In-situ synthesis of g-C3N4 with nitrogen vacancy and cyano group via one-pot method for enhanced photocatalytic activity
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-06-05 |
| Journal | Scientific Reports |
| Authors | Xiang Bi, LiâZhong Wang, Ds Zhai, Lei Wang, Hui Yang |
| Institutions | Shaanxi University of Science and Technology, Taizhou Vocational and Technical College |
| Citations | 3 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research details the successful in-situ, one-pot synthesis of graphitic carbon nitride (g-C3N4) engineered with nitrogen vacancies (VN) and cyano groups, resulting in significantly enhanced visible-light photocatalytic performance.
- Core Achievement: The VN-g-C3N4 catalyst was synthesized via thermal polymerization of urea under a nitrogen (N2) atmosphere, which successfully introduced structural defects (VN and cyano groups).
- Performance Boost: The modified catalyst achieved 94.6% removal of Acetaminophen (ACT) in 2 hours, representing a 1.6-fold increase compared to pure g-C3N4. Rhodamine B (RhB) degradation reached 81%.
- Structural Improvements: The introduction of defects increased the BET surface area from 27.5 to 35.7 m2g-1, providing more active reaction sites.
- Electronic Structure Modulation: Defects narrowed the band gap from 2.63 eV to 2.56 eV, extending visible light absorption and shifting the (002) XRD peak slightly (from 27.2° to 27.7°).
- Kinetics Enhancement: Electrochemical tests confirmed enhanced charge separation efficiency and a reduced carrier recombination rate, evidenced by a shorter average carrier lifetime (8.40 ns vs. 10.87 ns for pure g-C3N4).
- Reaction Mechanism: Trapping experiments identified holes (h+) and singlet oxygen (1O2) as the dominant active species, contributing 67.3% and 63.0%, respectively, to the degradation process.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Catalyst Designation | VN-g-C3N4 | N/A | Nitrogen vacancy and cyano group modified g-C3N4 |
| Synthesis Method | One-pot thermal polymerization | N/A | Urea precursor, N2 atmosphere |
| BET Surface Area | 35.7 | m2g-1 | VN-g-C3N4 (Pure g-C3N4: 27.5 m2g-1) |
| Band Gap (Eg) | 2.56 | eV | VN-g-C3N4 (Pure g-C3N4: 2.63 eV) |
| (002) XRD Peak Shift | 27.7 | ° | Slight red-shift from 27.2° (pure g-C3N4) |
| Average Carrier Lifetime (Tav) | 8.40 | ns | VN-g-C3N4 (Pure g-C3N4: 10.87 ns) |
| RhB Degradation Rate (k) | 0.0132 | min-1 | 1.4-fold higher than pure g-C3N4 |
| ACT Removal Efficiency | 94.6 | % | 2 hours, 8 W LED lamp |
| Conduction Band (CB) Potential | -1.15 | V | vs. NHE (Mott-Schottky intercept) |
| Valence Band (VB) Potential | 1.41 | V | vs. NHE (Calculated from Eg) |
| Primary Active Species (h+) Contribution | 67.3 | % | Contribution to RhB degradation |
| Primary Active Species (1O2) Contribution | 63.0 | % | Contribution to RhB degradation |
| Cyano Group FTIR Peak | 2175 | cm-1 | Asymmetric stretching vibration |
Key Methodologies
Section titled âKey MethodologiesâThe VN-g-C3N4 catalyst was synthesized via a controlled thermal polymerization process using urea and deionized water under a nitrogen atmosphere.
- Precursor Preparation: 6 g of urea and 1 mL of deionized water were thoroughly mixed and placed in a covered crucible.
- Initial Heating Stage: The mixture was heated to 100 °C at a rate of 0.5 °C/min and held for 1 hour.
- Polymerization Stage: The temperature was subsequently raised to 500 °C at a rate of 5 °C/min.
- Calcination: The material was held at 500 °C for 2 hours under a controlled Nitrogen (N2) atmosphere to induce nitrogen vacancies and cyano groups.
- Structural Characterization:
- XRD: Used to confirm the triazine framework and measure the (002) peak shift.
- BET Analysis: Used to determine specific surface area and pore size distribution (ASAP2020).
- FTIR and XPS: Used to confirm the presence of N-vacancies and the terminal cyano groups (2175 cm-1 peak).
- Photocatalytic Testing:
- RhB Degradation: Tested using 30 mg catalyst in 50 mL of 30 mg/L RhB solution under a 40 W LED white lamp.
- ACT Removal: Tested using 10 mg catalyst in 50 mL of 10 mg/L ACT solution under an 8 W LED lamp.
- Electrochemical Analysis: Electrochemical Impedance Spectroscopy (EIS), transient photocurrent response, and Mott-Schottky plots were measured using a three-electrode cell (0.2 mol L-1 Na2SO4 electrolyte) to assess charge kinetics.
- Active Species Detection: Electron Paramagnetic Resonance (EPR) spectroscopy was performed using DMPO, DMSO, and TEMP as spin trapping agents to identify hydroxyl (â˘OH), superoxide (â˘O2-), and singlet oxygen (1O2) radicals.
Commercial Applications
Section titled âCommercial ApplicationsâThis highly efficient, metal-free, visible-light-responsive photocatalyst is ideal for environmental remediation and sustainable chemical processing.
- Wastewater Treatment:
- Efficient removal of persistent organic pollutants (POPs) and pharmaceutical compounds (e.g., Acetaminophen, Paracetamol) from industrial and domestic effluents.
- Degradation of synthetic dyes (e.g., Rhodamine B) in textile and chemical industry wastewater.
- Sustainable Water Purification: Integration into advanced oxidation processes (AOPs) for low-energy, ambient-temperature water purification systems.
- Catalyst Manufacturing: The facile, one-pot synthesis method using low-cost urea makes the VN-g-C3N4 scalable for commercial catalyst production.
- Air Purification/NOx Removal: While the study focused on water, g-C3N4 derivatives are known for photocatalytic NOx removal, suggesting potential application in air quality control systems.
- Hydrogen Production: Defect-engineered g-C3N4 is a key material in photocatalytic hydrogen evolution, offering potential use in green energy technologies.
View Original Abstract
In-situ synthesis of g-C<sub>3</sub>N<sub>4</sub> 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<sub>3</sub>N<sub>4</sub>. Compared to pure g-C<sub>3</sub>N<sub>4</sub>, the (200) crystal plane in XRD of synthesized g-C<sub>3</sub>N<sub>4</sub> showed slight red-shift, and the BET surface areas had changed from 27.5 to 35.7 m<sup>2</sup>¡g<sup>-1</sup>, which could provide more reaction center and active site. TEM confirmed that g-C<sub>3</sub>N<sub>4</sub> and V<sub>N</sub>-g-C<sub>3</sub>N<sub>4</sub> 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<sub>N</sub>-g-C<sub>3</sub>N<sub>4</sub> demonstrated briefly red-shift, PL intensity and lifetime of carriers declined in comparison with pure g-C<sub>3</sub>N<sub>4</sub>. Electrochemical test results showed that enhanced charge separation efficiency and low recombination rate of charge carriers of V<sub>N</sub>-g-C<sub>3</sub>N<sub>4</sub>. 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<sub>N</sub>-g-C<sub>3</sub>N<sub>4</sub> was 81%, which was 1.4-fold as high as that of g-C<sub>3</sub>N<sub>4</sub> in visible light. The degradation contribution from the active species were h<sup>+</sup> (67.3%) ><sup>1</sup>O<sub>2</sub>(63.0%)>â˘OH (49.4%) >â˘O<sub>2</sub><sup>-</sup> (20.3%) > e<sup>-</sup> (20.1%) > H<sub>2</sub>O<sub>2</sub>(0.2%), and V<sub>N</sub>-g-C<sub>3</sub>N<sub>4</sub> exhibited excellent ACT removal rate, which was 1.6-fold higher than that of pure g-C<sub>3</sub>N<sub>4</sub> in visible light. This study provides an efficient photocatalyst for the treatment of toxic wastewater.