Separation Efficiency Of Charge Carriers Research Articles

Visible light activation of ferrate(VI) by oxygen doped ZnIn2S4/black phosphorus nanolayered heterostructure: Accelerated oxidation of trimethoprim

The increasing consumption of antibiotics and their subsequent release to wastewater or groundwater and ultimately to the water supply (or drinking water) has great concerns. This paper presents a visible light (VL) activated ferrate(VI) (FeVIO42-, Fe(VI)) system to degrade the selected antibiotic, trimethoprim (TMP), efficiently. An oxygen doped ZnIn2S4 nanosheet (O-ZIS) coupled with a black phosphorus (BP) heterostructure (O-ZIS/BP), is fabricated by a simple electrostatic self-assembly method. The O-ZIS/BP photocatalyst is comprehensively characterized by surface and analytical techniques, which show superior separation efficiency of the photoinduced charge carriers in the heterostructure. A VL-O-ZIS/BP-Fe(VI) system achieves more than 80% removal in 1.0 min and complete removal of TMP in 3.0 min. Comparatively, only ⁓7% and ⁓24% of TMP are degraded by O-ZIS/BP and Fe(VI) in 1.0 min, respectively. The degradation experiments using probe molecules of reactive species and electron paramagnetic resonance (EPR) measurements reveal involvement of superoxide (O2-•), hydroxyl radical (•OH), and iron(V)/iron (IV) (FeV/FeIV) species in the mechanism of TMP degradation. Oxidized products of TMP are identified and reaction pathways are given. Theoretical calculations predict the initial attack on the TMP molecule by the reactive species in the VL-O-ZIS/BP-Fe(VI) system. The activation of Fe(VI) by VL-heterostructure photocatalysts accelerates the degradation of antibiotics, demonstrating its potential for water depollution.

One-step preparation of novel Bi-Bi2O3/CdWO4 Z-scheme heterojunctions with enhanced performance in photocatalytic NH3 synthesis

This study focuses on the design and synthesis of a novel ternary composite photocatalyst, Bi-Bi2O3/CdWO4, using a one-step solvothermal method. A comprehensive investigation was conducted to analyze the morphology, specific surface area, structure, optical property, and photoelectric chemical property of the composite. The incorporation of Bi-Bi2O3 was found to significantly impact the growth of CdWO4 crystals, resulting in a morphological transformation into nanoparticles. This morphological change has been shown to enhance the specific surface area of the catalyst, thereby improving its catalytic performance. Furthermore, the incorporation of Bi-Bi2O3 has been demonstrated to greatly enhance the light absorption capability of CdWO4, which also favored the photocatalytic N2 fixation (PNF) reaction. However, after conducting a comprehensive analysis of different Bi-BiO3/CdWO4 and two reference samples Bi/CdWO4 and Bi2O3/CdWO4, it was determined that the improvement of photogenerated charge carrier separation efficiency is the decisive factor determining the performance of the ternary composite catalyst. The closely bound Bi-Bi2O3 on the CdWO4 surface triggers the formation of a heterojunction structure at their interface. By analyzing the band structure of CdWO4 and Bi2O3, it is suggested that the heterojunction operates through a Z-scheme mechanism. The Bi metal serves as a bridge that intimately binds CdWO4 and Bi2O3, facilitating the rapid migration of electrons and improved charge separation. Therefore, the Bi-Bi2O3/CdWO4 composite exhibits high performance in PNF reactions. The optimal 7.5% Bi-Bi2O3/CdWO4 catalyst presents a PNF rate of 434.9 μmol L−1 g−1 h−1 under simulated sunlight irradiation, which is 4.9 times that of pure CdWO4. These findings from this study may offer valuable insights into the design and synthesis of new photocatalysts for PNF.

2D/2D Mn0.5Cd0.5In2S4/g-C3N4 heterojunctions with controllable charge transfer pathways for effective photocatalytic H2 production and antibiotics removal

The separation efficiency of photoinduced electron-hole pairs has an important function in photocatalytic reactions. In this work, the MnxCd1−xIn2S4 solid solutions with tunable band edge positions were fabricated by a facile hydrothermal route. Benefit from the regulation of band edge positions, the charge migration is regulated from type-I mechanism (MnIn2S4/g-C3N4 and CdIn2S4/g-C3N4) to type-II mechanism (Mn0.5Cd0.5In2S4/g-C3N4), which boosts the separation efficiency of charge carriers for photocatalytic reactions. The fabricated Mn0.5Cd0.5In2S4/g-C3N4 nanocomposites exhibit superior photocatalytic hydrogen production and tetracycline hydrochloride (TCH) photodegradation as compared to the g-C3N4 nanosheets, MnIn2S4, CdIn2S4, as well as the Mn0.5Cd0.5In2S4 solid solution. Based on the XPS test and the determination of band edge position, the type-II heterojunction photocatalytic mechanism is proposed to illustrate the transfer path of the charge carriers. This work offers a newfangled perspective for exploring an effective photocatalytic system.

Rational design of Ce-doped CdS/N-rGO photocatalyst enhanced interfacial charges transfer for high effective degradation of tetracycline

The charge carrier separation efficiency and the adsorption capacity of the photocatalyst usually affect the degradation rate of antibiotics. Herein, Cerium-doped leaf-like CdS (Ce-CdS) modified with ultrathin N-doped rGO (N-rGO) composites were successfully constructed (Ce-CdS/N-rGO) to investigate the removal efficiency of tetracycline (TC). X-ray photoelectron spectroscopy (XPS) and photoelectrochemical results revealed that Ce ions doped in CdS acting as the electron capture sites facilitated the interfacial charge transfer. Theoretical calculation (DFT) results indicated that the interfacial effect between Ce-CdS and ultrathin N-rGO promoted the transfer of photogenerated electrons under the synergistic effect between the doping and interface modification strategy. The optimized Ce5-CdS/N-rGO20 composites had the maximum TC removal capability (94.5%) and maintained a stable cycling performance. In addition, the adsorption-driven photocatalytic degradation pathway of TC was studied through mass spectrometry (MS) and in-situ Fourier transform infrared spectroscopy (in-situ FTIR). This study will provide an effective strategy for the construction of efficient photocatalytic composites for wastewater treatment.

Constructing nanoparticle-assembled CdS microspheres on a FeVO4 nanopolyhedrons photoanode for enhanced photoelectrochemical performance

Improving the light energy utilization to augment the charge carrier concentration and modulating the band alignment to facilitate charge carrier transport and separation are essential for semiconductor photoanode to achieve high-efficiently photoelectrochemical (PEC) performance. Herein, a novel FeVO4 nanopolyhedrons photoanode modified by nanoparticle-assembled CdS microspheres is constructed through an in-situ solid-state transformation and a chemical bath deposition, successively, to augment the concentration of carriers by improving light utilization and facilitate efficient transport and separation of carriers by building type-II structure for efficient PEC performance. The constructed nanoparticle-assembled CdS microspheres modified FeVO4 nanopolyhedrons photoanode generates a drastic improvement in photocurrent, which is 29 times higher than that of pristine FeVO4 nanopolyhedrons photoanode at 0.4 V vs. Ag/AgCl under AM 1.5 G simulated solar light irradiation. The experimental measurements of light absorption evidence that the modification of nanoparticle-assembled CdS microspheres substantially improves light harvesting ability of FeVO4 nanopolyhedrons from 300 to 800 nm for substantially generating charge carriers. Spectral measurements of X-ray photoelectron spectroscopy evidence that a band alignment of type-II structure is established at FeVO4/CdS interface, building directional interface charge transport channel for efficient transfer and separation of photoinduced charge carriers. This study offers a referable strategy for designing photoanodes to achieve PEC performance from the perspective of light energy utilization and interface energetics engineering.

Hydrothermal Synthesis of Heterostructured g-C3N4/Ag-TiO2 Nanocomposites for Enhanced Photocatalytic Degradation of Organic Pollutants.

In this study, heterostructured g-C3N4/Ag-TiO2 nanocomposites were successfully fabricated using an easily accessible hydrothermal route. Various analytical tools were employed to investigate the surface morphology, crystal structure, specific surface area, and optical properties of as-synthesized samples. XRD and TEM characterization results provided evidence of the successful fabrication of the ternary g-C3N4/Ag-TiO2 heterostructured nanocomposite. The heterostructured g-C3N4/Ag-TiO2 nanocomposite exhibited the best degradation efficiency of 98.04% against rhodamine B (RhB) within 180 min under visible LED light irradiation. The g-C3N4/Ag-TiO2 nanocomposite exhibited an apparent reaction rate constant 13.16, 4.7, and 1.33 times higher than that of TiO2, Ag-TiO2, and g-C3N4, respectively. The g-C3N4/Ag-TiO2 ternary composite demonstrated higher photocatalytic activity than pristine TiO2 and binary Ag-TiO2 photocatalysts for the degradation of RhB under visible LED light irradiation. The improved photocatalytic performance of the g-C3N4/Ag-TiO2 nanocomposite can be attributed to the formation of an excellent heterostructure between TiO2 and g-C3N4 as well as the incorporation of Ag nanoparticles, which promoted efficient charge carrier separation and transfer and suppressed the rate of recombination. Therefore, this study presents the development of heterostructured g-C3N4/Ag-TiO2 nanocomposites that exhibit excellent photocatalytic performance for the efficient degradation of harmful organic pollutants in wastewater, making them promising candidates for environmental remediation.

Thermally Induced Orderly Alignment of Porphyrin Photoactive Motifs in Metal-Organic Frameworks for Boosting Photocatalytic CO2 Reduction.

Efficient transfer of charge carriers through a fast transport pathway is crucial to excellent photocatalytic reduction performance in solar-driven CO2 reduction, but it is still challenging to effectively modulate the electronic transport pathway between photoactive motifs by feasible chemical means. In this work, we propose a thermally induced strategy to precisely modulate the fast electron transport pathway formed between the photoactive motifs of a porphyrin metal-organic framework using thorium ion with large ionic radius and high coordination number as the coordination-labile metal node. As a result, the stacking pattern of porphyrin molecules in the framework before and after the crystal transformations has changed dramatically, which leads to significant differences in the separation efficiency of photogenerated carriers in MOFs. The rate of photocatalytic reduction of CO2 to CO by IHEP-22(Co) reaches 350.9 μmol·h-1·g-1, which is 3.60 times that of IHEP-21(Co) and 1.46 times that of IHEP-23(Co). Photoelectrochemical characterizations and theoretical calculations suggest that the electron transport channels formed between porphyrin molecules inhibit the recombination of photogenerated carriers, resulting in high performance for photocatalytic CO2 reduction. The interaction mechanism of CO2 with IHEP-22(Co) was clarified by using in-situ electron paramagnetic resonance, in-situ diffuse reflectance infrared Fourier transform spectroscopy, in-situ extended X-ray absorption fine structure spectroscopy, and theoretical calculations. These results provide a new method to regulate the efficient separation and migration of charge carriers in CO2 reduction photocatalysts and will be helpful to guide the design and synthesis of photocatalysts with superior performance for the production of solar fuels.

Unconventional strategies to break through the efficiency of light‐driven water splitting: A review

AbstractSemiconductor‐based solar‐driven water splitting technology is an environmentally friendly and cost‐effective approach for the production of clean fuels. The overall solar‐to‐hydrogen efficiency of semiconductor‐based photo(electro)catalysts is jointly determined by factors, such as light absorption efficiency of the photo(electro)catalysts, internal separation efficiency of charge carriers, and injection efficiency of surface charges. However, the traditional improvement strategies, such as morphology control, functional layer modification, and band alignment engineering, still have certain limitations in enhancing the conversion efficiency of the photo(electro)catalytic water splitting. Recently, unconventional enhancement strategies based on surface plasmonic effects, piezoelectric effects, thermoelectric effects, and magnetic effects have provided unique pathways for improving the solar‐to‐hydrogen efficiency of photo(electro)catalysts. Therefore, this review outlines the fundamental concepts of these physical effects and elucidates their intrinsic mechanisms in enhancing the efficiency of photo(electro)catalysts for water splitting process through practical application examples. Ultimately, the future development of unconventional strategies for enhancing photo(electro)catalytic water splitting is envisioned.

Highly Stable Photocatalytic Dry and Bi-Reforming of Methane with the Role of a Hole Scavenger for Syngas Production over a Defective Co-Doped g-C3N4 Nanotexture

Photocatalytic reduction of CO2 with CH4 through the dry reforming of methane (DRM) is an attractive approach to recycling greenhouse gases into valuable chemicals and fuels; however, this process is quite challenging. Although there is growing interest in designing efficient photocatalysts, they are less stable, and have lower photoactivity when employed for DRM reactions. Herein, we developed a noble metal-free hierarchical graphitic carbon nitride (HC3N4) loaded with cobalt (Co) for highly efficient and stable photocatalytic dry reforming of methane to produce synthesis gases (CO and H2). The performance of the newly designed Co/HC3N4 composite was tested for different reforming systems such as the dry reforming of methane, bi-reforming of methane (BRM) and reforming of CO2 with methanol–water. The performance of HC3N4 was much higher compared to bulk g-C3N4, whereas Co/HC3N4 was found to be promising for higher charge carrier separation and visible light absorption. The yield of CO and H2 with HC3N4 was 1.85- and 1.81-fold higher than when using g-C3N4 due to higher charge carrier separation. The optimized 2% Co/HC3N4 produces CO and H2 at an evolution rate of 555 and 41.2 µmol g−1 h−1, which was 18.28- and 1.74-fold more than using HC3N4 during photocatalytic dry reforming of methane (DRM), with a CH4/CO2 feed ratio of 1.0. This significantly enhanced photocatalytic CO and H2 evolution during DRM was due to efficient charge carrier separation in the presence of Co. The CH4/CO2 feed ratio was further investigated, and a 2:1 ratio was best for CO production. In contrast, the highest H2 was produced with a 1:1 feed ratio due to the competitive adsorption of the reactants over the catalyst surface. The performance of the composite was further investigated for bi-reforming methane and methanol. Using photocatalytic CO2 reduction with CH4/H2O, the production of CO and H2 was reduced, whereas significantly higher CO and H2 evolved using the BRM process involving methanol. Using methanol with CO2 and H2O, 10.77- and 1.39-fold more H2 and CO efficiency was achieved than when using dry reforming of methane. The composite was also very stable for continuous synthesis gas production during DRM in consecutive cycles. Thus, a co-assisted g-C3N4 nanotexture is promising for promoting photocatalytic activity and can be further explored in other solar energy applications.

Addition of graphene oxide to ZIF-8/HKUST-1 composite for enhanced adsorptive and photocatalytic removal of congo red in wastewater

Ternary composites comprised of graphene oxide (GO), ZIF-8, and HKUST-1 with varying amounts of GO were successfully synthesized via the solvothermal method. Based on the photoluminescence characterization, the GO/ZIF-8/HKUST-1 composite presents a more efficient charge carrier separation and transfer compared to pristine HKUST-1 and ZIF-8. As a result, electron-hole recombination was hindered due to the presence of GO as an electron mediator in the heterojunction. The dark adsorption kinetics data for the removal of Congo Red (CR) dye fit well with the pseudo-second order model. The photocatalytic degradation performance of the GO/ZIF-8/HKUST-1 composite was investigated by means of degrading CR dye under UV-LED irradiation. The photodegradation efficiency of the GO(10)/ZIF-8/HKUST-1 composite for the removal of CR dye was 91.81% within 60 min of irradiation. The trapping experiments showed that hydroxyl and superoxide radicals are the main reactive species. The results of this study indicate that ternary composites comprised of MOFs as photocatalysts have great potential for degrading pollutants in aquatic environments.

Constructing a hexagonal/orthorhombic WO3 phase junction for enhanced photochromism

Mixed-phase composites with an optimal phase ratio show greater light utilization than their monophasic counterparts. This approach can be applied to develop mixed-phase photochromic tungsten oxide (WO3), which shows a rapid photoresponse and high-contrast coloring. Therefore, this paper optimized the phase ratio of hexagonal WO3 (h-WO3·0.33H2O) and orthorhombic WO3·H2O (o-WO3·H2O) to form a homojunction. To enhance its photochromism, nanostructured WO3 was produced via a one-step hydrothermal strategy, in which its phase structure and morphology were controlled by regulating the reaction temperature during precursor synthesis. Various material characterization techniques were carried out to reveal the complex crystal nucleation and growth of phase junctions. h-WO3·0.33H2O nanoparticles dominated the systems, while o-WO3·H2O nanoblocks also appeared from 41.77 wt% to 56.50 wt% at a low hydrothermal synthesis temperature, producing a mixture of both polymorphs. The improved photochromic properties (from light yellow to black-green) of the mixed-phase WO3 composite compared with pure h-WO3·0.33H2O (from gray-white to dark gray) was attributed to the formation of a phase junction between h-WO3·0.33H2O and o-WO3·H2O. The photoelectrochemical results showed that this resulted in highly efficient charge carrier separation and transfer. The strong visual rendering of the black-green state may be useful for developing intelligent displays and similar devices.

Simultaneously promoting adsorption and charge separation in Z-scheme ZnO/Cu2O heterojunctions for efficient removal of tetracycline

Exploring novel materials with both high adsorption capacity and photocatalytic properties is urgent in environmental remediation. In this work, a Z-scheme ZnO/Cu2O heterostructure with a large surface area of 45.42 m2/g was constructed by using the liquid phase reduction method. Compared to pure ZnO and pure Cu2O, the as-synthesized ZnO/Cu2O nanocomposites exhibited excellent capacity of adsorption and photodegradation for tetracycline (TC), which was degraded 95.3% of TC within 120 min under simultaneous adsorption and photocatalytic processes. Theory and experimental analysis manifested that the excellent adsorption-photocatalytic activity can be attributed to the large BET specific surface area, the efficient charge carrier separation and the high redox capability. The results of this study identified the potential advantages of ZnO/Cu2O composites for removing antibiotics to purify water resources and protect the environment.

Integration of Ag Plasmonic Metal and WO3/InGaN Heterostructure for Photoelectrochemical Water Splitting.

In this study, a Ag/WO3/InGaN hybrid heterostructure was successfully developed by sputtering and molecular beam epitaxy techniques, to obtain unique Ag nanospheres adorned with cauliflower-like WO3 nanostructure over the InGaN nanorods (NRs). Exploiting the localized surface plasmon resonance of Ag, the Ag/WO3/InGaN heterostructure exhibited superior photoabsorption ability in the visible region (400-700 nm) of the solar spectrum, with a surface plasmon resonance band centered around 440 nm. Comprehensive analysis through photoluminescence spectroscopy, photocurrent measurements, and electrochemical impedance spectroscopy revealed that the Ag/WO3/InGaN hybrid heterostructure significantly enhances the charge carrier separation and transfer kinetics leading to improved overall photoelectrochemical (PEC) performance. The photocurrent density of the Ag/WO3/InGaN photoanode is 1.17 mA/cm2, which is about 2.72 times higher than that of pure InGaN NRs under visible light irradiation. The photoanode exhibited excellent stability for about 12 h. From the study, it has been found that the maximum applied bias photon-to-current efficiency (ABPE) is ∼1.67% at the applied bias of 0.6 V. The improved PEC water splitting efficiency of the Ag/WO3/InGaN photoanode is attributed to the synergistic effects of localized surface plasmon resonance (LSPR), efficient charge carrier separation and transport, and the presence of a Schottky junction. Consequently, the plasmonic metal-assisted heterojunction-based semiconductor Ag/WO3/InGaN demonstrates immense potential for practical applications in photoelectrochemical water splitting.

Recent Progress on Semiconductor Heterogeneous Photocatalysts in Clean Energy Production and Environmental Remediation

Semiconductor-based photocatalytic reactions are a practical class of advanced oxidation processes (AOPs) to address energy scarcity and environmental pollution. By utilizing solar energy as a clean, abundant, and renewable source, this process offers numerous advantages, including high efficiency, eco-friendliness, and low cost. In this review, we present several methods to construct various photocatalyst systems with excellent visible light absorption and efficient charge carrier separation ability through the optimization of materials design and reaction conditions. Then it introduces the fundamentals of photocatalysis in both clean energy generation and environmental remediation. In the other parts, we introduce various approaches to enhance photocatalytic activity by applying different strategies, including semiconductor structure modification (e.g., morphology regulation, co-catalysts decoration, doping, defect engineering, surface sensitization, heterojunction construction) and tuning and optimizing reaction conditions (such as photocatalyst concentration, initial contaminant concentration, pH, reaction temperature, light intensity, charge-carrier scavengers). Then, a comparative study on the photocatalytic performance of the various recently examined photocatalysts applied in both clean energy production and environmental remediation will be discussed. To realize these goals, different photocatalytic reactions including H2 production via water splitting, CO2 reduction to value-added products, dye, and drug photodegradation to lessen toxic chemicals, will be presented. Subsequently, we report dual-functional photocatalysis systems for simultaneous energy production and pollutant photodegradation for efficient reactions. Then, a brief discussion about the industrial and economical applications of photocatalysts is described. The report follows by introducing the application of artificial intelligence and machine learning in the design and selection of an innovative photocatalyst in energy and environmental issues. Finally, a summary and future research directions toward developing photocatalytic systems with significantly improved efficiency and stability will be provided.

Construction of P-C3N4/C3N5 isotypic heterojunction for effective degradation of organic pollutants

BackgroundPhotocatalysis was an effective method for organic pollutant degradation, and graphitic carbon nitride g-C3N4 and g-C3N5 were famous two-dimensional semiconductors. Compared to the allotypic heterojunction, the band alignment and compatibility of isotypic heterojunction were superior. MethodsIn this work, an organic isotypic heterojunction was constructed via coupling phosphorus-doped C3N4 (P-C3N4) and g-C3N5. The characteristics were evaluated using transmission electron microscope, Fourier transform infrared, X-ray diffractometer, X-ray photoelectron spectrum, ultraviolet-visible (UV–vis) diffuse reflection spectrum, electronic spin resonance (ESR) analysis, photoluminescence spectrometer, electrochemical impedance spectroscopy, and photocurrent analysis. SignificantIsotypic heterojunction displayed high UV–vis light harvest, high separation efficiency of photo-induced charge carriers, and low surface resistance. Additionally, an internal-electric-field was established at the interface, which was beneficial for spatial separation of photo-induced charge carriers. As expected, the Rhodamine B (RhB) degradation efficiency was 7.3 and 12.3 times higher than that of the P-C3N4 and g-C3N5. Radical trapping experiment and ESR analysis indicated that •O2−, •OH, hole, 1O2, and electron played joint role in RhB degradation. In this work, a photocatalyst with excellent photocatalytic degradation properties was designed, and it provided a simple and novel strategy for environmental remediation.

Novel visible-light-active P-g-CN-based α-Bi2O3/WO3 ternary photocatalysts with a dual Z-scheme heterostructure for the efficient decomposition of refractory ultraviolet filters and environmental hormones: Benzophenones

The ubiquitous and refractory benzophenone (BP)-type ultraviolet filters, which are also endocrine disruptors, were commonly detected in the aquatic matrix and could not be efficiently removed by conventional wastewater treatment processes, thus causing extensive concern. Herein, a novel ternary nanocomposite, P-g-CN/α-Bi2O3/WO3 (P-gBW), was successfully fabricated by mixing cocalcinated components and applied to the decomposition of BP-type ultraviolet filters. The dual-Z-scheme heterostructure of P-gBW enhances visible-light absorption, efficiently facilitates separation and mobility, and prolongs the lifetime of photoinduced charge carriers via double charge transfer mechanisms. The optimum 95 wt% P-gBW exhibited excellent photocatalytic activity, degrading 96% 4-hydroxy benzophenone (4HBP) within 150 min and 93% 2,2′,4,4′-tetrahydroxybenzophenone (BP-2) within 100 min under visible-light illumination, respectively. The pseudo-first-order rate constant of 4HBP (1.15 h−1) was 6.8-, 3.1-, 3.3- and 2.2-fold higher than those of WO3, P-g-CN, α-Bi2O3, and P-g-CN/α-Bi2O3, respectively, while that of BP-2 (1.71 h−1) was 5.2-, 2.2-, 3.2- and 1.5-fold higher, respectively. The improved photocatalytic degradation was attributed to efficient photoinduced charge carrier separation and migration and prevented the recombination of electron holes, as verified by photoluminescence, transient photocurrent response, and electrochemical impedance spectroscopy. Trapping experiments, electron paramagnetic resonance, and band energy position indicated an efficient dual-Z-scheme heterostructure.

Carbazole‐Based Donor‐Acceptor Conjugated Microporous Polymers for Efficient Visible‐Light‐Driven Photocatalytic H2 Evolution†

Comprehensive SummaryConjugated microporous polymers (CMPs) featuring extended π‐structures, large specific surface area and tailor‐made functionalities are a class of promising organic photocatalysts for hydrogen evolution reaction (HER) from water. However, the photocatalytic activities of most CMPs are severely hindered by slow charge transfer rate and fast charge recombination process. Herein, we develop a strategy for the synthesis of donor‐acceptor CMPs through nickel(0)‐catalyzed Yamamoto cross‐coupling of 3,6‐dibromo‐9‐(4‐bromophenyl)carbazole (CZ) with 5,5'‐dibromo‐2,2'‐bipyridine (DBPy) for efficient HER from water. The PCZN‐4 prepared with a 2 : 3 stoichiometric ratio of CZ to DBPy exhibited the highest photocatalytic hydrogen evolution rate of 7160 μmol·g–1·h–1, which was nearly equal to 179 times and 143 times that of PCZN‐1 (40 μmol·g–1·h–1) and PCZN‐6 (50 μmol·g–1·h–1) obtained by Yamamoto homocoupling of CZ and DBPy, respectively. Compared to the homocoupling counterparts, the enhanced photocatalytic activity of PCZN‐4 results from improved separation efficiency of charge carriers. Interestingly, the photocatalytic H2 evolution performance of PCZN‐4 could be further improved up to 17080 μmol·g–1·h–1 by adjusting pH of the aqueous solution. This work offers a novel approach for improving photocatalytic efficiency by tuning the chemical structures and surrounding microenvironment of the polymer backbone.

Mechanism insights into visible light-induced crystalline carbon nitride activating periodate for highly efficient ciprofloxacin removal

The development of suitable and efficient periodate activation methods is currently a hot research topic. In this study, a novel efficient photocatalytic activation strategy using crystalline carbon nitride (CCN) and visible light (Vis) to activate PI for pollutant degradation was proposed. In the CCN/PI/Vis system, 100% ciprofloxacin hydrochloride (CIP) degradation was achieved within 10 min which was much higher than polymerized carbon nitride (PCN)/PI/Vis system. Besides, CCN/PI/Vis system demonstrated outstanding CIP removal activity in a wide range of pH, anions and organic matter, and natural water environments. Mechanistic studies demonstrated that the CCN/PI/Vis system decomposed CIP via nonradical/radical mixing processes dominated by 1O2 and electron transfer. The excellent degradation ability depends on the establishment of an electron cycle among CCN, PI, and CIP. In which, CCN generated photogenerated electrons, CIP acted as an electron donor, and PI served as an electron acceptor. Due to the extended in-plane periodicity and reduced interlayer distance and the formation of ordered electron transport channels caused by the increase of crystallinity, CCN had stronger light absorption and more efficient charge carriers separation and mobility than PCN, resulting in more durable and efficient photogenerated electron and thus much enhanced synergetic photocatalytic and PI activation ability of CCN.

Ni (II) doping induced lattice distortion in Zn3In2S6/BiOBr-OVs for boosting photocatalytic removal of antibiotics and Cr (Ⅵ) performance

Ni doping was used to create S-scheme heterojunction Ni-Zn3In2S6/BiOBr photocatalyst with an oxygen vacancy. This catalyst could remove both metronidazole and Cr (VI). The addition of Ni replaced Zn in the lattice of Zn3In2S6, inducing the generation of lattice distortion and increase the separation efficiency of charge carriers. For MNZ and Cr (VI), N-ZISB-2 (with 2 wt% Ni doping and 15 wt% BiOBr loading) demonstrated the best photocatalytic removal ability (MNZ: 99.31 %, Cr (VI): 99.83 %). The results of XRD and TEM indicated the successful substitution of Ni.The outcomes of XPS, UPS, and ESR demonstrated that the S-scheme heterojunction mechanism was followed by N-ZISB-x. Most intermediates of degradation had little ecological toxicity. In this work, we propose three potential routes for MNZ deterioration. XPS was used to confirm Cr (VI)'s reduction process. This investigation looked at the impact of oxygen vacancies and lattice distortion on photocatalytic performance.

Constructing CdIn2S4/ZnS type-I band alignment heterojunctions by decorating CdIn2S4 on ZnS microspheres for efficient photocatalytic H2 evolution

In this study, a series of promising binary hybrid heterojunction CdIn2S4/ZnS (CIS/ZnS) were constructed via a facile hydrothermal method. Credible characterization methods including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis diffuse reflectance spectra (DRS) were carried out to investigate the physicochemical properties the as-obtained photocatalysts. Photocatalytic water splitting for hydrogen evolution was performed to evaluate the photocatalytic activity of the photocatalyst. The results indicate that the light-harvesting ability could be markedly enhanced by decorating CdIn2S4 on ZnS microspheres. Compared with the pristine CdIn2S4 and ZnS, the hybrid photocatalysts present more efficient photocatalytic hydrogen production performance. Among composite photocatalysts, the 5% CIS/ZnS sample manifests the highest photocatalytic hydrogen production rate of 10.80 mmol g−1 h−1, which is 2.6 and 5.4 times higher than that of ZnS and CdIn2S4, respectively. Moreover, a type-I band alignment mechanism was prudently put forward to interpret the photocatalytic hydrogen generation activity. The boosted photocatalytic hydrogen evolution activities of CIS/ZnS can be attributed to the enhanced light-harvesting ability, efficient separation and transfer of the photo-induced charge carriers, and inhibition of electrons and holes recombination of binary hybrid CIS/ZnS photocatalysts.