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Hydrogen energy, as one clean energy, is one of the important ways to decarbonize in the future. The advancement of doping and constructing defect engineering in graphitic carbon nitride (g-C 3 N 4) show promise for artificial photosynthesis for H 2 evolution using solar energy. Unfortunately, it is still difficult to generate g-C 3 N 4 that has been co-modified by doping and defect and investigate their synergistic effects. In this study, potassium thioacetate was used first-time as a potassium source and dehydrogenation agent to prepare g-C 3 N 4 decorated by K+ ions and cyano groups with enhanced H 2 evolution by a one-step method in an air atmosphere. The presence of K+ ions can increase the density of electron clouds in the delocalized π bond of the heptazine ring. The cyano group may successfully delocalize the solitary valence electrons in conjugated heterocycles since it is a potent electron-withdrawing group. These outcomes allow the modified catalysts to achieve improved H 2 evolution activity, reduced interfacial transfer resistance, and increased light absorption and photocurrent. Finally, K(0.05)-CN's photocatalytic hydrogen evolution rate (HER) rose to 1319 μmol h−1 g−1, which is five-fold better than that of CN, and the normalized HER reached 118 μmol h−1 m−2, which was much higher than other reports. This research not only offers a fresh approach to creating photocatalysts with good H 2 evolution efficiency but also advances a deep understanding of how structural defects and alkali metal doping affect photocatalytic activity. [ABSTRACT FROM AUTHOR]

One of the most important methods for modifying semiconductors is defect engineering, but only the right quantity of defects in the right chemical environment can produce desirable results. Heat treatment processes associated with g-C3N4 are occasionally carried out in N2 atmosphere, however, the catalytic performance of g-C3N4 produced by direct condensation of only nitrogen-rich precursors in N2 atmosphere is often unsatisfactory. This is typically attributed to the introduction of numerous defects, but the actual relationship between the formation of defects and the N2 atmosphere is rarely explained, and the resulting quantity of defects is difficult to control. We propose that the melam to melem transition is restricted due to the lack of O2 during the heat treatment of the nitrogen-rich precursor of g-C3N4 in N2 atmosphere, which leads to a substantial quantity of defects in the synthesized g-C3N4. To enhance its photocatalytic property, we propose a method to reduce the quantity of defects due to calcinating in N2 atmosphere by protonating the precursor in a way that increases the polymerization of the product. The test analysis indicated that only a moderate quantity of defects that contribute to electron excitation and enhance the separation efficiency and density of photogenerated carriers were retained, and the hydrogen evolution performance of the prepared catalyst was significantly improved. [ABSTRACT FROM AUTHOR]

The photocatalytic water splitting capability of metal‐free graphitic carbon nitride (g‐C3N4) photocatalyst is determined by its microstructure and photoexcited electrons transfer. Herein, a segmented structure was developed, consisting of alternant g‐C3N4 nanotubes and graphitic carbon rings (denoted as Cr‐CN‐NT). The Cr‐CN‐NT showed ordered structure and ultralong length/diameter ratio of 150 nm in diameter and a few microns in lengths, which promoted electron transport kinetics and elongated photocarrier diffusion length and lifetime. Meanwhile, the local in‐plane π‐conjugation was formed and extended in Cr‐CN‐NT, which could improve charge carrier density and prohibit electron–hole recombination. Accordingly, the average hydrogen evolution rate of Cr‐CN‐NT reached 9245 μmol h−1 g−1, which was 61.6 times that of pristine CN, and the remarkable apparent quantum efficiency (AQE) of Cr‐CN‐NT reached up to 12.86 % at 420 nm. This work may provide a pathway for simultaneous morphology regulation and in‐plane modification of high‐performance photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tunable carbon vacancy g-C 3 N 4 is synthesized by wood pyrolysis induced etching. • CO x gas effectively tailors physicochemical and photoelectric properties of g-C 3 N 4. • Small particle sizes and amorphization transition in phase structure is achieved. • This photocatalyst exhibits nearly 20 times improvement in H 2 evolution. Post-thermal treatment is a widely employed technique for the fabrication of graphitic carbon nitride (g-C 3 N 4) with thin-layered, porous and defect-rich structures for photocatalytic hydrogen evolution. Here, the synthesis of catalysts is assisted with wood pyrolysis, which triggers an etching on g-C 3 N 4 by released trace carbon oxides gases. Specifically, a nickel foam is used as the substrate to hold a piece of pine wood on top of bulk g-C 3 N 4 , thereby preventing interfacial structural damage and introduction of impurities in a conventionally used solid state mixing process. Such a multicomponent atmosphere results g-C 3 N 4 with tunable carbon vacancies (TCCNx) and small particle sizes, and therefore a large specific surface area is obtained. The as-prepared TCCNx exhibits an improved photocatalytic hydrogen evolution rate of 3703 μmol·g−1·h−1, outperforming the bulk g-C 3 N 4 by ∼20 folds under visible light (λ > 420). The reason for enhanced photocatalytic performance is ascribed to a favorable optical property, rapid charge carrier separation, and efficient charge transfer processes. This unique top-down etching strategy provides valuable insights for designing efficient polymer photocatalysts with controllable properties. [ABSTRACT FROM AUTHOR]

The photocatalytic degradation of Rhodamine B (Rh B) wastewater using Ag/g-C3N4 composites has aroused great interests. To date, the composite is dominated by Ag nanoparticles (AgNPs) on the g-C3N4 surface. Only a few studies have concentrated on 1D Ag nanowires (AgNWs) wrapped with g-C3N4 which could bring some new aspects. The wrapped structures can provide large interface, which promotes the exciton dissociation. Moreover, AgNWs with high conductivity can facilitate a fast charge transfer from g-C3N4 and therefore suppress the charge recombination. Herein, a facile approach via a post-mechanical-mixing route has been used to fabricate 1D-2D AgNWs/g-C3N4 composites with enhanced photocatalytic activity for Rh B degradation. AgNWs staggered arrangement can form a conductive network for fast charge transfer. The light absorption of the hybrid in the visible-light region is increased due to the light-scattering from 1D AgNWs. Moreover, conformal contact between AgNWs and g-C3N4 promotes the separation of photo-induced electron-hole pairs. The AgNWs/g-C3N4 hybrid for 2 wt% achieves the best photocatalytic activity for Rh B dye degradation. This work reports an idea using 1D–2D metal-organic hybrid materials as photocatalysts and proposes a facile post-mechanical-mixing method for fabricating hybrids toward various applications. [ABSTRACT FROM AUTHOR]

Graphite carbon nitride (g-C 3 N 4) is an appealing metal-free photocatalyst for hydrogen evolution, but the potential has been limited by its poor visible-light absorption and unsatisfactory separation of photo-induced carriers. Herein, a facile one-pot strategy to fabricate carbon self-doped g-C 3 N 4 composite through the calcination of dicyanamide and trace amounts of dimethylformamide is presented. The as-obtained carbon self-doped catalyst is investigated by X-ray photoelectron spectroscopy (XPS), confirming the substitution of carbon atoms in original sites of bridging nitrogen. We demonstrate that the as-prepared materials display remarkably improved visible-light absorption and optimized electronic structure under the premise of principally maintaining the tri- s -triazine based crystal framework and surface properties. Furthermore, the carbon doped g-C 3 N 4 composite simultaneously weakens the transportation barrier of charge carriers, suppresses charge recombination and raises the separated efficiency of photoinduced holes and electrons on account of the extension of pi conjugated system. As a result, carbon self-doped g-C 3 N 4 exhibits 4.3 times greater photocurrent density and 5.2 times higher hydrogen evolution rate compared with its bulk counterpart under visible light irradiation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • PtO nanodots are homogeneously dispersed on the host photocatalyst. • The size of PtO nanodots is smaller than Pt nanoparticles. • PtO nanodots display superior activity in co-catalyzing hydrogen evolution. • PtO nanodots exhibit high durability. Abstract PtO nanodots (∼2.5 nm) with high crystallinity are homogeneously deposited on the surface of g-C 3 N 4 by a two-step refluxing-calcination method. XPS analysis indicates that a strong interaction is formed between PtO and g-C 3 N 4 , which is beneficial for the transportation of charge carriers from g-C 3 N 4 to the co-catalyst and therefore results in a prolonged carrier life time in the composite. A series of electrochemical tests, including EIS, LSV and OCVD prove that PtO can significantly enhance the conductivity and light response of g-C 3 N 4 compared with Pt. PtO and Serving as hydrogen evolution sites, the highly dispersed PtO nanodots can shorten the diffusion path lengths for photogenerated electrons in the host photocatalyst as well as suppress the undesired hydrogen oxidation reaction. Remarkably, PtO coupled g-C 3 N 4 (0.19 wt% Pt) exhibits excellent hydrogen production activity, giving a turnover frequency of 552.7 h−1, which is 51 times that of Pt nanoparticles confined g-C 3 N 4. The PtO nanodots also display high photostability and would not agglomerate into clusters or be reduced by the photogenerated electrons even after 40 h of irradiation. The present work also provides a new method for synthesis of high performance co-catalysts with low Pt content used in other photocatalytic reactions and energy applications. [ABSTRACT FROM AUTHOR]

A facile and green method was developed to fabricate porous graphitic carbon nitride (g-C 3 N 4 ) nanosheets by simply pre-polymerizing melamine at 350 °C for 2 h. A porous structure was formed in the resulted g-C 3 N 4 (CN-350). Consequently, the specific surface area and pore volume of CN-350 was greatly enhanced, resulting in superior performance in photocatalytic hydrogen evolution and dye degradation. The hydrogen evolution rate and degradation constant of CN-350 were 11.2 and 8.8 times higher than that of bulk g-C 3 N 4 under visible light irradiation. The porous structure not only provided CN-350 with abundant active catalytic sites and cross-plane diffusion channels to facilitate the charge and mass transportation, but also promoted the charge separation in the photocatalytic reaction. This work provided a promising method for mass-production of highly active and stable g-C 3 N 4 -based photocatalysts for environmental and energetic applications. [ABSTRACT FROM AUTHOR]

Abstract: As an amorphous or semicrystalline material, graphitic carbon nitride (g‐C3N4) displays poor photocatalytic activity owing to rapid recombination of the photogenerated charge carriers, which is mainly caused by a high density of defects in the graphitic structure. In this work, a porous O‐doped g‐C3N4 (P‐CNO) nanosheet with a highly ordered architecture is fabricated by introducing a novel hydrothermal treatment to the precursor before the final thermal condensation. The photocatalytic hydrogen evolution rate (HER) and HER per surface area of P‐CNO are 13.9 and 1.7 times higher than that of bulk g‐C3N4. The improved photocatalytic activity is ascribed to a synergistic effect of O doping, a porous sheet‐like morphology, and increased crystallinity. This work also provides a new approach for the synthesis of other polymer‐based photocatalysts with high crystallinity and excellent performance. [ABSTRACT FROM AUTHOR]

Hexagonal WO 3 (h-WO 3 ) was prepared by using Na 2 SO 4 and (NH 4 ) 2 ·SO 4 as capping agents under different hydrothermal conditions. XRD, SEM and TEM results indicated that three types of morphologies, including h-WO 3 rods with exposed (2 0 0) facets, h-WO 3 nanosheets with exposed (0 0 2) facets and h-WO 3 with corn cob-like structure and no preferred direction, could be obtained by tuning the capping agents and pH. Specifically, h-WO 3 nanosheets with exposed (0 0 1) facets have the best visible photocatalytic properties due to its high specific surface area and charge separation nature on the (0 0 2) high energy facets. [ABSTRACT FROM AUTHOR]

Polymeric carbon nitride as a low-cost and robust photocatalyst has been limited by the rapid recombination of photo-generated electron–hole pairs and low visible light utilization efficiency. It is demonstrated a ternary heterostructured photocatalyst polymeric graphitic carbon nitride (for simplicity, g-C 3 N 4 ) coupled with Bi 4 Ti 3 O 12 /Bi 2 Ti 2 O 7 (BTO) by a simple route of electrospinning/calcination. This optimal photocatalyst shows efficient reproducible hydrogen evolution (638 μmolh −1 g −1 ) under visible light, which is about 7.6 times higher than BTO and 1.55 times higher than g-C 3 N 4 . The optimal loading of BTO nanorods on g-C 3 N 4 increases light absorption to generate more photoelectrons and simultaneously promotes separation and transfer of photoinduced electrons and holes, which arises from the intrinsic electric field formed between the (Bi 2 O 2 ) 2+ slabs and the (Bi m−1 TiO 3m+1 ) units in Bi 2 Ti 2 O 7 and Bi 4 Ti 3 O 12 . On the basis of further obtained temperature dependent experimental results through the Arrhenius relationship, mechanism of temperature dependent spontaneous polarization is proposed. This study offers new insight into the design of efficient ternary heterostructured advanced materials for water treatment to resolve the energy crisis problem. [ABSTRACT FROM AUTHOR]

Two-dimension layered polymeric carbon nitride possessing unique electronic structure and high specific surface area exhibits immense potentials for visible light driven photocatalytic activity for hydrogen production by the decomposition of water molecules. Herein, porous polymeric carbon nitride nanosheets were obtained by lithium chloride ions in situ intercalating bulk materials in thermal polycondensation process and followed by liquid exfoliation in water. The porous nanosheets show two-dimension layered structure with the thickness of 2–3 nm, a high density in-plane pores with 2–3 nm diameter, a higher surface area (186.3 m 2 g −1 ), enlarged bandgap (by 0.16 eV), prolonged charge carrier lifetime, enhanced electronic transport ability, increased charge carrier density and improved photocurrent responses, which could significantly give rise to photocatalytic activity. The results highlight the crucial role of 2D porous structure, high specific surface area and unique electronic structure on the photocatalytic performance of polymeric carbon nitride materials. [ABSTRACT FROM AUTHOR]

The ZnWO 4 nanorods were fabricated by template-free hydrothermal route and characterized by X-ray diffraction, scanning electron microscopy, Raman, fluorescence and UV–visible spectra. The ZnWO 4 nanorods were descended from ZnWO 4 nanosheets with the increase of the pH value. The correlations among these optical spectra were studied and the results showed that the ZnWO 4 nanorods had good crystallinity and few oxygen-vacancy defects comparing with ZnWO 4 nanosheets. Fluorescence emission and UV–visible transmission spectra of ZnWO 4 nanorods were increased, while the fluorescence excitation and UV absorption spectra were decreased in the wavelength region of 250–325 nm. This phenomenon was reversed in the wavelength region of 325–400 nm. The ZnWO 4 nanorods displaying superior photocatalytic activity were suitable to be photocatalytic materials which could absorb selectively ultraviolet in the wavelength of 325–400 nm for their low recombination probability of light excited electron–hole. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide hybridized hierarchical ZnO nanorods (RGO/ZnO) were fabricated through thermal treatment of aqueous solution containing metallic Zn powder, Zn(NO 3 ) 2 ·6H 2 O, graphene oxide (GO), and NaOH at 110 °C. This one-spot, additives-free method successfully made metallic Zn powder a reducing agent of GO, a precursor of ZnO, and also a morphology controller of RGO/ZnO. RGO/ZnO nanohybrids with 4 wt-% of RGO displayed optimal photocurrent and photocatalytic response under UV irradiation with 10 times and 2.2 times that of pure ZnO nanoflowers, respectively. Strong coupling and electronic interaction between GO and ZnO were verified by using XPS measurement and photoelectrochemical technique. The combination of supreme absorption (of UV light and dye), suppressed photogenerated carriers recombination, and decreased solid interlayer resistance of nanohybrids contributed to their superior photochemical properties. [ABSTRACT FROM AUTHOR]

Ferrophotocatalytic degradation is considered as a promising strategy for environmental remediation. In this work, layered perovskite La 2 Ti 2 O 7 was synthesized by a hydrothermal method. The La 2 Ti 2 O 7 powders obtained under magnetic fields exhibit rectangular nanosheets with about ten nanometers in thickness, 400 nanometers in width and several micrometers in length. The La 2 Ti 2 O 7 nanosheets expose dominant {0 0 1} facets and other secondary {0 1 0} and {1 0 0} facets. The well-dispersed nanosheets enjoy narrower band gaps, better ferroelectricity and better photocatalytic ability toward ofloxacin pollutant in comparison with the powders prepared without a magnetic field. The La 2 Ti 2 O 7 nanosheets require 20 min to photodegrade 90% of ofloxacin. Their photodegradation effect is enhanced after polarization, and further improved under an ultrasonic vibration within only 10 min to degrade above 90% ofloxacin pollutant, which is superior to the recent reports. The photogenerated electrons play a main role through •O 2 − and •OH radicals. The strong built-in electric field and fewer domain boundaries in the ferroelectric nanocrystallites after polarization effectively separate the photogenerated electron-hole pairs and promote their migration to surface for photodegradation reaction. This work is helpful to develop high-performance ferrocatalysts and promote the ferroelectric application in water remediation. La 2 Ti 2 O 7 nanosheets were synthesized by a hydrothermal method under magnetic field, whose photocatalytic ability is enhanced through controlling morphology, adjusting bandgap, polarization, and piezoelectric effect. [Display omitted] • La 2 Ti 2 O 7 nanosheets were controlled by a hydrothermal method under magnetic field. • The La 2 Ti 2 O 7 nanosheets enjoy a narrower bandgap and better ferroelectricity. • Its photocatalytic ability is improved after polarization and under pressure. • The photogenerated electrons play main roles through •O 2 – and •OH radicals. [ABSTRACT FROM AUTHOR]

Cu/Cu2O nano-heterostructure hollow spheres with a submicron diameter (200–500 nm) were prepared by a microwave-assisted hydrothermal method using Cu(OAc)2·H2O, PVP and ascorbic acid solution as the precursors. The morphology of the products could evolve with the hydrothermal time from solid spheres to thick-shell hollow spheres, then to thin-shell hollow spheres, and finally to nanoparticles. Moreover, the content of Cu in the products could be controlled by adjusting the hydrothermal time. The spontaneous forming of the hollow structure spheres was found to result from the Ostwald ripening effect during the low temperature (100 °C) hydrothermal reaction process. The photocatalytic degradation activities on MO under visible-light irradiation and the gas sensing activities toward the oxidizing NO2 gas of different Cu/Cu2O nano-heterostructure hollow spheres were investigated. As a result, the Cu/Cu2O nano-heterostructure hollow spheres obtained at the hydrothermal time of 30 min, with a rough/porous thin-shell structure and a Cu content of about 10.5 wt%, exhibited the best photocatalytic and gas sensing performances compared with others. [ABSTRACT FROM AUTHOR]

ZnO nanorods with controllable surface defects was synthesized by high-temperature quenching method, and the recombination of photogenerated electron–hole pairs had been drastically suppressed, thus significantly improving the photocatalytic reactivity. The as-prepared samples were characterized for the surface structure, chemical state, phase structure as well as optical absorption using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fluorescent spectrophotometer (PL), diffuse reflectance UV–visible spectroscopy (DRS) and zeta potential. With XPS valence band spectra characterization, its light absorption enhancement in UV–vis range was found due to induced additional electronic states above the valence band edge. Specific types of defects related to the quenching process were further investigated. Moreover, the concentration of surface defects and the recombination of carriers were controllable by quenching temperature, also affected by cooling rates. It provides a time-saving and straightforward method to suppressed recombination of photo-induced carriers and increased UV–vis light absorption for highly efficient ZnO-based photocatalyst applied to environmental remediation. [ABSTRACT FROM AUTHOR]

Abstract: A one-pot simple and cost-effective calcination method has been developed for preparing nanoroded zinc oxide (ZnO) with greatly enhanced photocatalytic activity. The nanocatalyst possessing smaller surface area synthesized by calcining zinc acetate dehydrate, however, acquired higher normalized rate constant than other reported ZnO nano/micromaterials. The samples characterized by XPS spectra denoted the photocatalytic activity enhancement might associate with oxygen vacancies. Notably, the ZnO nanorods were chemically stable and could be easily recycled for four times without obvious decrease in photocatalystic activity. This simple, cost-effective, high-yield method with excellent performance of resulting products could be extended to study oxygen vacancies and also provide new avenue for potential industrial applications. [Copyright &y& Elsevier]

Highlights: [•] Multilayer SnO2 core–shell microspheres were successfully synthesized via a simple microwave hydrothermal treatment. [ • ] The effect of both hydrothermal and calcination temperatures to the morphology were studied. [•] The photocatalytic activity was improved by the large thin shell and large specific surface area. [Copyright &y& Elsevier]

Highlights: [•] Honeycomb Ag/ZnO heterostructures were prepared. [•] It shows rapid photocatalytic activity and excellent chemical stability. [•] BET surface area of the prepared Ag/ZnO heterostructures is 46.7m2/g. [•] The surface state was investigated by XPS. [•] Excellent photocatalytic activity depends on porous structure and heterostructures. [ABSTRACT FROM AUTHOR]

Ag/BiPO4 heterostructures were synthesized by a hydrothermal method combined with an impregnation technique. The heterostructures exhibit much higher activity than pure BiPO4 for degradation of methylene blue, which may be primarily ascribed to highly efficient photogenerated electron–hole pair separation. They also show good recyclability and slightly strong absorption in the visible region. In addition, the possible mechanism for the enhanced photocatalytic properties of Ag/BiPO4 heterostructures is discussed. Moreover, radical scavengers experiments confirmed that holes are the main active species instead of hydroxyl radicals when coupled with the BiPO4 surface by the noble nanocrystalline metal Ag. [ABSTRACT FROM AUTHOR]

In this work, BiO/BaTiO heterostructure were prepared through a solid milling and annealing process. It was found that Bi dissolved in the BaTiO lattice and the chemical bond was constructed between the interface of BiO and BaTiO after annealing process. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-visible absorption spectra were used to characterize the BiO/BaTiO heterostructure. Furthermore, UV-induced catalytic activities of the BiO/BaTiO heterostructure was studied by a degradation reaction of methyl orange (MO) dye. The band gap of the BiO/BaTiO heterostructure was estimated to be 3.0 eV. Compared with pure BiO powders, the BiO/BaTiO heterostructure had a much higher catalytic activity. An excellent performance of the photocatalytic property of the BiO/BaTiO heterostructure is ascribed to high mobility of species and effective separation of photogenerated carriers driven by the photoinduced potential difference generated at the BiO/BaTiO junction interface, demonstrating that the BiO/BaTiO heterostructure is a promising candidate as a photocatalyst. [ABSTRACT FROM AUTHOR]

Abstract: Three-dimensional flower-like SnO2/Ag heterostructures were self-assembled via a simple microwave hydrothermal treatment of a mixture of tin (II) dichloride dihydrate (SnCl2·2H2O), sodium citrate (Na3C6H5O7·2H2O) and silver nitrate (AgNO3) in an alkali solution. The morphological, structural and optical properties of the heterostructures were investigated by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence spectra (PL) and Raman spectra, and a detailed formation mechanism was discussed. The photocatalytic activities of the samples were evaluated by degradation of rhodamine B (RhB) in an aqueous solution under ultraviolet light irradiation. Morphology and photocatalytic activity of the SnO2/Ag heterostructures were tailored as the addition amount of Ag. SnO2/Ag heterostructures with 3% content of Ag showed best photocatalytic performance. [Copyright &y& Elsevier]

Abstract: SnO2 hollow microtubes (MTs) are prepared by electrospinning. A detailed microstructure and mechanism study of the synthesized SnO2 MTs has been carried out. The SnO2 hollow MTs provide promising photocatalytic characteristics, with ultra-fast degradation and stable repeatability. These good degradation and repeatability characteristics are dominated by the large surface area and effective separation of photoinduced carriers provided by the MT morphology and fine particle size building the porous shell of SnO2 MTs. [Copyright &y& Elsevier]

Abstract: ZnO/BaTiO3 nanofiber heterostructures with highly uniformly dispersed ZnO nanoparticles grown on primary BaTiO3 nanofibers have been obtained by the combination of an electrospinning and a hydrothermal process. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the ZnO/BaTiO3 nanofiber heterostructures. Furthermore, their UV-induced catalytic activities were studied by a degradation reaction of methyl orange (MO) dye. Compared with pure ZnO powders, ZnO/BaTiO3 nanofiber heterostructures showed better performance of the photocatalytic property, which was ascribed to the synergistic effects of photogenerated electron and hole pair separation and high specific surface area. [Copyright &y& Elsevier]

Abstract: ZnWO4 nanorods are successfully synthesized by a template-free hydrothermal method, and are characterized in detail by X-ray diffractometer (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The results show that the ZnWO4 nanorods with wolframite structure are well-crystallized single crystallites. The crystallinity of the products is influenced by the pH value of initial precursor suspension. The width and length of the synthesized samples increase with hydrothermal reaction temperature. The photocatalytic efficiency of the ZnWO4 nanorods for degradation of methylene blue (MB) in aqueous solution under UV light irradiation declines greatly with increasing crystallinity. The ZnWO4 nanorods prepared at pH of 4 have the best activity in photo-degradation of MB. After six recycles, photocatalytic activity loss of the catalyst is not obvious. [Copyright &y& Elsevier]

Abstract: In this work, monodispersed silver nanoparticles decorated SiO2 nanofibers were synthesized by electrospinning method, followed by thermal treatment at 600°C. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) were used to characterize the composite nanofibers. Accordingly, the detailed formation mechanism of SiO2/Ag composite nanofibers was discussed. Furthermore, an excellent catalytic activity of SiO2/Ag composite fibers was observed by a degradation reaction of methyl orange (MO) dye. [Copyright &y& Elsevier]

Abstract: A UV light-assisted route has been used to synthesis coral SnO2 nanoparticles. Annealing is introduced to crystallize samples and exclude impurities without changing the morphology. Powder X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–vis spectra are used to characterize the SnO2 samples and the detailed formation mechanism is discussed based on the experiment results. The products are of different sizes and morphologies depending on the light irradiation time. Compared with commercial SnO2, the coral SnO2 have improved photocatalytic performance toward methyl orange (MO) solution due to its large high specific surface. [Copyright &y& Elsevier]

Abstract: A room temperature solid-state reaction has been used to prepare crystalline tin-doped ZnO. Zinc nitrate hexahydrate, cetyltrimethyl ammonium bromide, stannic chloride pentahydrate and sodium hydroxide with proper ratios were ground together. As-synthesized samples were characterized by inductively coupled plasma analysis (ICP), scanning electron microscopy (SEM) and X-ray powder diffraction (XRD); The products were of different morphologies, well dispersed and exhibited good crystallinity, it is also found that the growth direction and morphology of ZnO depend on the amount of Sn doped, which is mainly caused by the difference in sizes between Zn and Sn atoms as well as the change of pH value. Moreover, gas sensing and photocatalytic properties of the obtained products were studied. The materials showed a high gas response to ethanol vapor, and the gas response can reach a maximum of R a/R g =124. In addition, tin-doped ZnO materials exhibited improved photocatalytic performance toward methyl orange (MO) solution under a current density of 0.03mgL−1 comparison with undoped ZnO. [Copyright &y& Elsevier]

Abstract: Spindle-like α-Fe2O3/ZnO core-shell structures were synthesized by a simple two-step method of microwave hydrothermal synthesis. The as-prepared products were characterized by X-ray diffraction, transmission electron microscopy, high-resolution TEM and selected area electron diffraction. Furthermore, photocatalytic activity was measured through the degradation of methyl orange solution. And the results of degradation reveal that the spindle-like α-Fe2O3/ZnO nanocomposites exhibit better photocatalytic activities (3.5 times improvement) than those of the pure spindle-like α-Fe2O3 under ultraviolet irradiation. A mechanism was proposed based on which the electrons excited in the photocatalytic process. [Copyright &y& Elsevier]

To achieve better photocatalytic performance, we proposed a facile solid-state reaction method to produce CeO2/ZnO heterostructures. Ceria and zinc oxide were synthesized simultaneously by thoroughly grinding the mixture of zinc acetate dihydrate, cerium nitrate hexahydrate and sodium hydroxide. The morphology of the as-prepared heterostructures varies dramatically as different amount of ceria was introduced in the composition. The photocatalytic performance of CeO2/ZnO heterojunctions was 4.6 times higher than that of pure ZnO. The enhanced photocatalytic activity could be ascribed to that more electrons and holes could transport to the surface of catalysts and react with the pollution due to the extended light-responsive range, accelerated migration, increased specific surface area and suppressed recombination of photogenerated carriers. [ABSTRACT FROM AUTHOR]

ZnO/Bi 2 O 3 heterojunction was prepared by solid state reaction method at room temperature. The as-prepared nanostructures were characterized as the assembled nanosheets of ZnO on which Bi 2 O 3 nanoparticles were well dispersed. Further studies revealed that the morphology and photocatalytic property could be regulated by tuning the amount of Bi 2 O 3 . The introduction of Bi 2 O 3 can lead to the enhancement of solar light absorption, and the 5% ZnO/Bi 2 O 3 samples exhibited the best photocatalytic activity under the solar light irradiation. The excellent photocatalytic performances could be ascribed to the synergistic effects of the hierarchical nanostructures and the effective separation of photogenerated carriers. Moreover, the hydroxyl radicals ( OH) are found to be the main active species generated in the oxidation reaction of RhB over ZnO/Bi 2 O 3 photocatalyst. Therefore, our work demonstrated a facile way to prepare hierarchical nanostructures with excellent photocatalytic performance using solid state method at room temperature. [ABSTRACT FROM AUTHOR]

Monoclinic phase La 2 Ti 2 O 7 and orthorhombic phase Bi 4 Ti 3 O 12 with layered crystal structure constructed by the perovskite slab were widely used in photocatalysis. Their electronic structures are the most crucial factor in high photocatalytic activity. Bi-doped La 2 Ti 2 O 7 gradually converts to La-doped Bi 4 Ti 3 O 12 with the incorporation of bismuth ions, and the two phases build an S-scheme heterojunction. More oxygen vacancies were introduced into the S-scheme heterojunction after heat treatment in a nitrogen atmosphere. The 0.1BTO/LTO-OV sample exhibits the largest NO removal efficiency of 52% and only 5.6 ppb NO 2 intermediate generation. The improved NO removal efficiency was ascribed to the synergistic effect of oxygen vacancies, doping and heterojunction, providing a new insight into the photocatalytic NO removal. The photocatalytic mechanism was eventually proposed on the basis of trapping experiments. [Display omitted] • S-scheme heterojunctions of Bi-doped La 2 Ti 2 O 7 and La-doped Bi 4 Ti 3 O 12 were prepared. • Oxygen vacancies were introduced into the heterojunction. • NO removal ratio reaches 52% with only 5.6 ppb NO 2 intermediate generation. • High NO removal ratio was ascribed to oxygen vacancies, doping and heterojunction. • Several active radicals play roles in the NO removal. [ABSTRACT FROM AUTHOR]

The development of feasible, highly stable and easily recycled metal-free photocatalysts has drawn great attention for wastewater purification. Herein, dip-coating followed with thermal polymerization is developed for in situ growth of boron doped graphitic carbon nitride (BCN) on carbon fiber cloth (CFc) as flexible film photocatalysts. HNO 3 treatment on CFc is used to improve the surface hydrophilicity of CF, which is beneficial for the adsorption and nucleation of BCN precursor on CFc in aqueous solution. Boric acid not only works as the boron source but also causes a porous morphology of BCN due to the gasification of water generated from boric acid decomposition during heating process. Because of the close contact between CFc and BCN, CFc induces BCN to better crystalize. Furthermore, the film-photocatalyst exhibits high mechanical stability and recyclability. The porous sheet-like structures, together with the boron doping and CFc support, can improve light capture, charge separation and transport, and dye adsorption. Our work provides a thinking for component and morphology regulation of film-based flexible catalysts towards reusable photocatalysis under outdoor sunlight. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The 0D/2D anatase/graphene composites are synthetized by a facile hydrothemal method. • Graphene modification results in the changes in the structure of the anatase and red shift. • Graphene modification leads to obvious increase of the Ti3+ ions content. • Graphene modification can effectively trap electrons to enhance the separation of charges. • Anatase/graphene exhibit excellent synergistic photocatalytic activity for Cr(VI) and RhB. Abstract In this study, a novel anatase/graphene (0D/2D)-based composite photocatalyst is synthesized through a facile hydrothemal method using graphene oxide (GO), titanium sulfate (Ti(SO 4) 2) and hydrazine hydrate (N 2 H 4 ·H 2 O) as precursors. The study reveals that the surface-dispersed anatase nanoparticles adhere well to the flake-like graphene. Compared with pure anatase nanoparticles, the anatase/graphene composite showed a significantly modified crystal structure in the crystallinity of the anatase phase and surface area. The involvement of graphene also dramatically enhanced the absorption of visible light and provided a shift in the absorption edge towards red wavelengths. From the analysis of the fluorescence spectra, it is demonstrated that the recombination dynamics of the photogenerated charge (electron-hole) pairs can be effectively inhibited by the compounded graphene and hence improve the efficiency of the charge carrier separation. The dramatically improved reduction of Cr(VI) is achieved through the visible light photocatalytic activity provided by the anatase/graphene composite. The rate of the reaction measured for the composite is 4.83-fold and 9.78-fold greater than that of the pure anatase under ultraviolet and visible light irradiation, respectively. Moreover, the synergism of the RhB degradation with the reduction of Cr(VI) also dramatically improves the latter. Additionally, we present an analysis of a potential alternate system for the improvement of photocatalytic activity. [ABSTRACT FROM AUTHOR]

Through the adoption of various experimental tests, FDTD simulations and DFT calculations, a systematic study of the internal transfer mechanism of photogenerated carriers and the mechanism of photocatalytic performance enhancement of the noble metal Ag0 loading on layered graphite-phase carbon nitride nanosheets (LGCNs) have been studied, and a thorough analysis of the mechanism has been provided. [Display omitted] • Enhanced photocatalysis performance and transfer mechanism of carriers are studied. • The active species trapping experiment indicates that h+ and ·O 2 – play the main role. • The FDTD shows the presence of Ag0 enhances the interfacial electromagnetic field. • The DFT calculations indicate the work function, band structure, and DOS of samples. • The internal carriers transfer mechanism of samples is explained exhaustively. A series of surface-dispersed Ag0 modified lamellar-graphite-phase carbon nitride nanosheets (Ag/LGCNs) are synthesized by a straightforward method to construct the noble metal/semiconductor heterojunction. The localized surface plasmon resonance (LSPR) effect results in an optimum degradation rate (K app) for rhodamine B ∼ 5.53 × 10−2∙min−1 (9 times higher than that of pure LGCNs), and the sample exhibited outstanding stability. The experiments with sacrificial reagents showed that the h+ and ∙O 2 – are primary active photocatalytic species in the present samples. The optical and photo-electro-chemical studies of the samples, confirm enhanced photo-responsiveness and photogenerated carriers' separation and transport with an appropriate amount of Ag0. The corresponding mechanism is formulated using photocurrent analysis, impedance analysis, finite-difference time-domain (FDTD) simulation and density functional theory (DFT). FDTD simulation evidenced an intense electromagnetic field at the Ag/LGCN's interface under visible radiation attributable to the LSPR effect of Ag0 nanoparticles and an increased field intensity with the size of Ag0 nanoparticles. The DFT computations show that the difference in Fermi energy level and the work function contributes to an interfacial built-in electric field between Ag0 nanoparticles and LGCNs. Furthermore, the mechanism for reduced band gap and improved photocatalytic performance for Ag/LGCNs is explained by the energy band studies. [ABSTRACT FROM AUTHOR]

Oxygen-vacancy-induced one-dimensional (1D) CeO 2 nanotubes (CeNT) has successfully loaded on two-dimensional (2D) graphitic carbon nitride (g-C 3 N 4) by simple methods for investigating the performance of photocatalytic degradation of sewage. The results of characterization analyses have proved that the CeNT are uniformly dispersed on the surface of the g-C 3 N 4 nanosheets. The electron paramagnetic resonance (EPR) spectra signal exhibited the existence of oxygen vacancies in CeNT. Photoluminescence spectra (PL), UV–vis diffuse reflectance spectra (UV–vis DRS) and photoelectrochemical measurements demonstrated that the appropriate amount of CeNT (28 mg) can effectively improve the separation efficiency of photogenerated charge carriers and the photoresponse property of the samples. The rhodamine B (RhB) degradation experiments verify the same results that the photocatalytic degradation efficiency of the samples for RhB increased initially, followed by a decreased, meanwhile the degradation activity didn't decrease prominently after four circles. Also, the reactive species trapping experiment indicated that the holes (h+) and superoxide radicals (∙O 2 -) played major role in the photocatalytic reaction. Finally, the enhanced photocatalytic performance can be attributed to the synergistic effects of the oxygen vacancies in CeNT and a new charge transfer mechanisms of Step-scheme heterojunction for electron separation, which could provide a new green solution for photocatalytic sewage treatment. [Display omitted] A sustainable approach for the interfacial optimization of one-dimensional CeO 2 nanotubes loaded two-dimensional graphite carbon nitride with synergistic enhancement of visible-light-driven photoelectric and photocatalytic pollutant degradation is reported. • A series of CeNT/g-C 3 N 4 composites were prepared by a suitable and reliable possess. • The EPR spectra indicated the presence of oxygen vacancies over CeNT. • Appropriate CeNT modification can enhance the separation efficiency of the carriers. • The active species trapping experiment indicated that h+ and·O 2 - played major role. • The enhanced photocatalysis ascribed to optimization of S-scheme heterojunction. [ABSTRACT FROM AUTHOR]

A Z-scheme MoS 2 /Ag 2 S/AgVO x ternary heterostructure was successfully synthesized by a facile hydrothermal method. The as-prepared MoS 2 /Ag 2 S/AgVO x ternary composite has been characterized by electron microscopy, XRD, XPS, UV-Vis DRS, PL, electrochemistry and ESR. TEM characterization revealed that Ag 2 S, Ag nanoparticles and AgVO x nanorods were dispersed homogeneously over the surface of MoS 2 nanosheets The prepared heterojunction showed enhanced photocatalytic performance compared with single MoS 2 and AgVO x. And 6%-MoS 2 /Ag 2 S/AgVO x heterojunction exhibits highest photocatalytic degradation efficiency, which can degrade fuchsine around 75% under visible light within 180 min. The enhanced photocatalytic activity can be attributed to the efficient separation of photogenerated charge carriers, the strong redox ability and enhancement of visible-light absorption derived from the construction of Z-scheme heterostructure. In-situ formed metallic Ag 2 S act as the electron mediator and Ag nanoparticles possess the surface plasmon resonance (SPR) effect. The prepared heterojunction showed decreased photoluminescence and increased photoelectrochemical performance, indicating high separation rate of photoinduced charge carriers. Furthermore, a possible degradation mechanism of fuchsine solution was proposed. And the results of radical trapping experiments indicated that superoxide radicals (∙O 2 -) and holes (h+) play major role during the photocatalytic degradation process. This work demonstrates an interesting Z-scheme photocatalytic system for photocatalysis applications. A distinctive synthesis route and corresponding novel mechanism for ternary Z-Scheme heterostructure MoS 2 /Ag 2 S/AgVO x nanocomposites with enhanced visible light and fast interfacial charges transfer is reported. [Display omitted] • The Z-scheme MoS 2 /Ag 2 S/AgVO x were prepared by a facile hydrothermal method. • The dual effect of MoS 2 facilitated the form of Ag 2 S, and boost theseparation of carriers. • 6%-MoS 2 /Ag 2 S/AgVO x showed the highest photoelectric and photocatalytic activity. • The ESR spectra indicated ·O 2 - and h+ played a major role in photocatalytic reaction. • The enhanced photocatalysis ascribed to construction of Z-scheme heterojunction. [ABSTRACT FROM AUTHOR]

[Display omitted] • HNO 3 is used to tailor chemical structures and intermolecular interactions of melem. • The PM-CN exhibits smaller π-π stacking distance and more stacking layers. • The H 2 evolution activity of PM-CN is 18 times higher than the reference g-C 3 N 4. Additional pre-modification on precursors or post-treatment on polymeric graphitic carbon nitride (g-C 3 N 4) induces variation in physicochemical and optoelectronic properties. However, the enhancement is still limited because the treatment is done either before the formation of the repeated units melem or after the formation of the polymer plane. Accordingly, the tailoring of the crystalline phase, nanomorphology and electronic band structure on g-C 3 N 4 is less efficient. Herein, we propose a novel strategy to obtain highly efficient g-C 3 N 4 by tailoring of molecular structures and intermolecular interactions of intermediates. A protonated melem derived g-C 3 N 4 (PM-CN) is fabricated via recalcination of HNO 3 -treated melem intermediates. The HNO 3 treatment induces oxygen-containing functional groups on melem molecules and NO 3 – inserted into adjacent stacking layers, which results in a favorable crystalline order. In addition, porous structure with large specific surface area is obtained since release of gases occurs during recalcination of HNO 3 -treated melem. These features endow favorable charge transport conditions and large driving force for hydrogen production. The prepared PM-CN exhibits a promising photocatalytic activity under visible light with a hydrogen production rate up to 3.085 mmol h−1 g−1. This study provides a novel strategy for optimize the crystalline phase and nanostructure of polymers for energy-related applications. [ABSTRACT FROM AUTHOR]