatalyst for the treatment of toxic wastewater. g-C3N4 Nitrogen vacancies Porous material Acetaminophen RhB Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction As a metal-free polymeric semiconductor photocatalyst, graphitic carbon nitride (g-C 3 N 4 ) had been attracted intensive attention [ 1 ] . The g-C 3 N 4 was composed of tris-triazine (C 6 N 7 ) unit. Its abundant source, non-toxic, inexpensive, excellent thermal and chemical stability, easy preparation process and narrow band gap structure (~ 2.7 eV vs NHE) [ 2 ] , which beneficially promoted it as an appropriate visible-light responsive photocatalyst for organic pollutants removal [ 3 ] , photocatalytic hydrogen production [ 4 ] , photocatalytic nitrogen fixation [ 5 ] , CO 2 photoreduction [ 6 ] and photocatalytic NOx removal [ 7 ] . However, it still suffered from unavailability of sunlight beyond 460 nm, small BET surface area and high recombination rate of electron-hole pairs owing to the absence of active sites [ 8 ] . To address these challenges, several modification methods have been employed. Among these, bandgap engineering is a prevalent technique for enhancing the properties of g-C 3 N 4 materials. This approach can improve the light absorption capacity of g-C 3 N 4 , extend the light absorption into longer wavelength regions, and facilitate charge separation and transmission. During the photocatalytic process, photogenerated electrons and holes tend to recombine, which diminishes photocatalytic efficiency. Bandgap engineering can alter the energy band structure to create an appropriate energy level distribution, thereby inhibiting charge recombination and extending charge lifetimes. Furthermore, bandgap engineering can enhance both the photocatalytic reaction rate and selectivity; additionally, the introduction of defects can increase the number of active sites. By adsorbing reactant molecules to lower the activation energy, this method can further promote photocatalytic reactions and enhance photocatalytic activity [ 9 ] . Dong et al. designed and prepared g-C 3 N 4 with stacked coral like magnetic sulfur doped nitrogen vacancies by combining polymerization and precipitation. The 0.1g/L photocatalyst could photocatalytic degradation 5 mg/L of 2,4,6-TCP to 95% within 60 min under visible light. This high removal rate was attributed to nitrogen vacancies, which widened the visible light absorption range and shortened the electron transfer path [ 10 ] . Li et al. successfully synthesized g-C 3 N 4 with nitrogen vacancy network structure for photodegradation of Propylparaben. Compared with bulk g-C 3 N 4 , it shows larger specific surface area, stronger light absorption capacity, higher charge carrier transfer and separation efficiency. According to the characterization results and density functional theory calculations, nitrogen vacancies can capture electrons and promote the adsorption of oxygen. The Propylparaben removal rate of the best sample is 94.3%, which is 3.37 times higher than that of the bulk g-C 3 N 4 [ 11 ] . Preeyanghaa et al. designed g-C 3 N 4 containing carbon vacancies by using simple formalin assisted thermal polymerization method for melting CN precursors, in which the carbon vacancies can be adjusted by changing the dose of formalin. It was applied to photocatalytic degradation of tetracycline solution. Experimental studies and theoretical calculations show that oxygen is adsorbed on the carbon vacancy, and then a large number of reactive oxygen species, including · O 2 − and · OH are produced, which play an important role in the degradation and mineralization of tetracycline [ 12 ] . Chen et al. Designed g-C 3 N 4 photocatalyst co modified by C vacancy and F, and used sodium perfluoronoxybenzene sulfonate as the model pollutant. The research showed that the synthesized material maintained the inherent structure of g-C 3 N 4 , and had higher conduction band potential, narrower band gap and longer electronic life. The removal rate of sodium perfluoronoxybenzene sulfonate was 99.3% in 30 minutes [ 13 ] .Nguetsa Kuate et al. synthesized black g-C 3 N 4 photocatalyst by one-step calcination of urea and phloroglucinol B for the degradation of tetracycline in seawater under visible light irradiation. The experimental results showed that the photocatalytic degradation rate of tetracycline was 92% within 2 hours at room temperature, which was 1.3 times that of pure g-C 3 N 4 . This excellent photocatalytic degradation can be attributed to the reduction of charge transfer distance due to the thickness of ultra-thin nanosheets, the separation of photogenerated carriers promoted by cyano defects and the enhancement of photocatalytic activity due to the photothermal effect of the material [ 14 ] . A large number of studies have shown that the photocatalytic activity of g-C 3 N 4 has been significantly improved through defects and band gap engineering. Inspired by the above, we prepared g-C 3 N 4 material with rich defects via one-pot in-situ synthesis, and thoroughly discussed the mechanism of photocatalytic reaction of g-C 3 N 4 material with rich nitrogen vacancies and cyano group. The precursor was heat-treated under nitrogen atmosphere and then forming nitrogen vacancies and cyano groups, which could validly narrow the bandgap, enhance visible light absorption, and promote the separation of photo-generated electrons/holes. Therefore, the g-C 3 N 4 with rich nitrogen vacancies and cyano groups could greatly improve photocatalytic performance for Acetaminophen and RhB degradation. 2. Experiment 2.1. Synthesis of catalysts Bulk g-C 3 N 4 was synthesized by thermal polymerization of urea under air condition. 6g urea and 1mL deionized water were fully mixed and placed in a covered crucible, heated to 100 ℃ at a heating rate of 0.5 ℃/min and kept at 100 ℃ for 1 hour, then continued heating to 500 ℃ at a heating rate of 5 ℃/min and kept at 500 ℃ for 2 hours at air condition. The synthesis method of g-C 3 N 4 with rich nitrogen vacancies was similar to Bulk g-C 3 N 4 , The only difference was the reaction atmosphere was nitrogen instead of air. The g-C 3 N 4 with rich nitrogen vacancies was labelled as V N -g-C 3 N 4 . 2.2. Characterization The X-ray diffraction (XRD) patterns were tested to determine the phase structures of prepared materials using Rigaku D/max2200PC diffractometer with Cu Kα radiation (λ = 1.542 Å). The Brunauer-Emmett-Teller (BET) method was carried out on ASAP2020, the specific surface area and pore size were analyzed by nitrogen adsorption-desorption test. Fourier transform infrared (FTIR) spectra were performed by a Bruker-VERTEX80v spectrometer. Transmission electron microscopy (TEM, JEOL JEM-ARM300F) measurement was performed to check the microstructure of the samples. UV-vis diffuse reflectance absorption spectrum in the range of 200–800 nm was recorded on Cary 5000, of which BaSO 4 was used as reference. X-ray photoelectron spectra (XPS) and VBXPS were collected on an AXIS SUPRA utilizing the reference of C1s (284.6 eV) with an excitation source of 150 W Al Kα X-rays (1486.6 eV). The photoluminescence (PL) spectra and time-resolved fluorescence decay spectra of catalysts were analyzed by a fluorescence spectrophotometer (Edinburgh Instruments, FS5) equipped with xenon lamp source (150 W) at an excitation wavelength of 340 nm. 2.3. Photocatalytic and electrochemical test of g-C 3 N 4 and V N -g-C 3 N 4 Electrochemical impedance spectroscopy measurements, photocurrent intensity response measurements and Mott–Schottky curve were measured by an electrochemical workstation (CHI600E, China) based on a conventional three electrode cell. 10 mg of catalyst on glassy carbon electrode substrate (1cm×1cm) was used as working electrode. The graphite electrode and Ag/AgCl electrodes were used as counter electrode and reference electrode, respectively. The Na 2 SO 4 aqueous solution was used as the electrolyte (0.2 mol L − 1 , 200 mL). The frequency range was from 10 − 2 Hz to 10 5 Hz, and the amplitude of the applied sine wave potential in each case was 5 mV for the EIS measurements. Incident light was obtained from a 300 W xenon lamp. The photocatalytic activity of catalsyts was tested by degradation of RhB in an aqueous solution under 40W LED white lamp. Firstly, catalsyts samples (30 mg) were mixed with RhB aqueous solution (50 mL, 30 mg/L). After stirring for enough time in dark to achieve adsorption equilibrium, the catalyst was collected and placed again in the RhB solution with same concentration to test the photocatalytic properties. The percentage of degradation was recorded as C/C 0 , where C and C 0 referred to the absorbance of the RhB solution after a certain time interval (30 min) and the initial absorbance corresponding to concentration, respectively. Acetaminophen (ACT) was degraded under 8 W LED lamp. Firstly, the photocatalyst (10 mg) was mixed with ACT aqueous solution (10 mg/L, 50 ml) to achieve adsorption equilibrium, and then the photocatalyst was centrifuged collected and put into the solution under the same conditions to test the photocatalytic performance. 2.4 The detection of free radicals and trapping experiments of active species under visible-light The electron paramagnetic resonance (EPR) experiment was tested on Bruker EMX-plus instrument, which discovered the free radicals in reaction. Samples for EPR measurement were executed by using DMPO (5,5-dimethyl-l-pyrroline N-oxide), DMSO (dimethyl sulfoxide) and 2,2,6,6-tetramethylpiperidine (TEMP) as the spin trapping agent (reagent concentration 0.1mol L − 1 , catalyst concentration 50 mg/L.) under visible light. We used isopropanol (IPA), Catalase (CAT), L-Histidine, P-benzoquinone (PBQ), Triethanolamine (TEOA) and AgNO 3 as quenchers of hydroxyl (•OH), hydrogen peroxide (H 2 O 2 ), singlet oxygen ( 1 O 2 ) super oxygen (•O 2 − ), holes (h + ) and electron (e − ), respectively. Catalysts (30 mg) containing different trapping agents (0.01mol/L) were distributed in 50ml RhB solution (30mg/L) for characterizing photocatalytic performance. 3. Results and discussion The microstructure, composition and morphology of g-C 3 N 4 and V N -g-C 3 N 4 samples were measured by XRD. Figure 1a presented two characteristic XRD peaks of samples, the strong diffraction (002) peak at about 2θ = 27.2° was associated with the interlayer stacking of aromatic systems and the low-angle (100) peak at 2θ = 13.1° was corresponded to repeating motifs of in-plane tri-s-triazine units structure for g-C 3 N 4 (JCPDS NO.87-1526) [15] . V N -g-C 3 N 4 exhibited the same typically characteristic peaks as that of g-C 3 N 4 , which confirmed its basic triazine framework of g-C 3 N 4 without changing the basic structure of during N 2 treatment. Compared with g-C 3 N 4 , the XRD peaks of V N -g-C 3 N 4 was broadened and weakened, suggesting that the in-plane orderly structure clearly decreased and the interlayer stacking became less order. Partially enlarged image (Fig. 1b) was observed as the peak at 27.2° has shifted to 27.7°. According to the Bragg diffraction equation, the slight shift of peak (002) to the positive direction could be decreased in interlayer stacking distance from 0.328 to 0.322 nm, which might be due to the N-atomic variation in the plane. The structural properties of materials were analyzed by the N 2 adsorption-desorption measurement. Figure 1c showed that all the isotherms were type IV with hysteresis loops of type H3 at a relative pressure range of 0.6-1.0, demonstrating the presence of mesoporous. The BET surface area gradually subjoined from 27.5 m 2 g − 1 (g-C 3 N 4 ) to 35.7 m 2 g − 1 (V N -g-C 3 N 4 ). The increase of BET surface area might be owing to the nitrogen-vacancy defects in the structural units. The Barret-Joyner-Halenda analysis of pore size distributions from 2 to 30 nm for g-C 3 N 4 and V N -g-C 3 N 4 in Fig. 1d, showing the introduction of nitrogen vacancies significantly increased specific surface area and provided abundant active reaction sites for photocatalytic reaction . Figure 2 showed the TEM images of the g-C 3 N 4 and V N -g-C 3 N 4 , porous morphology was observed on the g-C 3 N 4 and V N -g-C 3 N 4 surface. The porous structure was beneficial for photogenerated electron and hole transmission, extended carrier life and excellent capture ability. The surface of g-C 3 N 4 sample (Fig. 2a) was fully glossy. However, the surface of V N -g-C 3 N 4 sample (Fig. 2b) showed the state of intertwined nanosheets, demonstrating the presence of nitrogen vacancy on the V N -g-C 3 N 4 surface. The SAED pattern revealed that bright continuous concentric rings owing to diffraction by the (002) planes of V N -g-C 3 N 4 . Therefore, we could inferred nitrogen vacancy were formed in the heat-treatment process at nitrogen atmosphere. FTIR spectra was a very useful tool for analysis of variable chemical structure in material. As shown in Fig. 3, the V N -g-C 3 N 4 sample showed the typical FTIR patterns which was similarly to that of g-C 3 N 4 , suggesting the basic atomic structure of g-C 3 N 4 was still remained after the different atmosphere. The broad peak at 3000–3500 cm − 1 was originated from N-H stretching vibration or O-H adsorbed hydroxyl species and amino group from precursor [16] . The bond strength of V N -g-C 3 N 4 was enhanced, suggesting more content of N-H or O-H in V N -g-C 3 N 4 . The peaks in the region from 850 to 1800 cm − 1 corresponded to skeletal vibration of C-N-C, C-N and C = N in aromatic ring. The sharp absorption peak at 812 cm − 1 owing to the bending mode of the 3-s-triazine unit, illustrating the existence of the basic melon units with NH/NH 2 groups. Compared with g-C 3 N 4 , the peak of V N -g-C 3 N 4 was weaken trend, indicating it had less heptazine rings. The presence of nitrogen vacancy broke the structure of the triazine skeleton and decrease the content of NH/NH 2 groups. A distinct peak at 2175 cm − 1 of V N -g-C 3 N 4 had stronger than that of g-C 3 N 4 , which corresponded to asymmetric stretching vibration of cyano-groups [17] . The terminal C ≡ N triple bond carried positive charge and acted as electron acceptor for accelerating the charge transfer, which was formed during the opening of s-triazine heterocycles and the lattice N loss. The formation of nitrogen vacancy and cyano groups could improve the photocatalytic performance. Figure 4a-b showed the UV–Vis DRS and the calculated bandgap for the g-C 3 N 4 and V N -g-C 3 N 4 . In Fig. 4a, compared with g-C 3 N 4 , the absorption edges of V N -g-C 3 N 4 displayed a slight red-shift. The band gap values in Fig. 4b showed that the band gap of samples narrowed from 2.63 eV (g-C 3 N 4 ) to 2.56 eV (V N -g-C 3 N 4 ). A narrower band gap was achieved, which should be due to the introduction of nitrogen vacancies. To know the separation and transfer efficiency of photoexcited electron-hole pairs, the steady PL results under the excitation wavelength of 340 nm were shown in Fig. 4c. The peak at about 470 nm was stemmed from the direct electron (e − ) and hole (h + ) recombination of band transition. Wherein V N -g-C 3 N 4 with a amount of nitrogen vacancies clearly exhibited much lower intensity than g-C 3 N 4 , indicating that the recombination of carriers of V N -g-C 3 N 4 could be basically inhibited after introduction of nitrogen vacancies and cyano groups, since the nitrogen vacancies and cyano groups could trap photogenerated electrons for promoting the separation of photogenerated electrons and holes [18] . Besides, to comprehend the charge-separation kinetics, the exciton lifetime was calculated by fitting the time-resolved PL decay curves (Fig. 4d) and the average lifetime (τ av ) was depended on the following equation, where B and τ denoted the relative amplitude and decay lifetimes, respectively . The parameters in this equation were given in Table 1. The short lifetime (τ 1 ) was owing to electrons trapped in shallow states and the long lifetime (τ 2 ) corresponded to deep states before the recombination with the holes in the VB. The τ av for V N -g-C 3 N 4 (8.40 ns) was shorter than that of g-C 3 N 4 (10.87 ns), indicating enhanced electron and hole dissociation. The outstanding decrease in PL intensity and lifetime of carriers was attributed to the nitrogen vacancies and cyano groups, which might improve the efficiency of charge carrier transfer and enhance photocatalytic reaction activity. The XPS analysis was performed to further investigate the chemical bond valence information of g-C 3 N 4 and V N -g-C 3 N 4 . The survey spectra was shown in Fig. 5a. For g-C 3 N 4 and V N -g-C 3 N 4 , the total peak of C 1s (Fig. 5b) was consisted of three peaks: C–C/C = C (284.6 eV), C–NH/C–OH (286.2 eV) and N = C–N (288.1 eV). The N 1s peak of g-C 3 N 4 in the high-resolution spectra (Fig. 5c) was composed of three peaks, which corresponded to N–2C (398.6 eV), N–3C (399.8 eV) and N–H (401.1 eV). It was interesting that N–3C peak of V N -g-C 3 N 4 slightly negatively shifted from 399.8 to 399.5 eV, which might be due to the formation of cyano. It was noteworthy that the peak ratio between N–2C and N–3C significantly declined from 2.785 for g-C 3 N 4 to 1.578 for V N -g-C 3 N 4 , indicating the loss of N–2C during thermal polymerization under nitrogen atmosphere. Figure 5d showed the O 1s spectra peak at 532.3 eV was ascribed to the hydroxyl or adsorbed water. The peak intensity at 532.3 eV of V N -g-C 3 N 4 was stronger than that of g-C 3 N 4 , showing that the V N -g-C 3 N 4 could easily absorb dye molecules during the dye degradation owing to the presence of nitrogen defects. The existence of lone electron-pair in photocatalysts was further verified by electron paramagnetic resonance (EPR) spectroscopy. If there were nitrogen vacancy in g-C 3 N 4 -based materials, a single Lorentzian line with a g value around 2.0025 could be observed in EPR spectroscopy, which can be attributed to the unpaired electrons on sp 2 -carbon atoms within the π-conjugated aromatic rings [19] . Figure 5e showed the EPR signal intensity of V N -g-C 3 N 4 was sharply decreased in comparsion with g-C 3 N 4 , which might be owing to oxygen atom replaced nitrogen atom forming covalent bonds with C and reducing the number of unpaired electrons. Based on the results of XPS and EPR, as illustrated in Fig. 5f, the structural schematic of g-C 3 N 4 and V N -g-C 3 N 4 was derived from urea as the primary substance under varying atmospheric conditions. To further comprehend the charge transfer and separation efficiency, electrochemical impedance spectroscopy and transient photocurrent responses were tested by electrochemical workstation. As shown in Fig. 6a, The semicircle of high frequency in the Nyquist plot implied a charge transfer process, and the diameter of the semicircle reported the charge transfer resistance. The smaller diameter of the V N -g-C 3 N 4 suggested a quicker charge transfer process after introducing cyano groups and nitrogen vacancies, showing that cyano groups and nitrogen vacancies acted active center for reducing the recombination of photogenerated electron-hole pairs. g-C 3 N 4 and V N -g-C 3 N 4 displayed positive photocurrents by several on-off cycles. Moreover, the photocurrent intensity of V N -g-C 3 N 4 was higher than g-C 3 N 4 , indicating V N -g-C 3 N 4 had more charge separation efficiency by introducing cyano groups and nitrogen vacancies (Fig. 6b). Figure 6c demonstrated the Mott-Schottky plots of the functional relationship of 1/C 2 and applied potential. The positive Mott-Schottky plots slope suggested that g-C 3 N 4 and V N -C 3 N 4 were classified as a n-type semiconductor. The intercept of Mott-Schottky plot at the abscissa was considered as the flat band position, which was − 1.28 eV and − 1.15eV (versus NHE) for g-C 3 N 4 and V N -g-C 3 N 4 , respectively. The flat band level was approximately equal to the conduction band minimum [20] . According to flat band level and Eg, the energy-band structure diagram of g-C 3 N 4 and V N -g-C 3 N 4 were shown in Fig. 6d. As shown in the figure, the valence band position, conduction band position, and band gap width of g-C 3 N 4 are 1.35 eV, -1.28 eV, and 2.63 eV, respectively. Similarly, the valence band position, conduction band position, and band gap width of V N -g-C 3 N 4 are 1.41 eV, -1.15 eV, and 2.56 eV, respectively. The photocatalytic activity of samples were tested via RhB degradation as found in Fig. 7a. Adsorption for 1 h in the dark environment to achieve the adsorption–desorption equilibrium before the photodegradation. The RhB removal rate of g-C 3 N 4 was about 58% in 120 min. In comparison, the RhB photodegradation of V N -g-C 3 N 4 was significantly improved after the appearance of nitrogen vacancies and cyano groups, V N -g-C 3 N 4 presented 81% of RhB removal in 120 min. The rate constant for RhB degradation by V N -g-C 3 N 4 was about 1.4 times that of g-C 3 N 4 . Thus, the formation of nitrogen vacancies and cyano groups were beneficial for providing more active sites for charge separation efficiency and photocatalytic reaction. According to the results of RhB removal results, the relevant kinetic characteristics constants were shown in Fig. 7b. RhB photocatalytic degradation reaction was conformed with first-order reaction kinetic equation. k for g-C 3 N 4 and V N -g-C 3 N 4 were 0.0072 and 0.0132 min − 1 , respectively. Figure 7c illustrates the degradation rate of g-C 3 N 4 and V N -g-C 3 N 4 after being irradiated in an ACT solution for 2 hours. In the absence of a photocatalyst, the degradation rate achieved through visible light irradiation over 2 hours is merely 2%. The degradation rate of g-C 3 N 4 stand at 56.3%. However, by introducing defects, the degradation rate of V N -g-C 3 N 4 in 2 hours reaches 94.6%, representing a significant increase of 47 times compared to the case without photocatalyst and 1.6 times higher than that of g-C 3 N 4 prior to modification. To further understand the RhB photodegradation process, isopropanol (IPA), Catalase (CAT), L-Histidine, P-benzoquinone (PBQ), Triethanolamine (TEOA) and AgNO 3 were used as quenchers for hydroxyl (•OH), hydrogen peroxide (H 2 O 2 ), singlet oxygen ( 1 O 2 ) super oxygen (•O 2 − ), holes (h + ) and electron (e − ), respectively. As shown in Fig. 8a, the degradation rate of RhB dropped to 31.0%, 60.1% and 60.3% after the addition of IPA, PBQ and AgNO 3 , respectively. The removal of RhB suggested no obvious change while the introduction of CAT into the system. However, when TEOA and L-Histidine were added as scavengers for h + and 1 O 2 , the RhB degradation was declined from 80.4–13.1% and 17.4%, respectively. Thus h + and 1 O 2 had played an important role in RhB removal. In order to determine which active group played important role in the photocatalytic process, DMPO, DMSO and TEMP were chosen to investigate •OH, •O 2 − and 1 O 2 radicals. Under dark conditions, no signals of •OH, •O 2 − or 1 O 2 radicals could be surveyed in any of the g-C 3 N 4 and V N -g-C 3 N 4 systems (Fig. 8b-d). Under the light conditions, •O 2 − could not be detected in either g-C 3 N 4 or V N -g-C 3 N 4 systems, indicating •O 2 − was not major active group in photocatalytic reaction. •OH signal was appeared in g-C 3 N 4 system but not in V N -g-C 3 N 4 system, •OH signal of g-C 3 N 4 system exhibited a 1:2:2:1 quadruple EPR signal, which was ascribed to DMPO − OH substance [21] . g-C 3 N 4 and V N -g-C 3 N 4 had low valance band and could insufficiently oxidize water to •OH (E θ (•OH/H 2 O) = + 2.34 V vs NHE) [22] , suggesting •OH in V N -g-C 3 N 4 system couldn’t be further formed by O 2 . 1 O 2 signal was found in both g-C 3 N 4 and V N -g-C 3 N 4 systems, which exhibited a 1:1:1 triple EPR signal due to the presence of TEMPO obtained by the oxidation of TEMP by 1 O 2 [23] . However, the EPR intensity of 1 O 2 signal for V N -g-C 3 N 4 was much weaker than g-C 3 N 4 , which showed there were much more 1 O 2 content in g-C 3 N 4 due to nitrogen vacancy could effectively capture electrons and limit the movement of photogenerated electrons [24] . thus, the formation pathways of free radicals of V N -g-C 3 N 4 in the photocatalytic system was described in Fig. 9. The oxygen species adsorbed on the material's surface combine with photogenerated electrons to produce superoxide radicals, which then undergo oxidation by holes to transform into singlet oxygen active species. These active species catalyze the oxidation of pollutants within the system, effectively degrading them. Conclusions In summary, g-C 3 N 4 containing nitrogen vacancies and cyano group was successfully synthesized by one-pot method using urea as the precursor. Compared with normal g-C 3 N 4 , the degradation rates of RhB and ACT were increased by 1.4 times and 1.6 times, respectively, indicating that the improvement in photocatalytic efficiency is attributed to enhaned BET surface area and introduction of nitrogen vacancy and cyano group, which broadened the spectrum and increased electron transfer efficiency. The capture experiment of active species shows that h + and 1 O 2 are the main active species. Therefore, this study provides an effective reference for designing stable, safe, and efficient photocatalysts and treatment processes to remove highly toxic organic pollutants in water environments. Declarations Author Contribution Xiang BI, Gao-Hui DU and Li-Zhong WANG wrote the main manuscript text and Dong-Hua ZHAI prepared Fig 7. Hui YANG and Lei WANG prepared literature research and conclusion verification. All authors reviewed the manuscript. Acknowledgement This research was funded by General Research Project of Basic Science (Natural Science) in Higher Education Institutions of Jiangsu Province (No. 23KJB430035) and excellent teaching team in the Blue Project of Jiangsu Province universities. Data availability All data generated or analysed during this study are included in this published article. References Ahmed M A, Mahmoud S A, Mohamed A A. Unveiling the photocatalytic potential of graphitic carbon nitride (gC 3 N 4 ): a state-of-the-art review[J]. RSC advances, 2024, 14(35): 25629-25662. Gomari K A, Hafeez H Y, Mohammed J, et al. A recent development and future prospect of g–C 3 N 4 –based photocatalyst for stable hydrogen (H 2 ) generation via photocatalytic water-splitting[J]. International Journal of Hydrogen Energy, 2024, 85: 598-624. Zhou B, Liu Q, Zheng C, et al. Enhanced Fenton-Like Catalysis via Interfacial Regulation of g-C 3 N 4 for Efficient Aromatic Organic Pollutant Degradation[J]. 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Scrutinizing the role of tunable carbon vacancies in g-C 3 N 4 nanosheets for efficient sonophotocatalytic degradation of Tetracycline in diverse water matrices: Experimental study and theoretical calculation[J]. Chemical Engineering Journal, 2023, 452: 139437. Chen W, Fu S, Li X, et al. C vacancy and F decorated g-C 3 N 4 for boosting photocatalytic ozonation of sodium p-perfluorinated nonoxybenzenesulfonate[J]. Chemical Engineering Journal, 2024, 480: 148059. Nguetsa Kuate L J, Chen Z, Lu J, et al. Photothermal-assisted photocatalytic degradation of tetracycline in seawater based on the black g-C 3 N 4 nanosheets with cyano group defects[J]. Catalysts, 2023, 13(7): 1147. Yao Q, Chen K, Oh W C. Direct Z-scheme photocatalytic removal of ammonia via the narrow band gap BiOCl/g-C 3 N 4 hybrid catalyst upon visible light irradiation[J]. Fullerenes, Nanotubes and Carbon Nanostructures, 2024, 32(6): 621-629. Lee Y J, Jeong Y J, Cho I S, et al. Facile synthesis of N vacancy g-C 3 N 4 using Mg-induced defect on the amine groups for enhanced photocatalytic• OH generation[J]. Journal of Hazardous Materials, 2023, 449: 131046. Song S, Zou X, Kang Y, et al. Single-color and two-color femtosecond pump–probe experiments on graphitic carbon nitrides revealing their charge carrier kinetics[J]. The Journal of Physical Chemistry C, 2023, 127(22): 10617-10628. Wei D, Wu J, Wang Y, et al. Dual defect sites of nitrogen vacancy and cyano group synergistically boost the activation of oxygen molecules for efficient photocatalytic decontamination[J]. Chemical Engineering Journal, 2023, 462: 142291. Hu J, Liu H, Sun C, et al. Precise Defect Engineering with Ultrathin Porous Frameworks on g-C3N4 for Synergetic Boosted Photocatalytic Hydrogen Evolution[J]. Industrial & Engineering Chemistry Research, 2024, 63(6): 2665-2675. Zhu D, Zhou Q. Nitrogen doped g-C 3 N 4 with the extremely narrow band gap for excellent photocatalytic activities under visible light[J]. Applied Catalysis B: Environmental, 2021, 281: 119474. Zhu L, Shen D, Zhang H, et al. Fabrication of Z-scheme Bi 7 O 9 I 3 /g-C 3 N 4 heterojunction modified by carbon quantum dots for synchronous photocatalytic removal of Cr (Ⅵ) and organic pollutants[J]. Journal of Hazardous Materials, 2023, 446: 130663. Xi Y, Chen W, Dong W, et al. Engineering an interfacial facet of S-scheme heterojunction for improved photocatalytic hydrogen evolution by modulating the internal electric field[J]. ACS Applied Materials & Interfaces, 2021, 13(33): 39491-39500. Maksimchuk N V, Puiggalí-Jou J, Zalomaeva O V, et al. Resolving the Mechanism for H 2 O 2 Decomposition over Zr (IV)-Substituted Lindqvist Tungstate: Evidence of Singlet Oxygen Intermediacy[J]. ACS catalysis, 2023, 13(15): 10324-10339. Yang H, Sun S, Duan R, et al. Mechanism insight into enhanced photocatalytic hydrogen production by nitrogen vacancy-induced creating built-in electric field in porous graphitic carbon nitride nanosheets[J]. Applied Surface Science, 2023, 631: 157544. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 05 Jun, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 14 Mar, 2025 Reviews received at journal 13 Mar, 2025 Reviewers agreed at journal 07 Mar, 2025 Reviews received at journal 24 Jan, 2025 Reviews received at journal 23 Jan, 2025 Reviewers agreed at journal 19 Jan, 2025 Reviewers agreed at journal 18 Jan, 2025 Reviewers invited by journal 18 Jan, 2025 Editor assigned by journal 13 Jan, 2025 Editor invited by journal 13 Jan, 2025 Submission checks completed at journal 10 Jan, 2025 First submitted to journal 22 Dec, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5695645","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":400496909,"identity":"48a5310e-a5cd-464e-abbc-27ad7e2b8d5c","order_by":0,"name":"Xiang BI","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1ElEQVRIie3RvwqCQBzA8ZMDXc5cXaxXMIQkfJkTB5dsbjA5CG668HXaOjmw5exNAhsbik5yDLux4b5w/BD8wP0BwGT6w0IIAFdzPn5DfRIhfTLOlGmT2EFL/jjt87PXNT3YJSlxOj5J1gcbN0d5KRi4Zj6QeUrQFk9vTEDOXdoWzGIrYFGREh+FP4hFmidtcwSRIi8tArlwaYmRPRCiQYaziIDyJZOzzMdtHlG0mSaxJ6P7jVYLp1Y31pdJUDtymowJtdRjYjVsnf9V1YeYTCaT6VtvH7VChFy81wUAAAAASUVORK5CYII=","orcid":"","institution":"Taizhou Polytechnic College","correspondingAuthor":true,"prefix":"","firstName":"Xiang","middleName":"","lastName":"BI","suffix":""},{"id":400496910,"identity":"2d91cbcf-6641-4066-9b37-c415e0d4d46c","order_by":1,"name":"Li-Zhong WANG","email":"","orcid":"","institution":"Taizhou Polytechnic College","correspondingAuthor":false,"prefix":"","firstName":"Li-Zhong","middleName":"","lastName":"WANG","suffix":""},{"id":400496911,"identity":"5cd81642-470c-413d-a4ae-2530c786fc0e","order_by":2,"name":"Dong-Hua ZHAI","email":"","orcid":"","institution":"Taizhou Polytechnic College","correspondingAuthor":false,"prefix":"","firstName":"Dong-Hua","middleName":"","lastName":"ZHAI","suffix":""},{"id":400496913,"identity":"1d556b27-9f48-4bae-9e9a-db4c062207b3","order_by":3,"name":"Lei WANG","email":"","orcid":"","institution":"Taizhou Polytechnic College","correspondingAuthor":false,"prefix":"","firstName":"Lei","middleName":"","lastName":"WANG","suffix":""},{"id":400496914,"identity":"55ec8139-0216-4b31-8f3c-81754262bd0a","order_by":4,"name":"Hui YANG","email":"","orcid":"","institution":"Taizhou Polytechnic College","correspondingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"YANG","suffix":""},{"id":400496915,"identity":"c2892424-6e78-47d2-b7bd-958ff28e1feb","order_by":5,"name":"Gao-Hui DU","email":"","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Gao-Hui","middleName":"","lastName":"DU","suffix":""}],"badges":[],"createdAt":"2024-12-23 00:38:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5695645/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5695645/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-03286-z","type":"published","date":"2025-06-05T15:57:36+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":73658368,"identity":"e5268daa-153b-4091-a179-cf6651eee261","added_by":"auto","created_at":"2025-01-13 10:45:05","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":566356,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns (a), magnification of the corresponding (002) peak (b), Nitrogen adsorption-desorption isotherms (c) and BJH pore size distributions (d) of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"file.png","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/987c0d14466e27b8eb66dee2.png"},{"id":73658371,"identity":"c78269f5-9c8e-4076-a0f0-c44a54008330","added_by":"auto","created_at":"2025-01-13 10:45:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":366990,"visible":true,"origin":"","legend":"\u003cp\u003eTEM images of g-C3N4 (a) and VN-g-C3N4 (b) and the inset showed the selected area electron diffraction (SAED) pattern of VN-g-C3N4\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/7bc1869bb6116c91d21d034a.png"},{"id":73658372,"identity":"4248e816-31c9-4e0a-bff1-da5636e4ce44","added_by":"auto","created_at":"2025-01-13 10:45:06","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":489018,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/ec8a9606ee5bd52d95ae81ae.png"},{"id":73658636,"identity":"f7180bb6-7b6c-476b-a866-e63cdfb953a6","added_by":"auto","created_at":"2025-01-13 10:53:06","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":531859,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Vis DRS (a), energy band gap values (b), steady photoluminescence (c) and time-resolved PL decay spectra (d) of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/461f177bd48a5b15913684aa.png"},{"id":73658639,"identity":"0b18dd67-7c66-4f74-97f6-f7f701353094","added_by":"auto","created_at":"2025-01-13 10:53:06","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":921928,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of survey (a), C1s (b), N1s (c), O1s (d), room-temperature EPR spectra (e) and the possible chemical structure of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/86c4c745d4bd1524a2dec973.png"},{"id":73658370,"identity":"17d92193-df87-417b-aff4-6b19ca8643ef","added_by":"auto","created_at":"2025-01-13 10:45:06","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":494816,"visible":true,"origin":"","legend":"\u003cp\u003eNyquist plots (a), transient photocurrent response curves (b), Mott–Schottky plots (c) and energy-band structure diagram of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/aa0e3a34131876acc1e5961e.png"},{"id":73658378,"identity":"f1e99659-bca3-4908-bfc9-8ac330dcff64","added_by":"auto","created_at":"2025-01-13 10:45:06","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":293042,"visible":true,"origin":"","legend":"\u003cp\u003eDegradation of RhB, kinetic fitting of the RhB degradation (b) and ACT removal under visible light (c) of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/a8799bd2edeadb912ced1970.png"},{"id":73658637,"identity":"da05419c-2ec0-42be-9e33-27daccb65d9f","added_by":"auto","created_at":"2025-01-13 10:53:06","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":659668,"visible":true,"origin":"","legend":"\u003cp\u003eDegradation of RhB over V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with IPA, CAT, L-Histidine, PBQ, TEOA and AgNO\u003csub\u003e3\u003c/sub\u003e as quenchers (a). EPR spectra of superoxide radicals (•O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e−\u003c/sup\u003e) (b) hydroxyl radicals (•OH) (c), and singlet oxygen (\u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e) (d) spin-trapped by DMPO, DMSO and TEMP, respectively. EPR conditions: reagent concentration 0.1mol L\u003csup\u003e−1\u003c/sup\u003e, catalyst concentration 50 mg/L.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/d0f5c586d5011bf87f239a4d.png"},{"id":73658375,"identity":"aab517fb-e86e-440a-9240-af1a8c70367e","added_by":"auto","created_at":"2025-01-13 10:45:06","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":178153,"visible":true,"origin":"","legend":"\u003cp\u003eThe formation pathways of free radicals of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e in the photocatalytic system\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/ab66c97f9db2eab59d5405d2.png"},{"id":84242587,"identity":"88f488ef-0e53-4eac-b352-b1152f6ac0ff","added_by":"auto","created_at":"2025-06-09 16:09:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6042303,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5695645/v1/a74ff91b-2aaa-4f58-9753-9e019263fb5a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"In-situ Synthesis of g-C 3 N 4 with Nitrogen Vacancy and Cyano Group via One-pot Method for Enhanced Photocatalytic Activity","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eAs a metal-free polymeric semiconductor photocatalyst, graphitic carbon nitride (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) had been attracted intensive attention \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. The g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was composed of tris-triazine (C\u003csub\u003e6\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003e) unit. Its abundant source, non-toxic, inexpensive, excellent thermal and chemical stability, easy preparation process and narrow band gap structure (~\u0026thinsp;2.7 eV vs NHE) \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e, which beneficially promoted it as an appropriate visible-light responsive photocatalyst for organic pollutants removal \u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e, photocatalytic hydrogen production \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e, photocatalytic nitrogen fixation \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e, CO\u003csub\u003e2\u003c/sub\u003e photoreduction \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e and photocatalytic NOx removal \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. However, it still suffered from unavailability of sunlight beyond 460 nm, small BET surface area and high recombination rate of electron-hole pairs owing to the absence of active sites \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. To address these challenges, several modification methods have been employed. Among these, bandgap engineering is a prevalent technique for enhancing the properties of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e materials. This approach can improve the light absorption capacity of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, extend the light absorption into longer wavelength regions, and facilitate charge separation and transmission. During the photocatalytic process, photogenerated electrons and holes tend to recombine, which diminishes photocatalytic efficiency. Bandgap engineering can alter the energy band structure to create an appropriate energy level distribution, thereby inhibiting charge recombination and extending charge lifetimes. Furthermore, bandgap engineering can enhance both the photocatalytic reaction rate and selectivity; additionally, the introduction of defects can increase the number of active sites. By adsorbing reactant molecules to lower the activation energy, this method can further promote photocatalytic reactions and enhance photocatalytic activity\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDong et al. designed and prepared g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with stacked coral like magnetic sulfur doped nitrogen vacancies by combining polymerization and precipitation. The 0.1g/L photocatalyst could photocatalytic degradation 5 mg/L of 2,4,6-TCP to 95% within 60 min under visible light. This high removal rate was attributed to nitrogen vacancies, which widened the visible light absorption range and shortened the electron transfer path\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e. Li et al. successfully synthesized g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with nitrogen vacancy network structure for photodegradation of Propylparaben. Compared with bulk g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, it shows larger specific surface area, stronger light absorption capacity, higher charge carrier transfer and separation efficiency. According to the characterization results and density functional theory calculations, nitrogen vacancies can capture electrons and promote the adsorption of oxygen. The Propylparaben removal rate of the best sample is 94.3%, which is 3.37 times higher than that of the bulk g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. Preeyanghaa et al. designed g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e containing carbon vacancies by using simple formalin assisted thermal polymerization method for melting CN precursors, in which the carbon vacancies can be adjusted by changing the dose of formalin. It was applied to photocatalytic degradation of tetracycline solution. Experimental studies and theoretical calculations show that oxygen is adsorbed on the carbon vacancy, and then a large number of reactive oxygen species, including \u003cb\u003e\u0026middot;\u003c/b\u003eO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e and \u003cb\u003e\u0026middot;\u003c/b\u003eOH are produced, which play an important role in the degradation and mineralization of tetracycline\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. Chen et al. Designed g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e photocatalyst co modified by C vacancy and F, and used sodium perfluoronoxybenzene sulfonate as the model pollutant. The research showed that the synthesized material maintained the inherent structure of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, and had higher conduction band potential, narrower band gap and longer electronic life. The removal rate of sodium perfluoronoxybenzene sulfonate was 99.3% in 30 minutes\u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e.Nguetsa Kuate et al. synthesized black g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e photocatalyst by one-step calcination of urea and phloroglucinol B for the degradation of tetracycline in seawater under visible light irradiation. The experimental results showed that the photocatalytic degradation rate of tetracycline was 92% within 2 hours at room temperature, which was 1.3 times that of pure g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. This excellent photocatalytic degradation can be attributed to the reduction of charge transfer distance due to the thickness of ultra-thin nanosheets, the separation of photogenerated carriers promoted by cyano defects and the enhancement of photocatalytic activity due to the photothermal effect of the material\u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. A large number of studies have shown that the photocatalytic activity of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e has been significantly improved through defects and band gap engineering.\u003c/p\u003e \u003cp\u003eInspired by the above, we prepared g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e material with rich defects via one-pot in-situ synthesis, and thoroughly discussed the mechanism of photocatalytic reaction of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e material with rich nitrogen vacancies and cyano group. The precursor was heat-treated under nitrogen atmosphere and then forming nitrogen vacancies and cyano groups, which could validly narrow the bandgap, enhance visible light absorption, and promote the separation of photo-generated electrons/holes. Therefore, the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with rich nitrogen vacancies and cyano groups could greatly improve photocatalytic performance for Acetaminophen and RhB degradation.\u003c/p\u003e"},{"header":"2. Experiment","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Synthesis of catalysts\u003c/h2\u003e \u003cp\u003eBulk g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was synthesized by thermal polymerization of urea under air condition. 6g urea and 1mL deionized water were fully mixed and placed in a covered crucible, heated to 100 ℃ at a heating rate of 0.5 ℃/min and kept at 100 ℃ for 1 hour, then continued heating to 500 ℃ at a heating rate of 5 ℃/min and kept at 500 ℃ for 2 hours at air condition. The synthesis method of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with rich nitrogen vacancies was similar to Bulk g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, The only difference was the reaction atmosphere was nitrogen instead of air. The g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with rich nitrogen vacancies was labelled as V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Characterization\u003c/h2\u003e \u003cp\u003eThe X-ray diffraction (XRD) patterns were tested to determine the phase structures of prepared materials using Rigaku D/max2200PC diffractometer with Cu Kα radiation (λ\u0026thinsp;=\u0026thinsp;1.542 \u0026Aring;). The Brunauer-Emmett-Teller (BET) method was carried out on ASAP2020, the specific surface area and pore size were analyzed by nitrogen adsorption-desorption test. Fourier transform infrared (FTIR) spectra were performed by a Bruker-VERTEX80v spectrometer. Transmission electron microscopy (TEM, JEOL JEM-ARM300F) measurement was performed to check the microstructure of the samples. UV-vis diffuse reflectance absorption spectrum in the range of 200\u0026ndash;800 nm was recorded on Cary 5000, of which BaSO\u003csub\u003e4\u003c/sub\u003e was used as reference. X-ray photoelectron spectra (XPS) and VBXPS were collected on an AXIS SUPRA utilizing the reference of C1s (284.6 eV) with an excitation source of 150 W Al Kα X-rays (1486.6 eV). The photoluminescence (PL) spectra and time-resolved fluorescence decay spectra of catalysts were analyzed by a fluorescence spectrophotometer (Edinburgh Instruments, FS5) equipped with xenon lamp source (150 W) at an excitation wavelength of 340 nm.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Photocatalytic and electrochemical test of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eElectrochemical impedance spectroscopy measurements, photocurrent intensity response measurements and Mott\u0026ndash;Schottky curve were measured by an electrochemical workstation (CHI600E, China) based on a conventional three electrode cell. 10 mg of catalyst on glassy carbon electrode substrate (1cm\u0026times;1cm) was used as working electrode. The graphite electrode and Ag/AgCl electrodes were used as counter electrode and reference electrode, respectively. The Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e aqueous solution was used as the electrolyte (0.2 mol L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 200 mL). The frequency range was from 10\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e Hz to 10\u003csup\u003e5\u003c/sup\u003e Hz, and the amplitude of the applied sine wave potential in each case was 5 mV for the EIS measurements. Incident light was obtained from a 300 W xenon lamp. The photocatalytic activity of catalsyts was tested by degradation of RhB in an aqueous solution under 40W LED white lamp. Firstly, catalsyts samples (30 mg) were mixed with RhB aqueous solution (50 mL, 30 mg/L). After stirring for enough time in dark to achieve adsorption equilibrium, the catalyst was collected and placed again in the RhB solution with same concentration to test the photocatalytic properties. The percentage of degradation was recorded as C/C\u003csub\u003e0\u003c/sub\u003e, where C and C\u003csub\u003e0\u003c/sub\u003e referred to the absorbance of the RhB solution after a certain time interval (30 min) and the initial absorbance corresponding to concentration, respectively. Acetaminophen (ACT) was degraded under 8 W LED lamp. Firstly, the photocatalyst (10 mg) was mixed with ACT aqueous solution (10 mg/L, 50 ml) to achieve adsorption equilibrium, and then the photocatalyst was centrifuged collected and put into the solution under the same conditions to test the photocatalytic performance.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 The detection of free radicals and trapping experiments of active species under visible-light\u003c/h2\u003e \u003cp\u003eThe electron paramagnetic resonance (EPR) experiment was tested on Bruker EMX-plus instrument, which discovered the free radicals in reaction. Samples for EPR measurement were executed by using DMPO (5,5-dimethyl-l-pyrroline N-oxide), DMSO (dimethyl sulfoxide) and 2,2,6,6-tetramethylpiperidine (TEMP) as the spin trapping agent (reagent concentration 0.1mol L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, catalyst concentration 50 mg/L.) under visible light. We used isopropanol (IPA), Catalase (CAT), L-Histidine, P-benzoquinone (PBQ), Triethanolamine (TEOA) and AgNO\u003csub\u003e3\u003c/sub\u003e as quenchers of hydroxyl (\u0026bull;OH), hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e), singlet oxygen (\u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e) super oxygen (\u0026bull;O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e), holes (h\u003csup\u003e+\u003c/sup\u003e) and electron (e\u003csup\u003e\u0026minus;\u003c/sup\u003e), respectively. Catalysts (30 mg) containing different trapping agents (0.01mol/L) were distributed in 50ml RhB solution (30mg/L) for characterizing photocatalytic performance.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eThe microstructure, composition and morphology of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e samples were measured by XRD. Figure\u0026nbsp;1a presented two characteristic XRD peaks of samples, the strong diffraction (002) peak at about 2θ = 27.2° was associated with the interlayer stacking of aromatic systems and the low-angle (100) peak at 2θ = 13.1° was corresponded to repeating motifs of in-plane tri-s-triazine units structure for g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (JCPDS NO.87-1526) \u003csup\u003e[15]\u003c/sup\u003e. V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e exhibited the same typically characteristic peaks as that of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, which confirmed its basic triazine framework of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e without changing the basic structure of during N\u003csub\u003e2\u003c/sub\u003e treatment. Compared with g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, the XRD peaks of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was broadened and weakened, suggesting that the in-plane orderly structure clearly decreased and the interlayer stacking became less order. Partially enlarged image (Fig.\u0026nbsp;1b) was observed as the peak at 27.2° has shifted to 27.7°. According to the Bragg diffraction equation, the slight shift of peak (002) to the positive direction could be decreased in interlayer stacking distance from 0.328 to 0.322 nm, which might be due to the N-atomic variation in the plane. The structural properties of materials were analyzed by the N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption measurement. Figure\u0026nbsp;1c showed that all the isotherms were type IV with hysteresis loops of type H3 at a relative pressure range of 0.6-1.0, demonstrating the presence of mesoporous. The BET surface area gradually subjoined from 27.5 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e− 1\u003c/sup\u003e (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) to 35.7 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e− 1\u003c/sup\u003e (V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e). The increase of BET surface area might be owing to the nitrogen-vacancy defects in the structural units. The Barret-Joyner-Halenda analysis of pore size distributions from 2 to 30 nm for g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e in Fig.\u0026nbsp;1d, showing the introduction of nitrogen vacancies significantly increased specific surface area and provided abundant active reaction sites for photocatalytic reaction .\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;2 showed the TEM images of the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, porous morphology was observed on the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e surface. The porous structure was beneficial for photogenerated electron and hole transmission, extended carrier life and excellent capture ability. The surface of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e sample (Fig.\u0026nbsp;2a) was fully glossy. However, the surface of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e sample (Fig.\u0026nbsp;2b) showed the state of intertwined nanosheets, demonstrating the presence of nitrogen vacancy on the V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e surface. The SAED pattern revealed that bright continuous concentric rings owing to diffraction by the (002) planes of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. Therefore, we could inferred nitrogen vacancy were formed in the heat-treatment process at nitrogen atmosphere.\u003c/p\u003e\n\u003cp\u003eFTIR spectra was a very useful tool for analysis of variable chemical structure in material. As shown in Fig.\u0026nbsp;3, the V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e sample showed the typical FTIR patterns which was similarly to that of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, suggesting the basic atomic structure of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was still remained after the different atmosphere. The broad peak at 3000–3500 cm\u003csup\u003e− 1\u003c/sup\u003e was originated from N-H stretching vibration or O-H adsorbed hydroxyl species and amino group from precursor \u003csup\u003e[16]\u003c/sup\u003e. The bond strength of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was enhanced, suggesting more content of N-H or O-H in V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. The peaks in the region from 850 to 1800 cm\u003csup\u003e− 1\u003c/sup\u003e corresponded to skeletal vibration of C-N-C, C-N and C = N in aromatic ring. The sharp absorption peak at 812 cm\u003csup\u003e− 1\u003c/sup\u003e owing to the bending mode of the 3-s-triazine unit, illustrating the existence of the basic melon units with NH/NH\u003csub\u003e2\u003c/sub\u003e groups. Compared with g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, the peak of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was weaken trend, indicating it had less heptazine rings. The presence of nitrogen vacancy broke the structure of the triazine skeleton and decrease the content of NH/NH\u003csub\u003e2\u003c/sub\u003e groups. A distinct peak at 2175 cm\u003csup\u003e− 1\u003c/sup\u003e of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e had stronger than that of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, which corresponded to asymmetric stretching vibration of cyano-groups \u003csup\u003e[17]\u003c/sup\u003e. The terminal C ≡ N triple bond carried positive charge and acted as electron acceptor for accelerating the charge transfer, which was formed during the opening of s-triazine heterocycles and the lattice N loss. The formation of nitrogen vacancy and cyano groups could improve the photocatalytic performance.\u003c/p\u003e\n\u003cp\u003eFigure 4a-b showed the UV–Vis DRS and the calculated bandgap for the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. In Fig.\u0026nbsp;4a, compared with g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, the absorption edges of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e displayed a slight red-shift. The band gap values in Fig.\u0026nbsp;4b showed that the band gap of samples narrowed from 2.63 eV (g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) to 2.56 eV (V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e). A narrower band gap was achieved, which should be due to the introduction of nitrogen vacancies. To know the separation and transfer efficiency of photoexcited electron-hole pairs, the steady PL results under the excitation wavelength of 340 nm were shown in Fig.\u0026nbsp;4c. The peak at about 470 nm was stemmed from the direct electron (e\u003csup\u003e−\u003c/sup\u003e) and hole (h\u003csup\u003e+\u003c/sup\u003e) recombination of band transition. Wherein V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e with a amount of nitrogen vacancies clearly exhibited much lower intensity than g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, indicating that the recombination of carriers of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e could be basically inhibited after introduction of nitrogen vacancies and cyano groups, since the nitrogen vacancies and cyano groups could trap photogenerated electrons for promoting the separation of photogenerated electrons and holes \u003csup\u003e[18]\u003c/sup\u003e. Besides, to comprehend the charge-separation kinetics, the exciton lifetime was calculated by fitting the time-resolved PL decay curves (Fig.\u0026nbsp;4d) and the average lifetime (τ\u003csub\u003eav\u003c/sub\u003e ) was depended on the following equation, where B and τ denoted the relative amplitude and decay lifetimes, respectively .\u003c/p\u003e\n\u003cdiv\u003e\n \u003cdiv align=\"left\"\u003e\u003cimg src=\"https://myfiles.space/user_files/122228_c8a1650c59388082/122228_custom_files/img1736764281.png\"\u003e\u003cbr\u003e\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eThe parameters in this equation were given in Table 1. The short lifetime (τ\u003csub\u003e1\u003c/sub\u003e) was owing to electrons trapped in shallow states and the long lifetime (τ\u003csub\u003e2\u003c/sub\u003e) corresponded to deep states before the recombination with the holes in the VB. The τ\u003csub\u003eav\u003c/sub\u003e for V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (8.40 ns) was shorter than that of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e (10.87 ns), indicating enhanced electron and hole dissociation. The outstanding decrease in PL intensity and lifetime of carriers was attributed to the nitrogen vacancies and cyano groups, which might improve the efficiency of charge carrier transfer and enhance photocatalytic reaction activity.\u003c/p\u003e\n\u003cp\u003eThe XPS analysis was performed to further investigate the chemical bond valence information of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. The survey spectra was shown in Fig.\u0026nbsp;5a. For g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, the total peak of C 1s (Fig.\u0026nbsp;5b) was consisted of three peaks: C–C/C = C (284.6 eV), C–NH/C–OH (286.2 eV) and N = C–N (288.1 eV). The N 1s peak of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e in the high-resolution spectra (Fig.\u0026nbsp;5c) was composed of three peaks, which corresponded to N–2C (398.6 eV), N–3C (399.8 eV) and N–H (401.1 eV). It was interesting that N–3C peak of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e slightly negatively shifted from 399.8 to 399.5 eV, which might be due to the formation of cyano. It was noteworthy that the peak ratio between N–2C and N–3C significantly declined from 2.785 for g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e to 1.578 for V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, indicating the loss of N–2C during thermal polymerization under nitrogen atmosphere. Figure\u0026nbsp;5d showed the O 1s spectra peak at 532.3 eV was ascribed to the hydroxyl or adsorbed water. The peak intensity at 532.3 eV of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was stronger than that of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, showing that the V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e could easily absorb dye molecules during the dye degradation owing to the presence of nitrogen defects. The existence of lone electron-pair in photocatalysts was further verified by electron paramagnetic resonance (EPR) spectroscopy. If there were nitrogen vacancy in g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e-based materials, a single Lorentzian line with a g value around 2.0025 could be observed in EPR spectroscopy, which can be attributed to the unpaired electrons on sp\u003csup\u003e2\u003c/sup\u003e-carbon atoms within the π-conjugated aromatic rings \u003csup\u003e[19]\u003c/sup\u003e. Figure\u0026nbsp;5e showed the EPR signal intensity of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was sharply decreased in comparsion with g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, which might be owing to oxygen atom replaced nitrogen atom forming covalent bonds with C and reducing the number of unpaired electrons. Based on the results of XPS and EPR, as illustrated in Fig.\u0026nbsp;5f, the structural schematic of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was derived from urea as the primary substance under varying atmospheric conditions.\u003c/p\u003e\n\u003cp\u003eTo further comprehend the charge transfer and separation efficiency, electrochemical impedance spectroscopy and transient photocurrent responses were tested by electrochemical workstation. As shown in Fig.\u0026nbsp;6a, The semicircle of high frequency in the Nyquist plot implied a charge transfer process, and the diameter of the semicircle reported the charge transfer resistance. The smaller diameter of the V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e suggested a quicker charge transfer process after introducing cyano groups and nitrogen vacancies, showing that cyano groups and nitrogen vacancies acted active center for reducing the recombination of photogenerated electron-hole pairs. g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e displayed positive photocurrents by several on-off cycles. Moreover, the photocurrent intensity of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was higher than g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, indicating V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e had more charge separation efficiency by introducing cyano groups and nitrogen vacancies (Fig.\u0026nbsp;6b). Figure\u0026nbsp;6c demonstrated the Mott-Schottky plots of the functional relationship of 1/C\u003csup\u003e2\u003c/sup\u003e and applied potential. The positive Mott-Schottky plots slope suggested that g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e were classified as a n-type semiconductor. The intercept of Mott-Schottky plot at the abscissa was considered as the flat band position, which was − 1.28 eV and − 1.15eV (versus NHE) for g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, respectively. The flat band level was approximately equal to the conduction band minimum \u003csup\u003e[20]\u003c/sup\u003e. According to flat band level and Eg, the energy-band structure diagram of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e were shown in Fig.\u0026nbsp;6d. As shown in the figure, the valence band position, conduction band position, and band gap width of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e are 1.35 eV, -1.28 eV, and 2.63 eV, respectively. Similarly, the valence band position, conduction band position, and band gap width of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e are 1.41 eV, -1.15 eV, and 2.56 eV, respectively.\u003c/p\u003e\n\u003cp\u003eThe photocatalytic activity of samples were tested via RhB degradation as found in Fig.\u0026nbsp;7a. Adsorption for 1 h in the dark environment to achieve the adsorption–desorption equilibrium before the photodegradation. The RhB removal rate of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was about 58% in 120 min. In comparison, the RhB photodegradation of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was significantly improved after the appearance of nitrogen vacancies and cyano groups, V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e presented 81% of RhB removal in 120 min. The rate constant for RhB degradation by V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was about 1.4 times that of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. Thus, the formation of nitrogen vacancies and cyano groups were beneficial for providing more active sites for charge separation efficiency and photocatalytic reaction. According to the results of RhB removal results, the relevant kinetic characteristics constants were shown in Fig.\u0026nbsp;7b. RhB photocatalytic degradation reaction was conformed with first-order reaction kinetic equation. k for g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e were 0.0072 and 0.0132 min\u003csup\u003e− 1\u003c/sup\u003e, respectively. Figure\u0026nbsp;7c illustrates the degradation rate of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e after being irradiated in an ACT solution for 2 hours. In the absence of a photocatalyst, the degradation rate achieved through visible light irradiation over 2 hours is merely 2%. The degradation rate of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e stand at 56.3%. However, by introducing defects, the degradation rate of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e in 2 hours reaches 94.6%, representing a significant increase of 47 times compared to the case without photocatalyst and 1.6 times higher than that of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e prior to modification.\u003c/p\u003e\n\u003cp\u003eTo further understand the RhB photodegradation process, isopropanol (IPA), Catalase (CAT), L-Histidine, P-benzoquinone (PBQ), Triethanolamine (TEOA) and AgNO\u003csub\u003e3\u003c/sub\u003e were used as quenchers for hydroxyl (•OH), hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e), singlet oxygen (\u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e) super oxygen (•O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e−\u003c/sup\u003e), holes (h\u003csup\u003e+\u003c/sup\u003e) and electron (e\u003csup\u003e−\u003c/sup\u003e), respectively. As shown in Fig.\u0026nbsp;8a, the degradation rate of RhB dropped to 31.0%, 60.1% and 60.3% after the addition of IPA, PBQ and AgNO\u003csub\u003e3\u003c/sub\u003e, respectively. The removal of RhB suggested no obvious change while the introduction of CAT into the system. However, when TEOA and L-Histidine were added as scavengers for h\u003csup\u003e+\u003c/sup\u003e and \u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e, the RhB degradation was declined from 80.4–13.1% and 17.4%, respectively. Thus h\u003csup\u003e+\u003c/sup\u003e and \u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e had played an important role in RhB removal. In order to determine which active group played important role in the photocatalytic process, DMPO, DMSO and TEMP were chosen to investigate •OH, •O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e−\u003c/sup\u003e and \u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e radicals. Under dark conditions, no signals of •OH, •O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e−\u003c/sup\u003e or \u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e radicals could be surveyed in any of the g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e systems (Fig.\u0026nbsp;8b-d).\u003c/p\u003e\n\u003cp\u003eUnder the light conditions, •O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e−\u003c/sup\u003e could not be detected in either g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e or V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e systems, indicating •O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e−\u003c/sup\u003e was not major active group in photocatalytic reaction. •OH signal was appeared in g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e system but not in V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e system, •OH signal of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e system exhibited a 1:2:2:1 quadruple EPR signal, which was ascribed to DMPO − OH substance \u003csup\u003e[21]\u003c/sup\u003e. g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e had low valance band and could insufficiently oxidize water to •OH (E\u003csup\u003eθ\u003c/sup\u003e(•OH/H\u003csub\u003e2\u003c/sub\u003eO) = + 2.34 V vs NHE) \u003csup\u003e[22]\u003c/sup\u003e, suggesting •OH in V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e system couldn’t be further formed by O\u003csub\u003e2\u003c/sub\u003e. \u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e signal was found in both g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e systems, which exhibited a 1:1:1 triple EPR signal due to the presence of TEMPO obtained by the oxidation of TEMP by \u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e \u003csup\u003e[23]\u003c/sup\u003e. However, the EPR intensity of \u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e signal for V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was much weaker than g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, which showed there were much more \u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e content in g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e due to nitrogen vacancy could effectively capture electrons and limit the movement of photogenerated electrons \u003csup\u003e[24]\u003c/sup\u003e. thus, the formation pathways of free radicals of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e in the photocatalytic system was described in Fig.\u0026nbsp;9. The oxygen species adsorbed on the material's surface combine with photogenerated electrons to produce superoxide radicals, which then undergo oxidation by holes to transform into singlet oxygen active species. These active species catalyze the oxidation of pollutants within the system, effectively degrading them.\u003c/p\u003e\n\n"},{"header":"Conclusions","content":"\u003cp\u003eIn summary, g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e containing nitrogen vacancies and cyano group was successfully synthesized by one-pot method using urea as the precursor. Compared with normal g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, the degradation rates of RhB and ACT were increased by 1.4 times and 1.6 times, respectively, indicating that the improvement in photocatalytic efficiency is attributed to enhaned BET surface area and introduction of nitrogen vacancy and cyano group, which broadened the spectrum and increased electron transfer efficiency. The capture experiment of active species shows that h\u003csup\u003e+\u003c/sup\u003e and \u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e are the main active species. Therefore, this study provides an effective reference for designing stable, safe, and efficient photocatalysts and treatment processes to remove highly toxic organic pollutants in water environments.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eXiang BI, Gao-Hui DU and Li-Zhong WANG wrote the main manuscript text and Dong-Hua ZHAI prepared Fig 7. Hui YANG and Lei WANG prepared literature research and conclusion verification. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThis research was funded by General Research Project of Basic Science (Natural Science) in Higher Education Institutions of Jiangsu Province (No. 23KJB430035) and excellent teaching team in the Blue Project of Jiangsu Province universities.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAhmed M A, Mahmoud S A, Mohamed A A. Unveiling the photocatalytic potential of graphitic carbon nitride (gC\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e): a state-of-the-art review[J]. RSC advances, 2024, 14(35): 25629-25662.\u003c/li\u003e\n\u003cli\u003eGomari K A, Hafeez H Y, Mohammed J, et al. 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ACS Applied Materials \u0026amp; Interfaces, 2021, 13(33): 39491-39500.\u003c/li\u003e\n\u003cli\u003eMaksimchuk N V, Puiggal\u0026iacute;-Jou J, Zalomaeva O V, et al. Resolving the Mechanism for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e Decomposition over Zr (IV)-Substituted Lindqvist Tungstate: Evidence of Singlet Oxygen Intermediacy[J]. ACS catalysis, 2023, 13(15): 10324-10339.\u003c/li\u003e\n\u003cli\u003eYang H, Sun S, Duan R, et al. Mechanism insight into enhanced photocatalytic hydrogen production by nitrogen vacancy-induced creating built-in electric field in porous graphitic carbon nitride nanosheets[J]. Applied Surface Science, 2023, 631: 157544.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"g-C3N4, Nitrogen vacancies, Porous material, Acetaminophen, RhB","lastPublishedDoi":"10.21203/rs.3.rs-5695645/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5695645/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn-situ synthesis of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e containing nitrogen vacancies and cyano group via one-pot method using urea as the precursor. The structural, morphological or electrochemical properties of synthesized photocatalysts were characterized by XRD, BET analysis, TEM, FTIR, UV-DRS, PL, XPS and EPR. It was found that the nitrogen vacancy was successfully introduced into g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. Compared to pure g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, the (200) crystal plane in XRD of synthesized g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e showed slight red-shift, and the BET surface areas had changed from 27.5 to 35.7 m\u003csup\u003e2\u003c/sup\u003e\u003cb\u003e\u0026middot;\u003c/b\u003eg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which could provide more reaction center and active site. TEM confirmed that g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e were porous materials, and FTIR, XPS as well as EPR could prove the presence of nitrogen vacancies and cyano group. The UV-Vis absorption edge of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e demonstrated briefly red-shift, PL intensity and lifetime of carriers declined in comparison with pure g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. Electrochemical test results showed that enhanced charge separation efficiency and low recombination rate of charge carriers of V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e. The photocatalytic activity of the photocatalysts was researched by RhB degradation and ACT removal under visible light irradiation, the results showed the rate of RhB degradation on the V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e was 81%, which was 1.4-fold as high as that of g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e in visible light. The degradation contribution from the active species were h\u003csup\u003e+\u003c/sup\u003e (67.3%) \u0026gt;\u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e(63.0%)\u0026gt;\u0026bull;OH (49.4%) \u0026gt;\u0026bull;O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e (20.3%)\u0026thinsp;\u0026gt;\u0026thinsp;e\u003csup\u003e\u0026minus;\u003c/sup\u003e (20.1%)\u0026thinsp;\u0026gt;\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e(0.2%), and V\u003csub\u003eN\u003c/sub\u003e-g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e exhibited excellent ACT removal rate,which was 1.6-fold higher than that of pure g-C\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e in visible light. This study provides an efficient photocatalyst for the treatment of toxic wastewater.\u003c/p\u003e","manuscriptTitle":"In-situ Synthesis of g-C 3 N 4 with Nitrogen Vacancy and Cyano Group via One-pot Method for Enhanced Photocatalytic Activity","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-13 10:45:01","doi":"10.21203/rs.3.rs-5695645/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-03-14T10:16:45+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-03-13T05:54:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"48996624094343520174832579106958938494","date":"2025-03-07T06:22:41+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-01-24T16:48:21+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-01-23T18:23:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"11650623447893324007007264524494124513","date":"2025-01-19T05:34:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"172267559673286972935339229411454228625","date":"2025-01-18T19:08:23+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-01-18T18:50:03+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-01-13T15:13:28+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-01-13T10:49:19+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-01-10T13:19:22+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2024-12-23T00:36:45+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b843f806-9787-44ed-989e-27f9220a7339","owner":[],"postedDate":"January 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-06-09T16:02:49+00:00","versionOfRecord":{"articleIdentity":"rs-5695645","link":"https://doi.org/10.1038/s41598-025-03286-z","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-06-05 15:57:36","publishedOnDateReadable":"June 5th, 2025"},"versionCreatedAt":"2025-01-13 10:45:01","video":"","vorDoi":"10.1038/s41598-025-03286-z","vorDoiUrl":"https://doi.org/10.1038/s41598-025-03286-z","workflowStages":[]},"version":"v1","identity":"rs-5695645","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5695645","identity":"rs-5695645","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}