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This study involves a heterojunction (denoted as PPMS) with an intimate heterointerface and S-scheme architecture, which consisted of a conjugated polymer of protonated PyDTDO-3 featuring a donor-acceptor (D-A) configuration and a 2D-layered MoS2. The optimal PPMS-0.5% heterojunction exhibits a remarkable efficiency of 75.4 mmol g−1h−1in generating H2when subjected to visible light illumination, representing an approximately 4.6 times enhancement compared to pure PyDTDO-3. To elucidate the photocatalytic mechanism, a range of characterization methods were utilized and calculations using density functional theory were carried out. The disparity in the work function between PyDTDO-3 and MoS2results in the creation of a Fermi-level gap. Consequently, the establishment of a built-in electric field facilitates the occurrence of the electrons in MoS2spontaneously transferring to PyDTDO-3 at the interface. The consumption of hole on the valence band of MoS2is accelerated by the electron transfer from the lowest unoccupied molecular orbital (LUMO) of PyDTDO-3, according to a kinetic study using femtosecond transient absorption spectra (fs-TAS). Moreover, the S-scheme PPMS exhibits a lower Gibbs free energy (ΔGH*, 0.77 eV) in comparison to the individual component, indicating it facilitates the formation of the transitional state (H*) and the effective desorption of molecular hydrogen on PPMS. Both the promoting directed charge migration and the increasing active sites contribute to the boosted photocatalytic H2evolution.

The construction of Z-scheme heterostructures using matching band semiconductors is an effective strategy for producing highly efficient photocatalysts. In this study, MgIn2S4(MIS) was grown in situ on In2O3microrods created with an In-based MOF material (In-MIL-68) as a template to successfully establish a unique MIS-In2O3heterojunction with a well-matched Z-scheme interface charge transfer channel. Tetracycline (TC) as a typical antibiotic was chosen as the target pollutant to evaluate the photocatalytic activity. After 120 min of visible light irradiation, the MIS-In2O3-(10:1) material had the greatest photocatalytic degradation activity of tetracycline with 96.55%, which was 2.39 and 4.26 times that of MIS and In2O3, respectively. The improved photocatalytic activity is attributed to the in situ growth of MIS on In2O3, forming a Z-scheme heterojunction at the interface, which not only increases the specific surface area, exposes the abundant active site, and improves light utilization but also facilitates the migration and separation of photogenic carriers. The photocatalytic degradation products of TC were detected by liquid chromatography–mass spectrometry (LC-MS), and a preliminary degradation pathway was proposed. Radical capture experiments and ESR analysis confirmed that the main active species were holes (h+), superoxide radicals (•O2–), and superoxide and hydroxyl radicals (•OH). Finally, combined with band position analysis, this study proposes a direct Z-scheme heterojunction mechanism to improve the photocatalytic degradation of tetracycline in MIS under visible light.

The fabrication of S-scheme heterojunctions with fast charge transfer and good interface contacts, such as intermolecular π–π interactions, is a promising approach to improve photocatalytic performance. A unique two-dimensional/two-dimensional (2D/2D) S-scheme heterojunction containing TpPa-1-COF/g-C3N4nanosheets (denoted as TPCNNS) was developed. The established maximum interfacial interaction between TpPa-1-COF NS and g-C3N4NS may result in a π–π conjugated heterointerface. Furthermore, the difference in the work functions of TpPa-1-COF and g-C3N4results in a large Fermi level gap, leading to upward/downward band edge bending. The spontaneous interfacial charge transfer from g-C3N4to TpPa-1-COF at the π–π conjugated interface area results in the presence of a built-in electric field, according to the charge density difference analysis based on density functional theory calculations. Such an enhanced built-in electric field can efficiently drive directional charge migration via the S-scheme mechanism, which enhances charge separation and utilization. Thus, an approximately 2.8 and 5.6 times increase in the photocatalytic hydrogen evolution rate was recorded in TPCNNS-2 (1153 μmol g−1h−1) compared to pristine TpPa-1-COF and g-C3N4NS, respectively, under visible light irradiation. Overall, this work opens new avenues in the fabrication of 2D/2D π–π conjugated S-scheme heterojunction photocatalysts with highly efficient hydrogen evolution performance.

A novel feature extraction method based on the energy cumulant of Choi-Williams distribution has been proposed, which copes with the complex electromagnetic environment and varied signal styles. The energy cumulant of Choi-Williams distribution has been calculated from the accumulations of each frequency sample value with different time samples. Preceding this procedure, the time frequency distribution via Choi-Williams distribution has been processed through base noise reduction. Henceforth, a simulation analysis based on the discriminability and recognition effect of the proposed features in a low SNR environment has been carried out. In the discriminability experiment, the kernel fuzzy C-means clustering algorithm has been employed for classifying the radar pulse modulated radiation source signals. In the recognition effect analysis, the deep belief network has been proposed to employ the input feature vectors for training to achieve the radar emitter recognition and classification. Simulation results demonstrate that the proposed feature extraction method is feasible and robust in radar emitter classification and recognition even at a low SNR.

Hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) have aroused great interest, but the high price of platinum group metals (PGMs) limits their development. The electronic reconstruction at the interface of a heterostructure is a promising strategy to enhance their catalytic performance. Here, MoO2/Ni heterostructure was synthesized to provide effective HER in an alkaline electrolyte and exhibit excellent HOR performance. Theoretical and experimental analyses prove that the electron density around the Ni atom is reduced. The electron density modulation optimizes the hydrogen adsorption and hydroxide adsorption free energy, which can effectively improve the activity of both HER and HOR. Accordingly, the prepared MoO2/Ni@NF catalyst reveals robust HER activity (η10= 50.48 mV) and HOR activity (j0= ∼1.21 mA cm–2). This work demonstrates an effective method to design heterostructure interfaces and tailor the surface electronic structure to improve HER/HOR performance.

Recently, the seawater desalination process has gained widespread attention due to lack of drinking water. Among several membrane distillation methods for desalination, vacuum membrane distillation (VMD) is one of the emerging technologies that has mostly focused. In this study, an integrated heat and mass transfer model for the VMD process is established and the simulation results are validated with experimental data available in the literature. The numerical model is solved using in-house coding in Mathcad. The effect of some influential process parameters like feed circulation velocity, feed temperature, salinity, and heat transfer coefficient (HTC) on VMD flux is investigated. Moreover, the influence of some membrane characteristics like membrane porosity, membrane pore size and membrane thickness on permeate flux is also considered. Furthermore, the effect of some operating parameters on temperature polarization is also presented in this paper. Results of the numerical model indicated that the VMD flux enhanced with an increase in velocity, feed temperature, membrane porosity, membrane pore size, and HTC, whereas permeate flux declined with an increase in salt concentration, vacuum pressure, and membrane thickness. The maximum increase in permeate flux was 21.62 kg/m2h by increasing feed temperature from 35°C to 65°C at a constant feed velocity of 1.0 m/s. Additionally, it was confirmed that an optimum value of the membrane parameter is preferable for a substantial improvement in overall VMD performance.

In this paper, we developed an integrated model of coal gasification with methanol synthesis reactor using Aspen Plus®. Gasification process and methanol synthesis are modelled and simulated based on low grade coal of Thar coalfield. After validation of the simulation results with experimental data, the thermodynamic analysis of integrated process is carried out to predict the optimal methanol yield. Moreover, the influence of reactor operating temperature and pressure, CO2/H2ratio and amount of catalyst, on the methanol synthesis is investigated. The results indicated that for coal input feed of 60 kg/s, the syngas flow rate of 9.4 kg/s was obtained in the gasification section. Whereas, the optimal methanol yield of 23.8% and 28.2% are obtained for Vanden Bussche (VB) and Graaf model, respectively in methanol synthesis reactor. Furthermore, the optimal operating temperature in methanol reactor was 210°C and 240°C for Graaf model and VB model, respectively.

Highly ordered TiO2nanotube arrays (TiO2NTs) were prepared by anodic oxidizing method on a surface of Ti substrate. Fabrication of nitrogen-doped TiO2nanotube arrays (N-TiO2NTs) was carried out by immersion in ammonia solution. CdS nanoparticles loaded N-doped TiO2nanotube arrays (CdS/N-TiO2NTs) were obtained by successive ionic layer adsorption and reaction (SILAR) technique. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL) emission spectra and ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy (DRS). The results indicate that the TiO2nanotube diameter and wall thickness are 100 nm to 120 nm and 20 nm to 30 nm, respectively. Moreover, the morphology and structure of the highly ordered TiO2NTs are not affected by N-doping. Furthermore, CdS nanoparticles are evenly distributed on the surface of TiO2NTs. Finally, the photocatalytic activity of CdS/N-TiO2NTs was evaluated by degradation of MO under visible-light irradiation. Compared with TiO2NTs, N-TiO2NTs, CdS/N-TiO2NTs exhibited enhanced photocatalytic properties, and the highest degradation rate of CdS/N-TiO2NTs could reach 97.6 % after 90 min of irradiation.

Highly ordered TiO2nanotube (TiO2NT) arrays were prepared by anodic oxidizing method on the surface of the Ti substrate. Nitrogen-doped TiO2nanotube (N-TiO2NT) arrays were carried out by ammonia solution immersion, and Ag nanoparticles loaded N-doped TiO2nanotube (Ag/N-TiO2NT) arrays were obtained by successive ionic layer adsorption and reaction (SILAR) technique. The samples were characterized by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) emission spectra, ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS). The result indicated that the diameter and wall thickness of the TiO2NT are 100–120 and 20–30 nm, respectively. Moreover, the morphology and structure of the highly ordered TiO2NTs were not affected by N-doping. Furthermore, Ag nanoparticles were evenly deposited on the surface of TiO2NTs in the form of elemental silver. Finally, the photocatalytic activity of Ag/N-TiO2NTs was evaluated by degradation of methyl orange (MO) under visible-light irradiation. The Ag/N-TiO2NTs exhibited enhanced photocatalytic properties, which could reach 95% after 90-min irradiation.

The effect of variable sodium concentrations on the anaerobic digestion performance of Sargassumsp. was investigated, and the variation in bacterial and archaeal communities was analyzed by high-throughput gene sequencing. Results showed that the maximum methane yield of 290.41 ± 34.21 mL of CH4g–1of volatile solids was obtained at a sodium concentration of 4.42 g L–1, increased by 38.1% compared to the control group. Meanwhile, higher volatile fatty acids production was observed at the sodium concentration of 4.42 g L–1. The inhibitory concentration values of 10%, 50%, and 90% occurred at the sodium concentrations of 6.3, 11.3, and 18.7 g L–1, respectively. The hydrolytic, acidogenic, and acetogenic bacteria and the hydrogenotrophic methanogens could normally metabolize at sodium concentrations of 2.46–24.08 g L–1, whereas the acetoclastic methanogens were severely inhibited at sodium concentrations greater than 20.15 g L–1. The microbial community structure showed that Paludibacterand Fibrobacterplayed a key role in the step of acidogenesis/acetogenesis at sodium concentration of 4.42 g L–1, while Defluviitaleaand Levilineawere the major acidogenic/acetogenic bacteria at sodium concentration of 20.15 g L–1. Methanosaetaand Methanosarcinawere the predominate methanogens at sodium concentration of 4.42 g L–1.

WO3, a visible-light responsive photocatalyst, absorbs light up to 480 nm with several intriguing advantages such as low cost, harmlessness, and stability in acidic and oxidative conditions. In this review, the relationship between the morphology control and the photocatalytic activity of WO3is analyzed in detail. In particular, the WO3exposed {002}-dominant facet with high-surface-energy generally shows excellent photocatalytic performance, and the quantum-confined WO3nanoparticles exhibit a promising future. Furthermore, some main strategies for improving the photocatalytic activity of WO3, such as surface hybridization with graphene, noble metal deposition, semiconductor coupling, and alkali hydroxide loading, are systematically summarized and highlighted. In the noble metal/WO3composite, the noble metal always works as an electron pool and catalyzes O2reduction through a multi-electron reduction process to form H2O2and H2O instead of the traditional single-electron process. In addition, the preparation methods, photocatalytic enhancement factors and possible photocatalytic mechanisms for the WO3/semiconductor composites are described. Moreover, various photocatalytic applications of WO3-based photocatalysts, such as photodegradation of organics, air purification, self-cleaning, CO2photoreduction, heavy metal ion treatment, hydrogen evolution from splitting water, and bacterial disinfection, are introduced and summarized. Finally, the main conclusions and future perspectives of WO3-based photocatalysts are pointed out. It is anticipated that this review could offer guidelines for designing novel WO3-based photocatalysts with low cost and high efficiency, which can possess promising prospects of application to meet the urgent demands of highly efficient solar energy conversion in the areas of renewable energy and environmental purification.

In this paper, size-controlled morphologies of (Y, Gd)VO4and (Y, Gd)VO4:Ln3+(Ln = Eu, Yb, Er, and Ho) were obtained viaa facile hydrothermal route, and their properties for drug delivery and photoluminescence were investigated. Monodisperse ellipsoid-like hollow (Y, Gd)VO4were designed by employing (Y, Gd)(OH)CO3colloidal spheres as a sacrificial template and NH4VO3as a vanadium source, and the formation mechanism could be interpreted by the Kirkendall effect. The control of particle size for hollow (Y, Gd)VO4was realized, facilitating their practical application. Mesoporous core–shell structured (Y, Gd)VO4:Ln3+@nSiO2@mSiO2were designed to improve the properties for drug release. Typically, red emission of YVO4:Eu3+predominated under 465 nm excitation; the upconversion spectra of YVO4:Yb3+, Er3+and YVO4:Yb3+, Ho3+revealed green and red color upon 980 nm excitation, respectively. The biocompatibility and drug release evaluations indicate the potential biological applications of the samples.

The H2Ti3O7 sheet-like products were successfully obtained during the formation process of titanate nanotubes via alkali hydrothermal synthesis. The morphological features and structural characteristics of the sheet-like products were studied systematically. Results indicate that three types of sheet-like structures, including layered structure, multi-layer nanosheets and single-layer nanosheet of titanate H2Ti3O7, were observed. The structural characteristics of these sheet-like products were determined by high-resolution structure analysis. It is found that the top/bottom surface of these sheet-like structures is the (010) plane of H2Ti3O7.

Ho3+/Yb3+/Tm3+ tri-doped Y2SiO5 phosphors were synthesized by the coprecipitation method. Bright white luminescence upon 980 nm near-infrared excitation can be observed for the sample at the optimum chemical composition of Y2SiO5: 5%Yb3+/0.4%Tm3+/0.1%Ho3+, and the measured white light consisting of blue, green, and red emissions can be fine-tuned in a wide range of pump power, which is intense and visible to the naked eye even with a pump power of 62 mw. Besides, the color coordinates and correlated color temperatures (CCTs) can also be adjusted between high and low, under different excitation pump powers, and the obtained optimal color coordinate (0.333, 0.319) is very close to the standard white light (0.333, 0.333) coordinate. Based on the dependence of the up-conversion emission intensity on the excitation power, we could confirm that energy transfer processes from Yb3+ to Tm3+ and Ho3+ ions took place simultaneously in the Ho3+/Yb3+/Tm3+ tri-doped Y2SiO5 phosphors, and produced red up-conversion emission, however, the blue and green emissions came from Tm3+ and Ho3+ ions, respectively. The white light may be a possible candidate for applications in the field of lighting, displays, and photonics.

Bismuth vanadate (BiVO4) is a promising photocatalyst for water pollution degradation and photocatalytic oxygen evolution. In this work, we prepared 2D/2D BiVO4–Bi4V2O10heterostructure with tight interfacial contact via a facile one-step hydrothermal process. The crystal structure and morphology of the samples could be easily regulated by changing the pH values of the solution. The BiVO4–Bi4V2O10heterostructure exhibited an enhanced photodegradation rate of Cr(VI) and oxygen evolution that of bare BiVO4, indicating that the synergistic effect and the interfacial fusions between BiVO4and Bi4V2O10can effectively promote the migration and separation rate of photoexcited charge carriers.

The H2Ti3O7sheet-like products were successfully obtained during the formation process of titanate nanotubes via alkali hydrothermal synthesis. The morphological features and structural characteristics of the sheet-like products were studied systematically. Results indicate that three types of sheet-like structures, including layered structure, multi-layer nanosheets and single-layer nanosheet of titanate H2Ti3O7, were observed. The structural characteristics of these sheet-like products were determined by high-resolution structure analysis. It is found that the top/bottom surface of these sheet-like structures is the (010) plane of H2Ti3O7.

Ho3+/Yb3+/Tm3+tri-doped Y2SiO5phosphors were synthesized by the coprecipitation method. Bright white luminescence upon 980 nm near-infrared excitation can be observed for the sample at the optimum chemical composition of Y2SiO5: 5%Yb3+/0.4%Tm3+/0.1%Ho3+, and the measured white light consisting of blue, green, and red emissions can be fine-tuned in a wide range of pump power, which is intense and visible to the naked eye even with a pump power of 62 mw. Besides, the color coordinates and correlated color temperatures (CCTs) can also be adjusted between high and low, under different excitation pump powers, and the obtained optimal color coordinate (0.333, 0.319) is very close to the standard white light (0.333, 0.333) coordinate. Based on the dependence of the up-conversion emission intensity on the excitation power, we could confirm that energy transfer processes from Yb3+to Tm3+and Ho3+ions took place simultaneously in the Ho3+/Yb3+/Tm3+tri-doped Y2SiO5phosphors, and produced red up-conversion emission, however, the blue and green emissions came from Tm3+and Ho3+ions, respectively. The white light may be a possible candidate for applications in the field of lighting, displays, and photonics.