H2O Precursor Research Articles

Transition Metal Oxides and Li2CO3 as Precursors for the Synthesis of Ni-Rich Single-Crystalline NCM for Sustainable Lithium-Ion Battery Production

Single-crystalline Ni-rich LiNi1-x-y Co x Mn y O2 (SC-NCM) cathode active materials promise to increase the lifetime of high energy Li-ion batteries. SC-NCM consist of large primary particles that offer low surface area, limiting detrimental chemical reactions while exhibiting high morphological stability. A typical SC-NCM synthesis starts from the same Ni1-x-y Co x Mn y (OH)2 and LiOH∙H2O precursors commonly used for conventional spherical poly-crystalline NCM (PC-NCM), but requires higher temperatures and additional post-processing. Consequently, the cost and environmental impact of the production of Ni-rich SC-NCM is higher compared to the production of PC-NCM. In this study, we demonstrate a synthesis of SC-NCM that does not require the same highly engineered precursors as used for PC-NCM. We propose a more energy-efficient and cost-effective route that involves simple blending of NiO, MnO, Co3O4 and Li2CO3 which yields single-crystalline LiNi0.83Co0.11Mn0.06O2 with 2–3 μm particle size and good structural quality. It is shown by in situ XRD during synthesis that—while the reaction suffers from slow kinetics—the elevated temperature and longer reaction time, which are in any case required for the crystal growth, are sufficient to also complete the reaction. Furthermore, it is shown that this material is structurally and electrochemically equivalent to the material commonly synthesized from hydroxide-based precursors.

Effect of different precursors on structural and luminescence properties of Mn3O4 nanoparticles prepared by co‐precipitation method

AbstractManganese oxide nanomaterials (Mn3O4) have been prepared from manganese salts of two different anions and studied the role of metal precursor. Manganous sulphate monohydrate and manganese oxalate were used as manganese metal precursors. The obtained Mn3O4 samples were characterized by x‐ray diffraction, transmission electron microscope, Fourier transform infrared spectroscopy, UV‐vis absorbance spectra and photoluminescence excitation spectra. The x‐ray diffraction reveals that the prepared nanoparticles are crystalline in nature with tetragonal structure. In addition, the x‐ray diffraction concludes that the lattice parameters were altered with change in the precursors. The transmission electron microscope exhibits the prepared manganese oxide particles were nano in scale between the ranges of 25 nm to 60 nm. The Fourier transform infrared spectrum confirmed the presence of manganese oxide. The luminescence intensity of the samples varies depending upon the precursors used. The sample comprising of mixed precursors shows higher luminescence intensity than the samples containing MnSO4 ⋅ H2O and MnC2O4 precursors. This is owing to the fact that the surface of the sample has a lower concentration of hydroxyl ions, which was confirmed from the Fourier transform infrared spectra.

High magnetic field-engineered high mass loading sulfides with well-ordered hierarchical nanostructures for all-solid-state supercapacitors

Low energy density is becoming the largest sore point of supercapacitors. Constructing all-solid-state asymmetric supercapacitors (AASCs) with high mass loading and high utilization of electrochemically active materials can largely remedy the drawback. Herein, well-ordered hierarchical porous NiCo2S4 pine needles on carbon cloth (CC) with a loading mass as high as 10.76 mg cm−2 (NCS-12 T) were fabricated by low-temperature topotactic vulcanization of the high-mass-loading (Ni, Co)(CO3)0.5(OH)·0·.11H2O precursor (NCCH-12 T) yielded under 12 T high magnetic field (HMF). The loading mass on each CC tends towards equivalence and increases remarkably with the rise of HMF by guaranteeing sufficient ion supply. Impressively, a high overall capacitance of 10.46F cm−2 at 5 mA cm−2 was achieved without sacrificing the specific capacitance and rate capability that are slightly superior to those of the low mass loading NiCo2S4 electrodes instead. The striking electrochemical performances are ascribed to the available ion and electron transport in the whole electrode, which results from the construction of three-dimensional hierarchical porous nanostructures and HMF-derived well-ordered and uniform deposition via boosting ion transport. Finally, the NCS-12 T-based AASCs with high mass loading exhibit a high energy density of 280 μWh cm−2 at the power density of 1.71 mW cm−2, exceeding most state-of-the-art supercapacitors.

Dry reforming of methane over the Ni/Y2O3-ZrO2 catalysts: Effects of the tunable surface oxygen species by modulating the zirconium precursors

The surface reactive oxygen species over Y2O3-ZrO2 supports were tuned by regulating the interaction between Y and Zr via modulating the zirconium precursors. It was revealed that the content of the surface adsorbed oxygen species (SAOS) over the catalyst with ZrO2 precursor was the highest, followed by the catalysts with Zr(OH)4 and ZrO(NO3)2·2H2O precursors. The difference of the Y-Zr interaction influenced the reactive oxygen species and the support structure and morphology. However, Ni dispersion was determined by the existence of the isolated Y2O3 due to the enhanced metal-support interaction. High Ni dispersion and abundant surface adsorbed oxygen species were beneficial to promote CH4 and CO2 reactivity. Nevertheless, CH4 dissociation facilitated by the SAOS was more remarkable than CO2 activation at low temperature. Thus, the improvement of the SAOS on carbon-resistant ability of the catalyst was only achieved at high temperature through balancing the carbon formation and elimination.

Tunable Ti3+-Mediated Charge Carrier Dynamics of Atomic Layer Deposition-Grown Amorphous TiO2

Amorphous titania (am.-TiO2) has gained wide interest in the field of photocatalysis, thanks to exceptional disorder-mediated optical and electrical properties compared to crystalline TiO2. Here, we study the effects of intrinsic Ti3+ and nitrogen defects in am.-TiO2 thin films via the atomic layer deposition (ALD) chemistry of tetrakis(dimethylamido)titanium(IV) (TDMAT) and H2O precursors at growth temperatures of 100–200 °C. X-ray photoelectron spectroscopy (XPS) and computational analysis allow us to identify structural disorder-induced penta- and heptacoordinated Ti4+ ions (Ti5/7c4+), which are related to the formation of Ti3+ defects in am.-TiO2. The Ti3+-rich ALD-grown am.-TiO2 has stoichiometric composition, which is explained by the formation of interstitial peroxo species with oxygen vacancies. The occupation of Ti3+ 3d in-gap states increases with the ALD growth temperature, inducing both visible-light absorption and electrical conductivity via the polaron hopping mechanism. At 200 °C, the in-gap states become fully occupied extending the lifetime of photoexcited charge carriers from the picosecond to the nanosecond time domain. Nitrogen traces from the TDMAT precursor had no effect on optical properties and only little on charge transfer properties. These results provide insights into the charge transfer properties of ALD-grown am.-TiO2 that are essential to the performance of protective photoelectrode coatings in photoelectrochemical solar fuel reactors.

Structural, optical and electrical properties of copper oxide nanoparticles prepared through microwave assistance

Microwave assisted co-precipitation method is used to synthesize copper oxide nanoparticles from various concentrations of CuCl2.2H2O (0.1 M - 0.5 M) precursors. Both CuO and Cu2O phases are observed from X-ray diffraction (XRD) pattern and further confirmed from Energy Dispersive X-ray Analysis (EDX) and selected area electron diffraction (SAED) data. The particle size of 43 to 27 nm determined from XRD data using Scherrer formula is in good relation with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images. The existence of reasonably uniform size and shape is clear from SEM. The band gaps determined from the UV-Visible absorption peaks and vibrational modes observed from Micro-Raman Scattering (MRS) analysis further confirm the presence of CuO and Cu2O phases. These results are also related to electrical conductivity at low temperatures which illustrate different types of conduction mechanisms. The samples show semiconducting behavior with improved electrical conductivity. Finally, the material is proposed to have applications in designing gas sensors and also in regulating electrical conductivity in drug delivery systems. Copyright © 2017 VBRI Press.

A liquid approach for the synthesis of M phase VO2 nanocrystals: Facile synthesis, characterization and reaction mechanism

Vanadium dioxide is considered to be a promising material in most fields because of its special reversible metal-insulator transition (MIT) near ambient temperature. Pure VO2(M) is usually synthesized by a hydrothermal method combined with a subsequent annealing process or one-step hydrothermal synthesis. Both synthetic routes have the disadvantages of long reaction times. In this report, a new synthesis method of VO2(M) nanoparticles was established under liquid conditions. First, the V2O4·2H2O precursor was prepared successfully by using N2H4·2HCl-reduced V2O5 under thermostatic stirring without any reagent auxiliary. Second, the V2O4·2H2O suspension in water transformed into VO2(M) nanocrystals under hydrothermal synthesis. The intermediate and final products were characterized by XRD, SEM, HRTEM, XPS and DSC. The morphology of prepared VO2(M) exhibits a snowflake-like structure (approximately 1.0–4.0 μm in length, 0.5–3.0 μm in width and 50–200 nm in thickness). The phase-transition temperature is 65.49 °C. In addition, the reaction route of "V2O4·2H2O →V2O4·xH2O → VO2(B) → VO2(M) transformation" and reaction mechanism were established by testing the precipitate at different times at the hydrothermal stage.

Synthesis of Nickel-loaded Sulfated Zirconia Catalyst and Its Application for Converting Used Palm Cooking Oil to Gasoline via Hydrocracking Process

The synthesis of the nickel-loaded sulfated zirconia catalyst (Ni-SZ) and its application for the hydrocracking process have been carried out. This work has been conducted to determine the activity and selectivity from various Ni concentrations loaded on sulfated zirconia (SZ) in the hydrocracking of used palm cooking oil. The synthesis technique was preceded by sulfation of ZrO2 through incipient wetness impregnation method using H2SO4 solution and then continued with the impregnation of Ni via hydrothermal method employing NiSO4 · 6H2O precursor salt. The hydrocracking process was performed in a fix-bed microreactor at the optimum temperature (350 °C). The SZ loaded with 3 wt% of Ni (Ni-SZ 3) successfully produced the highest liquid product (44.25 wt%) and selectivity on gasoline (100 %). Besides, the gasoline fraction in the liquid product was dominated by unwanted aromatics compounds. The excellent performance of Ni-SZ 3 due to it has high acidity value, specific surface area, and Ni content.

Biosynthesis of ZnO Nanoparticles Using Pumpkin Peel Extract (Cucurbita moschata) and its Applications as Semiconductor in Dye Sensitized Solar Cell (DSSC)

ZnO nanoparticles are semiconductor materials that can be used in Dye Sensitized Solar Cells (DSSC). ZnO nanoparticles can be synthesized using pumpkin peel extract (Cucurbita moschata) which functions as a reducing agent, stabilizer, and capping agent. Zn(CH3COO)2.2H2O precursor was used with a concentration of 0.15 M at various pH 7, 8, and 9 reacted with pumpkin peel extract. The functional groups of pumpkin peel extract were characterized using Fourier Transform Infrared Spectroscopy (FTIR), the samples were analyzed by TEM and XRD. The resulting ZnO nanoparticles were used as semiconductors in Dye Sensitized Solar Cell (DSSC) using dyes from mangosteen peel.The FTIR results showed the presence of functional groups O-H hydroxy, CH2, secondary amides (R-CO-NR2, C-H and phosphate (PO43-). XRD results showed that ZnO produced wurzhite crystals with a hexagonal system and the smallest crystal size was 18.99 nm. TEM results showed that ZnO synthesized at a concentration of 0.15 M and pH 8 had a spherical particle shape with a size of 24.90 nm, while the DSSC test results had an efficiency of 9.06 x 10-4%.

18.77 % Efficiency Organic Solar Cells Promoted by Aqueous Solution Processed Cobalt(II) Acetate Hole Transporting Layer

AbstractA robust hole transporting layer (HTL), using the cost‐effective Cobalt(II) acetate tetrahydrate (Co(OAc)2⋅4 H2O) as the precursor, was simply processed from its aqueous solution followed by thermal annealing (TA) and UV‐ozone (UVO) treatments. The TA treatment induced the loss of crystal water followed by oxidization of Co(OAc)2⋅4 H2O precursor, which increased the work function. However, TA treatment differently realize a high work function and ideal morphology for charge extraction. The resulting problems could be circumvented easily by additional UVO treatment, which also enhanced the conductivity and lowered the resistance for charge transport. The optimal condition was found to be a low temperature TA (150 °C) followed by simple UVO, where the crystal water in Co(OAc)2⋅4 H2O was removed fully and the HTL surface was anchored by substantial hydroxy groups. Using PM6 as the polymer donor and L8‐BO as the electron acceptor, a record high PCE of 18.77 % of the binary blend OSCs was achieved, higher than the common PEDOT:PSS‐based solar cell devices (18.02 %).

Thermal stability of MgO film on Si grown by atomic layer deposition using Mg(EtCp)2 and H2O

MgO films were deposited on Si via atomic layer deposition (ALD) using Mg(EtCp)2 and H2O precursors and their thermal stability was examined as a function of the post-deposition annealing (PDA) temperature. The characteristic self-limiting behavior of the ALD process was confirmed by changing several parameters, such as precursor pulsing times, deposition temperature, and number of cycles. The exceptional resulting step coverage was verified on a patterned wafer with a high aspect ratio. The band gap and dielectric constant of the as-deposited ALD-MgO film were extracted to be approximately 7.5 eV and 8.4, respectively, and were stable up to the PDA temperature of 700 °C. However, considerable outward diffusion of the underlying Si atoms toward MgO started to occur above 700 °C, and most of the MgO film was converted to an amorphous Mg-silicate phase at 900 °C with a thin layer of remaining MgO on top.

Formation, structure, and thermal stability evolution of ternesite based on a single-stage sintering process

Ternesite was prepared via a single-stage solid-state reaction from stoichiometric quantities of the CaCO3, SiO2 and CaSO4·2H2O precursors. In this paper, the formation, structure, and thermal stability evolution of ternesite during sintering were investigated ex situ after quenching. The optimal sintering temperature for the formation of high-purity ternesite was approximately 1200 °C for 12 h, of which the purity level can reach as high as 96.3%. The results from scanning electron microscopy analysis suggest that the formation of ternesite benefited from the preformation of the intermediate silicate phase. Increasing the sintering temperature from 1100 °C to approximately 1250 °C was favourable for the growth of ternesite crystals, and a prolonged duration can also promote this behaviour. The structural perfection and symmetry of ternesite crystals increased with its growth, which was demonstrated by a multimethod approach. By means of thermal analysis, the growth and structural development of ternesite crystals during sintering eventually resulted in a higher thermal stability.

Synthesis of Ni/NiO-TiO2 using sol-gel method and its activity in blue methylene degradation

The synthesis of Ni-TiO2 and NiO-TiO2 with titanium isopropoxide and (Ni(NO3)2·6H2O precursors using the sol gel method has been done. The calcination process was carried out by varying the order of the oxidation-reduction process and the temperature of calcination. The oxidation-reduction process produced Ni-TiO2 material. XRD analysis (X-Ray Diffraction Spectrophotometer) showed the smallest size of Ni-TiO2 particles was 7.44 nm and NiO-TiO2 was 8.53 nm. The addition of dopants caused the TiO2 band gap to become smaller. The smallest band gap due to Ni dopant was 2.68 eV while the smallest band gap due to the addition of NiO dopants was 2.81eV. SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray) results showed that the TiO2 surface which was doped with Ni and NiO had small and smooth surface compared to TiO2 without dopant. The synthesized material was then used for the photocatalytic activity test, that was the degradation of methylene blue. The highest degradation of methylene blue was in TiO2 doped with Ni was 76.93%, while in TiO2 doped with NiO was 80.63%.

Synthesis and Characterization of Fe-Al2O3 nanoparticles Prepared by Coprecipitation Method

In this study, iron-doped alumina (Fe-Al2O3) nanoparticles (NPs) containing 2 mol%, 4 mol%, and 6 mol% iron impurities were fabricated by the co-precipitation method in the presence of Al2(SO4)3.9H2O and Fe2(SO4)3.9H2O precursors. The prepared nanoparticles were heated at 1000 oC to study their physicochemical properties. The XRD results pointed out the multiphase for the samples. The morphological results revealed that the uniformity increased by increasing iron atoms rate. TEM analysis revealed that the particle with a size of 40 nm was obtained for 4% of the sample. The results of FT-IR analysis indicated that when the 2% impurity increases the AlO4 tetrahedra and AlO6 octahedral vibrational bond grow.

Synthesis of Pseudobrookite Fe2-xAlxTiO5 (0 ≤ x ≤ 0.5) Powders

Synthesis of Fe2-xAlxTiO5 (0≤x≤0.5) powders has been successfully conducted by using the solid state reaction method. The powders were made by mixing the ironstone-derived Fe2O3 and commercial TiO2 powder. Meanwhile, a commercial Al (NO3)3.9H2O precursor was used as the source of Al. The Fe2O3, TiO2, and Al(NO3)3.9H2O powders at the designated composition were mixed and then ground for 5 hours at 330 rpm in a planetary ball mill. Subsequently, the powder mixtures were calcined at 1100 °C for 1 h. Synchrotron x-ray diffractometry (SXRD) and scanning electron microscopy (SEM) techniques were used to characterize the phases and microstructures. SXRD data showed that a single-phase pseudobrookite Fe2TiO5 formed for all samples. A further quantitative analysis showed that the lattice parameter and cell volume values decreased with the increase of x which indicated the success of Al doping in the Fe2TiO5 structure. The morphology of Fe2-xAlxTiO5 grains from SEM images revealed an oval and elongated shapes, in accordance with the crystal structure of the phase.

Photocatalytic activity of biosynthesized α-Fe2O3 nanoparticles for the degradation of methylene blue and methyl orange dyes

Hematite (α-Fe2O3) nanoparticles (NPs) was biosynthesized using Vernonia amygdalina (V. amygdalina) leaves extract and Fe(NO3)3.9H2O precursor and characterized using X-ray diffraction (XRD), Ultraviolet–visible (UV-Vis), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) techniques. Moreover, the photocatalytic activity of synthesized sample calcined at 550 and 650 °C for the degradation of methyl orange (MO) and methylene blue (MB) dyes was studied and results indicated good catalytic activity towards MB at natural pH and efficient degradation at alkaline pH under sunlight irradiation. However, MO was efficiently degraded only in the presence of a small amount of H2O2 oxidant and that this disparity in photodegradation between the two dyes at similar experimental parameters could be due to difference in their molecular structure stability and HOMO-LUMO energy gap compared to VB-CB positions of catalyst α-Fe2O3 NPs.

Facile synthesis of Gd2O2SO4:Tb and Gd2O2S:Tb green phosphor nanopowders of unimodal size distribution and photoluminescence

Suppressing the crystallization and plate-like crystallite growth of RE2(OH)4SO4·2H2O compound by low-temperature (~4 °C) precipitation produced an amorphous RE2(OH)3.3(CO3)0.35SO4·2H2O precursor (RE = Gd1-xTbx) that can be decomposed to Gd2O2SO4:Tb and Gd2O2S:Tb green phosphor nanopowders of unimodal size distributions upon calcination in air at 1000 °C (average particle size ~156.9 nm) and in hydrogen at 800 °C (average particle size ~130.2 nm), respectively. The optimal RE3+ concentration for precursor synthesis was determined to be ~0.10 mol/L. Through detailed characterization by XRD, FTIR, DTA/TG, FE-SEM, TEM and particle sizing, the courses of phase/morphology evolution were clarified. Photoluminescence study found that the (Gd0.99Tb0.01)2O2SO4 and (Gd0.98Tb0.02)2O2S representative phosphors have quantum efficiencies of ~16.8% (λex = 275 nm) and 38.5% (λex = 286 nm), fluorescence lifetimes of ~3.70 and 1.75 ms and activation energies for thermal quenching of ~0.552 and 0.385 eV, respectively. The values are remarkably larger than those reported for Gd2O2S:Tb, which are considered to be due to higher purity, better crystallization and fewer luminescence-quenching defects of the product. Particularly, the (Gd0.99Tb0.01)2O2SO4 phosphor has negative thermal quenching up to ~150 °C and can retain over 85% of its room temperature emission intensity at 250 °C, which may enlighten its application in high-power LEDs.

Device Feasibility of Ferroelectric Field‐Effect Transistors Using Al‐Doped HfO2 Gate Insulator Deposited with H2O Oxygen Precursor during Atomic Layer Deposition Process

Metal–ferroelectric–metal (MFM) capacitors with Pt‐/Al‐doped HfO2 (Al:HfO2)/TiN structures are characterized to demonstrate the ferroelectricity of the Al:HfO2 thin films deposited by atomic layer deposition with H2O precursor at various annealing conditions. When the crystallization annealing temperature increases from 750 to 850 °C, the value of ferroelectric remnant polarization (2Pr) increases from 11.5 to 17.1 μC cm−2 for the postmetallization annealing (PMA) process, whereas it increases from 8.1 to 11.4 μC cm−2 for the postdeposition annealing (PDA) process. The variations in crystallinity of Al:HfO2 and interfacial properties between the electrodes are analyzed to explore the physical origins to initiate the differences in electrical properties of the MFM capacitors. Using the Al:HfO2 thin film prepared with PMA at 850 °C as a ferroelectric gate insulator, which exhibits a maximum value of 2Pr and polarization switching time as short as 1 μs, the ferroelectric field‐effect transistors (FeFETs) are fabricated with metal–ferroelectric–metal–insulator–semiconductor gate stack. The memory on/off ratios are secured to be 2.6 × 104 and 2.0 × 104 after a lapse of retention time of 105 s and after repeated program operations of 104 cycles, respectively.

A New Multi-Copper-Substituted Tetramer Tungstoantimonate: Synthesis, Photocatalytic and Electrochemical Properties

Under hydrothermal conditions, a new “S”-shaped Cu-substituted tetramer tungstoantimonate, HKNa2(H2en)6[Cu(en)(H2O)]2[KNaCu3(H2O)7(B-a-SbW9O33)2]2⋅16H2O (1, en = 1,2-ethylenediamine) was synthesized in reactions of the Na9[SbW9O33]·19.5H2O precursor with CuCl2⋅2H2O and potassium acetate in the presence of en and characterized by IR spectrum, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction, respectively. Polyoxoanion 1 consists of two asymmetric sandwich-type polyanions {KNaCu3(H2O)7(B-a-SbW9O33)2} linked by two structurally equivalent [Cu4(en)(H2O)]2+ bridges. The electrochemical properties and photocatalytic activities have been investigated, displaying outstanding photocatalytic and electrocatalytic activities for the photodegradation of MB and H2O2/NO2−/BrO3− reduction.

ZnO nanoparticles synthesized by co-precipitation method; Morphology and optoelectronic study

In this study, zinc oxide (ZnO) nanoparticles (NPs) were first synthesized using the co-precipitation method at the presence of Zn(NO3)2.6H2O precursor and calcined at 450 °C and 1000 °C. Then, the samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The XRD analysis was performed to evaluate the crystal structure. SEM and TEM analyses were also conducted to assess the morphology and the particle size of the material. Finally, the chemical compositions of the samples were investigated by energy dispersive x-rays (EDX) analyses. In this work, the crystallite Polygon shape ZnO NPs were fabricated in the range of 70-100 nm. We found that the intensity of the crystal plane of (002) increased by raising the temperature to 1000 °C.