g-C3N4 Catalyst Research Articles

Transition metal nickel nanoparticle-decorated g-C3N4 photocatalyst for improving tetracycline hydrochloride degradation

Metallic nickel nanoparticles (Ni0 NPs)-supported g-C3N4 have been developed using a solvothermal technique in N,N-dimethylformamide solvent. A uniformly dispersion of Ni0 NPs anchored on a g-C3N4 photocatalyst can improve the photocatalytic efficiency. The optimized Ni/g-C3N4 catalyst demonstrated a high photodegradation rate of TCH at 6.0 × 10−3 min−1 under LED light irradiation, which was approximately three times greater than that of the bare g-C3N4 catalyst. This superior performance originates from the capable separation of electron-hole pairs, facilitated by the strong interaction between Ni0 NPs and the host g-C3N4, as supported by optical and electrochemical property analysis. Our work provides a facile manner for the effective degradation of pollutants using heterojunction photocatalysts.

Heat-Assisted Visible Light Catalytic PMS for Diclofenac Degradation: Mn-Doped g-C3N4 Catalysts and Synergistic Catalytic Mechanism

Heat-Assisted Visible Light Catalytic PMS for Diclofenac Degradation: Mn-Doped g-C3N4 Catalysts and Synergistic Catalytic Mechanism

Bismuth doped g-C3N4 composites for enhanced photocatalytic degradation of ciprofloxacin

There is an increase in presence of various contaminants particularly related to antibiotics in the water sources affecting the environment. This study focusses on designing and development of innovative bismuth doped g-C3N4 for photocatalytic degradation of ciprofloxacin. Diverse Bi doped g-C3N4 catalysts, with metal loadings ranging from (0.5 – 2 wt%), were synthesized and characterized using advanced techniques. The introduction of Bi doped g-C3N4 drastically lowered the bandgap, with the introduction of Bi loadings. A highest ∼79% degradation was observed in 60 min using 1 wt% Bi doped g-C3N4, drastically outperforming bare g-C3N4 (∼63%). Kinetic studies were carried in the temperature range of (10 – 25°C), revealing an activation energy of 23.1 kJ/mol. Scavenging tests were carried with different additives (EDTA, IPA, AgNO3), among these lowest degradation (∼45%) was observed with EDTA which confirms that the h+ species controlling the degradation mechanism. Overall, this study reveals an improved photocatalytic activity attributed to better charge transfer and synergetic effects among Bi and g-C3N4, demonstrating the potential for pollutant removal present in wastewater.

Photocatalytic activation of peroxymonosulfate by Ti-oxo clusters grafted carbon nitride: Enhanced charge transfer and bisphenol A degradation efficiency

Photocatalytic peroxymonosulfate (PMS) activation process is promising for the organic wastewater treatment. A simple amide bonding strategy has been developed to synthesized Ti-oxo clusters (TiOCs)-g-C3N4 (TiOCs-CN) catalyst. The prepared TiOCs-CN was used to remove bisphenol A (BPA) under simulated sunlight-driven PMS. The experimental and computational results demonstrate that the incorporation of TiOCs can efficiently regulate the electronic structure of CN. Thus, an excellent performance with a BPA removal rate of 100 % and a totalorganic carbon(TOC) removal rate of 87.2 % within 40 min was achieved in the AM 1.5/PMS-TiOCs-CN system.Among, the reaction rate constant of AM 1.5/PMS-TiOCs-CN (97.24 × 10−3 min−1) is higher than that of AM 1.5/PMS-CN (25.10 × 10−3 min−1) by nearly 4 times. The synergistic effect of photocatalytic PMS activation greatly facilitated the generation of reactive radicals and obviously increased the removal rate of BPA. This work can offer inspiration for rational design of high efficiency photocatalysts in the PMS oxidation process for organic wastewater remediation.

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.

Metal Doped-MoS2/g-C3N4 Nanocomposites for Antibiotics Degradation with Photo-Fenton Reaction Process: Defect Engineering, Synergistic Effects, and Degradation Mechanisms

Currently, the energy crisis and environmental pollutions due to the growth of industrialization and urbanization become gradually a prominent and serious issue. Due to these reasons, we aimed to design photoactive metal-doped MoS2/g-C3N4 nanocomposites photocatalysts for the degradation of antibiotics. The degradation of organic pollutants with photocatalysis is considered as green, ecofriendly, economical, and promising methods. Herein, ultrathin g-C3N4 was prepared with simple method and combined with metal-doped MoS2 (Mg-doped MoS2) with varying the amounts of dopants. The prepared photocatalyst materials were tested for the degradation of ciprofloxacin in the photo-Fenton reaction process. The optimum amount of metal-doped MoS2/g-C3N4 nanocomposites photocatalysts showed enhanced catalytic performance and degrades 72% of ciprofloxacin while 52 and 48 % of degradations were achieved with MoS2 and g-C3N4 catalysts, respectively. Here, the key significant problems of the individual components were solved via synergistic effects in the photocatalytic degradation system. The results also offer an opportunity to enhance the electronic structures of the crystalline materials. Moreover, the metal-doping will also create defects on the MoS2 and improves the charge transfer ability of the photocatalyst. The results proved that the metal-doped MoS2/g-C3N4 nanocomposites photocatalysts could be a promising photo-Fenton catalyst system in the environmental remediation.

Enhanced Fenton Degradation of Tetracycline over Cerium-Doped MIL88-A/g-C3N4: Catalytic Performance and Mechanism.

Since enormous amounts of antibiotics are consumed daily by millions of patients all over the world, tons of pharmaceutical residuals reach aquatic bodies. Accordingly, our study adopted the Fenton catalytic degradation approach to conquer such detrimental pollutants. (Ce0.33Fe) MIL-88A was fabricated by the hydrothermal method; then, it was supported on the surface of g-C3N4 sheets using the post-synthetic approach to yield a heterogeneous Fenton-like (Ce0.33Fe) MIL-88A/10%g-C3N4 catalyst for degrading the tetracycline hydrochloride drug. The physicochemical characteristics of the catalyst were analyzed using FT-IR, SEM-EDX, XRD, BET, SEM, and XPS. The pH level, the H2O2 concentration, the reaction temperature, the catalyst dose, and the initial TC concentration were all examined as influencing factors of TC degradation efficiency. Approximately 92.44% of the TC was degraded within 100 min under optimal conditions: pH = 7, catalyst dosage = 0.01 g, H2O2 concentration = 100 mg/L, temperature = 25 °C, and TC concentration = 50 mg/L. It is noteworthy that the practical outcomes revealed how the Fenton-like process and adsorption work together. The degradation data were well-inspected by first-order and second-order models to define the reaction rate. The synergistic interaction between the (Ce0.33Fe) MIL-88A/10%g-C3N4 components produces a continuous redox cycle of two active metal species and the electron-rich source of g-C3N4. The quenching test demonstrates that •OH is the primary active species for degrading TC in the H2O2-(Ce0.33Fe) MIL-88A/10%g-C3N4 system. The GC-MS spectrum elucidates the yielded intermediates from degrading the TC molecules.

W single-atom mediated singlet oxygen formation on carbon nitride for powerful photocatalytic abatement of organic pollutants

Active single-atom W anchoring on graphitic carbon nitride (g-C3N4) with interplanar four-coordination with N was achieved via a microwave hydrothermal process followed by thermal polymerization. The optimal monoatomic W incorporated g-C3N4 (W-CN) catalyst exhibited a high photocatalytic activity toward a wide range of pharmaceutical and personal care products (PPCPs). The anchoring of W single atom narrowed the energy-band, negatively shifted the conduction band of g-C3N4, and promoted the charge transfer and photogenerated carrier separation. Moreover, W single-atom intercalation obviously favored the formation of singlet oxygen (1O2), as validated by the active species capture test and density functional theory (DFT) calculation, which played an important role in the photocatalytic degradation of PPCPs. The treatment of actual wastewater, toxicity assessment and hemp-pea-growth experiments further showed that the W-CN photocatalyst could effectively degrade the organic pollutants and reduce their poisonousness in the water environment. This work offers a facile route to obtain reactive g-C3N4 with single-metal active sites and some insights into its activity enhancement for the abatement of organic pollutant-containing wastewater.

Boosted photocatalytic performance of cobalt ferrite anchored g-C3N4 nanocomposite toward various emerging environmental hazardous pollutants degradation: insights into stability and Z-scheme mechanism.

In this study, a highly efficient CoFe2O4-anchored g-C3N4 nanocomposite with Z-scheme photocatalyst was developed by facile calcination and hydrothermal technique. To evaluate the crystalline structure, sample surface morphology, elemental compositions, and charge conductivity of the as-synthesized catalysts by various characterization techniques. The high interfacial contact of CoFe2O4 nanoparticles (NPs) with g-C3N4 nanosheets reduced the optical bandgap from 2.67 to 2.5eV, which improved the charge carrier separation and transfer. The photo-degradation of methylene blue (MB) and rhodamine B (Rh B) aqueous pollutant suspension under visible-light influence was used to investigate the photocatalytic degradation activity of the efficient CoFe2O4/g-C3N4 composite catalyst. The heterostructured spinel CoFe2O4 anchored g-C3N4 photocatalysts (PCs) with Z-scheme show better photocatalytic degradation performance for both organic dyes. Meanwhile, the efficiency of aqueous MB and Rh B degradation in 120 and 100min under visible-light could be up to 91.1% and 73.7%, which is greater than pristine g-C3N4 and CoFe2O4 catalysts. The recycling stability test showed no significant changes in the photo-degradation activity after four repeated cycles. Thus, this work provides an efficient tactic for the construction of highly efficient magnetic PCs for the removal of hazardous pollutants in the aquatic environment.

Enhanced hydrogen peroxide production under visible light via pyrimidine and glucose polymer modified graphitic carbon nitride in pure water

Photocatalytic H2O2 production by g-C3N4 (CN) has drawn intense research attention in the past decade. However, it suffers from drawbacks of weak light absorption capacity and rapid recombination of photogenerated electron-hole pairs. Here, we report a 4, 6-diamino-2-mercaptomidine (DAMP) and glucose (GLU) polymer modified CN (CN-DAMP-GLU) to enhance the photocatalytic performance of CN. The reported modified CN shows a high H2O2 production rate of 284.0 μmol g−1h−1 in pure water, surpassing most of the reported modified g-C3N4 catalysts. The mechanistic study confirms that the rapid conversion of •O2− is the key step in the visible-light-driven 2e− oxygen reduction reaction. This step favors efficient H2O2 generation and ensures the stable photocatalytic performance of the system. Experimental and DFT results further reveal that the donor-mediator-acceptor structure (polyfuran-DAMP-CN) with DAMP as the electron transfer mediator can inhibit the electron-hole recombination. We also demonstrate that this photocatalytic H2O2 production system can effectively degrade ciprofloxacin (CIP) through Fenton reaction. This work will promote the development of g-C3N4 for efficient photocatalytic production of H2O2 and possible applications in organic pollutant removal.

Enhancing photocatalytic reduction of Cr(VI) in water through morphological manipulation of g-C3N4 photocatalysts: A comparative study of 1D, 2D, and 3D structures

In this research, the dimensional catalysts of pure g-C3N4 photocatalysts (1D, 2D, and 3D) were investigated for the reduction of the highly toxic/carcinogenic Cr(VI) under visible light irradiation. The catalysts underwent explanation through various surface analysis techniques. According to the BET data, the specific surface area of the 3D catalyst was 1.3 and 7 times higher than those of the 2D and 1D CN catalysts, respectively. The 3D catalyst demonstrated superior performance, achieving an efficiency greater than 99% within 60 min under visible light irradiation in the presence of EDTA due to the abundance of active sites. The study also delved into the influence of factors such as the amount of EDTA-hole scavenger, pH, catalyst dosage, and temperature on the photocatalytic reduction of Cr(VI). Moreover, the 3D catalyst showed excellent reusability, maintaining an efficiency of more than 80% even after 10 cycles, and performed effectively in real water samples. The 3D CN catalyst, with its facile synthesis process, excellent visible light harvesting properties, high reduction efficiency that sustains over multiple cycles, and outstanding performance in real water samples, presents a significant advancement for practical applications in environmental remediation. This research contributes to a new understanding of developing efficient degradation methods for heavy metals in polluted water, highlighting the potential of 3D g-C3N4 catalysts in environmental cleanup efforts.

Synthesis of polymeric 2D-graphitic carbon nitride (g-C3N4) nanosheets for sustainable photodegradation of organic pollutants

A superficial, one step thermal polycondensation method has been employed for the manifestation of graphene like graphitic carbon nitride (g-C3N4) catalyst. The as synthesized g-C3N4 was well characterized by SEM and EDAX analysis, XRD, ATR-IR, FTIR, Fluorescence spectroscopy, Raman spectroscopy and UV–Visible spectroscopy which provide structural, morphological assemblage relating to the structure of g-C3N4. The g-C3N4 showed that an outstanding photochemical stability, morphology, conductive carbon framework and superior photocatalytic activity. The band gap value of g-C3N4 is 2.34 eV determined using Tauc plot. Due to low band gap (2.33 eV) and unique morphology which provides high separation and migration ability of the photogenerated charges, the g-C3N4 shows enhanced photocatalytic activity for the removal of many organic dyes such as Rhodamine B (RhB), Crystal Violet (CV), Methylene Blue (MB), Methyl Orange (MO), Naphthol Orange (NO) and a phenol derivative, p-Nitrophenol (p-NP). Among them, RhB dye was degraded almost 81 % at 90 min under sunlight irradiation in presence g-C3N4 while other dyes and p-NP was degraded at lower rate. From the experimental data, it was found that MO and p-NP degradation rate was least. The rate constant for degradation of Rh B is 1.1 × 10−2 min−1. Therefore, g-C3N4 can be used as an efficient photocatalyst for waste water treatment by the removal of such organic pollutants.

Ru–modified graphitic carbon nitride for the solar light–driven photocatalytic H2O2 synthesis

Hydrogen peroxide (H2O2) is an efficient and environmentally friendly oxidant as well as a promising energy-carrier alternative to hydrogen. Its solar light-driven photocatalytic synthesis from H2O and O2 is a high-prospect sustainable alternative to the industrial anthraquinone process. Hybrid Ru-modified graphitic carbon nitride (g-C3N4) catalysts were prepared by thermal polymerisation of melamine/Ru(III) acetylacetonate mixtures, and subsequent thermal exfoliation. Simultaneous Ru incorporation and thermal exfoliation impacted the morphology and the structure of the g-C3N4 sheets, and low-atomicity Ru species with small nanoclusters and single atoms were observed only in the Ru-modified exfoliated g-C3N4 photocatalysts. We demonstrated the potential of a joint thermal exfoliation and modification with Ru to enhance the H2O2 synthesis efficiency of the g-C3N4 photocatalyst under simulated sunlight. A volcano-type behavior was observed with increasing the Ru content, and the best performance was obtained for exfoliated g-C3N4 with an ultra-low Ru content of 0.019 wt.%, that outperformed both its bulk counterpart and the pristine exfoliated reference in terms of initial H2O2 synthesis rate and H2O2 formation rate constant. The enhanced performance was attributed to the presence of highly dispersed low atomicity Ru as well as to more accessible active sites and carrier migration channels. Quenching experiments revealed a mixed reactional pathway involving both two-step one-electron and one-step two-electron O2 reduction in the photocatalytic H2O2 production.

Construction of oxygen-doped g-C3N4/BiOCl (S-scheme) heterojunction: Efficient degradation of tetracycline in wastewater

Graphitic phase carbon nitride (g-C3N4) demonstrates significant promise in the photocatalytic degradation of organic pollutants, but the rapid recombination of photogenerated electron-hole pairs seriously restricts its degradation capacity. In this study, an innovative heterostructural anion regulation strategy based on g-C3N4 was proposed to significantly enhance the degradation performance of tetracycline. Initially, we regulated the electron configuration of g-C3N4 through O doping to optimize the active sites at the reaction interface. Subsequently, the S-scheme heterojunction was constructed by introducing BiOCl to stimulate the pumping effect and form efficient build-in electric field electron channels. The oxygen-doped g-C3N4/BiOCl (OCN/BiOCl) heterojunction material obtained through aforementioned modification exhibited a degradation efficiency of 89.33 % towards 20 mg·L−1 tetracycline (90 min light reaction, 30 min dark reaction), which was 2.5 times that of conventional g-C3N4 catalyst. In particular, density functional theory calculations and ultraviolet photoelectron spectroscopy jointly revealed the unique chemical environment and electronic structure between OCN and BiOCl due to the formation of the build-in electric field, thereby providing enhanced pathways for the migration of photogenerated currents. Meanwhile, the heterostructure significantly reduced the transport distance of photo-induced charge and minimizes the internal transmission resistance. It enhances the efficiency of separating photogenerated electrons and hole pairs, which is the key mechanism for greatly improving the photocatalytic degradation performance of OCN/BiOCl materials. In summary, the hetero-anion regulation strategy proposed in this study addresses the issue of rapid recombination of photogenerated charges in g-C3N4, providing a new perspective for efficient control of organic pollutants in the environment driven by g-C3N4 photocatalyst.

Photocatalytic degradation of sulfamethazine using g-C3N4/TiO2 heterojunction photocatalyst: Performance, mechanism insight and degradation pathway

In the present research, Z-scheme g-C3N4/TiO2 heterojunction composite photocatalysts with varied g-C3N4 content were successfully prepared using the sol-gel technique combined with calcination methods. The morphology, crystallinity, chemical composition, and optical properties of the synthesized catalysts were characterized employing a series of techniques. Sulfamethazine (SMZ) was selected as the model pollutant to evaluate the photocatalytic activity of the prepared catalysts employing a 500 W xenon lamp as the light source to simulate sunlight. The results demonstrated that within 180 min of irradiation, 94.8 % of SMZ was removed by using the optimal photocatalyst (0.4CN/TiO2 composite sample), affording an apparent first-order rate coefficient of 0.0152 min−1 which was 3.8 or 2.0 times as much as that involving single g-C3N4 or TiO2 catalyst, respectively. The effects of catalyst dosage, initial pH, different water matrices, different substrates, and inorganic ions on the performance of 0.4CN/TiO2 photocatalyst were explored. Furthermore, the 0.4CN/TiO2 composite also displayed satisfactory cyclic stability. The results of radical quenching experiments revealed that the key active species in SMZ degradation were hydroxyl radicals (•OH), superoxide radicals (O2•−), and holes (h+). The efficient separation of photo-generated electrons and holes originating in the formation of a Z-scheme g-C3N4/TiO2 heterojunction was evidenced by photoluminescence and electrochemical impedance spectroscopy determination and should be responsible for the enhanced catalytic activity of the 0.4CN/TiO2 sample. In addition, the plausible pathways for the aqueous degradation of SMZ were suggested according to the identified degradation intermediates employing the HPLC/MS technique. In summary, the current research provides a novel insight into the development of Z-scheme heterojunctions in the realm of organic pollutant treatment.

Production of alkyl levulinates as a versatile precursor by phosphomolybdate-impregnated g-C3N4 catalysts

Alkyl levulinates are a class of compounds that have diverse applications and show great promise as environmentally friendly fuel additives. These compounds are renewable, have a high energy density, and can easily be used with existing infrastructure. Therefore, they can play a significant role in contributing to the ongoing endeavors toward more sustainable and efficient energy solutions. In this study, alkyl levulinates (ALs) as fuel additives were synthesized using phosphomolybdate g-C3N4 (PMox/g-C3N4) as an efficient catalyst for the esterification reaction of levulinic acid (LA) with three diverse alcohols, namely ethanol, 1-butanol, and 1-hexanol. An experimental investigation assessed the impact of several key factors, such as temperature, the volumetric proportion of LA to alcohol, reaction time, catalyst loading, and catalyst amount, on the chemical process under study. For ethyl levulinate (EL) a 76 % yield was obtained at 130 °C, 8 h reaction time, LA: ethanol 1:12, and 20 mg catalyst. Also, a > 99 % yield was obtained for the butyl levulinate (BL) production at 130 °C, 8 h reaction time, LA: alcohol proportion of 1:12, and 10 mg catalyst. Hexyl levulinate (HL) was achieved with 71 % yield under the optimal condition of 230 °C, 8 h reaction time, LA: hexanol 1:20, and 10 mg catalyst.

Recent progresses in synthesis and modification of g-C3N4 for improving visible-light-driven photocatalytic degradation of antibiotics.

Graphitic carbon nitride (g-C3N4) is a widely studied visible-light-active photocatalyst for low cost, non-toxicity, and facile synthesis. Nonetheless, its photocatalytic efficiency is below par, due to fast recombination of charge carriers, low surface area, and insufficient visible light absorption. Thus, the research on the modification of g-C3N4 targeting at enhanced photocatalytic performance has attracted extensive interest. A considerable amount of review articles have been published on the modification of g-C3N4 for applications. However, limited effort has been specially contributed to providing an overview and comparison on available modification strategies for improved photocatalytic activity of g-C3N4-based catalysts in antibiotics removal. There has been no attempt on the comparison of photocatalytic performances in antibiotics removal between modified g-C3N4 and other known catalysts. To address these, our study reviewed strategies that have been reported to modify g-C3N4, including metal/non-metal doping, defect tuning, structural engineering, heterostructure formation, etc. as well as compared their performances for antibiotics removal. The heterostructure formation was the most widely studied and promising route to modify g-C3N4 with superior activity. As compared to other known photocatalysts, the heterojunction g-C3N4 showed competitive performances in degradation of selected antibiotics. Related mechanisms were discussed, and finally, we revealed current challenges in practical application.

Constructing Te doped-CeO2/g-C3N4 heterojunction nanocomposite for visible-light-driven photodegradation of dye pollutant

Industrial wastewater is a particular threat to humans and the surrounding environment, therefore, the design of visible light photocatalysts is urgently required for wastewater treatment. Here, Te-doped CeO2 (CeTeO2) and its heterostructure composite with g-C3N4 (CeTeO2/g-C3N4) catalysts were synthesized via simple sol-gel and ultrasonication techniques. Several characterization tools were used to confirm the composition, morphology, structure, light absorption, and surface features of the CeTeO2 and CeTeO2/g-C3N4 samples. XRD and FTIR confirmed the structural features, BET analysis showed CeTeO2/g-C3N4 gains higher surface area, SEM analysis revealed the morphology, and EDX confirmed the elemental composition. Optical band gaps 2.85 eV and 2.67 eV for CeTeO2 and CeTeO2/g-C3N4 were calculated from UV–vis data. The synthesized catalysts were tested for photocatalytic application, and CeTeO2/g-C3N4 showed excellent results against methylene blue (MB), having 99.9 % degradation efficiency in 60 min. The excellent catalytic results were credited to the S-scheme CeTeO2/g-C3N4 heterojunction, which broadened the absorption in visible spectra and increased redox ability. A model of charge transfer was proposed based on the results that were attained.

Insights into bimetallic single-atom-doped g-C3N4 photo-catalysts for CO2 conversion to HCOOH: A DFT study

Developing low-cost, high-efficiency non-noble metallic photocatalytic materials is crucial for CO2 reduction. This paper investigates the substitution of noble metals dopant to a bimetallic non-noble Fe/Co dopant for g-C3N4 to enhance the photocatalytic CO2 reduction performance via density functional theory (DFT) calculations. This study examines the structure, electronic properties, CO2 adsorption configurations, and the transition states and Gibbs free energy of CO2 reduction to HCOOH on noble metal Pt/g-C3N4 doped, single-atom Fe/g-C3N4 doped, and bimetallic Fe/Co doped g-C3N4 catalysts, revealing the mechanisms of catalyst-mediated CO2 reduction. The results demonstrate that the introduction of Fe/Co bimetallic atoms leads to more efficient charge transfer, attributed to the synergistic and electronic effects of the bimetallic coupling, with a charge of 1.264, which is 2.2 and 1.2 times greater than that of Pt and Fe doped g-C3N4, respectively. Furthermore, the stronger adsorption energy of CO2 molecules on Fe/Co/g-C3N4 compared to pure g-C3N4, Pt/g-C3N4, and Fe/g-C3N4 indicates that adsorption on Fe/Co/g-C3N4 is more conducive to CO2 activation. The CO2 reduction reaction (CO2RR) calculations reveal that Fe/Co/g-C3N4 exhibits a lower reaction barrier of 0.789 eV compared to noble metal-doped Pt and single-atom Fe, due to the reduction of the reaction mechanism's energy barrier by the Fe/Co bimetallic doped g-C3N4, which facilitates a more effective reduction of CO2 to HCOOH. As a result, Fe/Co/g-C3N4 emerges as an effective alternative to noble metal-based photocatalysts. This study provides theoretical guidance for the preparation of efficient non-noble metal photocatalysts.

Photocatalytic peroxydisulfate activation for dissolved organic matter degradation in eutrophic lake water using S-scheme BiVO4/g-C3N4 3D/2D heterojunction under visible light

Large amounts of carbon are stored primarily in dissolved organic matter (DOM), which plays an important indicator of lake eutrophication. However, removing DOM from eutrophic lakes remains a major challenge. Herein, a novel S-scheme flower-like microsphere BiVO4/nanosheet g-C3N4 3D/2D heterojunction was successfully constructed using a two-step method for DOM degradation of real eutrophic lake water in the presence of peroxydisulfate (PDS). 1.0-BiVO4/g-C3N4/PDS exhibited highly efficient photocatalytic performance with an 87.8 % removal rate of DOM for 60 min, which was 5.3 and 8.9 times higher than BiVO4/PDS and g-C3N4/PDS, respectively. Sulfate radical (·SO4−), hydroxyl radical (·OH) and singlet oxygen (1O2) were mainly responsible for DOM degradation in the 1.0-BiVO4/g-C3N4/PDS system, and the transformation pathway of 1O2 was emphatically analyzed. In addition, the changes of fluorescence components in DOM were detected using synchronous fluorescence spectra, second derivative spectra, and two-dimensional correlated spectroscopy analysis. Humic-like fluorescence, fulvic-like fluorescence, and protein-like substances were removed higher than 85.30 %, 73.02 %, and 67.23 % by the 1.0-BiVO4/g-C3N4 catalyst activating the PDS under visible light (VL), respectively. When the toxicity of catalytically treated eutrophic lake water was estimated by growth inhibition of Escherichia coli, the biotoxicity of DOM decreased continuously in the BiVO4/g-C3N4/PDS/VL coupling process. Theoretical calculations and photoelectrochemical tests suggested that the BiVO4/g-C3N4/PDS catalytic activity enhancement was attributed to the S-scheme mechanism and hybrid advanced oxidation process. It is expected that this work can provide new insight into DOM degradation in eutrophic lake water by the heterogeneous photocatalysis combined with the PDS activation system.