Facile fabrication of g-C3N4 QDs/BiVO4 Z-scheme heterojunction towards enhancing photodegradation activity under visible light

Novel Ag-bridged dual Z-scheme g-C3N4/BiOI/AgI plasmonic heterojunction: Exceptional photocatalytic activity towards tetracycline and the mechanism insight

Rational design and synthesis of highly efficient and robust photocatalysts with positive exciton splitting and interfacial charge transfer for environmental applications is critical. Herein, aiming at overcoming the common shortcomings of traditional photocatalysts such as weak photoresponsivity, rapid combination of photo-generated carriers and unstable structure, a novel Ag-bridged dual Z-scheme g-C₃N₄/BiOI/AgI plasmonic heterojunction was successfully synthesized using a facile method. Results showed that Ag-AgI nanoparticles and three-dimensional (3D) BiOI microspheres were decorated highly uniformly on the 3D porous g-C₃N₄ nanosheet, resulting in a higher specific surface area and abundant active sites. The optimized 3D porous dual Z-scheme g-C₃N₄/BiOI/Ag-AgI manifested exceptional photocatalytic degradation efficiency of tetracycline (TC) in water with approximately 91.8% degradation efficiency within 165 min, outperforming majority of the reported g-C₃N₄-based photocatalysts. Moreover, g-C₃N₄/BiOI/Ag-AgI exhibited good stability in terms of activity and structure. In-depth radical scavenging and electron paramagnetic resonance (EPR) analyses confirmed the relative contributions of various scavengers. Mechanism analysis indicated that the improved photocatalytic performance and stability were ascribed to the highly ordered 3D porous framework, fast electron transfer of dual Z-scheme heterojunction, desirable photocatalytic performance of BiOI/AgI and synergistic effect of Ag plasmas. Therefore, the 3D porous Z-scheme g-C₃N₄/BiOI/Ag-AgI heterojunction had a good prospect for applications in water remediation. The current work provides new insight and useful guidance for designing novel structural photocatalysts for environment-related applications.

One-step calcination synthesis of 2D/2D g-C3N4/WS2 van der Waals heterojunction for visible light-induced photocatalytic degradation of pharmaceutical pollutants

It is well-documented that accumulation of pharmaceutically active compounds (PhACs), such as antibiotics, in aquatic ecosystems is a prominent environmental hazard. Herein, a series of 2D materials-based heterojunctions, conceptualized based on the integration of graphitic carbon nitride (g-C₃N₄) with tungsten disulfide (WS₂), was fabricated through a facile one-step calcination process, and systematically evaluated for eliminating tetracycline (TC) and sulfamethoxazole (SMX) from aqueous matrices. The microstructure, optical properties, and surface chemistry of the as-prepared composites were examined with a range of microscopy and spectroscopy techniques. In comparison with pristine g-C₃N₄ or bare WS₂, the g-C₃N₄/WS₂ material, with optimal WS₂ loading, showed significantly improved photocatalytic activity, towards degradation of TC (84%) and SMX (96%), under visible light. Free radical scavenging experiments revealed that superoxide anions and hydroxyl radicals were predominantly responsible for the rapid breakdown of the PhACs. In addition, the dissociation intermediates and residues were identified and the plausible photocatalytic degradation pathways of TC and SMX over the as-constructed 2D/2D heterojunction were discussed. Further, the photocatalysis end products were non-toxic, as inferred via the resazurin cell viability assay, employing Escherichia coli as a model organism. Most importantly, the 2D/2D g-C₃N₄/WS₂ architecture was structurally resilient and exhibited a fairly stable cycling performance for persistent usage in wastewater treatment. The outcomes of this study testify that 2D/2D heterojunction of g-C₃N₄ fragments and WS₂ nanosheets holds great promise for destroying antibiotics or their metabolites, usually present in wastewaters.

Novel g-C3N4/BiVO4 heterostructured nanohybrids for high efficiency photocatalytic degradation of toxic chemical pollutants

Novel heterostructured hybrid catalysts are essential for the efficient photocatalytic removal of organic pollutants from wastewater generated by the pharmaceutical and textile industries. In this study, novel g-C₃N₄/BiVO₄ nanohybrid catalysts were prepared using a solvothermal technique, and examined their structural and optical properties using different characterizations. The X-ray diffraction analysis confirmed the monoclinic crystal phase of BiVO₄. Field emission scanning electron microscopy (FESEM) images revealed that g-C₃N₄ sheets anchored on the surface of BiVO₄ nanospheres. X-ray photoelectron spectroscopy (XPS) analysis confirmed the oxidation states of g-C₃N₄/BiVO₄ composite sample. UV-Vis DRS spectroscopy analysis revealed that the composite (2.08 eV) sample had a reduced bandgap compared to other samples. The photocatalytic properties of the prepared samples were tested in the presence of organic methylene blue (MB) and antibiotic tetracycline (TC) pollutants under visible light illumination. The hybrid composite catalyst exhibited enhanced photocatalytic degradation efficiency of MB (88%) and TC (89%) pollutants at elevated rate constants of 0.0128 and 0.01174 min^-1, respectively. The improved catalytic performance of the composite catalyst is due to the heterojunctions between g-C₃N₄ and BiVO₄ that successfully reduced the rate of charge carrier recombination in the catalyst system. Scavenger experiments revealed that O₂^●- and h⁺ radicals played a main role in the degradation of the chemical pollutants. The developed g-C₃N₄/BiVO₄ heterostructured catalyst is a suitable candidate for removing contaminants from industrial wastewater because of its facile fabrication and exceptional photocatalytic activity under visible light irradiation.

Construction of direct FeMoO4/g-C3N4-2D/2D Z-scheme heterojunction with enhanced photocatalytic treatment of textile wastewater to eliminate the toxic effect in marine environment

A novel FeMoO₄/g-C₃N₄-2D/2D Z-scheme heterojunction photocatalyst was prepared via wet chemical method. The observed structural morphology of FeMoO₄/g-C₃N₄ reveals the 2D-iron molybdate (FeMoO₄) nanoplates compiled with the 2D-graphitic carbon nitride (g-C₃N₄) nanosheets like structure. The photocatalytic activity of the g-C₃N₄, FeMoO₄, and FeMoO₄/g-C₃N₄ composites were studied via the degradation of Rhodamine B (RhB) as targeted textile dye under visible light irradiation (VLI). The optimal FeMoO₄/g-C₃N₄ (1:3 ratio of g-C₃N₄ and FeMoO₄) composite show an enhanced degradation performance with rate constant value of 0.02226 min^-1 and good stability even after three cycles. Thus, the h+ and O₂^•－are the key radicals in the degradation of RhB under VLI. It is proposed that the FeMoO₄/g-C₃N₄ Z-scheme heterojunction effectively enhances the transfer and separation ability of e^-/h⁺ pairs, by the way increasing the photocatalytic efficiency towards the RhB degradation. Thus, the newly constructed Z-scheme FeMoO₄/g-C₃N₄ heterojunction photocatalyst is a promising material for the remediation of wastewater relevant to elimination of toxic effect in marine environment.

Type II Heterojunction Formed between {010} or {012} Facets Dominated Bismuth Vanadium Oxide and Carbon Nitride to Enhance the Photocatalytic Degradation of Tetracycline

Both type II and Z schemes can explain the charge transfer behavior of the heterojunction structure well, but the type of heterojunction structure formed between bismuth vanadium oxide and carbon nitride still has not been clarified. Herein, we rationally prepared bismuth vanadium oxide with {010} and {012} facets predominantly and carbon nitride as a decoration to construct a core-shell structure with bismuth vanadium oxide wrapped in carbon nitride to ensure the same photocatalytic reaction interface. Through energy band establishment and radical species investigation, both {010} and {012} facets dominated bismuth vanadium oxide/carbon nitride composites exhibit the type II heterojunction structures rather than the Z-scheme heterojunctions. Furthermore, to investigate the effect of type II heterojunction, the photocatalytic tetracycline degradations were performed, finding that {010} facets dominated bismuth vanadium oxide/carbon nitride composite demonstrated the higher degradation efficiency than that of {012} facets, due to the higher conduction band energy. Additionally, through the free radical trapping experiments and intermediate detection of degradation products, the superoxide radical was proven to be the main active radical to decompose the tetracycline molecules. Therein, the tetracycline molecules were degraded to water and carbon dioxide by dihydroxylation-demethylation-ring opening reactions. This work investigates the effect of crystal planes on heterojunction types through two different exposed crystal planes of bismuth vanadate oxide, which can provide some basic research and theoretical support for the progressive and controlled synthesis of photocatalysts with heterojunction structures.

Interfacial Bi-S bonds modulate band alignment for efficient solar water oxidation

Introducing suitable interfacial chemical bonds into heterojunctions can increase the charge carrier density, propel the charge separation, and facilitate interfacial charge extraction in photoanodes for photoelectrochemical (PEC) water oxidation. However, tuning chemical bonds at heterojunction interfaces and elucidating their influences on band alignment and the associated evolution of PEC performance remain elusive. Herein, Bi-S bonds were introduced into the interface of a CdIn₂S₄ (CIS)/Bi₂WO₆ (BWO) heterojunction. In situ irradiated X-ray photoelectron spectroscopy and electron spin resonance signals confirm that the Bi-S bond transforms the band alignment from type II to the direct Z-scheme, significantly enhancing the carrier separation efficiency. Theoretical calculations show that the Bi-S bond not only acts as an atomic-level charge transfer channel, but also changes the migration pathway and distance within the heterojunction. As a result, the optimized CIS/BWO photoanode exhibits a relatively high PEC performance of 4.25 mA cm^-2 at 1.23 V vs. RHE (V_RHE) and a low onset potential of 0.30 V_RHE. This work presents a new avenue to construct comprehensively improved photoanodes by tuning the interfacial structures at the atomic level.

Novel BiVO4-nanosheet-supported MoS2-nanoflake-heterostructure with synergistic enhanced photocatalytic removal of tetracycline under visible light irradiation

This paper describes a simple in-situ hydrothermal technique for the production of BiVO₄/MoS₂ binary nanocomposites as visible-light-driven catalysts. The as-prepared samples were analyzed by structural, morphological, compositional, optical, surface area, and photocurrent analyses. The lattice fringe spaces at 0.304 nm and 0.612 nm were indexed to the (112) and (002) crystal planes of BiVO₄ and MoS₂, respectively. Antibacterial photocatalytic capabilities were assessed using tetracycline (TC). Consequently, it was observed that the BiVO₄/MoS₂ nanocomposite demonstrated improved antibacterial removal ability compared with the pristine samples. The BiVO₄/MoS₂ nanocomposite exhibited 97.46% removal of TC compared with the pure BiVO₄ (43.76%) and MoS₂ (35.28%) samples within 90 min. Thus, the photocatalytic performance was observed to follow the given order: BiVO₄/MoS₂ nanocomposite > BiVO₄ > MoS₂. The removal of TC after 90 min of irradiation was approximately 97.46%, 96.62%, 95.59%, and 94.45% after the 1st, 2nd, 3rd, and 4th cycles, respectively. Thus, the recycling tests revealed the stability of the photocatalyst, which exhibited a TC removal efficiency of 94.45% without distinct decay, even after the 4th cycle. According to the trapping results, hydroxyl radicals and holes were the key species and demonstrated a greater influence on the photocatalytic performance than superoxide radicals. The increased activity of the BiVO₄/MoS₂ nanocomposite may be attributed to its large surface area and tunable bandgap, which accelerate the charge-transport characteristics of the photocatalytic system. This insight and synergetic effects can provide a new approach for the development of novel heterostructure photocatalysts.

Oxygen vacancy-rich 2D GO/BiOCl composite materials for enhanced photocatalytic performance and semiconductor energy band theory research

Bismuth-based materials are extensively studied for photocatalytic applications because of their unique crystal structure. Herein, we reported a binary graphene oxide (GO)/BiOCl composite material prepared by a hydrothermal method and analyzed its photodegradation mechanism through the semiconductor energy band theory. The degradation rate of the GO/BiOCl composite towards Rhodamine B could reach 93.6% within 8 min, and its performance exceeded that of most photocatalysts. The influencing factors for improving the photocatalytic activity are as follows: (1) abundant oxygen vacancies generated on the tight recombination interface; (2) a 2D-2D electron transfer channel between GO and BiOCl; and (3) GO acting as a load to provide more reaction sites for BiOCl nanosheets. This work provides a simple solution and theoretical explanation for the rapid degradation of pollutants, and has broad application prospects.

Emerging bismuth-based direct Z-scheme photocatalyst for the degradation of organic dye and antibiotic residues

Organic dye and antibiotic residues are some of the key substances that can contaminate the environment due to their wide usage in various industries and modern medicine. The degradation of these substances present in waterbodies is essential while contemplating human health. Photocatalysts (PSs) are promising materials that develop highly reactive species instantly by simple solar energy conversion for degrading the organic dye and antibiotic residues and converting them into nontoxic products. Among numerous semiconductors, the bismuth (Bi)-containing PS has received great attention due to its strong sunlight absorption, facile preparation, and high photostability. Owing to the technology advancement and demerits of the traditional methods, a Bi-containing direct Z-scheme PS has been developed for efficient photogenerated charge carrier separation and strong redox proficiency. In this review, a synthetic Bi-based Z-scheme heterojunction that mimics natural photosynthesis is described, and its design, fabrication methods, and applications are comprehensively reviewed. Specifically, the first section briefly explains the role of various semiconductors in the environmental applications and the importance of the Bi-based materials for constructing the Z-scheme photocatalytic systems. In the successive section, overview of Z-scheme PS are concisely discussed. The fourth and fifth sections extensively explain the degradation of the organic dyes and antibiotics utilizing the Bi-based direct Z-scheme heterojunction. Eventually, the conclusions and future perspectives of this emerging research field are addressed. Overall, this review is potentially useful for the researchers involved in the environmental remediation field as a collection of up-to-date research articles for the fabrication of the Bi-containing direct Z-scheme PS.

Dual-Engine Powered Paper Photoelectrochemical Platform Based on 3D DNA Nanomachine-Mediated CRISPR/Cas12a for Detection of Multiple miRNAs

This work proposed a novel double-engine powered paper photoelectrochemical (PEC) biosensor based on an anode-cathode cooperative amplification strategy and various signal enhancement mechanisms, which realized the monitoring of multiple miRNAs (such as miRNA-141 and miRNA-21). Specifically, C₃N₄ quantum dots (QDs) sensitized ZnO nanostars and BiOI nanospheres simultaneously to construct a composite photoelectric layer that amplified the original photocurrent of the photoanode and photocathode, respectively. Through the independent design and partition of a flexible paper chip to functionalize injection holes and electrode areas, the bipolar combination completed the secondary upgrade of signals, which also provided biological reaction sites for multitarget detection. With the synergistic participation of a three-dimensional (3D) DNA nanomachine and programmable CRISPR/Cas12a shearing tool, C₃N₄ QDs lost their attachment away from the electrode surface to quench the signal. Moreover, electrode zoning significantly reduced the spatial cross talk of related substances for multitarget detection, while the universal trans-cleavage capability of CRISPR/Cas12a simplified the operation. The designed PEC biosensor revealed excellent linear ranges for detection of miRNA-141 and miRNA-21, for which the detection limits were 5.5 and 3.4 fM, respectively. With prominent selectivity and sensitivity, the platform established an effective approach for trace multitarget monitoring in clinical applications, and its numerous pioneering attempts owned favorable reference values.

Construction of a Z-scheme g-C3N4/NBGO/BiVO4 heterostructure with visible-light driven photocatalytic degradation of tetracycline: efficiency, reaction pathway and mechanism

In this study, an aminated graphene-like biochar (NGBO) was used as a solid-state electron mediator at a g-C3N4/BiVO4 interface to construct a hybrid Z-scheme system (g-C3N4/NBGO/BiVO4) for the photocatalytic degradation of tetracycline (TC) from aqueous solutions.

Construction of direct Z-scheme photocatalyst by the interfacial interaction of WO3 and SiC to enhance the redox activity of electrons and holes

The direct Z-scheme heterojunction structure benefits separation and migration of photoinduced carriers while maintaining original redox ability of each component. Nowadays, most Z-scheme structures are fabricated by g-C₃N₄ with other narrow band photocatalysts due to its low conduction band (CB). In this paper, SiC, another kind of photoelectric semiconductor with low CB, was employed to prepare direct Z-scheme photocatalyst with 2D WO₃ by simple water oxidation precipitation method. The component and interface band structure of Z-scheme heterojunction WO₃/SiC (WS) were verified by XPS, KPFM, Mott-Schottky method. The photodegradation efficiency and rate constant values of WS-1 for degrading RhB enhanced 2.5 and 5.3 times respectively compared with pristine WO₃. Radical capture experiments and ESR tests affirmed that WS-1 photocatalyst produced •OH and •O₂^－active species, which further confirmed the photogenerated carriers were transmitted through the Z-scheme mode in principle. Band structure investigation showed that the direct Z-scheme structure assembled by WO₃ with high valence band (VB) and SiC with low CB could maintain the high photocatalytic activity of active species. Therefore, this study offers a feasible method for construction of a novel and efficient direct Z-scheme photocatalyst.

Enhanced photocatalytic degradation activity of Z-scheme heterojunction BiVO4 /Cu/g-C3 N4 under visible light irradiation

A novel BiVO₄ /Cu/g-C₃ N₄ heterostructure photocatalyst was synthesized by thermal condensation, hydrothermal, and in situ precipitation method. The microscopic morphology and chemical composition of the synthesized samples were analyzed by XRD, SEM, FT-IR, XPS, and other characterizations. BiVO₄ /Cu/g-C₃ N₄ (BiVO₄ /Cu:g-C₃ N₄ mass ratio was 1:1) photocatalyst had the optimal photocatalytic degradation activity for tetracycline (TC) wastewater under visible light irradiation (120 min, 74.8%). The introduction of Cu and Z-scheme heterojunction was further confirmed by UV-vis, PL, EIS, and capture mechanism analysis, which effectively accelerated the separation and transfer rate of photogenerated electron holes and enhanced the strong oxidation of h⁺ and •O₂ ^- active species. BiVO₄ /Cu/g-C₃ N₄ heterojunction photocatalytic material has potential application value in the removal of refractory pollutants in wastewater. PRACTITIONER POINTS: A novel Z-scheme BiVO₄ /Cu/g-C₃ N₄ photocatalyst with excellent photocatalytic activities and stability was prepared to treat tetracycline (TC) wastewater. 1:1 CBCN (BiVO₄ /Cu:g-C₃ N₄ mass ratio was 1:1) photocatalyst exhibited the highest photocatalytic performance for TC wastewater. The Z-scheme heterojunction and Cu act as the interfacial charge transfer medium accelerated the transfer and separation of carriers.

Enhanced the Efficiency of Photocatalytic Degradation of Methylene Blue by Construction of Z-Scheme g-C3N4/BiVO4 Heterojunction

Both non-metallic g-C3N4 and BiVO4 are novel photocatalysts responsive to visible light, but their low charge separation efficiency restricts their inconspicuous photocatalytic activity. In this paper, direct Z-type g-C3N4/BiVO4 photocatalyst was constructed by calcination and hydrothermal for the degradation of methylene blue. The existence of g-C3N4/BiVO4 heterojunction was confirmed by the detailed study of its chemical structure and morphology by various characterization methods, such as X-ray diffraction (XRD), Scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The evaluation of photocatalytic performance showed that the MB degradation performance of 1.0-CN/BVO was significantly enhanced, which was 4.528 times and 2.387 times higher than pristine BiVO4 and g-C3N4, respectively, which was mainly due to the enhanced light capture ability and effective electron transfer in the photocatalytic reaction. The 1.0-CN/BVO composite exhibited extremely catalytic stability and recyclability.

An Overview of the Recent Progress in Polymeric Carbon Nitride Based Photocatalysis

Recently, polymeric carbon nitride (g-C₃ N₄ ) as a proficient photo-catalyst has been effectively employed in photocatalysis for energy conversion, storage, and pollutants degradation due to its low cost, robustness, and environmentally friendly nature. The critical review summarized the recent development, fundamentals, nanostructures design, advantages, and challenges of g-C₃ N₄ (CN), as potential future photoactive material. The review also discusses the latest information on the improvement of CN-based heterojunctions including Type-II, Z-scheme, metal/CN Schottky junctions, noble metal@CN, graphene@CN, carbon nanotubes (CNTs)@CN, metal-organic frameworks (MOFs)/CN, layered double hydroxides (LDH)/CN heterojunctions and CN-based heterostructures for H₂ production from H₂ O, CO₂ conversion and pollutants degradation in detail. The optical absorption, electronic behavior, charge separation and transfer, and bandgap alignment of CN-based heterojunctions are discussed elaborately. The correlations between CN-based heterostructures and photocatalytic activities are described excessively. Besides, the prospects of CN-based heterostructures for energy production, storage, and pollutants degradation are discussed.

Structural Tunability on Naphthalimide-Based Dendrimer Gelators via Glaser Coupling Interaction with Tailored Gelation Solvent Polarity and Stimuli-Responsive Properties

To date, most of the low-molecular-weight gels are found serendipitously, and modification on known gelator structures via organic synthesis is an efficient methodology to prepare gel series. However, a simple, direct, and rational modification method for a known gelator is still a challenge. Herein, we employ Glaser coupling reaction to synthesize a novel dendrimer gelator BisDEC with the (ALS₂)₂ structure, starting from terminal alkyne-based gelator DEC with the ALS₂ structure. This structural change results in gels with distinct gelation solvents, mechanical properties, and stimuli-responsive abilities. The gelation abilities of DEC and BisDEC in nonpolar and polar solvents, respectively, have been examined and discussed by several experiments and Hansen constants. It is also shown that the BisDEC gel system shows intriguing self-healing, self-supporting, and grinding chromism properties.

Constructing CeO2/nitrogen-doped carbon quantum dot/g-C3N4 heterojunction photocatalysts for highly efficient visible light photocatalysis

Ternary CeO₂/nitrogen-doped carbon quantum dot (NCQD)/graphitic carbon nitride (g-C₃N₄) heterojunction nanocomposites were prepared by a high-temperature calcination and hydrothermal method and tested for degrading tetracycline (TC) and generating H₂. Compared with CeO₂ and g-C₃N₄, the Z-scheme CeO₂/NCQDs/g-C₃N₄ (CSNx, where x represents the amount of CeO₂ in wt%) nanoparticles showed a higher TC photodegradation capacity and H₂ evolution ability owing to enhanced efficient charge separation and photocatalytic stability. CSN5 showed the best photodegradation activity for TC degradation (100 mL, 20 mg L^-1; 100% degradation in 60 min; λ≥ 420 nm) and the highest H₂ evolution rate of 1275.42 μmol h^-1 g^-1 was approximately 3.73- and 32.25-times higher than those of pristine g-C₃N₄ (341.85 μmol h^-1 g^-1) and pure CeO₂ (39.55 μmol h^-1 g^-1), respectively. Superoxide (˙O₂^-) and hydroxyl (˙OH) radicals were also confirmed to be formed on the sample surface for TC photocatalytic degradation. As an electronic medium, NCQDs transferred electrons between the g-C₃N₄ and CeO₂ interface to promote the electron-hole separation. This work affords a helpful perspective for synthesizing efficient charge separation and environmentally friendly photocatalysts by controlling the surface heterostructure.

A novel Strategy of Lock-in Effect between Conjugated Polymer and TiO2 towards Dramatic Enhancement of Photocatalytic Activity under Visible Light

To design novel conjugated polymers and improve interfacial interaction with semiconductor is one of directions to develop high-efficient photocatalysts with harvesting photons and boosting catalytic activities. Herein, two novel linear conjugated polymers poly[(thiophene-ethylene-thiophene)-thiophene] (PTET-T) and poly[(thiophene-ethylene-thiophene)-thiophene-3-carboxylic acid] (PTET-T-COOH) were successfully synthesized by a simple Stille coupling reaction. Their heterojunction with TiO2, i.e, PTET-T/TiO2 (C1) and PTET-T-COOH/TiO2 (C2), exhibited outstanding photocatalytic activity for degrading Rhodamine B, methylene blue and tetracycline. The energetic "lock-in effect" between PTET-T-COOH and TiO2 through carboxyl groups and hydroxyl groups interaction has been proved to greatly improve the interface charge transfer ability and suppress the electron-hole recombination in PTET-T-COOH/TiO2. Thus, by regulating the dosage of polymers, the 15% PTET-T-COOH/TiO2 showed the optimized photocatalytic activity with excellent chemical stability, and its kinetic rate constant was determined to be 41.7 times of that of TiO2. This work provided a new effective strategy of designed and explored organic semiconductor-inorganic heterojunction photocatalysts with broaden absorption, repeatability and high-charge mobility.

Surfactants-assisted preparation of BiVO4 with novel morphologies via microwave method and CdS decoration for enhanced photocatalytic properties

The development of a highly efficient and rapid method for the accurate preparation of photocatalysts with novel morphologies is a hot research topic. The different morphologies of BiVO₄ was prepared using surfactants-assisted microwave method, and demonstrated irregular (no surfactant), octahedral (sodium dodecyl benzene sulfonate), olive-like (polyvinylpyrrolidone) and hollow structures (ethylenediaminetetraacetic acid), respectively. The BiVO₄-CdS were synthesized using the chemical-bath-deposition method with different morphologies of BiVO₄ as the substrates. The hollow structure of BiVO₄ displayed the highest photocatalytic performance. Moreover, the photodegradation rates of the hollow structure BiVO₄-CdS on tetracycline hydrochloride and ciprofloxacin were about 1.8 and 1.5 times higher than the corresponding BiVO₄, indicating that the Z-scheme heterojunction can improve the photogenerated electron pairs separation efficiency. Furthermore, the regulation mechanism of morphology and energy-band position, as produced using the surfactants, has also been thoroughly investigated in this work, which provides a novel insight into the efficient and rapid preparation of photocatalysts with special morphology and high performance.

Enhanced photocatalytic removal of amoxicillin with Ag/TiO2/mesoporous g-C3N4 under visible light: property and mechanistic studies

In present study, an efficient ternary Ag/TiO₂/mesoporous g-C₃N₄ (M-g-C₃N₄) photocatalyst was successfully synthesized through depositing Ag nanoparticles (NPs) on the surface of TiO₂/M-g-C₃N₄ heterojunction. Ag/TiO₂/M-g-C₃N₄ nanocomposite displayed the highest degradation efficiency for amoxicillin (AMX) compared to TiO₂/M-g-C₃N₄ heterojunction, M-g-C₃N₄, and bulk-g-C₃N₄ (B-g-C₃N₄). The removal efficiency of AMX in real situation, surface water (SW), hospital wastewater (HW), and waste water treatment plant (WWTP) also were studied to illustrate the effectiveness of Ag/TiO₂/M-g-C₃N₄ photocatalysts. The vulnerable atoms in AMX structure were revealed through DFT calculation. Additionally, the dominating active groups produced in time of the photocatalytic procedure were determined on account of free radical trapping experiments and ESR spectra. The mechanism of photocatalytic degradation was proposed and verified. The transfer of the electrons and the inhibition of the recombination of photogenerated electron-holes were enhanced effectively under the synergistic effect of the Ag NPs and TiO₂. As a consequence, the catalytic activity of the composite was improved under visible light.

Scheelite-related MBi1-xV1-xMoxO4 (MII- Ca, Sr) solid solution-based photoanodes for enhanced photoelectrochemical water oxidation

The photoelectrochemical properties of scheelite-related MBi_1-xV_1-xMo_xO₄ (M^II = Ca, Sr, x = 0.1 to 0.9) solid solutions deposited on conductive glass (coated with SnO₂, F-doped) have been investigated as photoanodes in photoelectrochemical (PEC) water splitting. The variation of the final annealing temperature during the preparation of the conduction electrodes as well as the value of substitution x have been shown to affect the PEC performance. The micropowders of MBi_1-xV_1-xMo_xO₄ (M^II = Ca, Sr, x = 0.1 to 0.9) samples were first fabricated vi a solid-state method; they were characterised by SEM microscopy and powder and single crystal X-ray diffraction, and the band gap values were estimated using diffusive reflectance data. The value of substitution x = 0.1 in the cases of samples containing calcium and strontium affords the highest PEC performance reported for the whole range of substitution. These results demonstrate a promising approach for the beneficial utilization of BiVO₄-substituted scheelite-related solid solutions in photo-electrochemical cells towards efficient and inexpensive photoanodes.

Ag as Cocatalyst and Electron-Hole Medium in CeO2 QDs/Ag/Ag2Se Z-scheme Heterojunction Enhanced the Photo-Electrocatalytic Properties of the Photoelectrode

A recyclable photoelectrode with high degradation capability for organic pollutants is crucial for environmental protection and, in this work, a novel CeO₂ quantum dot (QDs)/Ag₂Se Z-scheme photoelectrode boasting increased visible light absorption and fast separation and transfer of photo-induced carriers is prepared and demonstrated. A higher voltage increases the photocurrent and 95.8% of tetracycline (TC) is degraded by 10% CeO₂ QDs/Ag₂Se in 75 minutes. The degradation rate is superior to that achieved by photocatalysis (92.3% of TC in 90 min) or electrocatalysis (27.7% of TC in 90 min). Oxygen vacancies on the CeO₂ QDs advance the separation and transfer of photogenerated carriers at the interfacial region. Free radical capture tests demonstrate that •O₂⁻, •OH, and h⁺ are the principal active substances and, by also considering the bandgaps of CeO₂ QDs and Ag₂Se, the photocatalytic mechanism of CeO₂ QDs/Ag₂Se abides by the Z-scheme rather than the traditional heterojunction scheme. A small amount of metallic Ag formed in the photocatalysis process can form a high-speed charge transfer nano channel, which can greatly inhibit the photogenerated carrier recombination, improve the photocatalytic performance, and help form a steady Z-scheme photocatalysis system. This study would lay a foundation for the design of a Z-scheme solar photocatalytic system.

Fabrication of metal-free PTET-T-COOH/g-C3N4 heterostructure for enhancing photocatalytic activity

In this research work, we successfully fabricated a range of PTET-T-COOH/g-C₃N₄ heterostructures via a simple method. The as-prepared PTET-T-COOH/g-C₃N₄ heterostructures show enhanced photocatalytic degradation activity as compared to pure g-C₃N₄. For the photocatalytic degradation of RhB, the optimal PTET-T-COOH/g-C₃N₄-1% heterostructure is nearly 3.83 times that of the pure g-C₃N₄. The enhancement of photocatalytic performance is ascribed to three aspects: one is the strong interaction between PTET-T-COOH and g-C₃N₄; the second is the larger surface area of the PTET-T-COOH/g-C₃N₄ heterostructure compared to that of pure g-C₃N₄; the third is the effectively improved transferability of photogenerated carriers. In addition, the whole photocatalytic reaction mechanism over the PTET-T-COOH/g-C₃N₄ heterostructure is provided. This work may offer a hopeful method to synthesize any other heterostructure with high stability and superior photocatalytic activity.

The metal-free PTET-T-COOH/g-C₃N₄ heterostructure exhibits a high degradation rate for RhB under visible light irradiation.

Visible-light-driven CQDs@MIL-125(Ti) nanocomposite photocatalyst with enhanced photocatalytic activity for the degradation of tetracycline

In the present study, a novel photocatalyst, CQDs@MIL-125(Ti) (CQDs = carbon quantum dots), was prepared via a solvothermal procedure. The photocatalytic properties were tested by the degradation of tetracycline (TC) with a 250 W Xe lamp (λ > 420 nm). Compared with pure MIL-125(Ti), the 10 wt% CQDs@MIL-125(Ti) photocatalyst can significantly improve the degradation process of TC, and the degradation efficiency can reach 90% within 4 h. The enhancement in the photocatalytic performance is due to the CQDs, which can promote the absorption of visible light and also efficiently accelerate the separation of photogenerated electron–hole pairs. We have also demonstrated that superoxide radicals (·O₂⁻) and holes (h⁺) play crucial roles in the photocatalytic degradation of TC through capture experiments. The current work provides a new idea for constructing high-efficiency photocatalysts based on MIL-125(Ti).

A novel CQDs@MIL-125(Ti) photocatalyst had been synthesized by a facile solvothermal process for the degradation of TC. The possible degradation mechanism was proposed based on the active species trapping experiments.