Special Layered Structure Research Articles

Coupling CoIr Nanoalloys with MXene by Lewis Acidic Molten Salt Etching for Wide-pH-Environment Hydrogen Evolution Reaction.

Metal/MXene-based materials show broad prospects in energy conversation through the strong metal-support interaction (SMSI). However, the difficulty and harshness of synthesis heavily limit their further application. Herein, using Lewis acidic molten salt to etch MAX as a precursor of MXene, a more convenient and safer strategy is designed to in situ construct the MXene-supported CoIr nanoalloy (CoIr/MXene) catalyst through Ti─O─M bond. The special layered structure and oxygen-containing functional group of MXene regulate the SMSI upon CoIr nanoalloys. Moreover, the contact angle and in situ Raman test results exhibit good interface hydrophilicity of MXene, enhancing the water adsorption on interfaces, and accelerating the mass transfer process. As a result, CoIr/MXene shows high hydrogen evolution reaction (HER) performance, which only needs overpotentials of 34 and 50mV to drive a current density of 10mA cm-2 in alkaline and acidic media, respectively, with excellent stability. Especially, in alkaline media, CoIr/MXene possesses 6 times higher HER mass activity (4.297 A mgIr -1) than commercial Pt/C catalysts (0.686 A mgPt -1) at the potential of 50mV, indicating larger active site density and intrinsic activity for CoIr/MXene. This work expands the application of the molten salt assist etching strategy and provides new insight for the development of metal/MXene-based catalysts.

UV aging resistance improvement of SBS modified asphalt binder by organic layered double hydroxide and naphthenic oil: Its preparation, properties and mechanism

To enhance the UV aging resistance of SBS modified asphalt, LDHs and naphthenic oil were selected to modify it compositely. Firstly, organic treatment for LDHs was carried out through the combination of surface modification method and intercalation modification method to improve its compatibility with asphalt, and effectiveness of organic treatment was evaluated through the microscopic testing methods. Then, organic LDHs/SBS modified asphalt binders were developed by melt blending method, on this basis, appropriate naphthenic oil was added for composite modification. Subsequently, the conventional physical properties, storage stability and rheological properties tests were carried out to evaluate the comprehensive properties of the prepared modified asphalt containing LDHs and naphthenic oil. On this basis, TOPSIS method was conducted for multi-index optimization to determine the optimal dosages of LDHs and naphthenic oil. Finally, UV aging resistance of the developed modified asphalt was also evaluated, and reaction mechanism was explored with FTIR and FM. Test results show that stearic acid (SA) was successfully absorbed on the surface of LDHs, and -SO32- in ultraviolet light absorber (UVT) has successfully entered the interlayer galleries of LDHs, thus achieving the organic treatment for LDHs. Organic LDHs can significantly improve the high temperature properties and storage stability of SBS modified asphalt, and naphthenic oil can also improve the storage stability of SBS modified asphalt at the proper dosage. In addition, the two modifiers can both effectively improve the UV aging resistance of SBS modified asphalt. Based on the multi-index optimization results, it is recommended that the optimal dosages of LDHs and naphthenic oil are 2 % and 2.5 %, respectively, and at this conditions, comprehensive properties of the prepared modified asphalt can achieve the best. Microstructure characterization tests results reveal that LDHs and naphthenic oil are only simply dispersed in asphalt and do not cause the structural damage of SBS modified asphalt. Meanwhile, the special layered structure of LDHs can hinder the mobility of asphalt molecular chains, which enhances the interaction force between asphalt molecular chains and SBS modifier molecular chains, thus improving the road properties of SBS modified asphalt.

Preparation of Zirconium-Based MOF-Derived Phosphide on GO/MXene Double Substrates for High-Performance Asymmetric Supercapacitors.

At present, it is very necessary to select and prepare suitable positive and negative electrode materials to fabricate high-performance asymmetric supercapacitors. Metal-organic frameworks (MOFs) have garnered significant attention in the energy storage field due to their high conductivity. As a branch, the zirconium organic framework (UIO-66) is a promising porous material due to its large specific surface area and abundant Zr centers. Graphene oxide (GO) and MXene are very suitable as substrate materials for conducting an MOF due to their abundant active sites and adjustable interlayer distance. The GO/MXene@NiZrP prepared through an in situ composite of GO and Mxene with the hydrothermal method and calcining method showed excellent electrochemical performance. Compared with the precursor UIO-66, the specific capacitance of the final product GO/MXene@NiZrP increases more than ten times, mainly because of its special layered porous structure, and GO/MXene@NiZrP has a larger specific surface area, pore volume, and surface defects caused by unstable Zr4+ than those of UIO-66. Using GO/MXene@NiZrP as the positive electrode and biochar (BC) as the negative electrode, an asymmetric supercapacitor, BC//GO/MXene@NiZrP, is assembled. After 10,000 cycles at a current density of 10 A g-1, the capacitance retention remains at 83.3%, showing excellent cycle stability.

Composite PEDOT-PSS based highly sensitive electrochemical sensors for sensing glucose from human saliva

Here we report two composites, especially two different 2D materials and Au nanoparticle composite with conducting polymer PEDOT-PSS as electrodes for highly sensitive, cost effective and reliable biosensors. Conducting polymer composite electrodes of AuNP/WS2/PEDOT-PSS and AuNP/GO/PEDOT-PSS were prepared by electrochemical deposition and were studied using various structural and electrochemical techniques. XRD, FTIR and SEM have been used for structural characterization which confirmed the elemental compositions of these composite electrodes. Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) were used to examine the charge transfer kinetics and electroactive properties of the modified electrodes. Impedance spectra analysis had shown the reduced charge transfer resistance and diffusive property of AuNP/WS2/PEDOT-PSS electrodes compared to AuNP/GO/PEDOT-PSS. To demonstrate biosensing advantages of these electrodes, interaction between covalently immobilized glucose oxidase (GlOx) enzyme and D-glucose was monitored via chronoamperometry and CV. GlOx/AuNP/WS2/PEDOT-PSS/ITO yielded wider linear range from 0.74 to 440.67 µM towards the oxidation of glucose with high selectivity and lower limit of detection (LOD) of 1 µM. AuNP/GO/PEDOT-PSS/ITO composite electrode exhibited linearity in the range 3.84–373.33 µM and LOD 2.33 µM. Better sensitivity and wider linear range of GlOx/AuNP/WS2/PEDOT-PSS/ITO has been assigned to special layered structure as sheets formed by incorporation of WS2 to PEDOT-PSS. Validation of the glucose sensors has shown satisfactory results using real saliva samples. Study suggests use of conducting polymer, 2D layered material and metal nanoparticle composite electrodes based sensors offer wider linearity range and higher sensitivity for stable, reliable, cost- effective sensor electrodes which can be used easily in non-clinical diagnostics.

Anion Structure Regulation of Cobalt Silicate Hydroxide Endowing Boosted Oxygen Evolution Reaction.

Transition metal silicates (TMSs) are attempted for the electrocatalyst of oxygen evolution reaction (OER) due to their special layered structure in recent years. However, defects such as low theoretical activity and conductivity limit their application. Researchers always prefer to composite TMSs with other functional materials to make up for their deficiency, but rarely focus on the effect of intrinsic structure adjustment on their catalytic activity, especially anion structure regulation. Herein, applying the method of interference hydrolysis and vacancy reserve, new silicate vacancies (anionic regulation) are introduced in cobalt silicate hydroxide (CoSi), named SV-CoSi, to enlarge the number and enhance the activity of catalytic sites. The overpotential of SV-CoSi declines to 301mV at 10mA cm-2 compared to 438mV of CoSi. Source of such improvement is verified to be not only the increase of active sites, but also the positive effect on the intrinsic activity due to the enhancement of cobalt-oxygen covalence with the variation of anion structure by density functional theory (DFT) method. This work demonstrates that the feasible intrinsic anion structure regulation can improve OER performance of TMSs and provides an effective idea for the development of non-noble metal catalyst for OER.

Atomically engineered Al-doped LaOCl for chlorine-ion batteries

LaOCl belongs to one kind of promising solid electrolyte for chlorine-ion batteries due to its excellent electric insulation performance and special layered structure. However, LaOCl still suffers from poor chlorine-ion conductivity. Then, we proposed microstructure modulation of LaOCl to solve this problem based on Al doping method. Firstly, we carried out first-principles and ab-initio molecular dynamics (AIMD) calculations to investigate the internal relation among structure stability, chlorine-ion conductivity and related physicochemical properties of Al doped LaOCl(La1-xAlxOCl). It is found that La0.75Al0.25OCl not only possesses most stable structure but also demonstrates the best ductility. Moreover, La0.75Al0.25OCl also possesses much lower chlorine-ion diffusion energy barrier than LaOCl(0.40 eV vs.0.78 eV) and its chlorine-ion conductivity goes as high as 5.4 × 10−3 S/cm at 300K. This is attributed to the optimal reconstruction of La–Cl coordination structure induced by Al dopant, which weakens the limiting effect of La–Cl bond as far as possible. Meanwhile,La0.75Al0.25OCl exhibits excellent electrical insulating property due to its wide band gap of 5.87 eV. In addition, La0.75Al0.25OCl exhibits wide electrochemical window with La and Al metal acted as anode materials, respectively (1.92–9.66 V for La and 0–7.74 V for Al). At this stage, La0.75Al0.25OCl solid electrolyte requires no chlorine-ion uptake and loss in the process of oxidation and reduction, indicating its excellent electrochemical stability.

Evolution of solidification structure and mechanical properties of Al7050 alloy under hypergravity

The article discussed the effects of hypergravity fields on the dendrite structure, macrosegregation, and mechanical properties of Al7050 alloy. Compared to normal gravity, the average size of α-Al grains at the bottom of the sample was significantly reduced under hypergravity. The melt superheating temperature influenced atomic clusters, which, along with dendrite fragmentation, facilitated heterogeneous nucleation. Subsequently, the "crystal rain" mechanism led to the migration and accumulation of primary crystals. The emergence of coarse columnar dendrites under hypergravity may result from high-speed forced convection transferring solutes at the dendrite tips, thereby promoting dendrite growth through increased concentration gradients. Under hypergravity, Zn, Mg, and Cu elements were enriched at the bottom of the sample, possibly due to solutes expelled during α-Al dendrite growth entering the liquid phase. The denser solute-rich liquid settled at the bottom under hypergravity, precipitating numerous secondary phases. The compressive strength and strain of the hypergravity specimen increased due to its special density-dependent layered structure.

Experimental study on fatigue failure properties of mudstone interlayers under discontinuous loading in salt cavern gas storage

During the operation of an underground salt cavern gas storage, Fatigue failure occurs in the surrounding rock of gas storage reservoirs under non-continuous gas injection and extraction loading. Due to the special layered salt rock structure in China, the mudstone interlayer is the weak part of the gas storage. It is necessary to study the effect of stress magnitude and interval time on the fatigue mechanical properties of mudstone. Graded upper stress limit interval fatigue (GUIF) test and graded lower stress limit interval fatigue (GLIF) test were carried out on mudstone respectively. And different interval times were set to investigate the effect of interval time on the mechanical properties of mudstone. With the increase in the interval time, the fatigue life and peak strain of the mudstone increased. Under the same interval time, the lower-limit interval test result showed a significantly higher fatigue life than the upper-limit interval test result. The stress–strain curve exhibited three stages: scattered–dense–scattered. During the unloading phase, the modulus of elasticity increased with increasing stress levels, indicating that the internal structure of the mudstone is extremely sensitive to the stress. In the (GUIF) test, the average residual strain increased with the increase in the interval time, and the residual strain during the cycle after the time interval under different grades was lower than the residual strain before the time interval; the results of the (GLIF) test showed the opposite trend. In the (GUIF) test, the average creep strain increased with increasing interval time under the same stress level, and the average creep strain was greater than the average residual strain, and the creep stage had a greater effect on mudstone damage than the fatigue stage. The post-fatigue creep strain was significantly greater than the pre-fatigue creep strain. The research results can be useful in ensuring the stable operation of gas storage in salt caverns.

Structure design of a BiOF solid electrolyte with remarkably outstanding fluoride ion diffusion performance induced by Ga doping

BiOF is considered as a potential excellent solid electrolyte for fluoride ion batteries due to its special layered structure.

Strengthening the mechanical properties and corrosion resistance of Ni[sbnd]W coatings by PDA-functionalized h-BN nanosheets

PDA-functionalized h-BN nanomaterials (Ph-BN) were used to reinforce the electrodeposited NiW coatings. Compared with the h-BN nanomaterial, Ph-BN has better dispersion in the plating solution, which can effectively improve the mechanical and corrosion resistance of the coating. Compared with the NiW coating, the microhardness value of the Ni-W/Ph-BN coating (662.8 Hv) was increased by 33.47 % and the friction coefficient (0.382) was reduced by 41.86 %. This is due to the special ceramic composite layered structure of Ph-BN namely the combination of flexible unit PDA structure and rigid unit h-BN structure, which will synergistically hinder the shedding of the coating during the friction process and help to improve the wear resistance of the coating. The Rct value of Ni-W/Ph-BN is 34,500 Ω•cm2, which is 105.36 % higher compared to NiW coating. Ni-W/Ph-BN also has the smallest corrosion rate (0.0465 mm•a−1), which is 45.74 % lower relative to NiW coating. The uniformly dispersed Ph-BN nanosheets in the coating prolong the corrosion path for corrosive ions. Besides, the PDA has the effect of anchoring Fe2+/ Fe3+, which will be beneficial for the composite coating corrosion resistance improvement.

Use of montmorillonite to improve flame retardancy, thermal stability and reducing smoke toxicity of chicken feather protein‐based rigid polyurethane foam

AbstractThe aim of this article is to solve the problem of improving the flame retardancy of rigid polyurethane foam (RPUF) while improving the environmental pollution caused by flame retardancy. Using the special layered structure of montmorillonite (MMT) and the stable chemical bond formed by the reaction with chicken feather (CF) protein, RPUF co‐modified with MMT and CF was successfully prepared by using the “one‐step method” of all‐water foaming. It was found by experiments and theoretical calculations that the addition of MMT improved the flame retardancy of the samples. When 3 wt% of MMT was added, RPUF‐CF1/MMT3 had the highest initial decomposition temperature and the largest activation energy, and its thermal stability was the best. In addition, RPUF‐CF1/MMT3 had the smallest peak heat release rate (28.77, 32.04, and 42.18 kW/m2) and total heat release (1.87, 2.15, and 2.38 MJ/m2) at different radiation fluxes. Meanwhile, RPUF‐CF1/MMT3 had the smallest smoke density (32.17 and 28.32), the largest light transmission (57.05% and 60.91%), the lowest toxic gas emission and the lowest fire risk.Highlights Flame retardant modified bioprotein‐based RPUF by MMT is proposed. The flame retardant mechanism depends on the “sandwich biscuit” structure of MMT and its POSi bond with chicken hair protein. MMT‐modified RPUF can improve its thermal stability, flame retardancy and smoke toxicity.

Modulating electrodeposition of ultralow Pt into 2D MoCu-POMOF-derived MoO2/MoOC for boosted hydrogen evolution reaction

Electrochemical water splitting is regarded as a promising technology for production of high purity, high volume hydrogen. It is critical to create robust and highly active electrocatalysts in order to minimize the cost of hydrogen generation and enable large-scale commercial production. In this work, a new 2D MoCu-POMOF, [Cu(4-pyz)]4@(PMo12O40) (4-pyz = 4-(pyridin-4-yl)benzoic acid) was prepared by a simple hydrothermal method, in which PMo12 nanocluster was encapsulated into cavity of 2D Cu-MOF. The successful establishment of the model in addition to the goal of uniformly dispersed Mo sources target oxygen-rich PMo12 nanoclusters can also provide rich Mo source and self-oxidative properties for MoO2 formation. Cu-MOF provides a special layered structure, which ensures the integrity and stability of the structure and provides a rich C source for pyrolysis and improves the conductivity. Ultralow Pt nanoparticles can reduce free energy of hydrogen evolution, which are embedded in MoO2/MoOC with porous structure and high electrochemical active surface area. MoO2/MoOC and highly dispersed Pt nanoparticles synergistically promote the HER catalysis. Pt@MoO2/MoOC demonstrated the excellent HER activity with a low overpotential of 98.99 mV vs. RHE. This work yielded highly active and high stability molybdenum-based HER electrocatalysis and provides the potential for energy conversion.

Investigation on the photocatalytic degradation properties of BiOX on carbendazim and its mechanism

AbstractBismuth Oxyhalide (BiOX, X=Cl, Br, I) has been widely used in water purification, environmental remediation and other fields due to its special layered structure and good photocatalytic performance. In this work, BiOCl, BiOBr and BiOI photocatalysts were successfully synthesized by a simple solvothermal method and first applied to the mineralization and degradation of carbendazim (CBZ). The degradation performance of BiOX to CBZ was studied under different light sources and different pH conditions. And the influence mechanism of the degradation performance of the three catalysts were revealed by analyzing the structure, morphology, specific surface area, optical performance, energy band structure, and electronic density of state of the materials. The results showed that, under the irradiation of metal halide lamp, the photocatalytic activity of BiOBr was the best when the pH was at 7. The degradation efficiency reached 99 % after 3 h and more than 90 % CBZ molecules could be mineralized. The BiOBr catalyst had good stability in four cycles. Furthermore, it was found that the main active species were h+ and ⋅O2− in the photodegradation process by free radical trapping experiment. Based on the density functional theory (DFT) calculation, it was demonstrated that different halogen atoms had different density of state contribution intensity in atomic orbitals, different band gap width and different light response capabilities by the analysis of its energy band structure and partial wave density of state (PDOS), resulting in different photocatalytic performance under different energy light irradiation.

Monte Carlo simulation study of rare earth/polypropylene composite shielding 120 KV medical X-ray

Rare earth is widely used as a ray shielding material due to its special electron layer structure, and Monte Carlo simulations are also widely used in ray shielding. Therefore, in this paper, based on the Monte Carlo simulation algorithm and FLUKA program, three kinds of rare earth, Gd2O3, Nd2O3, and La2O3, were selected as shielding fillers to prepare rare earth/polypropylene composite materials, and their shielding effect on X-ray at 120KV tube voltage was simulated. It is found that the three rare earths as shielding fillers have a shielding effect on X-ray under 120KV tube voltage, and Gd2O3 has the best effect on X-ray attenuation. When the thickness of the material is 0.06 cm, the shielding rate of pure Gd2O3 particles is 92.25%, and the rare earth/polypropylene composite material with a mass ratio of 1: 1 at the same thickness can also shield 32.74% of rays. Increasing the thickness of the composite or the amount of rare earth filling can improve the shielding effect of the composite, but the effect of increasing the amount of rare earth filling is more significant.

Designing NbTiTa-Cr/Al refractory complex concentrated alloys with balanced strength-ductility-oxidation resistance properties: Insights into oxidation mechanisms

Limited tensile ductility, poor oxidation resistance, and the ductility-oxidation resistance trade-off are key bottlenecks besetting refractory complex concentrated alloys (RCCAs). Here, in this study, by alloying ductile NbTiTa RCCAs with low content of Cr or Al, we design two novel single-phase RCCAs Nb40Ti40Ta10Cr10 (Cr10) and Nb45Ti30Ta15Al10 (Al10). These two alloys demonstrate excellent tensile strength-ductility combination (∼800 MPa, >20%) and the best oxidation resistance at 800 °C (<7.2 mg/cm2 after 20 h exposure) among all tensile-ductile RCCAs reported by far. Cr10 exhibits much slower oxidation kinetics compared with Al10, attributed to i) the dominant rutile-type Ti1–2x(Nb,Ta)xCrxO2 oxide that has lower volume mismatch with the alloy matrix compared with (Nb,Ta)2O5, as indicated by low Pilling-Bedworth ratio (PBR) values of 1.03–1.76; and ii) the alternative layer structure consisting of dense rutile and porous mixed oxides that is conducive to prohibiting stress cumulation and cracking. A new thermodynamic model connecting the Gibbs free energy of formation of a related oxide to the dynamically varied alloy compositions was proposed and used to unveil the dynamic formation mechanisms of oxides in Cr10 and Al10. The special alternative layer structure, mixed-oxides structure, voids, and/or cracks featured by oxide scales of Cr10 and/or Al10 are well-understood by combining detailed scanning transmission electron microscopy (STEM) studies, thermodynamic simulations, and stress analyses based on PBR evaluations.

Revealing the ultra-high high-temperature compressive mechanical properties and deformation mechanism of a heterostructured AlNp/Al nanocomposite

Heterostructured materials have attracted increasing attention owing to their superior mechanical properties. In this work, the high-temperature mechanical property and deformation mechanism of a heterostructured AlNp/Al composite were revealed by isothermal compression tests. The results showed that the superior compressive strength of the AlNp/Al composite could be maintained at both room temperature and high temperature of 300–500 °C during the whole deformation process. The strong pinning effect of the dispersive AlN nanoparticle (AlNp) on the matrix grains could prevent grain boundary softening and grain growth, as well as the special layered heterogeneous structure and network structure could avoid high temperature softening. The hot deformation mechanism of the AlNp/Al composite could be affected by the strain rate and deformation temperature. It was confirmed that continuous dynamic recrystallization (CDRX) dominated the whole deformation process when deformed at low strain rates (0.0001–0.01 s−1) and high temperatures (400–500 °C); while dynamic recovery (DRV) was the main mechanism at high strain rate (0.1–1 s−1) and low temperature (300–350 °C) Furthermore, the strain rate sensitivity exponent (m) was used to assess the relationship between peak stress and deformation temperature and strain rate, which could predict the instability region of the composite. It shows that the simultaneous action of high temperatures and high strain rates should be avoided during hot deformation. This work shed light on the microstructure design of the high-strength heat-resistant aluminum matrix composite.

Ni-doped Bi2O2CO3 nanosheet with H+/Zn2+ co-insertion for “rocking chair” zinc-ion battery

Developing insertion-type anode is key to advancing “rocking chair” zinc-ion batteries, though there are few reported insertion-type anodes. Herein, the Bi2O2CO3 is a high-potential anode, with a special layered structure. A one-step hydrothermal method was used to prepare Ni-doped Bi2O2CO3 nanosheet, and also a free-standing electrode consisting of Ni-Bi2O2CO3 and CNTs was designed. Both cross-linked CNTs conductive networks and Ni doping improve charge transfer. Ex situ tests (XRD, XPS, TEM, etc.) reveal the H+/Zn2+ co-insertion mechanism of Bi2O2CO3 and that Ni doping improves its electrochemical reversibility and structural stability. Therefore, this optimized electrode offers a high specific capacity of 159 mAh g−1 at 100 mA g−1, a suitable average discharge voltage of ≈0.400 V, and a long-term cycling stability of 2200 cycles at 700 mA g−1. Besides, the Ni-Bi2O2CO3//MnO2 “rocking chair” zinc-ion battery (based on the total mass of cathode and anode) delivers a high capacity of ≈100 mAh g−1 at 50.0 mA g−1. This work provides a reference for designing high-performance anode in zinc-ion batteries.

Perovskite-Like Strontium Bismuth Oxyhalides: Synthesis, Characterisation, Photocatalytic Activity and Degradation Mechanism

Recent studies have demonstrated that bismuth oxyhalides with a 2D structure inhibit the recombination of electron–hole pairs. Further, perovskite-like strontium bismuth-based compounds with a special layered Sillen X1 structure have shown potential for use as effective visible-light photocatalysts. Here, a series of strontium bismuth oxyhalide composites were prepared under different calcination conditions. The sample compositions were controlled by modulating the calcination temperature and the secondary calcination time. The synthesised catalysts were characterised by various techniques to identify the product compositions. Under visible-light irradiation, the degradation efficiencies and photocatalytic activities of the different catalysts towards rhodamine B (RhB) and 2-hydroxybenzoic acid (2-HBA) were measured via UV–Vis PDA and electron paramagnetic resonance analyses. To explore the degradation mechanism, scavengers were utilised to detect the radicals produced in the photodegradation test. SrBiO2Cl exhibited the best RhB degradation efficiency, of 0.0685 h−1, and SrBiO2Br exhibited a rate of 0.0984 h−1. At 25 °C and 1 atm, the CO2–CH4 photocatalytic conversion efficiencies of the optimised SrBiO2Cl and SrBiO2Br samples increased to 0.037 and 0.053 μmol g−1 h−1, respectively. The findings confirm that the catalysts are highly recyclable and effective for environmental remediation, achieving the objectives of green chemistry.

Correlations of Precursor and Carbon Coating with Electrochemical Property of 2D Graphitic Carbon Nitride (g-C3N4) Nanosheets as High-Reversibility Cathode of Nonaqueous Al-Ion Batteries

Al-ion batteries (AIBs) represent promising multivalent-ion battery alternatives to Li-ion batteries (LIBs). Exploration of cathode materials is the key to improving the electrochemical performance of AIBs. Here we demonstrate a promising AIB cathode candidate based on two-dimensional graphitic carbon nitride (g-C3N4) nanosheets with reversible de/embedding of [AlCl4]− anions in its special layered porous structure during the cyclic charge/discharge process. To address the sluggish ion/charge transportation kinetics that is inherently present in AIBs due to the intrinsically low conductivity of g-C3N4, we optimize different synthetic precursors of g-C3N4 including dicyandiamide, urea, and melamine and, further, develop a facile method for uniformly coating a N-doped carbon (N–C) coating layer on the optimal g-C3N4 derived from dicyandiamide. The resultant AIBs consisting of the g-C3N4@N–C cathode and Al metal anode in the AlCl3/[EMIm]Cl electrolyte exhibit an initial capacity of ∼54.9 mAh·g–1 at 0.2 C with a high Coulomb efficiency ∼99.9%, and they possess long-term cycling over 200 cycles. The underlying charge/discharge process of AIBs, revealed by the ex situ X-ray diffraction and scanning electron microscopy analyses, involves the extraction/insertion of Al species (mainly Al3+, AlCl4–, and Al2Cl7–) into the g-C3N4 crystal lattices with the formation of intermediate Al8C3N4 and (ClCN)3.

Room temperature ethanol sensor based on ZnO nanoparticles modified by WSe2 nanosheets

Ethanol gas sensors have been widely applied in food safety, biomedicine, and fuel processing. However, most ethanol sensors need to be operated at high temperature. The development of room temperature ethanol sensors with low cost and high sensitivity is still a challenge. Here, a low-cost room temperature ethanol gas sensor is realized by connecting interdigital electrodes (IDEs) coated with ZnO/WSe2 nanocomposite film in series with a quartz crystal resonator (QCR). The change in ethanol gas concentration can be converted into a frequency shift of the quartz resonator to generate a quasi-digital signal through the sensor. Compared with pure ZnO IDEs-SQCR sensor, the sensitivity of ZnO/WSe2 IDEs-SQCR sensor (4.87 Hz/ppm) has been significantly improved in ethanol concentration range of 0–400 ppm. This is mainly attributed to the introduction of WSe2 with good conductivity, which not only enables the composite to have a special layered three-dimensional structure conducive to the adsorption and diffusion of gas molecules, but also puts the resistance of the composite in a more sensitive tuning range. The proposed sensor can be fabricated on a printed circuit board (PCB) so as to reduce the cost of mass production.