Low-cost Preparation Research Articles

Nb/TiO2 oxides: A study of synthesis and electron transport mechanism as an ETL in a solar device

Efficient solar devices to energy conversion are the key to a sustainable future. TiO2 dye solar cells are systems that present limited energy conversion efficiency due to recombination reactions. An alternative to reduce the back-electron recombination is the insertion of new oxides in electron transport material, such as Nb. However, what are the changes in electron lifetime and collection time caused by Nb insertion in TiO2 photoanodes? This work aims to analyze TiO2 dye solar devices with different Nb proportions synthesized by an easy and low-cost particle preparation methodology, Pechini. The techniques performed were X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM), and X-ray fluorescence to particle characterization. To the electrochemical analysis of the cells, j-V curves, Electrochemical Impedance Spectroscopy (EIS), charge extraction, Intensity Modulated Photovoltage Spectroscopy (IMVS), and Intensity-Modulated Photocurrent Spectroscopy (IMPS) were performed. The results showed a mix of anatase and rutile phase to TiO2 with Nb insertion and at the 5% of Nb proportion has been able to generate a cell with better electrochemical parameters (PCE = 5.43 %; j = 6.34 mA cm−2). The creation of energy substates below the conduction band has been able to increase the collection time (0.1748 s) and electron lifetime (0.15514 s) when compared to the cell with bare TiO2, suppressing the back-electron recombination but also difficulting the collection reaction.

Synergistic adsorption and degradation of sulfamethazine by tobacco stalk-derived activated biochar: Preparation, mechanism insight and application

Green preparation of high value-added products from biomass waste for environmental remediation has received significant attention. In this work, activated biochars were developed through two-step thermal process using tobacco stalk as the precursor. Textural properties of biochar can be effectively tuned by adjusting carbonization and activation parameters. An optimized biochar (700TS-1000–5), carbonized at 700 ℃ and then thermally activated at 1000 ℃ for 5 h, showed higher specific surface area (905.61 m2 g−1), rich porous structure, and abundant surface functional groups. 700TS-1000–5 showed excellent performance with a removal capacity of 99.37 mg g−1 for sulfamethazine (SMT) in 720 min, which was 4.3 times that of pristine biochar (700TS). And the SMT removal was high-efficient under normal environmental pH range. Adsorption and degradation simultaneously occurred during the whole process, which mainly relied on defects, functional groups, and·OH radicals. Moreover, this typical sample showed outstanding recycling ability and effectiveness of column experiment. Compared with KOH-assisted chemical activation, thermal activation had minor environmental impact and lower preparation cost through environmental and economic assessment. These findings not only propose a simple protocol for high-value reuse of agricultural waste but also shed new light on applications of tobacco stalk-derived biochar.

Ti3C2 MXene quantum dots decorated mesoporous TiO2/Nb2O5 functional photoanode for dye-sensitized solar cells

Despite the apparent benefits of dye-sensitized solar cells (DSSCs), such as low-cost preparation, multicolor transparency, and a wide range of practical applications, the power conversion efficiency (PCE) still needs further improvement. In order to maximize the PCE, it is critical to devise an appropriate configuration of the photoanode that encourages charge generation and separation. Here, we have successfully altered the energy level alignment of the photoanode by introducing niobium oxide (Nb2O5) and Ti3C2 quantum dots (MQDs) into the photoanode, which has led to a substantial increase in both photocurrent and efficiency. Nb2O5 and Ti3C2 quantum dots are believed to exhibit higher light absorption, improved carrier separation, and expedited charge transfer due to their distinct band structure and optoelectronic characteristics. The DSSC device constructed with the target composite photoanode shows a remarkable PCE of 7.24%, far surpassing the standard device's efficiency of 4.60%.

Fluorescence Resonance Energy Transfer Properties and Auger Recombination Suppression in Supraparticles Self-Assembled from Colloidal Quantum Dots

Colloid quantum dots (CQDs) are recognized as an ideal material for applications in next-generation optoelectronic devices, owing to their unique structures, outstanding optical properties, and low-cost preparation processes. However, monodisperse CQDs cannot meet the requirements of stability and collective properties for device applications. Therefore, it is urgent to build stable 3D multiparticle systems with collective physical and optical properties, which is still a great challenge for nanoscience. Herein, we developed a modified microemulsion template method to synthesize quantum dot supraparticles (QD-SPs) with regular shapes and a high packing density, which is an excellent research platform for ultrafast optical properties of composite systems. The redshift of the steady-state fluorescence spectra of QD-SPs compared to CQD solutions indicates that fluorescence resonance energy transfer (FRET) occurred between the CQDs. Moreover, we investigated the dynamic processes of energy transfer in QD-SPs by time-resolved ultrafast fluorescence spectroscopy. The dynamic redshift and lifetime changes of the spectra further verified the existence of rapid energy transfer between CQDs with different exciton energies. In addition, compared with CQD solutions, the steady-state fluorescence lifetime of SPs increased and the fluorescence intensity decreased slowly with increasing temperature, which indicates that the SP structure suppressed the Auger recombination of CQDs. Our results provide a practical approach to enhance the coupling and luminescence stability of CQDs, which may enable new physical phenomena and improve the performance of optoelectronic devices.

Flexible Surface-enhanced Raman Scattering Strips Using Colloidal Ink of Gold-silver Alloyed Nanoparticles

Surface-enhanced Raman scattering (SERS) has been used for trace detection at the single-molecule level. The low-cost preparation of high-performance test strips has enabled the development of SERS techniques. In this study, oil-dispersible metal or alloy nanoparticles prepared by the Brust-Schiffrin method were used as "inks" in a ballpoint pen to handwrite SERS test strips on polytetrafluoroethylene (PTFE) membranes. Because of the good PTFE lipophilicity, the flexible substrates had good uniformity. The large laser damage threshold of the PTFE membrane also enabled increased laser powers for SERS testing. The Au and Ag alloy nanoparticle inks exhibited increased performance with larger proportions of Ag. The Au1Ag8 nanoparticles had the best properties, and those strips could detect 10-11-M Rhodamine 6G dyes in a 10-µL volume with an enhancement factor of 5.4×108. The SERS strips were used to demonstrate detection of malachite green, the use of which is prohibited in aquaculture and fish tanks.

Stable preparation of highly water-soluble ammonium polyphosphate by ion regulation

Water-soluble ammonium polyphosphate (APP) is an ideal phosphorus source to replace conventional phosphate fertilizers and improve phosphorus utilization. The industrial preparation of highly water-soluble APP is currently difficult owing to the associated harsh operating conditions and high raw material costs. Thus, a new strategy to stabilize the preparation of highly water-soluble APP was developed based on the addition of Mg2+ and SO42− ions to the raw materials. Product characterization demonstrated that Mg2+ inhibited the formation of water-insoluble long-chain polymers and stabilized the formation of crystalline type-I oligomeric APP, while the addition of SO42− induced the transformation of this oligomeric APP to amorphous acidic APP or polyphosphoric acid, further improving the product solubility. These effects were further investigated using reaction kinetics and density functional theory calculations. Compared with the pure phosphoric acid–urea system, the addition of Mg2+ and SO42− stabilized the average degree of polymerization of the product and simplified control of the production process. A pilot test showed that the use of this approach with wet-process phosphoric acid (WPA) as a raw material yields a product with superior solubility than the prevalent 18-58-0 (N-P2O5-K2O). In addition, the solubility of Ca2+ was increased from 2.3 g to 7.3 g/100 g APP, and the process cost was reduced by 17.7%. This study achieved the low-cost and stable preparation of highly water-soluble APP products from WPA, which could promote the industrial production of agricultural polyphosphates.

A Novel Lanthanum-based Solid Oxide Fuel Cell Electrolyte Composite with Enhanced Thermochemical Stability toward Perovskite Cathode

Lanthanum-based electrolytes for Solid Oxide Fuel Cells (SOFCs) gain extensive attention due to their lower activation energy and low-cost preparation to convert the energy stored in gaseous chemicals into electricity. In this context, a La9.33Si6O26-La0.8Sr0.2Ga0.8Mg0.2O2.55 (LSO-LSGM) SOFC electrolyte composite with various mass ratio LSO:LSGM (w/w) (5:0, 4:1, 3:2, 2:2, 2:3, 1:4) are successfully prepared for the first time using different LSO precursors with various mass target of 3g (LSO-LSGMA) and 5g (LSO-LSGMB), respectively. The result shows that the lower mass target in the synthesis of LSO induced formation of protoenstatite and coesite secondary phases on the composite of LSO-LSGM based on XRD, FTIR, and XPS analysis. The SEM micrograph suggests that agglomeration occurred more in LSO-LSGMA than in LSO-LSGMB. Generally, the composites signified high chemical stability on La0.8Sr0.2Co0.6Fe0.4O2.55 (LSCF) cathode based on the XRD analysis. The LSO-LSGMA composites which contained a high percentage of protoenstatite and coesite resulted in an additional peak of MgSi2Sr, especially for the sample with the mass ratio of 41 (LSO-LSGM41) suggesting that the chemical stability of LSO-LSGMA on LSCF cathode is much lower than LSO-LSGMB.

Digital microfluidics-based digital counting of single-cell copy number variation (dd-scCNV Seq)

Single-cell copy number variations (CNVs), major dynamic changes in humans, result in differential levels of gene expression and account for adaptive traits or underlying disease. Single-cell sequencing is needed to reveal these CNVs but has been hindered by single-cell whole-genome amplification (scWGA) bias, leading to inaccurate gene copy number counting. In addition, most of the current scWGA methods are labor intensive, time-consuming, and expensive with limited wide application. Here, we report a unique single-cell whole-genome library preparation approach based on digital microfluidics for digital counting of single-cell Copy Number Variation (dd-scCNV Seq). dd-scCNV Seq directly fragments the original single-cell DNA and uses these fragments as templates for amplification. These reduplicative fragments can be filtered computationally to generate the original partitioned unique identified fragments, thereby enabling digital counting of copy number variation. dd-scCNV Seq showed an increase in uniformity in the single-molecule data, leading to more accurate CNV patterns compared to other methods with low-depth sequencing. Benefiting from digital microfluidics, dd-scCNV Seq allows automated liquid handling, precise single-cell isolation, and high-efficiency and low-cost genome library preparation. dd-scCNV Seq will accelerate biological discovery by enabling accurate profiling of copy number variations at single-cell resolution.

Manganese‐Halide Single‐Crystal Scintillator Toward High‐Performance X‐Ray Detection and Imaging: Influences of Halogen and Thickness

AbstractScintillators, which can convert high‐energy ionizing radiation (e.g., X‐ or γ‐rays) into ultraviolet‐visible light, have been widely applied in medical and industrial fields. Developing new scintillation materials with high performance and low cost is very desirable in order to address the growing application demands. Among them, single‐crystal scintillators of organic‐inorganic hybrid metal halides (OIMHs) have attracted much attention because of their excellent optical transparency, suppressed light scattering, and facile solution preparation methods. Herein, three new centimeter‐sized (2‐DMAP)2MnX4 (2‐DMAP+ = 2‐dimethylaminopyridinium, X = Cl, Br, I) single crystals with high crystal quality are synthesized via the solvent evaporation method. Benefiting from the high optical transparency and remarkable luminescence property, (2‐DMAP)2MnBr4 delivers a high X‐ray light yield of 22 000 photons MeV−1, a low limit of detection of 9.50 nGy s−1, and an excellent X‐ray imaging spatial resolution of 20–25 lp mm−1. Moreover, the regulation of single‐crystal thickness from 0.31 mm to 3.03 mm can be easily achieved via a simple solution post‐treatment method, which has a significant influence on the transmittance, spatial imaging resolution, and detection limit. This work demonstrates a promising single‐crystal scintillator for the application of high‐resolution X‐ray imaging with low preparation cost and tunable thickness.

Constructing fast-ion-diffusion cathode-electrolyte-interphase to improve LiNi0.8Co0.1Mn0.1O2 cathode cyclic stability with composite polymer conductors

As one of the mainstream cathode materials used in power battery, it’s necessary for the LiNixCoyMn1-x-yO2 (NCM) to perform fast charge and discharge capabilities. However, the unstable cathode-electrolyte-interphase (CEI) at high charging/discharging rates causes cycling performance to degrade rapidly. Modified polyaniline (PANI) and polyethylene glycol (PEG) are adsorbed on layer-structured Ni-rich cathode, forming cathode-electrolyte-interphase CEI film with high electro-chemical stability and mechanical strength layer by coordinating interaction of hydrogen bonds with transition metals. When the carbon nanotubes (CNTs) or the -SO2F functional group in bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) enters PANI skeleton, the composition, morphology and thickness of CEI film would be influenced by the CNTs or -SO2F groups. The improved interface would enhance the cathode-electrolyte interface stability by providing a steady channel for Li+ transport. Hence, the optimized CEI film effectively inhibit the occurrence of side reactions, and the capacity retention of NCM@PANIPEG/LiTFSI||Li cells has been improved from ∼ 55% to ∼ 77% at 45 °C and 2.7–4.3 V (vs. Li+/Li) in 100 cycles at 1 C. This low cost and straightforward preparation process exhibit great application prospects in future industrial applications.

Synergistic Optimization of Energy Storage Density of PYN-Based Antiferroelectric Ceramics by Composition Design and Microstructure Engineering.

PbYb0.5 Nb0.5 O3 (PYN)-based ceramics, featured by their ultra-high phase-switching field and low sintering temperature (950°C), are of great potential in exploiting dielectric ceramics with high energy storage density and low preparation cost. However, due to insufficient breakdown strength (BDS), their complete polarization-electric field (P-E) loops are difficult to be obtained. Here, to fully reveal their potential in energy storage, synergistic optimization strategy of composition design with Ba2+ substitution and microstructure engineering via hot-pressing (HP) are adopted in this work. With 2mol% Ba2+ doping, a recoverable energy storage density (Wrec ) of 10.10Jcm-3 and a discharge energy density (Wdis )of 8.51Jcm-3 can be obtained, supporting the superior current density (CD )of 1391.97Acm-2 and the outstanding power density (PD ) of 417.59MWcm-2 . In situ characterization methods are utilized here to reveal the unique movement of the B-site ions of PYN-based ceramics under electric field, which is the key factor of the ultra-high phase-switching field. It is also confirmed that microstructure engineering can refine the grain of ceramics and improve BDS. This work strongly demonstrates the potential of PYN-based ceramics in energy storage field and plays a guiding role in the follow-up research.

Fabrication of wear-resistant and superhydrophobic aluminum alloy surface by laser-chemical hybrid methods

To achieve rapid, efficient, and low-cost preparation of large-scale stable aluminum alloy superhydrophobic surfaces, a new preparation method is proposed. The outer surface of the array micro-protrusions was coated with a layer of armor, which was the molten spatter produced during picosecond laser processing. The molten sputters and micro-protrusions combined to form micro–nano composite multi-layer structures. Through these special array micro–nano composite multi-layer structures and chemical modification, the wear-resistant and superhydrophobic properties of aluminum alloy surfaces were realized. According to test results, the array micro–nano composite structures prepared by picosecond laser and chemical modification had a water drop contact angle of 154.6° and a water drop rolling angle of 2°, exhibiting excellent superhydrophobic and anti-adhesion properties. Its self-cleaning, corrosion resistance and friction and wear behavior were systematically analyzed. The analysis results showed that the rolling droplets on the prepared surface could easily take away contaminants. The corrosion voltage and corrosion current density of the prepared superhydrophobic surface are significantly lower than that of the raw surface. In addition, a water drop contact angle of the aluminum alloy sample maintained at 145.1° after five wear tests, indicating the prepared surface after wear testing still had hydrophobic performance. The innovative method proposed in this study provides a simple and effective method for preparing large-scale wear-resistant superhydrophobic surface of aluminum alloy.

Single Crystalline Transparent Conducting F, Al, and Ga Co-Doped ZnO Thin Films with High Photoelectrical Performance.

Transparent conductive film (TCF) is a material that integrates electrical conductivity and optical transparency. It is widely used as an electrode material in thin-film solar cells. However, considerable progress is needed to facilitate its high performance and low-cost preparation. In this study, a preparation scheme for AlF3 and GaF3 co-doped ZnO (FAGZO) thin films was designed and implemented by magnetron sputtering (MS). The mutual restraint between the electrical properties and the wide-spectrum transmission performance of ZnO films was resolved. First-principles calculations showed that the doped ZnO system had n-type conductivity and that the most stable structure was the FO-AlZn-GaZn system. The experimental results verified the theoretical predictions. Single crystalline ZnO transparent conducting films (ZnO-TCFs) of high quality were achieved by MS. After rapid thermal annealing (RTA) treatment, the mobility reached 49.6 cm2/V s, and the resistivity decreased to 3.82 × 10-4 Ω cm. The AT was 90% between 380 and 1200 nm. Furthermore, the application of the prepared FAGZO film in perovskite solar cells (PSCs) has been verified. Compared to the reference indium tin oxide film, the PSCs using the FAGZO film showed higher JSC and power conversion efficiency. These results demonstrate that MS combined with anion and cation co-doping provides an effective means of exploring high-quality and high-performance ZnO-TCFs.

Facile Fabrication of Fe2O3/TiO2 Composite from Titanium Slag as Adsorbent for As(V) Removal from Aqueous Media

Mixed metal oxide composites have been widely used as adsorbents for the removal of heavy metal ions from wastewater. In this work, Fe2O3/TiO2 composite was sustainably prepared via the treatment of titanium slag with a low-concentration sulfuric acid solution (20%) and used for the removal of As(V) from aqueous solutions. The resulting products were characterized by X-ray diffraction (XRD), N2 adsorption−desorption, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The batch adsorption was employed to investigate the removal efficiency of the Fe2O3/TiO2 adsorbent toward As(V). The Langmuir and Freundlich isotherms were plotted in order to study the adsorption process. The adsorption of As(V) on FeO3/TiO2 fitted well with the Freundlich isotherm model, suggesting a multilayer adsorption process with an adsorption capacity of 68.26 mg·g−1. The adsorption kinetics study demonstrated that the adsorption behavior of the Fe2O3/TiO2 composite for the As(V) was pseudo-second-order. With low-cost preparation and high adsorption capacity, the prepared Fe2O3/TiO2 adsorbent could be used as an effective adsorbent for As(V) removal from contaminated water sources. The approach utilized in this research is viewed as a sustainable route for creating a proficient adsorbent for the purification of water.

Fe-based amorphous alloy wire as highly efficient and stable electrocatalyst for oxygen evolution reaction of water splitting

The slow kinetics of the oxygen evolution reaction (OER) leads to low energy conversion efficiency during water electrolysis, thus it is very important to develop efficient and economical electrocatalysts. With high surface energy and rich active centers, amorphous alloys show excellent potential as self-supporting oxygen evolution catalysts for water splitting. In this work, (Fe0.8Ni0.2)71Mo5P12C10B2 amorphous alloy wire was successfully prepared, and after 5 h immersed in 0.5 mol/L HNO3, the wire surface was covered by the block metallic oxide. At a current density of 10 mA/cm2 in an alkaline electrolyte, the electrochemical results show that the overpotential is only 254 mV and the Tafel slope is 49 mV/dec. After the 194 h stability test, its oxygen evolution performance is even comparable to the commercial RuO2, which has been proven to have excellent electrochemical stability and low preparation cost. The highly efficient catalytic performance mainly originated from the synergistic effect of multi-metal elements and the unique crack surface characteristics which expose more active sites. This work provides new insight into low-metal-cost materials for efficient and durable OER electrocatalysts and their industrial applications in the future.

Underwater Superoleophobic and Underoil Superhydrophilic Copper Benzene-1,3,5-tricarboxylate (HKUST-1) Mesh for Self-Cleaning and On-Demand Emulsion Separation.

Surfaces with underoil superhydrophilic (UOSHL) and underwater superoleophobic (UWOHB) have great potential for on-demand emulsion separation. However, the fabrication of underoil superhydrophilic based on wetting thermodynamic principles is quite challenging. Several previous studies have shown that some sarcocarps are able to spontaneously absorb water to moisturize themselves and have a unique UOSHL ability. By mimicking this unique ability of the sarcocarp, an outstanding UWOHB and UOSHL membrane was prepared. We choose 2300 mesh stainless steel mesh (SSM) as the substrate, then grow Cu and Cu(OH)2 on SSM by a simple electrochemical method, and finally grow HKUST-1 crystals via a fast in situ growth method. The whole preparation process is simple, low cost, and does not require complex and long-term hydrothermal reactions. By growing HKUST-1 crystals, the prepared surface successfully achieved the required UOSHL and UWOHB properties. When the water droplets come into contact with the membrane under n-hexane, it will diffuse and can completely spread out in 2 s. The as-prepared membrane exhibits outstanding anti-fouling and self-cleaning properties for rapeseed oil and crude oil with high viscosity underwater due to the special wetting. By prewetting the surface with an appropriate amount of the dispersion medium, it can rapidly and efficiently on-demand separate different emulsions. The separation efficiencies of water-in-oil emulsions and oil-in-water emulsions are above 99.00 and 97.00%. With their outstanding performance in self-cleaning, on-demand emulsion separation, low cost, and fast preparation, the as-prepared UOSHL and UWOHB HKUST-1 meshes show excellent potential for treating oily wastewater in practical applications.

Hierarchical superhydrophilic/superaerophobic 3D porous trimetallic (Fe, Co, Ni) spinel/carbon/nickel foam for boosting oxygen evolution reaction

Commercial oxygen evolution reaction catalysts are required operation under high current density to achieve rapid gas generation during electrochemical water splitting; however, oxygen bubbles readily cover active surfaces of electrodes, impeding reaction kinetics. Here, we introduce a facile, low-cost, and easy large-scale preparation strategy to synthesize trimetallic (Fe, Co, Ni) spinel/carbon/nickel foam (FeCoNiOx/C/NF) electrodes with 3D network structures, and demonstrate that oxygen bubbles can be rapidly removed from the surface of electrodes with superhydrophilic/superaerophobic properties. The resulting FeCoNiOx/C/NF electrodes exhibit a low overpotential of 221 mV with extremely low Tafel slope of 21 mV dec−1 at a current density of 10 mA cm−2 in 1 M KOH. At a high current density of 500 mA cm−2, FeCoNiOx/C/NF electrodes show a low overpotential of 325 mV with long-term stability for 250 h.

Two-Dimensional Metal Organic Framework derived Nitrogen-doped Graphene-like Carbon Nanomesh toward Efficient Electromagnetic Wave Absorption

Functional two-dimensional (2D) graphene-like carbon has the potential to be a good electromagnetic wave absorbing material due to its good electronic properties, but the preparation of 2D carbon via metal–organic frameworks (MOFs) derivation method is still a bottleneck. Herein, we fabricated ultrathin nitrogen-doped graphene-like carbon nanomesh (N-GN) via thermal exfoliation of 2D MOF (Zn-ZIF-L) directly. The species of the chloride salt that exfoliated Zn-ZIF-L have an effect on the nitrogen content, graphitization degree, pore size and specific surface area of N-GN. The Zn-ZIF-L derived N-GN exfoliated by KCl and LiCl simultaneously has the optimum reflection loss of −54 dB only with the thickness of 2.1 mm and the filler loading of 3 wt%. The excellent electromagnetic wave absorbing property is attributed to its favorable structure, micro-meso-macropores, N heteroatoms, abundant heterogeneous graphene-like carbon nanomesh interfaces and defects. Our simple and low-cost preparation process facilitates the large-scale production and application for electromagnetic wave absorbing material of functionalized graphene-like carbon.

Preparation of ultra-pure ammonium metavanadate via heterogeneous self-assembly crystallization

Although the demand for ultra-pure V2O5 in industry is significant, the current technologies used to obtain the principal precursor, ammonium metavanadate, in high purity are costly and low-yielding. In this study, a cost-efficient and high-yielding heterogeneous self-assembly crystallization (HSC) process is proposed for obtaining large, high-purity NH4VO3 crystals. The method entails establishing a wide crystallization window, controlling the NH3 mass transfer rate and buffering the pH of the mother liquor with CO2 released during the pyrolysis of the ammonia source, (NH4)2CO3 to achieve the separation of chromium impurities, the most difficult-to-remove impurities in vanadium products, from the chromium-containing NaVO3 solution, and purification of NH4VO3 via reactive crystallization. Under the optimized crystallization conditions, namely an N/V mass ratio of 3.9, temperature of 60 °C, and pH of 12.5, the yield and purity of the obtained NH4VO3 in 20 g·L−1 V(V) simulated solution containing 0.05 g·L−1 Cr(VI) reached 93.09% and 99.99%, respectively, and the obtained NH4VO3 crystals were as large as 1.8 mm in size. In the case of a real leaching solution, the NH4VO3 yield and purity were higher than 80% and 99.99%, respectively, and the purity of final V2O5 reached 99.99%. The curbed pyrolysis rate of (NH4)2CO3 ensures heterogeneous nucleation and slow growth of NH4VO3 crystals to acquire large and pure crystals, and the excessive adsorption of Cr(VI) onto the crystal surface during self-assembly is avoided at the appropriate pH, thus guaranteeing efficient precipitation, crystallization, and purification. This study provides a reference strategy for the low-cost preparation to obtain high-purity V2O5.

Point-cavity-like carbon layer coated SnS nanotubes with improved energy storage capacity for lithium/sodium ion batteries

Tin monosulfide (SnS) is known as a prospective anode material for lithium/sodium ion batteries due to its high capacity, low cost, and easy preparation. Carbon coating is a powerful strategy to improve poor electronic conductivity and alleviate the large volume expansion of the SnS, thus achieving high electrochemical performances. However, the commonly used carbon coatings strategies usually generate interstices between the SnS and carbonaceous material, interrupting electron and ion transfer and unsatisfied accommodation of volume expansion. Herein, point-cavity-like carbon coated SnS nanotubes (CN/SnS) were synthesized by a close-knit mechanism using polyvinylpyrrolidone (PVP) and carbon nitride (g-C3N4) as carbon sources. The carbonyl group in PVP can form hexahydroxylated stannyl compound with Sn2+, and the amine group can generate CN bond with the g-C3N4 template in an aqueous solution, respectively. The unique construction of CN/SnS can successfully reinforce the electron and ion transfer capability and accommodate volume expansion. The reformative effectivity dramatically improves the energy storage properties of SnS electrode for LIBs/SIBs. The CN/SnS electrode can deliver high specific capacities of 547.7 mAh g−1 at 1.0 A g−1 after 300 cycles for lithium-ion batteries and 298.2 mAh g−1 at 0.1 A g−1 after 200 cycles for sodium-ion batteries, respectively. The structure design is practical and feasible, which could be used to develop high-performance transition metal sulfide/carbon composite anodes for LIBs and SIBs.