In situ loading of Ag(2)WO(4) on ultrathin g-C(3)N(4) nanosheets with highly enhanced photocatalytic performance

Recent advancements in the fabrication and photocatalytic applications of graphitic carbon nitride-tungsten oxide nanocomposites

The present review focuses on the widely used graphitic carbon nitride (g-C3N4)-tungsten oxide (WO3) nanocomposite in photocatalytic applications. These catalysts are widely employed due to their easy preparation, high physicochemical stability, nontoxicity, electron-rich properties, electronic band structure, chemical stability, low cost, earth-abundance, high surface area, and strong absorption capacity in the visible range. These sustainable properties make them predominantly attractive and unique from other photocatalysts. In addition, graphitic carbon nitride (g-C3N4) is synthesized from nitrogen-rich precursors; therefore, it is stable in strong acid solutions and has good thermal stability up to 600 °C. This review covers the historical background, crystalline phases, density-functional theory (DFT) study, synthesis method, 0-D, 1-D, 2-D, and 3-D materials, oxides/transition/nontransition metal-doped, characterization, and photocatalytic applications of WO3/g-C3N4. Enhancing the catalytic performance strategies such as composite formation, element-doping, heterojunction construction, and nanostructure design are also summarized. Finally, the future perspectives and challenges for WO3/g-C3N4 composite materials are discussed to motivate young researchers and scientists interested in developing environment-friendly and efficient catalysts.

The Photocatalytic Performance of P, Cl Doped Carboxylated Multiwalled Carbon Nanotube Modified Graphitic Carbon Nitride

Graphitized carbonitride (g-C₃N₄) is widely used in CO₂ reduction, hydrogen production, and degradation of toxic chemical dyes and antibiotics. It is a kind of photocatalytic material with excellent performance, and it has the advantages of being safe and nontoxic, having a suitable band gap (2.7 eV), and having a simple preparation and high stability, but because of its fast optical recombination speed and low visible light overutilization, the multifunctional application of g-C₃N₄ is seriously hindered. Compared with pure g-C₃N₄, MWCNTs/g-C₃N₄ have a red-shift in the visible range and a strong absorption in the visible region. Melamine and carboxylated multiwalled carbon nanotubes were used as raw materials to successfully prepare CMWCNT modified g-C₃N₄ doped with P, Cl by a high temperature calcination method. The effect of the addition amount of P, Cl on the photocatalytic performance of modified g-C₃N₄ was studied. The experimental results show that the multiwalled carbon nanotubes can accelerate the electron migration, and the doping of P, Cl elements can change the energy band structure of g-C₃N₄ and reduce the band gap. Through fluorescence analysis and photocurrent analysis, it is known that the incorporation of P, Cl reduces the recombination efficiency of photogenerated electron-hole pairs. In order to explore the application in the degradation of chemical dyes, the photocatalytic degradation efficiency of RhB under visible light was studied. The photocatalytic performance of the samples was evaluated by photodecomposition of aquatic hydrogen. The results showed that when the amount of ammonium dihydrogen phosphate was 10 wt %, the photocatalytic degradation efficiency was the highest, which was 21.13 times higher than that of g-C₃N_4.

Boosted photocatalytic effect of binary AgI/Ag2WO4 nanocatalyst: characterization and kinetics study towards ceftriaxone photodegradation

In modern chemistry, great interest has been paid to introducing outstanding photocatalysts for degrading organic pollutants. Herein, a highly efficient binary AgI/Ag₂WO₄ photocatalyst was prepared from AgI and Ag₂WO₄ nanoparticles (NPs) and characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), and Fourier transform infrared (FT-IR) techniques. In the Scherrer model, the average crystallite sizes of 34.9, 42.0, and 24.1 nm were estimated for the AgI, Ag₂WO₄, and the binary catalyst, while the values were 91, 13, and 85 nm by the Williamson-Hall model. FTIR confirmed the presence of W-O-W, O-W-O, Ag-I, and O-Ag-O bonds in the coupled material. DRS results showed absorption edge wavelengths of 451, 462, and 495 nm (corresponding to the band gap values of 2.75, 2.68, and 2.51 eV) for Ag₂WO₄, AgI, and AgI/Ag₂WO₄ catalyst, respectively. Synergistic photocatalytic activity of the coupled system was achieved towards ceftriaxone (CTX) in an aqueous solution (about 33% 10 ppm CTX solution was degraded without any optimization in the initial conditions of catal dose 0.3 g/L (Ag₂WO₄:AgI with mole ratio 1:2 and 30 min abrasion time), and irrad. time 45 min, C_CTX). This boosted effect depended on the AgI:Ag₂WO₄ mole ratio and grinding time for the mechanical preparation of the binary catalyst (optimums: mole ratio of 4:1 and time 30 min). The photodegradation kinetics obeyed the Hinshelwood model with the apparent first-order rate constant (k) of 0.013 min^-1 (t_1/2 = 53.30 min). Performing the COD on the photodegraded CTX solutions got a Hinshelwood plot with a slope of 0.019 min^-1 (t_1/2 = 36.5 min).

Hydrothermally constructed AgWO4-rGO nanocomposites as an electrode enhancer for ultrasensitive electrochemical detection of hazardous herbicide crisquat

The advancements in electrode materials with high efficiency has been prioritized to effectively monitor the presence of harmful pesticides concerning the environment. In such a way, we hydrothermally constructed a hybrid AgWO₄-rGO nanocomposites for the rapid electrochemical detection of crisquat (CQT). The structural, compositional, morphological and topographical characterization for AgWO₄-rGO nanocomposites is thoroughly performed to understand its electrocatalytic properties. The AgWO₄-rGO nanocomposites are used as an electrode enhancer (rGO@AgWO₄/GCE) for the electrochemical investigations towards CQT detection. The results indicated that the rGO@AgWO₄/GCE possessed an excellent catalytic activity with a wide linear detection range 1-1108 μM coupled with an ultrasensitive limit of detection (LOD) 0.0661 μM for electrochemical CQT detection. The rGO@AgWO₄/GCE CQT sensor also expressed remarkable sensitivity of 0.6306 μAμM^-1cm^-2 in addition to good selectivity and reproducibility. Furthermore, the commercial CQT, river water, tap water and washed vegetable water are used as a representative for real world analysis using rGO@AgWO₄/GCE and results are highly appreciable for the real time CQT detection. Our work proposes a novel hybrid rGO@AgWO₄ nanocomposites reinforced electrodes for ultra-trace level CQT detection with good reliability and can be advocated for real time detection of pesticides.

The synergy of photodeposited CoNi co-catalysts for the photocatalytic performance of C3N4/CdS nanosheets: optimized Gibbs free energy and Co–S bridging bonds

The photocatalytic performance of C₃N₄/CdS is enhanced by the photodeposited CoNi alloyed NPs: the synergy of the optimized Gibbs free energy of the CoNi co-catalysts and the formed Co–S bridging bonds between CoNi and CdS.

Rapid reduction of nitroarenes photocatalyzed by an innovative Mn3O4/α-Ag2WO4 nanoparticles

A novel photocatalyst based on the design of P-N heterojunction between hollow spherical Mn3O4 and nanorods shape of α-Ag2WO4 is synthesized using a sonication-deposition-precipitation route. The nanocomposite Mn3O4/α-Ag2WO4(60%) exhibits a great potential towards nitroarenes (including 4-nitrophenol, 4-nitro-aniline and 4-Nitro-acetanilide) reduction under visible light irradiation exceeding that of Mn3O4/α-Ag2WO4(40%) as well as their individual counterparts (3-5%). The Mn3O4/α-Ag2WO4(60%) catalyst exhibited an excellent photo-reduction activity comprised of 0.067 s-1 towards 4-nitrophenol (0.001 M) in only 60 s reaction time using NaBH4 (0.2 M). This was due to the successful formation of the Mn3O4/α-Ag2WO4 composite as validated by XRD, TEM-SAED, XPS, FTIR, UV-Vis diffuse reflectance and PL techniques. Decreasing the Eg value into 2.7 eV, the existence of a new (151) plane in the composite beside enhancement of the composite electrical conductivity (1.66 × 10-7 Ω-1 cm-1) helps the facile nitroarenes adsorption and hydrogenation. Transient photocurrent response and linear sweep voltammetry results prove the facilitation of photogenerated charge carriers separation and transport via improving electron lifetime and lessening recombination rate. The composite photocatalyst produced higher amounts of H2 production, when inserted in a typical reaction medium containing NaBH4, comprised of 470 µ mole/g exceeding those of the counterparts (35 µ mole/g). This photocatalyst is strikingly hydrogenated 4-nitrophenol under mild conditions (25 °C and 0.35 MPa pressure of H2) with magnificent rate constant equal 34.9 × 10-3 min-1 with 100% selectivity towards 4-aminophenol.

Construction of a new cascade photogenerated charge transfer system for the efficient removal of bio-toxic levofloxacin and rhodamine B from aqueous solution: Mechanism, degradation pathways and intermediates study

In this work, a novel cascade system (i.e., SnTCPP/g-C₃N₄/Bi₂WO₆) is successfully constructed using stannum (II) meso-tetra (4-carboxyphenyl) porphyrin (SnTCPP) as the key photovoltaic agent for the first time. Visible light driven photocatalytic experiments indicated that wt. 12% SnTCPP and 30% Bi₂WO₆ codecorated g-C₃N₄ demonstrates the highest photodecomposition capabilities for levofloxacin and rhodamine B, achieving 85.64% and 93.64% degradation rates, respectively. The dramatically enhanced photocatalytic performance mainly raised from the synergetic co-effects among SnTCPP, g-C₃N₄ and Bi₂WO₆, including: i) the incorporation of SnTCPP extends the visible light response of the binary Bi₂WO₆/g-C₃N₄ heterojunctions, resulting in the highly efficient visible light harvesting; ii) we find that the g-C₃N₄ not only serves as a promising supporter to trap electrons from Bi₂WO₆, but also as an interfacial electron-hole pairs transfer moderator, like "volleyball setter" to facilitate the charges transfer between Bi₂WO₆ and SnTCPP. The presence of the "setter" endows a cascade system for boosting the photodegradation efficiency of levofloxacin and rhodamine B. This study provides a promising design strategy to construct efficient g-C₃N₄ based heterojunctions suitable for removing pharmaceutical antibiotics and hazardous dyes from various real wastewaters.

Ultrathin Ag2WO4-coated P-doped g-C3N4 nanosheets with remarkable photocatalytic performance for indomethacin degradation

As a metal-free photocatalyst, the photocatalytic activity of graphitic carbon nitride (g-C₃N₄) remains restricted due to an insufficient visible-light absorption capacity, the rapid recombination of photoinduced carriers, and low surface area. Consequently, P-doped g-C₃N₄ (PCN) was successfully prepared via a single -step thermal polymerization technique using phytic acid biomass and urea, which exhibited remarkable photocatalytic activity for the degradation of indometacin (IDM). The IDM degradation rate was 7.1 times greater than that of pristine g-C₃N₄ (CN). Furthermore, Ag₂WO₄ was loaded onto the surface of the PCN, which formed a Z-scheme heterostructure that promoted the separation of photogenerated carriers. According to analyses of the chemical binding states of PCN, P atoms replaced carbon atoms in the CN framework. According to electron localization function analysis, the low ELF values of P-N facilitated the transfer of photoelectrons. The results of active species scavenging experiments confirmed that superoxide radicals were the primary active species in the photocatalytic degradation system. Finally, the photocatalytic degradation pathways of IDM were predicted through the identification of by-products and IDM reaction sites.

Unvealing the role of β-Ag2MoO4 microcrystals to the improvement of antibacterial activity

Crystal morphology with different surfaces is important for improving the antibacterial activity of materials. In this experimental and theoretical study, the antibacterial activity of β-Ag₂MoO₄ microcrystals against the Gram-positive bacteria, namely, methicillin-resistant Staphylococcus aureus (MRSA), and the Gram-negative bacteria, namely, Escherichia coli (E. coli), was investigated. In this study, β-Ag₂MoO₄ crystals with different morphologies were synthetized by a simple co-precipitation method using three different solvents. The antimicrobial efficacy of the obtained microcrystals against both bacteria increased according to the solvent used in the following order: water < ammonia < ethanol. Supported by experimental evidence, a correlation between morphology, surface energy, and antibacterial performance was established. By using the theoretical Wulff construction, which was obtained by means of density functional calculations, the morphologies with large exposition of the (001) surface exhibited superior antibacterial activity. This study provides a low cost route for synthesizing β-Ag₂MoO₄ crystals and a guideline for enhancing the biological effect of biocides on pathogenic bacteria by the morphological modulation.

Ag2O-decorated electrospun BiVO4 nanofibers with enhanced photocatalytic performance

Semiconductor photocatalysts are emerging as tools for pollutant degradation in industrial wastewater, air purification, antibacterial applications, etc. due to their use of visible light, which is abundant in sunlight. Here, we report a new type of p–n junction Ag₂O/BiVO₄ heterogeneous nanostructured photocatalyst with enhanced photocatalytic performance. P-type Ag₂O nanoparticles were in situ reduced and assembled on the surface of electrospun BiVO₄ nanofibers using ultraviolet (UV) irradiation; this process hindered the recombination of localized photogenerated electron–hole pairs, and hence resulted in the enhanced photocatalytic activity of the BiVO₄/Ag₂O nanocomposites. The photocatalytic activities of the obtained BiVO₄ and BiVO₄/Ag₂O nanocomposites were assessed by measuring the degradation of rhodamine B (RhB) under visible light. The 10 wt% Ag₂O/BiVO₄ sample yielded the optimum degradation of RhB (98.47%), much higher than that yielded by pure BiVO₄ nanofibers (64.67%). No obvious change in the XRD pattern of an Ag₂O/BiVO₄ sample occurred as a result of its use in the photocatalytic reaction, indicating its excellent stability. The high photocatalytic performance observed was attributed to the large surface-to-volume ratio of the essentially one-dimensional electrospun BiVO₄ nanofibers and to the in situ growth of p-type Ag₂O on the surface of the n-type BiVO₄ nanofibers.

Ag₂O doped electrospun BiVO₄ nanofibers with p–n junction heterogeneous structures show enhanced photocatalytic activity under visible light (photocatalytic efficiency: 98.47% within 100 min) and good cycling stability.

Construction of carbon-doped supramolecule-based g-C3N4/TiO2 composites for removal of diclofenac and carbamazepine: A comparative study of operating parameters, mechanisms, degradation pathways

An eco-friendly 2D heterojunction photocatalyst composites (BCCNT) consisting of carbon-doped supramolecule-based g-C₃N₄ (BCCN) layers and TiO₂ nanoparticles has been fabricated via an in-situ method. Based on the SEM and XPS results affirmed that the coaction of doped carbon and supramolecule precursors lead to the different morphology of pure g-C₃N₄, C-doped g-C₃N₄ have improved the photodegradation diclofenac (DCF) and carbamazepine (CBZ). And the degradation efficiencies of DCF and CBZ could reach 98.92% and 99.77%, which were separately corresponded to 30 min (min) and 6 h (h) of LED lamp illumination. Additionally, the effects of catalysis dosage, solution pH, natural organic matter (NOM), inorganic anions (Cl^-, SO₄^2-, NO₃^-) and different water matrices were deeply investigated. The scavenger experiments demonstrated that •O₂^-, h⁺ were main active species under visible irradiation. Furthermore, the photodegradation pathways of DCF and CBZ were detected by high-resolution mass spectrometry (HRMS) instruments and three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs). Eventually, the possible photocatalytic mechanisms of BCCNT were proposed.

Accelerated degradation of pollutants via a close interface connection in heterojunction, and special solid-liquid interactions

The solid-solid or solid-liquid interfaces are vital for the photocatalytic reaction. Herein, AgI nanoparticles (NPs) attached on the (0 1 1) plane of Ag₂WO₄ nanorods were synthesized by a facile method at room temperature. The co-crystalization of the two components caused their phase transformation and the existence of a strong interface interaction. Meanwhile, the porous batt-like morphology of AgI NPs provided more contact sites for organic pollutants to induce a strong interaction at the solid-liquid interface. The heterojunction nanocatalyst was found to be highly effective for the degradation and mineralization of various pollutants, including the endocrine-disrupting chemical bisphenol A, the antibiotics sulfamethoxazole and ciprofloxacin, and the azo-dye methyl orange under visible light (λ > 420 nm). Its photocatalytic rate was 91, 52, and 39 times higher than that of bulk AgI, standard TiO_2-xN_x, and the physical mixture of the two components, respectively. Further studies demonstrated that the strong interactions between the two components and the pollutants promoted the electron transfer from organic pollutants to AgI NPs and then from AgI NPs to Ag₂WO₄ nanorods, resulting in the rapid oxidation of pollutants and the formation of Ag NPs. The newly formed Ag NPs further accelerated the degradation of pollutants due to a SPR effect and an empty levels feeding role to produce h⁺ on Ag₂WO₄, which can oxidize surface-adsorbed H₂O into OH. This photocatalytic system provided a platform for understanding solid-solid and solid-liquid interface interaction and a novel design idea for water pollutants removal.

In-situ fabrication of Ag/P-g-C3N4 composites with enhanced photocatalytic activity for sulfamethoxazole degradation

A series of Ag/P-g-C₃N₄ composites with different Ag content were synthesized for the first time by thermal polymerization combined with photo-deposition method. The composites were characterized by X-ray powder diffraction, field emission scanning electron microscope coupled with energy-dispersive X-ray spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectra, N₂ absorption-desorption and X-ray photoelectron spectroscopy. Ag was successfully dispersed on the surface of P-g-C₃N₄. The photocatalytic performance of P-g-C₃N₄ and Ag/P-g-C₃N₄ was evaluated by degrading sulfamethoxazole (SMX) under visible light irradiation. In the presence of 5% Ag/P-g-C₃N₄, 100% of SMX was degraded within 20 min. The enhanced photocatalytic activity of Ag/P-g-C₃N₄ was attributed to the surface plasmon resonance effect of metallic Ag and Schottky barrier formed on the interface between Ag and P-g-C₃N₄, which could speed up the generation rate of electrons and holes and inhibit the recombination of photogenerated electron-hole pairs. The radical quenching tests indicated that holes and superoxide radicals were the dominant active species involved in SMX degradation. The synthesized materials maintained high catalytic activity after five cycle runs. The concentration and the intermediates during the degradation process were determined by LC-MS/MS, and the tentative degradation pathways of SMX in photocatalytic system were proposed.

A hybrid of g-C3N4 and porphyrin-based covalent organic frameworks via liquid-assisted grinding for enhanced visible-light-driven photoactivity

A series of 2D/2D photocatalysts, CuPor-Ph-COF/g-C₃N₄ composites, with superior photocatalytic performance were prepared by a liquid-assisted grinding method.

Effects of the preparation method of Pt/g-C3N4 photocatalysts on their efficiency for visible-light hydrogen production

Pt NPs have been loaded on ultrathin porous g-C₃N₄ nanosheets (CNS) by either a chemical reduction (CR) or a photoreduction (PR) method. The Pt/CNS-CR photocatalyst shows a much higher efficiency for H₂ evolution than that of the Pt/CNS-PR.

Controllable fabrication of α-Ag2WO4 nanorod-clusters with superior simulated sunlight photocatalytic performance

This work presents the greatly boosted photoactivity of α-Ag₂WO₄ nanorod-clusters fabricated by adjusting the molar ratio of raw materials.

Ultrafast spectroscopic study of plasmon-induced hot electron transfer under NIR excitation in Au triangular nanoprism/g-C3N4 for photocatalytic H2 production

Ultrafast spectroscopy reveals plasmon-induced hot electron transfer under NIR excitation in Au triangular nanoprism/g-C₃N₄ for photocatalytic H₂ evolution.

Research on the techniques of ultrasound-assisted liquid-phase peeling, thermal oxidation peeling and acid-base chemical peeling for ultra-thin graphite carbon nitride nanosheets

Graphite phase carbon nitride (g-C₃N₄) composite structure materials, as a kind of stable compound with graphite-like structure, has attracted more and more attention due to its excellent properties, such as being able to absorb solar energy, stable chemical and optical properties and having a suitable oxidation potential. However, its application in the field of photocatalysis is limited by its small specific surface area and poor dispersibility. To solve this problem, ultra-thin g-C₃N₄ nanosheets are often prepared using peeling methods. In this paper, the current status and mechanism of thermal oxidation peeling, ultrasound-assisted liquid-phase peeling and acid-base chemical peeling are reviewed in detail. In addition, the future research directions of ultra-thin graphite-like carbon nitride nanosheets are discussed.

The effects of bismuth (III) doping and ultrathin nanosheets construction on the photocatalytic performance of graphitic carbon nitride for antibiotic degradation

To further enhance the photocatalytic performance of graphitic carbon nitride (g-C₃N₄), we rationally combined two strategies (foreign metal doping and ultrathin nanosheet construction) to synthesize bismuth (III) (Bi³⁺) doped ultrathin g-C₃N₄ nanosheets (Bi-CNNS) via one-step thermal polymerization method using melamine as the raw material, bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) as the dopant source, and nitric acid (HNO₃) and acetic acid (AC) as soft templates for the ultrathin nanosheets construction. The Bi-CNNS catalysts exhibited an excellent photocatalytic performance in tetracycline (TC) degradation. The TC removal efficiency reached to be 94.1% in 30 min under visible-light irradiation over 0.03Bi-CNNS, which is 6.03 times higher than that of pure g-C₃N₄ (CN). The higher specific surface area, narrower bandgap, the improved photoexcited electron-hole pair transfer and separation efficiency, and prolonged carrier lifetimes in the Bi³⁺-doped ultrathin g-C₃N₄ nanosheets led to a significantly enhanced photocatalytic performance. The main radical species responsible for the degradation of tetracycline over 0.03Bi-CNNS were O₂^- and OH. Moreover, the possible photodegradation intermediate products of TC were detected by gas chromatography-mass spectroscopy (GC-MS), and a possible pathway was proposed.

Novel mesoporous TiO2@g-C3N4 hollow core@shell heterojunction with enhanced photocatalytic activity for water treatment and H2 production under simulated sunlight

A novel mesoporous TiO₂@g-C₃N₄ hollow core@shell heterojunction photocatalyst was engineered for the first time by in situ calcining and growing of cyanamide (CY) on the surface of TiO₂. The HTCN-1 possesses good structure and performance when the addition amount of CY is 1 mL. HTCN-1 shows high photocatalytic activity toward congo red (CR), rhodamine B (RhB), phenol and ciprofloxacin (CIP) with degradation efficiencies of 97%, 100%, 73%, and 74%, respectively. HTCN-1 also displays high photocatalytic activity for H₂ generation at rate of 7.9 μmol h^-1. A possible charger transfer mechanism and photocatalytic degradation mechanism of HTCN-1 are proposed basing on the experiment results. The enhanced photocatalytic activity may be attributed to the higher charge transfer efficiency of photogenerated electron-hole (e^--h⁺) pairs caused by close contacts, a larger interfacial area, and the higher barrier for conduction bending. What's more, HTCN-1 possesses relatively high stability during the entire photoreaction process. Given the unique spatial structure and superior photocatalytic characteristics of the HTCN-1, there is great potential for applications in water treatment and H₂ generation.

Ag2WO4 nanorods decorated with AgI nanoparticles: Novel and efficient visible-light-driven photocatalysts for the degradation of water pollutants

To develop efficient and stable visible-light-driven (VLD) photocatalysts for pollutant degradation, we synthesized novel heterojunction photocatalysts comprised of AgI nanoparticle-decorated Ag2WO4 nanorods via a facile method. Various characterization techniques, including XRD, SEM, TEM, EDX, and UV-vis DRS were used to investigate the morphology and optical properties of the as-prepared AgI/Ag2WO4 catalyst. With AgI acting as the cocatalyst, the resulting AgI/Ag2WO4 heterostructure shows excellent performance in degrading toxic, stable pollutants such as rhodamine B (RhB), methyl orange (MO) and para-chlorophenol (4-CP). The high performance is attributed to the enhanced visible-light absorption properties and the promoted separation efficiency of charge carriers through the formation of the heterojunction between AgI and Ag2WO4. Additionally, AgI/Ag2WO4 exhibits durable stability. The active species trapping experiment reveals that active species (O2•- and h+) dominantly contribute to RhB degradation. The AgI/Ag2WO4 heterojunction photocatalyst characterized in this work holds great potential for remedying environmental issues due to its simple preparation method and excellent photocatalytic performance.

Moderate Bacterial Etching Allows Scalable and Clean Delamination of g-C3N4 with Enriched Unpaired Electrons for Highly Improved Photocatalytic Water Disinfection

Delamination treatment is crucial in promoting the activity of bulk graphitic carbon nitride (g-C₃N₄). However, most of the currently used methods of exfoliating bulk g-C₃N₄ to achieve g-C₃N₄ thin layers suffer from low yield and environmental pollution. Herein, we developed a facile bacterial etching approach for the preparation of high-quality g-C₃N₄ nanosheets by exfoliating bulk g-C₃N₄ under room temperature. Morphology and physicochemical characterizations show that the bacteria-treated g-C₃N₄ (BT-CN) samples, especially BT-CN-2d, have a lamina-like two-dimensional (2D) in-plane porous structure, a significantly enlarged specific surface area (82.61 m² g^-1), and a remarkable narrow band gap (2.11 eV). X-ray photoelectron spectroscopy and electron paramagnetic resonance spectra confirm the dramatic enrichment of unpaired electron in the BT-CN-2d g-C₃N₄ nanosheets. EIS spectra and photocurrent tests indicate the fast electron transportation. As a result, the representative BT-CN-2d g-C₃N₄ photocatalyst shows an optimal visible light-driven photocatalytic performance in water disinfection (fourfold higher than bulk g-C₃N₄), as well as good cycle stability. This moderate and clean bacterial etching process can be realized in tens of gram scale in the laboratory and should be readily extended to kilogram scale. The present work provides fundamental knowledge about the scalable production of high-quality g-C₃N₄ by bioengineering method, offering extendable availability for designing and fabricating other functional 2D materials.

Combination of ultrasound-treated 2D g-C3N4 with Ag/black TiO2 nanostructure for improved photocatalysis

Herein, nanosheets of g-C₃N₄ (CN), prepared using a green ultrasonication process under various conditions, were combined with Ag/black TiO₂ nanocomposites (AgBT) to create two-dimensional (2D) CN/Ag/black TiO₂ tri-composites (CNAgBT). The thickness of the CN sheets varied with the ultrasonication conditions. The CNAgBT sample prepared using ultrasound-treated CN exhibited the highest average photocatalytic efficiencies for the degradation of two model pollutants, followed in decreasing order by AgBT, black TiO₂ (BT), sheet CN, bulk CN, and TiO₂. The order of pollutant degradation efficiencies by the photocatalysts was consistent with that of the charge carrier separation efficiencies. The degradation efficiency of the CNAgBT increased as the CN-to-AgBT ratio increased from 0.05 to 0.1, but decreased gradually for higher ratios between 0.15 and 0.20, indicating a lower optimal CN-to-AgBT ratio. A plausible photocatalytic degradation mechanism for the CNAgBT nanocomposites was proposed. Additionally, CNAgBT with a CN-to-AgBT ratio of 0.1 displayed a higher hydrogen generation rate with a maximum value of 21.5 mmol g^-1 over 5 h than those of the AgBT and BT. Overall, the CNAgBT prepared using ultrasonication-treated CNs showed enhanced photocatalytic performance for both pollutant degradation and hydrogen generation.

Immobilization of g-C3N4 nanosheets on diatomite via electrostatic adsorption and their photocatalytic activity

Graphitic carbon nitride (g-C₃N₄) nanosheets have been successfully immobilized on diatomite to form a g-C₃N₄/diatomite hybrid through a facile electrostatic adsorption method and subsequent calcination process. Electron microscopy studies confirm that the surface of the diatomite is tightly covered with g-C₃N₄ nanosheets. In addition, the characterization results of Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectra (XPS) verify that there is a strong interaction between the g-C₃N₄ and diatomite components inside the hybrids. The visible light absorption edge of the hybrids exhibits a significant redshift compared with the bare g-C₃N₄ nanosheets and diatomite, which leads to the improvement of visible light absorption and utilization. The photocatalytic results demonstrated that the photocatalytic performance for methyl orange and phenol degradation using the hybrids as photocatalysts has been obviously improved compared to that of g-C₃N₄ nanosheets, which may be ascribed to its adsorption/photocatalysis synergistic effect.

g-C₃N₄/diatomite hybrids were synthesized through an electrostatic adsorption method and subsequent calcination process.

Fabrication of an Ag/Ag2MoO4plasmonic photocatalyst with enhanced photocatalytic performance for the degradation of ciprofloxacin

The Ag/Ag₂MoO₄photocatalyst exhibited high photodegradation efficiency with 99.5% removal of CIP in 60 min and excellent stability in five consecutive cycles.

Preparation of phenyl group functionalized g-C3N4 nanosheets with extended electron delocalization for enhanced visible-light photocatalytic activity

Phenyl group functionalized g-C₃N₄ shows an improved light utilization and charges separation rate due to extended conjugation system, leading to a superior catalytic activity in a variety of photocatalytic systems.

Novel nanomagnetic Ag/β-Ag2WO4/CoFe2O4 as a highly efficient photocatalyst under visible light irradiation

The Ag/β-Ag₂WO₄/CoFe₂O₄ heterogeneous nanophotocatalyst exhibits high photocatalytic activity for the oxidation of alcohols and can be easily recycled using a permanent magnet. Also, the underlying mechanism for its activity is proposed.

Efficient water disinfection with Ag2WO4-doped mesoporous g-C3N4 under visible light

Ag₂WO₄/g-C₃N₄ composite photocatalyst was synthesized by polymerization of thiourea and ammonia chloride combined with the deposition-precipitation method, which was applied as an efficient visible-light driven photocatalyst for inactivating Escherichia coli (E. coli). The physicochemical properties of these photocatalysts were systematically characterized by various techniques such as SEM, TEM, XRD, FT-IR, BET, UV-vis DRS and PL. The synthesized photocatalysts exhibited outstandingly enhanced photocatalytic disinfection efficiency compared with that of pure g-C₃N₄ and Ag₂WO₄ under visible light. Furthermore, the optimal mass ratio of the Ag₂WO₄ to g-C₃N₄ was 5wt%, and a number of live bacteria could be completely inactivated with Ag₂WO₄(5%)/g-C₃N₄ (100μg/mL) after 90min under visible light irradiation. The high disinfection efficiency is due to the synergetic effect between g-C₃N₄ and Ag₂WO₄, including a good distribution of Ag₂WO₄ particles on the surface of g-C₃N₄ and an improved separation rate of photogenerated electron-hole pairs. The enhanced disinfection mechanism was also investigated using photogenerated current densities and electrochemical impedance spectroscopy (EIS). Considering the bulk availability and excellent disinfection activity of Ag₂WO₄/g-C₃N₄ composite, it is a promising solar-driven photocatalyst for cleaning the microbial contaminated water.

Graphitic carbon nitride nanosheets decorated with CuCr2O4 nanoparticles: Novel photocatalysts with high performances in visible light degradation of water pollutants

In this paper, CuCr₂O₄ nanoparticles were decorated on the surface of g-C₃N₄ nanosheets (g-C₃N₄-NS) by a facile refluxing process. The structure, composition, morphology, optical, textural, and thermal properties were characterized by XRD, EDX, SEM, TEM, UV-vis DRS, FT-IR, XPS, PL, BET, and TGA techniques. The photocatalytic performance of g-C₃N₄-NS/CuCr₂O₄ nanocomposites was assessed by degrading RhB and MB dyes and phenol under visible-light illumination. When the loading amount of CuCr₂O₄ was 10 wt%, the nanocomposite exhibited the highest activity. Activity of the g-C₃N₄-NS/CuCr₂O₄ (10%) nanocomposite refluxed for 3h and calcined at 520°C for 4h was almost 11.8 and 4.8 times greater than those of the bulk g-C₃N₄ and g-C₃N₄-NS photocatalysts in degradation of RhB, respectively. In the prepared nanocomposites, nanosheets of g-C₃N₄ act not only as CuCr₂O₄ support, but also as co-catalyst. The novel visible-light-active photocatalyst has considerable stability and it can be reused for five times without obvious loss of its photocatalytic activity.

Novel β-Ag2MoO4/g-C3N4 heterojunction catalysts with highly enhanced visible-light-driven photocatalytic activity

The kernel of photocatalysis research is the development of catalysts with remarkable photocatalytic activity.

Preparation of an ultrathin 2D/2D rGO/g-C3N4 nanocomposite with enhanced visible-light-driven photocatalytic performance

An ultrathin 2D/2D rGO/g-C₃N₄ nanocomposite was constructed using thermally exfoliated g-C₃N₄ nanosheets and graphene oxide (GO) as precursors by a simple solvent method.

Synthesis and characterization of Z-scheme In2S3/Ag2CrO4 composites with an enhanced visible-light photocatalytic performance

Efficient charge transfer at the interfaces of an In₂S₃/Ag₂CrO₄ composite, due to the formation of a Z-scheme system between In₂S₃ and Ag₂CrO₄, effectively facilitates photogenerated electron–hole pair separation.

Hybrid 0D-2D Nanoheterostructures: In Situ Growth of Amorphous Silver Silicates Dots on g-C3N4 Nanosheets for Full-Spectrum Photocatalysis

The smaller particle sizes, better dispersion, and more heterojunction interfaces can enhance the photocatalytic performance of photocatalysts. Herein, ultradispersed amorphous silver silicates/ultrathin g-C₃N₄ nanosheets heterojunction composites (a-AgSiO/CNNS) with intimate interfacial coupling effect were synthesized through the facile in situ precipitation of ultrafine a-AgSiO (∼5.2 nm) uniformly dispersed on the entire surface of hierarchical ultrathin CNNS. In this process, the ultrathin CNNS not only perform as the support to form heterostructures but also are employed as dispersant to confine the aggregation of a-AgSiO nanoparticles. Notably, the optimum photocatalytic activity of a-AgSiO/CNNS-500 composite is ∼36 and 13 times higher than that of CNNS toward the degradation of rhodamine B and tetracycline, respectively. The excellent photocatalytic activity can be attributed to the synergistic interactions of heterojunction with strong interfacial coupling effect, improved visible light absorbance, abundant heterojunction interfaces, and fully exposed reactive sites, which originate from the well-defined nanostructures such as uniform packing of the ultrasmall a-AgSiO, the intimate and maximum coupling interfaces between a-AgSiO and CNNS. We believe that such an easy and scalable synthetic strategy can be further extended to the fabrication of other ultrafine semiconductors coupled with g-C₃N₄ for increasing its photocatalytic performance.