Nanoporous ZnO nanostructures for photocatalytic degradation of organic pollutants

ZnO porous bamboo-leave-like nanorods and nanoporous networks were prepared by thermal conversion from Zn₂CO₃(OH)₂?H₂O bamboo-leave-like nanorods, Zn(OH)₂ nanoparticle networks and Zn(OH)₂ long nanostrand networks, respectively. Among them, the ZnO nanoporous networks prepared from Zn(OH)₂ nanostrands had the highest surface area of 78.57 m²/g and presented the best photocatalytic decomposition of organics. The morphologies of the Zn(OH)₂ nanostructures significantly depended on the solvent used for the precursors of aminoethanol and Zn(NO₃)₂ and then determined the corresponding structures and properties of the final ZnO nanostructures. The ethanol/water mixture solvent dramatically increased the stability of Zn(OH)₂ nanostrands. This is very beneficial for the collection and application of Zn(OH)₂ nanostrands.     

Scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry study on the enhanced visible photocatalytic mechanism of carbon-TiO2 nanohybrids

Carbon-TiO₂ nanohybrids (CTs, 5-10 nm TiO₂ nanocrystals evenly dispersed on carbon film) have been successfully prepared via a mild, one-step hydrothermal approach. The interactions and electronic structures of carbon and TiO₂ nanoparticles and the enhanced visible photocatalytic mechanism were investigated by scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry in detail. Meanwhile, it was demonstrated that the as-obtained CTs had a large BET specific surface area of 304.6 m²/g and showed excellent photocatalytic abilities towards organic (Rhodamine B, benzene) and inorganic pollutant (K₂Cr₂O₇) degradation in visible light. This work provided a new approach for the high performance catalyst design towards new energy sources and environmental issues.     

Green sonochemical synthesis and fabrication of cubic MnFe2O4 electrocatalyst decorated carbon nitride nanohybrid for neurotransmitter detection in serum samples

The binary nanomaterials and graphitic carbon based hybrid has been developed as an important porous nanomaterial for fabricating electrode with applications in non-enzymatic (bio) sensors. We report a fast synthesis of bimetal oxide particles of nano-sized manganese ferrite (MnFe₂O₄) decorated on graphitic carbon nitride (GCN) via a high-intensity ultrasonic irradiation method for C (30 kHz and 70 W/cm²). The nanocomposites were analyzed by powder X-ray diffraction, XPS, EDS, TEM to ascertain the effects of synthesis parameters on structure, and morphology. The MnFe₂O₄/GCN modified electrode demonstrated superior electrocatalytic activity toward the neurotransmitter (5-hydroxytryptamine) detection with a high peak intensity at +0.21 V. The appealing application of the MnFe₂O₄/GCN/GCE as neurotransmitter sensors is presented and a possible sensing mechanism is analyzed. The constructed electrochemical sensor for the detection of 5-hydroxytryptamine (STN) showed a wide working range (0.1–522.6 μM), high sensitivity (19.377 μA μM⁻¹ cm⁻²), and nano-molar detection limit (3.1 nM). Moreover, it is worth noting that the MnFe₂O₄/GCN not only enhanced activity and also promoted the electron transfer rate towards STN detection. The proposed sensor was analyzed for its real-time applications to the detection of STN in rat brain serum, and human blood serum in good satisfactory results was obtained. The results showed promising reproducibility, repeatability, and high stability for neurotransmitter detection in biological samples.     

间苯三酚-乙醛有机气凝胶的制备与表征

 以碳酸钠为催化剂,乙醇为溶剂,间苯三酚 乙醛为反应前躯体,经溶胶 凝胶、交联老化、二氧化碳超临界干燥制备出间苯三酚-乙醛(PA)有机气凝胶。扫描电镜观察和N2吸附测试结果表明：气凝胶具有较高的比表面积,是一种连续nm级３维网络结构的多孔材料,其比表面积为1 210 m²/g,平均孔径为11 nm,与传统有机气凝胶相比,提高了比表面积,一定程度上实现有机气凝胶的扩孔。     

Synergetic Photocatalytic Nanostructures Based on Au/TiO2/Reduced Graphene Oxide for Efficient Degradation of Organic Pollutants

Recently, there is crucial interest in the design and fabrication of nanocatalysts for efficient decomposition of organic pollutants in wastewater using visible light. This work reports the assembling fabrication of synergetic photocatalytic Au/TiO₂/RGO nanostructures by utilizing the reduced graphene oxide (RGO) as substrate material and efficient separator for electrons and holes. The Au/TiO₂ nanostructures with a ≈7 nm TiO₂ particles size are dispersed uniformly on RGO nanosheets. UV–vis diffuse reflectance spectroscopy verifies that Au/TiO₂/RGO nanocomposites show strong absorption of visible light. The degradation efficiency after 1 h for hydroquinone under visible light and UV light is ≈77% and ≈90%, respectively. Under visible light, the calculated apparent rates (k ) of the Au/TiO₂/RGO nanocomposites are 0.0112 and 0.0174 min^?1 for decomposition of methylene blue and hydroquinone. That are five times greater than that of bare TiO₂. The high photocatalytic activity is mainly attributed to the synergy between RGO and Au/TiO₂ nanostructure. The strategy of composite nanostructures assembling on RGO is ensured to have a great practicable potential for the designing of high efficient multielement composite nanoparticles catalysts.     

Preparation and photocatalytic properties of platelike NaNbO3 based photocatalysts

Two kinds of plate-like NaNbO₃ were separately prepared by the one- and two-step molten salt processes via topochemical micro-crystal conversion methods. Meanwhile, the composite photocatalysts were obtained via heating the mixture of corresponding NaNbO₃ powders and urea. Their photocatalytic activities were evaluated from the photodegradation of Rhodamine B under full arc and visible light irradiation of Xe lamp. The sample containing NaNbO₃ prepared by the one-step molten salt process and carbon nitride displays the highest activity. The enhancement of photocatalytic activity was attributed to the surface properties and the state of the carbon nitride.     

Electrospun one-dimensional graphitic carbon nitride-coated carbon hybrid nanofibers (GCN/CNFs) for photoelectrochemical applications

Coupling of graphitic carbon nitride (GCN) with electrospun carbon nanofibers (CNFs) enhanced the photoelectrochemical (PEC) performance of a pristine GCN photoanode. Polyacrylonitrile (PAN) was electrospun to form fibers that were then carbonized to form one-dimensional (1D) CNFs, which were then used to fabricate the GCN structure. The optimum GCN/CNFs hybrid structure was obtained by controlling the amount of GCN precursors (urea/thiourea). The surface morphology of the hybrid structure revealed the coating of GCN on the CNFs. Additionally, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction confirmed the phases of the GCN/CNFs hybrids. PEC results showed a higher photocurrent of 3 μA for the hybrid compared with that of 1 μA for the pristine GCN. The high photocurrent for the hybrid structures indicated the formation of heterojunctions that resulted from a lower recombination rate of charge carriers. Moreover, UTh_0.075 (0.075 g of urea and 0.075 g of thiourea) hybrid sample showed the highest performance of hydrogen generation with its numerical value of 437 μmol/g, compared to those of UTh_0.1(0.1 g of urea and 0.1 g of thiourea) and UTh_0.05 (0.05 g of urea and 0.05 g of thiourea) composite samples. This higher hydrogen production could be explained again with successful formation of heterojunctions between GCN and CNFs. Overall, we report a new approach for obtaining 1D hybrid structures, having better PEC performance than that of pristine GCN. These hybrids could potentially be used in energy-related devices.     

Preparation, characterization, and photocatalytic properties of silver carbonate

Silver carbonate (Ag₂CO₃) short rods were prepared using a precipitation method. It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflective spectra (DRS) and photocatalytic degradation of organic pollutants and destruction of E. coli measurements. The results of DRS suggested that the optical transition of Ag₂CO₃ was indirectly allowed, and its band gap was determined to be 2.08 eV. The prepared Ag₂CO₃ displayed a high activity towards degradation of phenol and MB under visible light. The total organic carbon (TOC) value decreased during the photocatalytic process, which suggests that phenol was truly photodegraded. The stability of Ag₂CO₃ was greatly improved when Na₂CO₃ was added into the photocatalytic system. In addition, Ag₂CO₃ displayed enhanced photocatalytic activities for the destruction of E. coli due to its photogenerated electron-hole pairs.     

Effects of morphology on photocatalytic performance of Zinc oxide nanostructures synthesized by rapid microwave irradiation methods

In this study, two different chemical solution methods were used to synthesize Zinc oxide nanostructures via a simple and fast microwave assisted method. Afterwards, the photocatalytic performances of the produced ZnO powders were investigated using methylene blue (MB) photodegradation with UV lamp irradiation. The obtained ZnO nanostructures showed spherical and flower-like morphologies. The average crystallite size of the flower-like and spherical nanostructures were determined to be about 55 nm and 28 nm, respectively. X-ray diffraction (XRD), scanning electronic microscopy (SEM), Brunauer–Emmett–Teller (BET), room temperature photoluminescence (RT-PL) and UV–vis analysis were used for characterization of the synthesized ZnO powders. Using BET N₂-adsorption technique, the specific surface area of the flower-like and spherical ZnO nanostructures were found to be 22.9 m²/gr and 98 m²/gr, respectively. Both morphologies show similar band gap values. Finally, our results depict that the efficiency of photocatalytic performance in the Zinc oxide nanostructures with spherical morphology is greater than that found in the flower-like Zinc oxide nanostructures as well as bulk ZnO.     

Use of 13C and 15N Mass Spectrometry to Study the Decomposition of Calamagrostis epigeios in Soil Column Experiments with and Without Ash Additions

Abstract

The dynamics of C and N in terrestrial ecosystems are not completely understood and the use of stable isotopes may be useful to gain further insight in the pathways of CO₂ emissions and leaching of dissolved organic carbon (DOC) and nitrogen (DON) during decomposition of litter. Objectives were (i) to study the decomposition dynamics of Calamagrostis epigeios, a common grass species in forests, using ¹³C-depleted and ¹⁵N-enriched plants and (ii) to quantify the effect wood ash addition on the decomposition and leaching of DOC and DON. Decomposition was studied for 128 days under aerobic conditions at 8°C and moisture close to field capacity in a spodic dystric Cambisol with mor-moder layer. Variants included control plots and additions of (i) Calamagrostis litter and (ii) Calamagrostis litter plus 4 kg ash m^?2.

• Decomposition of Calamagrostis resulted in a CO₂ production of 76.2 g CO₂–C m^?2 (10% of added C) after 128 days and cumulative DOC production was 14.0 g C m^?2 out of which 0.9g C m^?2 was Calamagrostis-derived (0.1% of added C). The specific CO₂ formation and specific DOC production from Calamagrostis were 6 times higher (CO₂) and 4 times smaller (DOC) than those from the organic layer. The amount of Calamagrostis-derived total N (NH₄ ⁺, NO₃ ^?, DON) leached was 0.7g N m^?2 (4.8% of added N). Cumulative DON production was 0.8g N m^?2 which was slightly higher than for the control. During soil passage, much of the DOC and DON was removed due to sorption or decomposition. DOC and DON releases from the mineral soil (17cm depth) were 6.3g C m^?2 and 0.5g N m^?2.

  Addition of ash resulted in a complete fixing of CO₂ for 40 days due to carbonatisation. Afterwards, the CO₂ production rates were similar to the variant without ash addition. Production of DOC (98.6g C m^?2) and DON (2.5g N m^?2) was marked, mainly owing to humus decay. However, Calamagrostis-derived DOC and Culamagrostis-derived total N were only 3.9g C m^?2 (0.5 YO of added C) and 0.5g N m^?2 (3.4% of added N). The specific DOC production rate from the organic layer was 6 times higher than that from Cularnagrostis. The results suggest that with increasing humification from fresh plant residues to more decomposed material (O_F and O_H layers) the production ratio of DOC/CO₂-C increases. Addition of alkaline substances to the forest floor can lead to a manifold increase in DOC production.

     

Nanoporous carbon microspheres as anode material for enhanced capacity of lithium ion batteries

Nanoporous carbon microspheres (NCMs) are prepared by a one-step carbonizing and activating resorcinol?formaldehyde polymer spheres (RFs) in inert and CO₂ atmosphere for anode materials of lithium-ion batteries (LIBs). Compared with RFs carbon microspheres (RF-C), after activating with hot CO₂, the NCMs with porous structure and high BET surface area of 2798.8 m² g^?1, which provides abundant lithium-ion storage site as well as stable lithium-ion transport channel. When RF-C and NCM are used to anode material for LIBs, at the same current density of 210 mA g^?1, the initial specific discharge capacity are 482.4 and 2575.992 mA h g^?1, respectively; after 50 cycles, the maintain capacity are 429.379 and 926.654 mA h g^?1, respectively. The porous spherical structure of NCM possesses noticeably lithium-ion storage capability, which exhibits high discharge capacity and excellent cycling stability at different current density. The CO₂ activating carbonaceous materials used in anode materials can tremendously enhance the capacity storage, which provides a promising modification strategy to improve the storage capacity and cyclic stability of carbonaceous anode materials for LIBs.     

镧掺杂介孔TiO2光催化剂的制备、表征及其光催化性能

以钛酸四正丁酯和硝酸镧为原料, 以P123为模板剂,采用模板法合成了La掺杂型介孔TiO₂光催化剂, 借助TGA-DSC、BET、XRD及UV-Vis等测试手段对样品进行了表征,并以苯酚为模型污染物考察了镧掺杂量对样品光催化活性的影响．结果表明: La掺杂介孔TiO₂光催化剂孔径分布较均匀(～10 nm),比表面积可达165 m²/g．与纯介孔TiO₂相比,经掺杂改性后的样品在紫外光区及可见光区的吸收显著增强,对光具有更高的利用率,La掺杂可显著提高介孔TiO₂的光催化活性.     

Photocatalytic photodegradation of xanthate over C, N, S-tridoped TiO2 nanotubes under visible light irradiation

C, N, S-tridoped TiO₂ nanotubes were synthesized via hydrothermal synthesis and post-treatment, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), the Brunauer-Emmett-Teller method (BET), and UV-vis diffuse reflectance spectroscopy (DRS). The UV-diffuse reflectance spectra of all the C, N, S-tridoped TiO₂ nanotubes greatly extended the absorption edge to the visible light region, and the absorbance in the visible region increased with increasing molar ratio of thiourea to Ti (R), which could be attributed to C, N, S-tridoping in the form of cation C-doping, interstitial N-doping, cation S-doping, and adsorbed ions’ states. The photocatalytic activity of C, N, S-tridoped TiO₂ nanotubes was evaluated by photocatalytic photodegradation of potassium ethyl xanthate (KEX) under visible light irradiation. It was found that the photocatalytic activity of the prepared samples increased with increasing molar ratio of thiourea to Ti (R). At R=6, the photocatalytic activity of the tridoped sample TNTS-6 reached a maximum value. With further increase in R, photocatalytic activity of the sample decreased, which could be attributed to the high visible light activity resulting from the balance between visible light absorption and recombination of electron/hole pairs.     

Polyol synthesis of polycrystalline cuprous oxide nanoribbons and their growth chemistry

A facile organic-solution method was developed for the synthesis of two-dimensional cuprous nanostructures. Ribbons as thin as 50 nm were successfully prepared by dissolving CuCl in ethylene glycol before raising the solution temperature to 150°C in air. Transmission electron microscopic studies revealed that the ribbon nanostructures obtained were polycrystalline, with nanocrystals present in the structures mostly less than 25 nm. Selective-area electron diffraction patterns taken from the ribbon nanostructures indicated that the chemical composition of the nanocrystals was Cu₂O, though X-ray photoelectron spectrometric analysis showed that the nanostructures also contained the Cu²⁺ phase. Growth factors including the molecular structure of the solvent and the counter-ion of copper in the precursor that may affect the formation of polycrystalline nanoribbons were examined. More importantly, the detail of chemistry involved in the step-by-step, dimensional growth of copper-based nanostructures in ethylene glycol is presented at the molecular level for the first time using the growth of the Cu₂O nanoribbon as an example. Ethylene glycol chelates Cu²⁺, which is produced from Cu⁺ undergoing disproportionation reactions, to form tetragonally elongated glycolates. A sequence of nucleophilic substitutions then takes place to bond glycolates together to yield stripe-like polymers before the polymers aggregate via van der Waals force into ribbon nanostructures. The Cu⁰ produced from the disproportionation reaction is crystallized out within the polymers and oxidized at elevated temperature by the dissolved O₂ in the solution to form Cu₂O nanocrystals.     

Synthesis and characterization of nitrogen-doped TiO2 coatings on reduced graphene oxide for enhancing the visible light photocatalytic activity

Nitrogen-doped TiO₂ coatings on reduced graphene oxide were prepared via a sonochemical synthesis and hydrothermal process. The nanocomposites showed improved photocatalytic activity due to their large specific surface areas (185–447 m²/g), the presence of TiO₂ in the anatase phase, and a quenched photoluminescence peak. In particular, GN3-TiO₂ (nitrogen-doped TiO₂ coatings on rGO with 3 ml of titanium (IV) isopropoxide) exhibited the best photocatalytic efficiency and degradation rate among the materials prepared. With nitrogen-doped on the reduced graphene oxide surface, the photocatalytic activity is enhanced approximately 17.8 times compared to that of the pristine TiO₂. The dramatic enhancement of activity is attributed to the nitrogen contents and rGO effectively promoting charge-separation efficiency and providing abundant catalytically active sites to enhance the reactivity. The composites also showed improved pollutant adsorption capacity, electron–hole pair lifetime, light absorption capability, and absorbance of visible light.     

Low temperature synthesis of iodine-doped TiO2 nanocrystallites with enhanced visible-induced photocatalytic activity

Iodine-doped TiO₂ nanocrystallites (denoted as I-TNCs) were prepared via a newly developed triblock copolymer-mediated sol-gel method at a temperature of 393 K. I-doping, crystallization and the formation of porous structure have been simultaneously achieved. The obtained particles were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV-vis spectrophotometer. The results indicated that the as-prepared I-TNCs possessed a diameter of ca. 5 nm with anatase crystalline structure and a specific surface area of over 200 m² g⁻¹. The presence of iodine expanded the photoresponse in visible light range, and led to enrich in surface hydroxyl group on the TiO₂ surface. Compared with the commercial photocatalyst P25, the I-TNCs significantly enhanced the photocatalytic efficiency in the degradation of rhodamine B and 2,4-dichlorophenol, and the I-TNCs with 2.5 mol% doping ratio exhibited the best photocatalytic activity.     

Preparation, characterization of Au (or Pt)-loaded titania nanotubes and their photocatalytic activities for degradation of methyl orange

TiO₂ nanotubes were prepared by hydrothermal method and Au (or Pt) was loaded on TiO₂ nanotubes by photodeposition method. The photocatalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and N₂ adsorption technique, respectively. The photocatalytic properties of the samples were also investigated. The results show that TiO₂ nanotubes with uniform diameter were prepared, and they have specific surface areas over 400 m²/g. The specific surface areas of TiO₂ nanotubes decrease with the increasing of calcining temperature, and crystalline phase of TiO₂ in the wall of nanotubes was transformed from anatase into rutile phase in calcination process. The photocatalytic activities of TiO₂ nanotubes are higher than that of nanosized TiO₂, and the photocatalytic activities of TiO₂ nanotubes were enhanced after loading Au (or Pt). After irradiation for 40 min under a 300 W of middle-pressure mercury lamp (MPML), the degradation rate of methyl orange solution using the Au/TiNT-500 (or Pt/TiNT-500) as a catalyst can reach 96.1% (or 95.1%). On the other hand, Au-loaded sample has evident adsorption peak in visible range, indicating that Au-loaded TiO₂ nanotubes are hopeful to become visible light photocatalyst.     

铁和镧共掺杂纳米二氧化钛光催化剂的制备、表征及其光催化活性

以葡聚糖为模板,钛酸四正丁酯、硝酸铁和硝酸镧为前驱体采用模板法制备了一系列铁、镧单掺杂及共掺杂纳米TiO₂光催化剂. 利用SEM、XRD、BET比表面积测定和UV-Vis等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以甲基橙溶液的光催化降解为模型反应,考察了不同掺杂的样品在紫外和可见光下的光催化性能. TiO₂材料具有较大的比表面积(约150 m²/g),铁和镧共掺杂纳米TiO₂在可见光区域有较强的吸收,在紫外和可见光条件下较纯TiO₂和单掺杂TiO₂对甲基橙溶液具有更好的光催化降解效果,且铁和镧的掺杂量显著影响该材料的催化性能. 当铁掺杂量为0.5mol%、镧掺杂量为0.3mol%,在500 ℃焙烧2 h所得光催化材料的催化性能最佳,焙烧4 h即可使甲基橙的降解率达98.8%,且该复合材料有较高的循环回收利用率,重复使用4次仍可使甲基橙的降解率保持在88%以上.     

Synthesis of Hierarchical (BiO)2CO3 Nanosheets Microspheres toward Efficient Photocatalystic Reduction of CO2 into CO

In this paper, hierarchical (BiO)₂CO₃ nanosheets microspheres were synthesized with dry ice as carbon source, and characterized by X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM) and UV–vis diffuse reflectance spectra (DRS). The photocatalytic results showed that (BiO)₂CO₃ display much higher photocatalytic activity than BiOCl and TiO₂ for photocatalystic reduction of CO₂ under UV-visible light. The photocatalytic mechanism study revealled that (BiO)₂CO₃ display better separation efficiency of photoinduced charge carriers due to the large interlayer spacing (1.3675 nm).     

Pillaring and photocatalytic properties of mesoporous α-Fe2O3/titanate nanocomposites via an exfoliation and restacking route

Mesoporous α-Fe₂O₃-pillared titanate nanocomposites have been successfully synthesized through an exfoliation−restacking route. Powder X-ray diffraction and N₂ adsorption-desorption isotherms revealed that the α-Fe₂O₃ pillared titanate has an interlayer distance of 3.27 nm, a specific surface area of 66 m²/g and an average pore size of 7.6 nm, suggesting the formation of a mesoporous pillared structure. UV-vis diffuse reflectance spectra show a red shift, indicative of a narrow band gap energy of ∼2.1 eV compared to the host layered titanate, which is essential in creating a visible light photocatalytic activity. The results of degradation of rhodamine B reveal that the present pillared mesoporous composites exhibit better photocatalytic activities than those of the pristine materials under visible irradiation, based on the band gap excitement and the dye-sensitized path, originated from their high surface area, mesoporosity and the electronic coupling between the host and the guest components.