N-doped Ti3C2-reinforced porous g-C3N4 for photocatalytic contaminants degradation and nitrogen reduction

Herein, a series of N-doped Ti3C2/porous g-C3N4 composites are ultrasonically prepared from N-doped Ti3C2 and porous g-C3N4 under N2 atmosphere. The structure, morphology, and optical characteristics of the as-prepared composites are characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, etc. Moreover, photocatalytic measurements show that N-doped Ti3C2 is an excellent modifier for porous g-C3N4 to heighten its photocatalytic activity. Only 44.1% of rhodamine B can be degraded by the photocatalysis of pristine porous g-C3N4, while the photocatalytic degradation ratio of rhodamine B can reach up to 97.5% for the optimal N-doped Ti3C2 loading composites under visible light for 15 min. Moreover, the photocatalytic tests of N2 fixation confirm that the optimal composites show the highest production yield of NH4+ (11.8 μmol gcat-1 h-1), which is 2.11-folds more than that of porous g-C3N4 (5.6 μmol gcat-1 h-1). The reinforced photocatalytic properties are revealed to profit from the more photogenerated electrons and holes' separation, higher ability for light response, and more abundant active sites. This work develops the route for boosting the photocatalytic properties of porous g-C3N4 with N-doped Ti3C2.

Boosted Photocatalytic Performance for Antibiotics Removal with Ag/PW12/TiO2 Composite: Degradation Pathways and Toxicity Assessment

Photocatalyst is the core of photocatalysis and directly determines photocatalytic performance. However, low quantum efficiency and low utilization of solar energy are important technical problems in the application of photocatalysis. In this work, a series of polyoxometalates (POMs) [H3PW12O40] (PW12)-doped titanium dioxide (TiO2) nanofibers modified with various amount of silver (Ag) nanoparticles (NPs) were prepared by utilizing electrospinning/photoreduction strategy, and were labelled as x wt% Ag/PW12/TiO2 (abbr. x% Ag/PT, x = 5, 10, and 15, respectively). The as-prepared materials were characterized with a series of techniques and exhibited remarkable catalytic activities for visible-light degradation tetracycline (TC), enrofloxacin (ENR), and methyl orange (MO). Particularly, the 10% Ag/PT catalyst with a specific surface area of 155.09 m2/g and an average aperture of 4.61 nm possessed the optimal photodegradation performance, with efficiencies reaching 78.19% for TC, 93.65% for ENR, and 99.29% for MO, which were significantly higher than those of PW12-free Ag/TiO2 and PT nanofibers. Additionally, various parameters (the pH of the solution, catalyst usage, and TC concentration) influencing the degradation process were investigated in detail. The optimal conditions are as follows: catalyst usage: 20 mg; TC: 20 mL of 20 ppm; pH = 7. Furthermore, the photodegradation intermediates and pathways were demonstrated by HPLC-MS measurement. We also investigated the toxicity of products generated during TC removal by employing quantitative structure-activity relationship (QSAR) prediction through a toxicity estimation software tool (T.E.S.T. Version 5.1.2.). The mechanism study showed that the doping of PW12 and the modification of Ag NPs on TiO2 broadened the visible-light absorption, accelerating the effective separation of photogenerated carriers, therefore resulting in an enhanced photocatalytic performance. The research provided some new thoughts for exploiting efficient and durable photocatalysts for environmental remediation.

Ultrafine ZnCo2O4 QD-incorporated carbon nitride mediated peroxymonosulfate activation for norfloxacin oxidation: performance, mechanisms and pathways

Recently, peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) are being actively investigated as a potential technology for water decontamination and many efforts have been made to improve the activation efficiency of PMS. Herein, a 0D metal oxide quantum dot (QD)-2D ultrathin g-C3N4 nanosheet (ZnCo2O4/g-C3N4) hybrid was facilely fabricated through a one-pot hydrothermal process and used as an efficient PMS activator. Benefiting from the restricted growth effect of the g-C3N4 support, ultrafine ZnCo2O4 QDs (∼3-5 nm) are uniformly and stably anchored onto the surface. The ultrafine ZnCo2O4 possesses high specific surface areas and shortened mass/electron transport route so that the internal static electric field (Einternal) formed in the interface between p-type ZnCo2O4 and the n-type g-C3N4 semiconductor could speed up the electron transfer during the catalytic reaction. This thereby induces the high-efficiency PMS activation for rapid organic pollutant removal. As expected, the ZnCo2O4/g-C3N4 hybrid catalysts significantly outperformed individual ZnCo2O4 and g-C3N4 in catalytic oxidative degradation of norfloxacin (NOR) in the presence of PMS (95.3% removal of 20 mg L-1 of NOR in 120 min). Furthermore, the ZnCo2O4/g-C3N4-mediated PMS activation system was systematically studied in terms of the identification of reactive radicals, the impact of control factors, and the recyclability of the catalyst. The results of this study demonstrated the great potential of a built-in electric field-driven catalyst as a novel PMS activator for the remediation of contaminated water.

Adducing Knowledge Capabilities of Instrumental Techniques Through the Exploration of Heterostructures' Modification Methods

The ongoing evolution of technology has facilitated the global research community to rapidly escalate the constant development of novel advancements in science. At the forefront of such achievements in the field of photocatalysis is the utilisation, and in oftentimes, the adaptation of modern instrumentation to understand photo-physical properties of complex heterostructures. For example, coupling in-situ X-ray Raman scattering spectroscopy for real-time degradation of catalytic materials.

Tunable band structure of synthesized carbon dots modified graphitic carbon nitride/bismuth oxychlorobromide heterojunction for photocatalytic degradation of tetracycline in water

In this study, graphitic carbon nitride (CN) decorated with carbon quantum dot (CQD) and bismuth oxychlorobromide (BiOCl_xBr_1-x) was fabricated by calcination and hydrothermal methods. The morphology characterization of the synthesized photocatalyst revealed that CQD and BiOCl_xBr_1-x solid solution were deposited on the CN surface. CQD served as the electron reservoir, which could reduce the recombination of electron-hole pairs, thus improving the overall photocatalytic performance. The synergistic effect of 1 wt% CQDs and BiOCl_0.75Br_0.25 markedly improved the interfacial charge transfer efficiency and light-harvesting capacity of the composite. The degradation rate of tetracycline (TC) over CN/CQD/BiOCl_0.75Br_0.25 was 83.4 % after 30 min and favorable stability with near-initial capacity under visible light irradiation. Meanwhile, the reaction mechanism of the photocatalytic performance was demonstrated by the analysis of the surface adsorption sites, efficient utilization of visible light, and charge carrier transfer. The degradation by-products and potential degradation pathways were also analyzed using liquid chromatography-mass spectrometry. Finally, the toxicity estimation software tool (T.E.S.T) analysis indicated that the toxicity of most intermediates was lower than TC. This work provideed a strategy for fabricating visible light (VL) photocatalyst with excellent photocatalytic activity, furnishing a new insight for interface charge transfer.

Synthesis and Property Examination of Er2FeSbO7/BiTiSbO6 Heterojunction Composite Catalyst and Light-Catalyzed Retrogradation of Enrofloxacin in Pharmaceutical Waste Water under Visible Light Irradiation

A new photocatalyst, Er2FeSbO7, was prepared by solid phase sintering using the high-temperature synthesis method for the first time in this paper. Er2FeSbO7/BiTiSbO6 heterojunction (EBH) catalyst was prepared by the solvent thermal method for the first time. Er2FeSbO7 compound crystallized in the pyrochlore-type architecture and cubelike crystal system; the interspace group of Er2FeSbO7 was Fd3m and the crystal cellular parameter a of Er2FeSbO7 was 10.179902 Å. The band gap (BDG) width of Er2FeSbO7 was 1.88 eV. After visible light irradiation of 150 minutes (VLGI-150min) with EBH as a photocatalyst, the removal rate (RR) of enrofloxacin (ENR) concentration was 99.16%, and the total organic carbon (TOC) concentration RR was 94.96%. The power mechanics invariable k toward ENR consistency and visible light irradiation (VLGI) time with EBH as a photocatalyzer attained 0.02296 min−1. The power mechanics invariable k which was involved with TOC attained 0.01535 min−1. The experimental results showed that the photocatalytic degradation (PCD) of ENR within pharmaceutical waste water with EBH as a photocatalyzer under VLGI was in keeping with the single-order reactivity power mechanics. The RR of ENR with EBH as a photocatalyzer was 1.151 times, 1.269 times or 2.524 times that with Er2FeSbO7 as a photocatalyst, BiTiSbO6 as a photocatalyst, or N-doping TiO2 (N-TO) as a photocatalyst after VLGI-150min. The photocatalytic activity, which ranged from high to low among above four photocatalysts, was as follows: EBHP > Er2FeSbO7 > BiTiSbO6 > N-TO. After VLGI-150min toward three periods of the project with EBH as a photocatalyst, the RR of ENR attained 98.00%, 96.76% and 95.60%. The results showed that the stability of EBH was very high. With appending trapping agent, it could be proved that the oxidative capability for degrading ENR, which ranged from strong to weak among three oxidic radicals, was as follows: superoxide anion > hydroxyl radicals (HRS) > holes. This work provides a scientific basis for the research and oriented leader development of efficient heterojunction catalysts.

Decontamination of emerging pharmaceutical pollutants using carbon-dots as robust materials

Environmental pollution is a critical issue that requires proper measures to maintain environmental health in a sustainable and effective manner. The growing persistence of several active pharmaceutical residues, such as antibiotics like tetracycline, and anti-inflammatory drugs like diclofenac in water matrices is considered an issue of global concern. Numerous sewage/drain waste lines from the domestic and pharmaceutical sector contain an array of toxic compounds, so-called "emerging pollutants" and possess adverse effects on entire living ecosystem and damage its biodiversity. Therefore, effective solution and preventive measures are urgently required to sustainably mitigate and/or remediate pharmaceutically active emerging pollutants from environmental matrices. In this context, herein, the entry pathways of the pharmaceutical waste into the environment are presented, through the entire lifecycle of a pharmaceutical product. There is no detailed review available on carbon-dots (CDs) as robust materials with multifunctional features that support sustainable mitigation of emerging pollutants from water matrices. Thus, CDs-based photocatalysts are emerging as an efficient alternative for decontamination by pharmaceutical pollutants. The addition of CDs on photocatalytic systems has an important role in their performance, mainly because of their up-conversion property, transfer photoinduced electron capacities, and efficient separation of electrons and holes. In this review, we analyze the strategies followed by different researchers to optimize the photodegradation of various pharmaceutical pollutants. In this manner, the effect of different parameters such as pH, the dosage of photocatalyst, amount of carbon dots, and initial pollutant concentration, among others are discussed. Finally, current challenges are presented from a pollution prevention perspective and from CDs-based photocatalytic remediation perspective, with the aim to suggest possible research directions.

Efficient Combination of G-C3 N4 and CDs for Enhanced Photocatalytic Performance: A Review of Synthesis, Strategies, and Applications

Recently, heterogeneous photocatalysts have achieved much interest on account of their great potential applications in resolving many tough energy and environmental troubles around the world through an ecologically sustainable way. Heterogeneous nanocomposites composed of graphitic carbon nitride (g-C₃ N₄ ) and carbon dots (CDs) possess broad spectrum absorption, appropriate electronic band structures, rapid carrier mobility, abundant reserves, excellent chemical stability, and facile synthesis methods, which make them promising composite photocatalysts for suitable applications such as photocatalytic solar fuels production and contaminant decomposition. With the rapid development in photocatalysis by hybridization of g-C₃ N₄ and CDs, a systematic summary and prospection of performance improvement are urgent and meaningful. This review first focuses on various kinds of effectively synthetic methods of composites. Following, the strategies available for enhanced performance, including morphology optimization, spectral absorption improvement, ternary or quaternary composition hybrid, lateral or vertical heterostructures construction, heteroatom doping, and so forth, are fully discussed. Then, the applications mainly in efficient photocatalytic hydrogen generation, photocatalytic carbon dioxide reduction, and organic pollutants degradation are systematically demonstrated. Finally, the remaining issues and prospect of further development are proposed as some kind of guidance for powerful combination of g-C₃ N₄ and CDs with high efficiency to photocatalysis.

Facile and Green Fabrication of Microwave-Assisted Reduced Graphene Oxide/Titanium Dioxide Nanocomposites as Photocatalysts for Rhodamine 6G Degradation

Organic pollutants, such as synthetic dyes, are treated to prevent them from contaminating natural water sources. One of the treatment methods is advanced oxidation process using a photocatalyst material as the active agent. However, many photocatalysts are hindered by their production cost and efficiency. In this study, nanocomposites consisting of reduced graphene oxide and titanium dioxide (rGO/TiO2) were prepared by a simple and green approach using the microwave-assisted method, and we utilized a graphene oxide (GO) precursor that was fabricated through the Tour method. The ratios of rGO/TiO2 in nanocomposites were varied (2:1, 1:1, and 1:2) to know the influence of rGO on the photocatalytic performance of the nanocomposites for rhodamine 6G degradation. Transmission electron microscopy (TEM) observation revealed that a transparent particle with a sheetlike morphology was detected in the rGO sample, suggesting that a very thin film of a few layers of GO or rGO was successfully formed. Based on scanning electron microscopy (SEM) observation, the rGO/TiO2 nanocomposites had a wrinkled and layered rGO structure decorated by TiO2 nanoparticles with average diameters of 125.9 ± 40.6 nm, implying that rGO layers are able to prevent TiO2 from agglomeration. The synthesized product contained only rGO and TiO2 in the anatase form without impurities that were proven by Raman spectra and X-ray diffraction (XRD). The nanocomposite with rGO/TiO2 ratio 1:2 (composite C) was found to be the best composition in this study, and it was able to degrade 82.9 ± 2.4% of the rhodamine 6G after UV irradiation for 4 h. Based on a time-resolved photoluminescence study at wavelength emission 500 nm, the average decay lifetime of R6G-rGO/TiO2 composites (2.91 ns) was found to be longer than that of the R6G-TiO2 sample (2.05 ns), implying that the presence of rGO in rGO/TiO2 composites successfully suppressed the electron-hole recombination process in TiO2 and significantly improved their photocatalytic performance. This study showed that the rGO/TiO2 nanocomposites synthesized through relatively simple and eco-friendly processes display promising prospects for photocatalytic degradation of dyes and other recalcitrant pollutants in a water stream.

Synthesis, Characterization, and Multifunctional Applications of Cu-Fe and Ni-Fe Nanomaterials

Cu-Fe and Ni-Fe nanomaterials (NMs) were successfully obtained via a coprecipitation route. Phase analysis and the micro- and physiochemical structure studies for the as-synthesized NMs were carried out with advanced techniques such as TEM, SEM, XRD, XPS, BET, DRS, TGA, and FTIR. Particles with size ranging from 25 to 70 nm were displayed by all the characterization techniques. A surface area of ∼4.48 and 36.52m²/g and band gap energies of ∼1.79 and 1.48 eV were calculated for Cu-Fe and Ni-Fe NMs, respectively. Saturation magnetization (Ms) ∼77.95 emu/g (for Cu-Fe) and 27.70 emu/g (for Ni-Fe) revealed superparamagnetism for both the NMs. The presence of ethanol and methanol as sacrificial agents contributed effectively toward electrocatalytic H-evolution as compared to pure NMs. Furthermore, under solar light irradiations, Cu-Fe and Ni-Fe NMs displayed 85 and 91% degradation during a time interval of 50 and 110 min, respectively, for toxic industrial methylene blue (MB) dye. Different operational variables such as the catalyst amount, pH values, various scavengers, reusability, and stability were thoroughly investigated. Moreover, in situ analysis was carried out in order to determine the mechanism for degradation reactions. A detailed study about various applications categorized the synthesized NMs as efficient candidates for toxic industrial waste cleanup and energy production at an industrial level.

Carbon quantum dots-decorated TiO2/g-C3N4 film electrode as a photoanode with improved photoelectrocatalytic performance for 1,4-dioxane degradation

In this study, carbon quantum dots (CQDs) were used to decorate a TiO₂/g-C₃N₄ (TCN) film electrode. The morphological, optical, and electrochemical properties of the TiO₂/g-C₃N₄/CQDs nanorod arrays (TCNC NRAs) film were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and electrochemical impedance spectroscopy (EIS). The improved optical properties, photoelectrochemical properties and photoelectrocatalytic (PEC) performance of photoanode can be observed by doping CQDs onto the TCN NRAs film. Compared with TiO₂ NRAs and TCN NRAs, the narrower band gap of 2.47 eV and longer lifetime of photoinduced electron-hole pairs were observed in the TCNC NRAs. Under visible light irradiation and a bias voltage of 1.2 V, the photocurrent density and 1,4-dioxane (1,4-D) removal rate of PEC process with TCNC NRAs electrode reached 0.16 mA/cm² and 77.9%, respectively, which was 2.5 times and 1.5 times of that with TCN NRAs electrode. TCNC NRAs electrode could keep >75% of the 1,4-D removal rate during five cycles tests. High PEC performance with TCNC NRAs electrode could be attributed to the enhanced charge separation and the change of electron transfer mechanism from typical heterojunction to Z-scheme, which may increase the active species production and change the dominant reactive species from O₂·^- to ·OH. Our experimental results should be useful for studying the degradation of 1,4-D and developing efficient PEC materials.

Recent Achievements in Development of TiO2-Based Composite Photocatalytic Materials for Solar Driven Water Purification and Water Splitting

Clean water and the increased use of renewable energy are considered to be two of the main goals in the effort to achieve a sustainable living environment. The fulfillment of these goals may include the use of solar-driven photocatalytic processes that are found to be quite effective in water purification, as well as hydrogen generation. H2 production by water splitting and photocatalytic degradation of organic pollutants in water both rely on the formation of electron/hole (e-/h+) pairs at a semiconducting material upon its excitation by light with sufficient photon energy. Most of the photocatalytic studies involve the use of TiO2 and well-suited model compounds, either as sacrificial agents or pollutants. However, the wider application of this technology requires the harvesting of a broader spectrum of solar irradiation and the suppression of the recombination of photogenerated charge carriers. These limitations can be overcome by the use of different strategies, among which the focus is put on the creation of heterojunctions with another narrow bandgap semiconductor, which can provide high response in the visible light region. In this review paper, we report the most recent advances in the application of TiO2 based heterojunction (semiconductor-semiconductor) composites for photocatalytic water treatment and water splitting. This review article is subdivided into two major parts, namely Photocatalytic water treatment and Photocatalytic water splitting, to give a thorough examination of all achieved progress. The first part provides an overview on photocatalytic degradation mechanism principles, followed by the most recent applications for photocatalytic degradation and mineralization of contaminants of emerging concern (CEC), such as pharmaceuticals and pesticides with a critical insight into removal mechanism, while the second part focuses on fabrication of TiO2-based heterojunctions with carbon-based materials, transition metal oxides, transition metal chalcogenides, and multiple composites that were made of three or more semiconductor materials for photocatalytic water splitting.

Kinetic and Mechanistic Study of Rhodamine B Degradation by H2O2 and Cu/Al2O3/g-C3N4 Composite

The classic Fenton reaction, which is driven by iron species, has been widely explored for pollutant degradation, but is strictly limited to acidic conditions. In this work, a copper-based Fenton-like catalyst Cu/Al2O3/g-C3N4 was proposed that achieves high degradation efficiencies for Rhodamine B (Rh B) in a wide range of pH 4.9–11.0. The Cu/Al2O3 composite was first prepared via a hydrothermal method followed by a calcination process. The obtained Cu/Al2O3 composite was subsequently stabilized on graphitic carbon nitride (g-C3N4) by the formation of C−O−Cu bonds. The obtained composites were characterized through FT-IR, XRD, TEM, XPS, and N2 adsorption/desorption isotherms, and the immobilized Cu+ was proven to be active sites. The effects of Cu content, g-C3N4 content, H2O2 concentration, and pH on Rh B degradation were systematically investigated. The effect of the catalyst dose was confirmed with a specific reaction rate constant of (5.9 ± 0.07) × 10−9 m·s−1 and the activation energy was calculated to be 71.0 kJ/mol. In 100 min 96.4% of Rh B (initial concentration 20 mg/L, unadjusted pH (4.9)) was removed in the presence of 1 g/L of catalyst and 10 mM of H2O2 at 25 °C, with an observed reaction rate constant of 6.47 × 10−4 s−1. High degradation rates are achieved at neutral and alkaline conditions and a low copper leaching (0.55 mg/L) was observed even after four reaction cycles. Hydroxyl radical (HO·) was identified as the reactive oxygen species by using isopropanol as a radical scavenger and by ESR analysis. HPLC-MS revealed that the degradation of Rh B on Cu/Al2O3/CN composite involves N-de-ethylation, hydroxylation, de-carboxylation, chromophore cleavage, ring opening, and the mineralization process. Based on the results above, a tentative mechanism for the catalytic performance of the Cu/Al2O3/g-C3N4 composite was proposed. In summary, the characteristics of high degradation rate constants, low ion leaching, and the excellent applicability in neutral and alkaline conditions prove the Cu/Al2O3/g-C3N4 composite to be a superior Fenton-like catalyst compared to many conventional ones.

Recent developments and challenges in practical application of visible-light-driven TiO2-based heterojunctions for PPCP degradation: A critical review

The ability of the TiO₂-based photocatalysis process to mineralize organic pollutants has attracted attention worldwide for the degradation of recalcitrant pharmaceuticals and personal care products (PPCPs). Nevertheless, (1) the limited exploitation of the solar spectrum, i.e., activation under UV light (only 2-3% of solar spectrum), and (2) the high recombination rate of photo-generated charge carriers, i.e., electrons and holes, have limited its application which can, however, be improved by developing a TiO₂-based heterojunction. The objective of this critical review paper is to discuss the recent developments (2009-2019) in visible-light-driven (VLD) TiO₂-based heterojunctions for PPCP degradation and their degradation mechanisms. Compared to the conventional heterojunctions, Schottky and Z-scheme heterojunctions, which are non-conventional heterojunctions, are found to be more effective for PPCP degradation due to their more efficient separation of charge carriers and the occurrence of redox reactions at a relatively higher redox potential. Furthermore, the enhancement strategies for the development of a VLD TiO₂-based heterojunction are also explored which can be achieved by selecting the (1) highly photocatalytically active {001} facet of anatase TiO₂, (2) synthesis methods governing the structural changes at the junction interface, and (3) heterojunction components which can efficiently generate the powerful •OH radicals. The challenges in practical applications are also discussed which include factors, viz., cost reduction, recycling, stability, byproducts analysis, evaluation of the environmental effectiveness, and reactor design and scale-up of the VLD TiO₂-based heterojunctions. Accordingly, the prospects of VLD TiO₂-based heterojunctions for PPCP degradation in real environmental applications are discussed.

Utilising anatase nano-seeds coupled with a visible-light antennae system (Cu–Pd–N) for effective photo-organic transformations

Bandgap tuning TiO₂ nano-seeds with a three-component strategy (Cu, Pd, and N) has facilitated the selective photo-oxidation of cyclic alcohols.

Carbon nitride nanoplatelet photocatalysts heterostructured with B-doped carbon nanodots for enhanced photodegradation of organic pollutants

Decorating electron-accepting materials on carbon nitride (C₃N₄) is a promising strategy to construct heterostructure catalysts for improved photocatalytic abilities. In this study, B-doped carbon-dots (B-C-dots) decorated C₃N₄ (C₃N₄/B-C-dots) catalysts were fabricated through the surface deposition. The benefits from integration of B-C-dots and C₃N₄ are four folds: (i) increasing surface area; (ii) improving visible light absorption; (iii) promoting the transfer of photoinduced carriers; and (iv) reducing the recombination of photoinduced carriers. The optimum photocatalytic activity of B-C-dots/C₃N₄ for Rhodamine B (Rh B) (or tetracycline hydrochloride (TC)) degradation was about 7.21 (6.56) and 4.80 (4.35) times higher than that of C₃N₄ and C-dots/C₃N₄, respectively, exhibiting both remarkable stability and repeatability. Moreover, enhanced photocatalytic activity of C₃N₄/B-C-dots could also be attributed to the type-II heterojunction formed between C₃N₄ and B-C-dots caused by B doping.

Construction of Z-Scheme g-C₃N₄/CNT/Bi₂Fe₄O₉ Composites with Improved Simulated-Sunlight Photocatalytic Activity for the Dye Degradation

In this work, ternary all-solid-state Z-scheme g-C₃N₄/carbon nanotubes/Bi₂Fe₄O₉ (g-C₃N₄/CNT/BFO) composites with enhanced photocatalytic activity were prepared by a hydrothermal method. The morphology observation shows that ternary heterojunctions are formed in the g-C₃N₄/CNT/BFO composites. The photocatalytic activity of the samples for the degradation of acid orange 7 was investigated under simulated sunlight irradiation. It was found that the ternary composites exhibit remarkable enhanced photocatalytic activity when compared with bare BFO and g-C₃N₄/BFO composites. The effect of the CNT content on the photocatalytic performance of the ternary composites was investigated. The photocatalytic mechanism of g-C₃N₄/CNT/BFO was proposed according to the photoelectrochemical measurement, photoluminescence, active species trapping experiment and energy-band potential analysis. The results reveal that the introduction of CNT as an excellent solid electron mediator into the ternary composites can effectively accelerate the electron migration between BFO and g-C₃N₄. This charge transfer process results in highly-efficient separation of photogenerated charges, thus leading to greatly enhanced photocatalytic activity of g-C₃N₄/CNT/BFO composites. Furthermore, the g-C₃N₄/CNT/BFO composites also exhibit highly-efficient photo-Fenton-like catalysis property.

Kinetic and Mechanistic Study on Catalytic Decomposition of Hydrogen Peroxide on Carbon-Nanodots/Graphitic Carbon Nitride Composite

The metal-free CDots/g-C3N4 composite, normally used as the photocatalyst in H2 generation and organic degradation, can also be applied as an environmental catalyst by in-situ production of strong oxidant hydroxyl radical (HO·) via catalytic decomposition of hydrogen peroxide (H2O2) without light irradiation. In this work, CDots/g-C3N4 composite was synthesized via an electrochemical method preparing CDots followed by the thermal polymerization of urea. Transmission electron microscopy (TEM), X-Ray diffraction (XRD), Fourier Transform Infrared (FTIR), N2 adsorption/desorption isotherm and pore width distribution were carried out for characterization. The intrinsic catalytic performance, including kinetics and thermodynamic, was studied in terms of catalytic decomposition of H2O2 without light irradiation. The second-order rate constant of the reaction was calculated to be (1.42 ± 0.07) × 10−9 m·s−1 and the activation energy was calculated to be (29.05 ± 0.80) kJ·mol−1. Tris(hydroxymethyl) aminomethane (Tris) was selected to probe the produced HO· during the decomposing of H2O2 as well as to buffer the pH of the solution. The composite was shown to be base-catalyzed and the optimal performance was achieved at pH 8.0. A detailed mechanism involving the adsorb-catalyze double reaction site was proposed. Overall, CDots/g-C3N4 composite can be further applied in advanced oxidation technology in the presence of H2O2 and the instinct dynamics and the mechanism can be referred to further applications in related fields.

Mesoporous TiO2 coated ZnFe2O4 nanocomposite loading on activated fly ash cenosphere for visible light photocatalysis

Several activated fly ash cenosphere (AFAC) supporting TiO2 coated ZnFe2O4 (TiO2/ZnFe2O4/AFAC) photocatalysts were prepared by sol-gel and hydrothermal methods. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (UV-DRS) and nitrogen adsorption analyses for Brunauer-Emmett-Teller (BET) specific surface area measurements. We found that the main components of spherical AFAC were mullite (Al6Si2O13) and SiO2; the crystallite size of the TiO2/ZnFe2O4 nanocomposite was less than 10 nm and its specific surface area was 162.18 m2 g-1. The TiO2/ZnFe2O4 nanocomposite had a band-gap of 2.56 eV, which would photodegrade 95% of rhodamine B (RhB) under visible light within 75 min. When hybridized with 0.02 g AFAC, the TiO2/ZnFe2O4/0.02 g AFAC photocatalyst with a band-gap of 2.50 eV could remove 97.1% of RhB and be reused three consecutive times with minor decrease in photocatalytic performance. However, the photocatalytic performance decreased to 91.0% on increasing the dosage of AFAC to 0.30 g. The mesoporous structure of all the photocatalysts and the strong adsorption ability of AFAC accounted for the notable performance.

The facile synthesis of a single atom-dispersed silver-modified ultrathin g-C3N4 hybrid for the enhanced visible-light photocatalytic degradation of sulfamethazine with peroxymonosulfate

A single-atom dispersed Ag loaded ultrathin g-C₃N₄ hybrid was prepared and used as a visible light-driven photocatalyst for SMT degradation in the presence of PMS.

Aconitic acid derived carbon dots as recyclable “on–off–on” fluorescent nanoprobes for sensitive detection of mercury(ii) ions, cysteine and cellular imaging

Aconitic acid is used as a new precursor for fabricating CDs and developing a sensitive “on–off–on” sensor for Hg²⁺, Cys and cellular imaging.