Feb 2024, Volume 18 Issue 2

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  • Effective dispersion of fillers in the matrix is considered an efficient method to enhance the gas separation performance of hybrid membranes. In this study, metal-organic framework (MOF) nanoparticles dispersed in organosilica sol were successfully obtained by introducing urea into the precursor solution during the synthesis process. It was observed that the organosilica hybrid membrane, incorporated with urea-modulated MOF nanoparticles, exhibited a 3.3-fold increase in CO2 [Detail] ...

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    Jiangyan Lu, Zhu Xiong, Yuhang Cheng, Qingwu Long, Kaige Dong, Hongguo Zhang, Dinggui Luo, Li Yu, Wei Zhang, Gaosheng Zhang

    Thallium is a highly toxic metal, and trace amount of thallium(I) (Tl+) in potable water could cause a severe water crisis, which arouses the exploitation of highly-effective technology for purification of Tl+ contaminated water. This report proposes the multi-layered Prussian blue (PB)-decorated composite membranes (PBx@PDA/PEI-FP) based on the aminated filter papers for Tl+ uptake. Extensively characterization by Fourier transform infrared spectrometer-attenuated total reflectance, scanning electron microscope, thermogravimetric analysis, X-ray photoelectron spectroscopy and X-ray diffraction were performed to confirm the in situ growth of cubic PB crystals on filter paper membrane surfaces via the aminated layers, and the successful fabrication of multi-layered PB overcoats via the increasing of aminated layers. The effect of PB layers on Tl+ removal by PBx@PDA/PEI-FP from simulated drinking water was evaluated as well as the influence of different experimental conditions. A trade-off between PB decoration layer number and PB distribution sizes is existed in Tl+ uptake by PBx@PDA/PEI-FP. The double-layered PB2@PDA/PEI-FP membrane showed the maximum sorption capacity, but its Tl+ uptake performance was weakened by the acid, coexisting ions (K+ and Na+) and powerful operation pressure, during filtrating a large volume of low-concentrated Tl+-containing water. However, the negative effect of coexisting ions on the Tl+ uptake could be effectively eliminated in weak alkaline water, and the Tl+ removal was increased up to 100% without any pressure driving for PB2@PDA/PEI-FP membrane. Most importantly, PB2@PDA/PEI-FP displayed the high-efficiency and high-selectivity in purifying the Tl+-spiked Pearl River water, in which the residual Tl+ in filtrate was less than 2 μg·L–1 to meet the drinking water standard of United States Environmental Protection Agency. This work provides a feasible avenue to safeguard the drinking water in remote and underdeveloped area via the energy-free operation.

    Ling Ge, Tao Liu, Yimin Zhang, Hong Liu

    Herein, the influence of the concentration design and comprehensive performance of the sulfate-phosphoric mixed acid system electrolyte is investigated to realize an electrolyte that maintains high energy density and stable operation at high temperatures. Static stability tests have shown that VOPO4 precipitation occurs only with vanadium(V) electrolyte. The concentration of vanadium ion of 2.0–2.2 mol·L–1, phosphoric acid of 0.10–0.15 mol·L–1, and sulfuric acid of 2.5–3.0 mol·L–1 are suitable for a vanadium redox flow battery in the temperature range from –20 to 50 °C. The equations for predicting the viscosity and conductivity of electrolytes are obtained by the response surface method. The optimized electrolyte overcomes precipitation generation. It has 2.8 times higher energy density than the non-phosphate electrolyte, and a coulomb efficiency of 94.0% at 50 °C. The sulfate-phosphoric mixed acid system electrolyte promotes the electrode reaction process, increases the current density, and reduces the resistance. This work systematically optimizes the concentrations of composition of positive and negative vanadium electrolytes with mixed sulfate-phosphoric acid. It provides a basis for the different valence states and comprehensive properties of sulfate-phosphoric mixed acid system vanadium electrolytes under extreme environments, guiding engineering applications.

    Yuxin Li, Junxin Guo, Rui Han, Zhao Wang

    Heteroatom doping and defect engineering have been proposed as effective ways to modulate the energy band structure and improve the photocatalytic activity of g-C3N4. In this work, ultrathin defective g-C3N4 was successfully prepared using cold plasma. Plasma exfoliation reduces the thickness of g-C3N4 from 10 nm to 3 nm, while simultaneously introducing a large number of nitrogen defects and oxygen atoms into g-C3N4. The amount of doped O was regulated by varying the time and power of the plasma treatment. Due to N vacancies, O atoms formed strong bonds with C atoms, resulting in O doping in g-C3N4. The mechanism of plasma treatment involves oxygen etching and gas expansion. Photocatalytic experiments demonstrated that appropriate amount of O doping improved the photocatalytic degradation of rhodamine B compared with pure g-C3N4. The introduction of O optimized the energy band structure and photoelectric properties of g-C3N4. Active species trapping experiments revealed ·O2 as the main active species during the degradation.

    Yulun Liu, Yaojie Zhu, Zuowei Yan, Ruixue Bai, Xilin Zhang, Yanbo Ren, Xiaoyu Cheng, Hui Ma, Chongyun Jiang

    Excitonic devices are an emerging class of technology that utilizes excitons as carriers for encoding, transmitting, and storing information. Van der Waals heterostructures based on transition metal dichalcogenides often exhibit a type II band alignment, which facilitates the generation of interlayer excitons. As a bonded pair of electrons and holes in the separation layer, interlayer excitons offer the chance to investigate exciton transport due to their intrinsic out-of-plane dipole moment and extended exciton lifetime. Furthermore, interlayer excitons can potentially analyze other encoding strategies for information processing beyond the conventional utilization of spin and charge. The review provided valuable insights and recommendations for researchers studying interlayer excitonic devices within van der Waals heterostructures based on transition metal dichalcogenides. Firstly, we provide an overview of the essential attributes of transition metal dichalcogenide materials, focusing on their fundamental properties, excitonic effects, and the distinctive features exhibited by interlayer excitons in van der Waals heterostructures. Subsequently, this discourse emphasizes the recent advancements in interlayer excitonic devices founded on van der Waals heterostructures, with specific attention is given to the utilization of valley electronics for information processing, employing the valley index. In conclusion, this paper examines the potential and current challenges associated with excitonic devices.

    Zulfiqar Ali, Jiliang Ma, Dongnv Jin, Rui Cui, Runcang Sun

    The use of functional materials such as carbon-bismuth oxyhalides in integrated photorefineries for the clean production of fine chemicals requires restructuring. A facile biomass-assisted solvothermal fabrication of carbon/bismuth oxychloride nanocomposites (C/BiOCl) was achieved at various temperatures. Compared with BiOCl and C/BiOCl-120, C/BiOCl-180 exhibited higher crystallinity, wider visible light absorption, and a faster migration/separation rate of photoinduced carriers. For the selective C–C bond cleavage of biomass-based feedstocks photocatalyzed by C/BiOCl-180, the xylose conversion and lactic acid yield were 100% and 92.5%, respectively. C/BiOCl-180 efficiently converted different biomass-based monosaccharides to lactic acid, and the efficiency of pentoses was higher than that of hexoses. Moreover, lactic acid synthesis was favored by all active radicals including superoxide ion (·O2), holes (h+), hydroxyl radical (·OH), and singlet oxygen (1O2), with ·O2 playing a key role. The fabricated photocatalyst was stable, economical, and recyclable. The use of biomass-derived monosaccharides for the clean production of lactic acid via the C/BiOCl-180 photocatalyst has opened new research horizons for the investigation and application of C–C bond cleavage in biomass-based feedstocks.

    Yayun Zhao, Dechuan Zhao, Chunlong Kong, Yichao Lin, Xuezhen Wang, Liang Chen

    Metal-organic framework/organosilica hybrid membranes on tubular ceramic substrates have shown great potential for the implementation of membrane technology in practical gas separation projects due to their higher permeance compared to commercial polymers. However, the selectivities of the reported membranes are moderate. Here, we have incorporated urea-modulated metal-organic frameworks into organosilica membranes to greatly enhance its separation performance. The urea-modulated metal-organic frameworks exhibit less-defined edges of crystallographic facets and high defect density. They can be well-dispersed in the organosilica layer, which substantially suppresses the interfacial defects between metal-organic frameworks and organosilica, which is beneficial for improving the selectivity of membranes for gas separation. The results have shown that the enhanced ideal selectivity of H2/CH4 was 165 and that of CO2/CH4 was 43, with H2 permeance of about 1.25 × 10−6 mol·m−2·s−1·Pa−1 and CO2 permeance of 3.27 × 10−7 mol·m−2·s−1·Pa−1 at 0.2 MPa and 25 °C. In conclusion, the high level of hybrid membranes can be used to separate H2 (or CO2) from the binary gas mixture H2/CH4 (or CO2/CH4), which is important for gas separation in practical applications. Moreover, the simple and feasible modulation of metal-organic framework is a promising strategy to tune different metal-organic frameworks for membranes according to the actual demands.

    Junfeng Zhao, Xudong Yang, Zhongqing Zhang, Shengpeng Xie, Fangfang Liu, Anjun Han, Zhengxin Liu, Yun Sun, Wei Liu

    Based on its band alignment, p-type nickel oxide (NiOx) is an excellent candidate material for hole transport layers in crystalline silicon heterojunction solar cells, as it has a small ΔEV and large ΔEC with crystalline silicon. Herein, to overcome the poor hole selectivity of stoichiometric NiOx due to its low carrier concentration and conductivity, silver-doped nickel oxide (NiOx:Ag) hole transport layers with high carrier concentrations were prepared by co-sputtering high-purity silver sheets and pure NiOx targets. The improved electrical conductivity of NiOx was attributed to the holes generated by the Ag+ substituents for Ni2+, and moreover, the introduction of Ag+ also increased the amount of Ni3+ present, both of which increased the carrier concentration in NiOx. Ag+ doping also reduced the c-Si/NiOx contact resistivity and improved the hole-selective contact with NiOx. Furthermore, the problems of particle clusters and interfacial defects on the surfaces of NiOx:Ag films were solved by UV-ozone oxidation and high-temperature annealing, which facilitated separation and transport of carriers at the c-Si/NiOx interface. The constructed c-Si/NiOx:Ag solar cell exhibited an increase in open-circuit voltage from 490 to 596 mV and achieved a conversion efficiency of 14.4%.

    Yanqi Feng, Hui Liu, Xiaoting Liu, Qiongqiong Lu

    Lithiumsulfur batteries have been intensively studied due to their high theoretical energy density and abundant sulfur resources. However, their commercial application is hindered by the low redox kinetics and high sulfur losses. In principle, in the design of cathodes and separators, the adsorption toward lithium-polysulfides should be enhanced and the conversion of soluble high-order lithium-polysulfides should be catalyzed. Herein, a KV3O8·0.75H2O separator is designed as an effective lithium-polysulfides mediator in lithiumsulfur batteries. The intercalated K+ would enlarge the interlayer spacing of vanadium oxides, preventing the collapse of the layer structure and improving the electrical/ion conductivity of the interface. Moreover, the KV3O8·0.75H2O modified separator possess a prior adsorption and high redox kinetics toward lithium-polysulfides due to the enhanced diffusion kinetics, which guarantees the high-rate capability and efficient utilization of sulfur. As a result, lithiumsulfur batteries exhibit a high capacity of 1362 mAh·g1 and a long lifespan with a low capacity loss of 0.073% per cycle. This work may provide an alternative way to establish a functional separator to balance the adsorption and conversion of polysulfides during the redox back and forth.

    Feng Zhang, Shuainan Xu, Xiumei Geng, Meixia Shan, Yatao Zhang

    Polymers of intrinsic microporosity shows great potential for dye adsorption and magnetic Fe3O4 are easy to be separated. In this work, hydrolyzed polymers of intrinsic microporosity-1/Fe3O4 composite adsorbents were prepared by phase inversion and hydrolysis process for cationic dye adsorption. The chemical structure and morphology of the composite adsorbents were systematically characterized by several characterization methods. Using methylene blue as the target dye, the influences of solution pH, contact time, initial dye concentration, and system temperature on the methylene blue adsorption process were investigated. The incorporation of Fe3O4 particle into hydrolyzed polymers of intrinsic microporosity-1 endow the adsorbent with high magnetic saturation (20.7 emu·g–1) which allows the rapid separation of the adsorbent. Furthermore, the adsorption process was simulated by adsorption kinetics, isotherms and thermodynamics to gain insight onto the intrinsic adsorption mechanism. In addition, the composite adsorbents are able to selectively adsorb cationic dyes from mixed dyes solution. Hydrolyzed polymers of intrinsic microporosity/Fe3O4 shows only a slight decrease for methylene blue adsorption after 10 adsorption/regeneration cycles, demonstrating the outstanding regeneration performance. The high adsorption capacity, outstanding regeneration ability, together with simple preparation method, endow the composite adsorbents great potential for selective removal of cationic dyes in wastewater system.

    Tao Huang, Xihong Zu, Jianhui Ma, Wenbin Jian, Xueqing Qiu, Wenli Zhang

    The widespread implementation of supercapacitors is hindered by the limited energy density and the pricey porous carbon electrode materials. The cost of porous carbon is a significant factor in the overall cost of supercapacitors, therefore a high carbon yield could effectively mitigate the production cost of porous carbon. This study proposes a method to produce porous carbon spheres through a spray drying technique combined with a carbonization process, utilizing renewable enzymatic hydrolysis lignin as the carbon source and KOH as the activation agent. The purpose of this study is to examine the relationship between the quantity of activation agent and the development of morphology, pore structure, and specific surface area of the obtained porous carbon materials. We demonstrate that this approach significantly enhances the carbon yield of porous carbon, achieving a yield of 22% in contrast to the conventional carbonization-activation method (9%). The samples acquired through this method were found to contain a substantial amount of mesopores, with an average pore size of 1.59 to 1.85 nm and a mesopore ratio of 25.6%. Additionally, these samples showed high specific surface areas, ranging from 1051 to 1831 m2·g−1. Zinc ion hybrid capacitors with lignin-derived porous carbon cathode exhibited a high capacitance of 279 F·g−1 at 0.1 A·g−1 and an energy density of 99.1 Wh·kg−1 when the power density was 80 kW·kg−1. This research presents a novel approach for producing porous carbons with high yield through the utilization of a spray drying approach.