One-step Thermal Polymerization Research Articles

Synergistic design of RuO2-MOx/g-C3N4 hybrid photocatalysts for efficient hydrogen evolution in aqueous solution

Embedding co-catalysts on graphitic carbon nitride (g-C3N4) is a promising strategy for improving photocatalytic H2 evolution, but identifying suitable co-catalysts remains a significant challenge. In this study, RuO2 nanoparticles (NPs) and metal oxides (MOx) as dual catalysts were embedded on g-C3N4 to enhance the photocatalytic activity. The RuO2–MOx (CuOx, NiOx, or CoOx)/g-C3N4 composites were synthesized using a one-step thermal polymerization and wet impregnation method, and used as photocatalysts for H2 evolution. Among them, the RuO2–CoOx/g-C3N4 photocatalyst demonstrated superior H2 evolution compared to the pristine g-C3N4, (NiOx, CuOx, or RuO2)/g-C3N4, and (RuO2–NiOx or RuO2–CuOx)/g-C3N4, achieving a hydrogen evolution rate of 5964 μmol g−1 h−1 per catalyst weight an aqueous solution containing triethanolamine (TEOA). The enhanced photocatalytic efficiency was attributed to the synergistic effect between RuO2 NPs and CoOx. Furthermore, the catalyst showed excellent stability during recovery and reuse cycles, with no structural changes observed through XPS, XRD, and STEM analyses. This study offers valuable insights into utilizing RuO2 NPS and MOx as suitable co-catalysts developing g-C3N4 photocatalysts for H2 evolution in aqueous solution.

Enhancing Internal Electric Field of Metal-Free Donor-Acceptor Conjugated Photocatalysts for Efficient Photocatalytic Degradation of Tetracycline and CO2 Reduction.

Constructing alternating donor-acceptor (D-A) units within g-C3N4 represents an effective strategy for enhancing photocatalytic performance through improved charge carrier separation while concurrently addressing energy shortages and facilitating wastewater remediation. Here, a series of D-A-type conjugated photocatalysts (CNBTC-X) are prepared using g-C3N4 as an acceptor unit and different masses of 5-bromo-2-thiophenecarboxaldehyde (BTC) as a donor unit by a one-step thermal polymerization. CNBTC-50 presents higher photocatalytic properties for CO2 reduction coupled with tetracycline (TC) removal than those of g-C3N4, CNBTC-10, CNBTC-30, and CNBTC-70. The introduction of the unique electron-donor-acceptor structure effectively drives the separation and transfer of photoinduced carriers while reducing the internal carrier transfer hindrance. Photocatalytic experiments reveal that the CNBTC-50 photocatalyst achieves up to 94.6% TC removal under visible light irradiation conditions. Compared with that of the pristine g-C3N4, the photocatalytic degradation reaction rate constant of CNBTC-50 is significantly increased by about 3.87 times. The study examines the influence of various reaction parameters on degradation activity, including catalyst concentration, pH, and TC concentration. Additionally, LC-MS is utilized to perform a comprehensive analysis of the intermediates and pathways involved in TC degradation. Furthermore, CNBTC-50 demonstrates remarkable photocatalytic CO2 reduction activity, achieving rates of 20.83 μmol g-1 h-1 (CO) and 9.36 μmol g-1 h-1 (CH4), which are 10.68 and 5.98 times more efficient than those of g-C3N4, respectively. This work aims to offer valuable guidance for the rational design of nonmetal D-A-structured catalysts and effectively integrates reaction systems to couple CO2 reduction with antibiotic removal.

Rosuvastatin calcium electrochemical sensor based on a sulfur doped graphitic carbon nitride modified glassy carbon electrode: A metal free analysis approach

This study explored the benefits of heteroatom doping to enhance sensor efficiency by developing a low-cost, metal-free electrochemical sensor. Melamine and sulfur powders were used as precursors in a one-step thermal polymerization technique to produce sulfur-doped graphitic carbon nitride (S-g-C3N4). The structural and morphological properties of the synthesized materials were extensively analyzed using several techniques, including XRD, XPS, SEM, HRTEM, and EIS. The results show a significant decrease in impedance, indicating improved conductivity. In addition, the doping approach significantly enhanced the reduction in current receptivity compared to unmodified graphitic carbon nitride (g-C3N4). We used differential pulse voltammetry (DPV) and cyclic voltammetry (CV) to instigate the electro-oxidation of Rosuvastatin calcium (ROS), as well as concentration-dependence and selectivity studies, using a sulfur-doped graphitic carbon nitride-modified glassy carbon electrode (S-g-C3N4@GCE). S-g-C3N4@GCE exhibited outstanding performance with an extremely low detection limit of 0.10 µM and a wide linear range (5–100 µM), highlighting its potential for highly sensitive assays and its exceptional capability to operate over a broad ROS concentration range.

A Z-scheme g-C3N4/TiO2 heterojunction for enhanced performance in protecting magnesium and nickel couple from galvanic corrosion

Large interfacial contact is crucial for designing novel heterostructure materials to achieve good photoelectrochemical performance. Herein, we prepared a composite photoanode consisting of titanium dioxide (TiO2) nanotubes and graphitic carbon nitride (g-C3N4) nanosheets for enhancing the photocathodic protection (PCP) capability of the nickel-coated Mg alloy (Mg/Ni). The composite g-C3N4/TiO2 (CN/TiO2) photoanode was achieved by depositing g-C3N4 on the TiO2 nanotubes grown titanium foil via a one-step thermal polymerization of melamine and thiourea mixture. A series of characterizations, including transmission electron microscope, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectra, manifested the successful deposition of g-C3N4 at the inner wall of the TiO2 nanotubes to achieve sufficient interfacial contact and the formation of a Z-scheme heterojunction to promote the charge carriers’ transfer and separation. Compared with the pure TiO2 photoanode, the heterojunction exhibited enhanced photoelectrochemical and photocathodic protection performances, which was confirmed by the electrochemical measurements. The heterojunction achieved a duration of 6.5 h to protect the Mg-Ni couple from galvanic corrosion, representing a tenfold enhancement compared with the uncoupled Mg/Ni electrode. These findings demonstrate the great potential of constructing a unique Z-scheme heterojunction with a sizeable interfacial contact area to enhance the PCP capability of metals.

The Impact of Polymerization Atmosphere on the Microstructure and Photocatalytic Properties of Fe-Doped g-C3N4 Nanosheets

Peroxymonosulfate (PMS, SO52−)-based oxidation is an efficient pathway for degrading organic pollutants, but it still suffers from slow degradation efficiency and low PMS utilization. In this work, we report the preparation of porous Fe-doped g-C3N4 catalysts by one-step thermal polymerization using urea and transition metal salts as precursors and investigate the effect of atmosphere conditions (air and nitrogen) on the catalytic performance. Systematic characterizations show that Fe-doped g-C3N4 prepared in air (FeNx-CNO) has a larger specific surface area (136.2 m2 g−1) and more oxygen vacancies than that prepared in N2 (FeNx-CNN, 74.2 m2 g−1), giving it more active sites to participate in the reaction. Meanwhile, FeNx-CNO inhibits the recombination of photogenerated carriers and improves the light utilization. The redox cycling of Fe(III) and Fe(II) species in the photocatalytic system ensures the continuous generation of SO5•− and SO4•−. Therefore, FeNx-CNO can remove CBZ up to 96% within 20 min, which is 3.4 times higher than that of CNO and 3.1 times higher than that of FeNx-CNN, and the degradation efficiency can still retain 93% after 10 cycles of reaction. This study provides an economical and efficient method for photocatalysis in the degradation of medicines in contaminated water.

Charge reconstruction from simultaneous Fe coordination and P/O co-doping in g-C3N4 for efficient photo-reductive recovery of uranium(VI)

The risk of radionuclide leakage always threats ecological security and human health, making the recovery of uranium from nuclear wastewater a meaningful and urgent issue. However, the low-cost and efficient capture of uranium remains a challenge at present. In this study, a homemade photocatalyst of iron coordinated graphitic carbon nitride (g-C3N4) co-doped with phosphorus and oxygen (OPFCN), which was facilely synthesized through a novel one-step thermal polymerization method, exhibited superior photoelectric efficiency and photocatalytic activity towards the photo-reductive capture of uranium(VI). The simultaneous Fe coordination and P/O co-doping in framework of g-C3N4 played a synergistic effect in charge reconstruction, in which electrons migration driven by coordinated Fe and lone electron pairs delocalization from doped P/O enormously increased electron density and enhanced charge transfer, thus effectively promoting the separation of photogenerated charge carriers. The specific surface area, pore volume and average pore size of OPFCN reached 70.2 m2·g−1, 0.157 cm3·g−1 and 7.78 nm, respectively, exhibiting a trend increasingly beneficial for photocatalytic adsorption and mass transfer with successive introduction of Fe, P and O into original g-C3N4. With the simultaneous introduction of Fe, P and O, the optical absorption edge underwent a significant redshift and fluorescence emission intensity dropped by 75 % compared to that of CN, demonstrating the enhanced visible light capturing ability and significantly inhibited recombination of photogenerated charge carriers in OPFCN. As a result, a uranium capture rate of over 98 % was achieved with catalyst dosage of only 5:1 at pH 5 with OPFCN, demonstrating its competitive photo-reductive activity towards uranium(VI) uptake compared with previously reported g-C3N4-based photocatalysts. Meanwhile, OPFCN exhibited remarkable reusability and stability with even over 65 % uranium recovery rate and almost unchanged peak patterns in XRD and FT-IR in fifth reuse recycle. Additionally, it was demonstrated that e− and O2•− were the direct active species to realize the photoreduction of uranium(VI) over OPFCN, in which e− played the dominant role. The modification method of simultaneous Fe coordination and P/O co-doping would be expected to effectively promote the utilization of g-C3N4-based photocatalysts towards photo-reductive recovery of uranium(VI) from radioactive wastewater.

Interplanar spacing and nanosheet thickness regulation of carbon nitride and its “cold” catalytic hydrogen production performance under 10 W LED irradiation

Investigation of hydrogen production catalysis under low-temperature and low-power light irradiation, such as LEDs, is important for energy conservation in cold natural conditions. Interlayer charge transfer in g-C3N4 nanosheets is influenced by the crystal face spacing and nanosheet thickness, due to rapid photogenerated carrier recombination and slow charge transfer, thus enhancing hydrogen production capabilities. Few studies have controlled both crystal face spacing and nanosheet thickness simultaneously. In this research, copper-phosphorus co-doped g-C3N4 was synthesized through one-step thermal polymerization, achieving both control over nanosheet thickness and crystal surface spacing. The hydrogen production rate of 0.5 %Cu/1 %P doped g-C3N4 was increased by 5.25 times and reached 958.98 μmol/g/h under 10 °C and 10 W LED illumination. Copper and phosphorus doping that reduced (002) surface spacing of g-C3N4, resulting in thinner nanosheets. This structural modification facilitated interlayer charge transfer and suppressed photogenerated carrier recombination. This research provides a novel insight and strategy for designing hydrogen production photocatalyst at low temperatures and with low energy consumption.

Performance and mechanic insights into potassium-oxygen co-doping graphic carbon nitride for UV photocatalytic oxidation of carbamazepine

Graphitic carbon nitride (g-C3N4) has good prospect in the field of photocatalysis, but its small specific surface area and low photogenerated carrier separation efficiency limit the large-scale application in photocatalytic wastewater treatment. In this study, the one-step thermal polymerization method was employed to synthesize potassium and oxygen co-doped g-C3N4 (OCN-3), which was used in photocatalytic degradation of carbamazepine (CBZ). Compared with the original g-C3N4, the pseudo first-order kinetic constant of CBZ degradation by OCN-3 was increased from 0.00820 min−1 to 0.17529 min−1 under UV irradiation. The results of competitive oxidation kinetics experiment demonstrated that ·OH played a main role in CBZ degradation. The photoelectric experiments and calculation based on density functional theory revealed that potassium and oxygen atoms can not only regulate the local electron density, but also reduce the band gap width and promote electron transfer as well as photogenerated carrier separation. Furthermore, OCN-3 was loaded on carbon cloth to prepare supported photocatalyst, which can be conveniently applied in continuous wastewater treatment reactor, and the results shows that the degradation efficiency of CBZ remains over 90% within 600 min continuous operation when the hydraulic retention time was 1.25 h.

One-step thermal polymerization synthesis of P and K co-doped two-dimensional porous g-C3N4 photocatalyst with enhanced visible light photocatalytic activity for RhB

To improve the reaction rate of g-C3N4 for the photocatalytic degradation of RhB, we have synthesized P and K co-doped porous g-C3N4 using a simple one-step thermal polymerization technique. The 3-P/K-CN-N sample showed the highest photocatalytic activity for RhB degradation under visible light irradiation. The first-order kinetic equation for 3-P/K-CN-N had a reaction rate constant of 0.10601 min−1, which was 13.59 times higher than that of pure g-C3N4. The internal reasons for improving the catalytic activity of the 3-P/K-CN-N are the synergistic effects of heteroatom doping and morphology regulation. The co-doping of P and K reduces the band gap, broadens the response range of visible light, and promotes the separation efficiency of photogenerated carriers. The decomposition of NH4Cl and KH2PO4 together at high temperatures promotes the formation of porous g-C3N4 with a large specific surface area and numerous surface active sites. This effectively shortens the distance of photogenerated carriers migrating from the bulk phase to the surface. Furthermore, the stability and repeatability were examined. After four cycles, the catalyst degrading efficiency decreased by only 5 %. This research provides a new reference for the preparation of highly efficient and stable photocatalysts.

Dimensionally integrated nanoarchitectonics with Cu nanoparticles embedded in g-C3N4 nanosheets for efficient photocatalytic hydrogen generation and dye degradation

High-efficiency and sustainable non-noble metal cocatalyst can reduce the reaction barrier of photocatalysis or electrocatalysis to promote the hydrogen evolution reaction, which provides a feasible method for large-scale hydrogen production. A one-step thermal polymerization method was developed to successfully incorporate copper (Cu) into graphite nitride carbon (g-C3N4) through a mechanochemical pre-treatment and subsequently thermal polymerization. The synthesis controlling is a key to arrange the distribution of Cu nanoparticles in g-C3N4 nanosheets. Photocatalytic hydrogen generation tests were carried out for Cu incorporated g-C3N4 nanosheets obtained at different temperatures. Cu incorporated g-C3N4 at 680 °C (CCN-680) revealed the best H2 generation rate of 2985 μmol g-1 h−1, which was 12.7 times of that of pure g-C3N4 nanosheets obtained at same temperature. Furthermore, the degradation of methylene blue (MB) indicated that sample CCN-680-3 with optimized Cu ratio revealed enhanced performance, in which the degradation rate of MB increased from 80 to 97 % within 60 min. The introduction of Cu narrowed the band gap of g-C3N4 nanosheets, expanded light response in visible region, and finally improved greatly the separation efficiency of photogenerated charge carriers. These results are significant for highly efficient and stable photocatalysts.

Preparation and Performance Study of S-Doped g-C3N4 Photocatalyst

In order to further improve the photocatalytic performance of pure CN, SCN (1:1), SCN (1:2), and SCN (2:1) photocatalysts were prepared using a one-step thermal polymerization method. The morphology of the prepared pure CN and SCN was characterized using SEM, XRD, UV, PL, and XPS to identify the reasons for their improved performance. Proved the photocatalytic degradation effect of prepared CN and SCN on RhB solution. The photocatalytic degradation efficiency of RhB by SCN (1:1) is 90.3%, which is nearly 1.72 times higher than that of CN52.38%. After a series of characterization, it was found that the SCN photocatalyst layer is thinner than the CN photocatalyst layer, and a large number of micron sized pores are distributed on the surface of SCN, increasing the specific surface area of SCN. Introducing an appropriate mass ratio of S element will improve the crystallinity of SCN photocatalysts. An appropriate mass ratio of SCN can reduce the band gap, which decreases from 2.70 eV corresponding to CN to 2.62 eV (1:1) of SCN. The photoresponse range undergoes a red shift, which is beneficial for the photocatalytic reaction and thus improves the performance of the photocatalyst. SCN can inhibit the recombination of photo generated electrons and holes, and improve the activity of photocatalysts.

Construction of stable heterogeneous catalysts with alkali metals loaded on weakly alkaline carbon-nitrogen materials for transesterification

It is important to enhance the basicity of solid catalysts for the application of heterogeneous catalysts in the synthesis of dimethyl carbonate. Notably, the role of the carrier in the supported solid base catalyst cannot be ignored. Herein, the catalyst (named 1.0Ca/g-C3N4 (M)), prepared by one-step thermal polymerization, achieved a yield of 68.4 % and a selectivity of 96.8 % for DMC and maintained its performance after four consecutive cycles at 130 °C. It could be seen from the characterization that the amino group on the surface of the carrier, as an electron pushing group, endowed the Ca connected at its end with more abundant valence electrons, so that the catalyst exhibited a higher alkalinity. This study provides a new reference for the development of multiphase catalysts in transesterification reactions.

Peroxydisulfate nonradical activation on C[dbnd]C engineered g-C3N4: Electron transfer mechanism for selective degradation of organic contaminants

The activation of peroxydisulfate (PDS) by g-C3N4-based catalysts has captured considerable interest; however, the oxidation prowess falls short of expectations, and the inherent processes remain enigmatic. Herein, a novel CC engineered g-C3N4 (CCN) was successfully developed via a one-step thermal polymerization method for the activation of PDS. Our findings revealed that the CCN/PDS system selectively degraded various organic contaminants, operated effectively across a wide pH range (3−9), and maintained high performance in the presence of common water impurities. Experiments and theoretical calculations indicated that the electron transfer process (ETP) was the primary mechanism for phenol degradation. The introduction of CC led to charge redistribution and improved conductivity in g-C3N4. This enhancement strengthened PDS adsorption at electron-deficient carbon sites and bolstered electron transfer between PDS and organic contaminants. Moreover, a nonradical pathway predicated on ETP emerged when phenol, PDS, and CCN were present, propelled by differences in molecular orbital energies. This study not only deepens our understanding of PDS activation through the ETP but also introduces a novel strategy for the removal of organic contaminants from water.

Facile synthesis of nitrogen vacancy-enriched polymeric carbon nitride via the trace manganese-induced precursor recrystallization process for photocatalytic degradation

A nitrogen vacancy-enriched polymeric carbon nitride (MNCN-1) is successfully prepared by one-step thermal polymerization of 3-amino-1,2,4-triazole crystals obtained by the recrystallization process induced via trace manganese species in this study. With a small amount, natural pH and anionic coexist conditions, MNCN-1 shows excellent performance in photocatalytic degradation of RhB, and it also shows good removal of antibiotic contaminants. Several analytical techniques results illustrate that the induction of trace manganese species facilitates the formation of nitrogen vacancies, and the nitrogen vacancies play a significant role in optimizing band structure and inhibiting the recombination of photo-generated carriers. MNCN-1 owns the maximum abundance of nitrogen vacancies. The increased N-vacancies cause a negative shift of the conduction potential, thus enhancing the thermodynamic driving forces and the kinetic of active radical generation. The much stronger reduction capability, increased involvement of trapped electrons in the ORR reaction and more abundant reaction centers for O2 molecules make the N-vacancy-enriched MNCN-1 achieve enhanced radicals’ generation through a two-step single-electron reduction reaction (O2 → •O2-→ H2O2). This study expands the strategy of constructing nitrogen-rich vacancies in polymeric carbon nitride, and elucidates the mechanism of its defective structure in enhancing the photocatalytic activity of PCN.

Mesoporous tubular g-C3N4 as an efficient metal-free photocatalyst with peroxymonosulfate to degrade carbamazepine

In advanced oxidation processes with metal-containing catalysts, metal dissolution usually leads to reduced efficiency and biotoxicity. Therefore, it is very important to find efficient non-metallic materials. In this work, a metal-free mesoporous tubular g-C3N4 was fabricated using melamine and urea mixed according to the mass ratios of 1:12 (TPCN12) by a facile one-step thermal polymerization method. Mesoporous tubular TPCN12 was proved to be successfully synthesized by scanning electron microscope (SEM) and X-ray diffraction (XRD). Then the degradation of carbamazepine (CBZ) by activating peroxymonosulfate (PMS) of TPCN12 under visible light was investigated. It was found that degradation rate constant of CBZ in TPCN12/Vis/PMS system (0.0939 min−1) exhibited great superiority over that in TPCN12/Vis system (0.0149 min−1) and in TPCN12/PMS system, which indicated TPCN12, Vis and PMS had a synergistic effect. The dominant role of the electron transfer and the primary contribution of the holes (h+) and •O2− reactive species were revealed in TPCN12/Vis/ PMS system. Furthermore, the system showed sufficient advantages over a wide pH range and high resistance to inorganic anions. In general, the TPCN12/Vis/PMS system was capable of high stability and recyclability. This metal-free mesoporous tubular catalyst was proposed to achieve efficient and green elimination of pharmaceutical organic pollutants.

Boosted photogenerated charge carrier separation by synergy of oxygen and phosphorus co-doping of graphitic carbon nitride for efficient 2-chlorophenol photocatalytic degradation

Although graphitic carbon nitride (g-C3N4) has been attracted with its unique band structure, the ease of recombination of charge and the poor light-capturing capability limits its application in degradation of organic pollutants. Herein, via simple one-step thermal polymerization, oxygen and phosphorus dopants are simultaneously introduced into the heptazine unit of g-C3N4. The obtained O and P co-doped g-C3N4 could completely remove 2-chlorophenol (2-CP) in 30 min, much superior to bulk g-C3N4. The density functional theory (DFT) calculations and experimental characterization demonstrate that the synergy of O and P co-doping leads to the changes in bandgap structure, thus obviously enhancing the light-capturing capability and promoting the charge carrier separation. Moreover, the synergy of O and P co-doping facilitates the adsorption and enrichment of oxygen molecules at phosphorus sites, contributing to the generation of abundant reactive oxygen radicals. These radicals actively participate in the subsequent degradation of organic pollutants.

Polymeric carbon nitride loaded with atomic Cu sites for improved CO2 photocatalytic conversion performance

CO2 photocatalytic conversion has been considered as a promising strategy to reduce CO2 level and produce chemical feedstocks. However, developing highly efficient photocatalysts still remains a challenge. Here, copper (Cu) single atom sites (SAs) have been loaded into polymeric carbon nitride (CN) framework through one-step thermal polymerization method. The Cu sites loaded in CN framework can not only enhance the visible light absorption, but also accelerate the mobility of charge carriers. The range of light absorption can be extended to a longer wavelength, and the recombination of photogenerated electron and hole pairs can be considerably suppressed. Furthermore, the valence band of obtained photocatalysts shift more negative with Cu loading, resulting in stronger reduction potential for CO2 photocatalytic conversion. As a result, the CO2 photocatalytic activity can be considerably enhanced a lot. By regulating the content of Cu, the CO production amount (1.62 μmol/g.h) can be enhanced 2.7 times higher than that of bulk CN (0.6 μmol/g.h). This work proposes a facile and eco-friendly way to modify CN photocatalyst, which is inspiring to design high efficiency photocatalysts.

Growth in situ of NiSe2/Ni hybrids in N-doped carbon nanotubes for enhanced overall water splitting

Interface engineering plays an important role to improve the performance of heterostructures. Growth in situ makes the heterostructures with ideal interface natures. Here, the growth in situ of Ni components occurred on N-doping carbon nanotube (Ni-N-CNT) by one-step thermal polymerization for excellent overall water splitting. NiSe2/Ni-N-CNT with well-developed interface was created by selenium treatment of Ni-N-CNT, which improved the carrier transfer efficiency and increased electrochemical active sites. The formation of NiSe2/Ni hybrids improved hydrogen evolution reaction (HER). Ni and Se sites were proved in different electrolytes. The overpotential of NiSe2/Ni-N-CNT at -10 mA·cm−2 was 196 and 220 mV, and Tafel slope is 52 and 70 mV/dec in acidic and alkaline solutions, respectively. NiSe2/Ni-N-CNT revealed well kinetic effect compared with other control samples both in HER and oxygen evolution reaction (OER). The voltage of the electrolytic cell with NiSe2/Ni-N-CNT||NiSe2/Ni-N-CNT electrode was 1.757 and 1.954 V at 10 and 40 mA·cm−2, respectively. NiSe2/Ni-N-CNT as an electrolytic cell electrode was stable for efficient overall water splitting after 9.5 h. The formation of NiSe2/Ni-N-CNT heterostructures supplied a utilizable approach for improving HER and OER to get highly efficient catalysts.

Efficient Activation of Peroxymonosulfate by V-Doped Graphitic Carbon Nitride for Organic Contamination Remediation.

Advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) activation have been developed as an ideal pathway for completely eradication of recalcitrant organic pollutants from water environment. Herein, the V-doped graphitic carbon nitride (g-C3N4) is rationally fabricated by one-step thermal polymerization method to activate PMS for contamination decontamination. The results demonstrate the V atoms are successfully integrated into the framework of g-C3N4, which can effectively improve light absorption intensity and enhance charge separation. The V-doped g-C3N4 displays superior catalytic performance for PMS activation. Moreover, the doping content has a great influence on the activation performances. The radical quenching experiments confirm •O2-, SO4•-, and h+ are the significant species in the catalytic reaction. This work would provide a feasible strategy to exploit efficient g-C3N4-based material for PMS activation.

One-step nitrogen defect engineering of polymeric carbon nitride for visible light-driven photocatalytic O2 reduction to H2O2

Polymeric carbon nitride (PCN) is an important metal-free photocatalyst for visible light-driven hydrogen peroxide (H2O2) production from O2 reduction. Herein, we synthesized the DPCN catalysts possessing nitrogen defects by one-step thermal polymerization of urea in N2 stream. As compared to the PCN conventionally synthesized in static air, X-ray photoelectrons spectroscopy (XPS) characterization disclosed that there are more pyridinic N defects in the DPCN catalysts, which is attributed to the removal of a proportion of NH3 released from urea pyrolysis by flowing N2. UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Mott–Schottky, steady-state and time-resolved photoluminescence (PL), and electrochemical impedance spectroscopy (EIS) characterizations revealed that the introduction of the nitrogen defects narrows down the band gap, improves the density of the photoexcited charge carriers, prolongs the lifetime of the charge carriers, and enhances the charge transfer efficiency. In visible light-driven photocatalytic O2 reduction to H2O2, the optimal DPCN catalyst afforded an activity of 4.35 times that of the PCN catalyst and a H2O2 concentration of 2.83 mmol L–1 after 10 h of visible light irradiation. This one-step thermal polymerization approach is valid when replacing N2 stream with Ar and He streams.