Facile Solid-state Route Research Articles

Enhanced ammonia sensing performance of barium hexaferrite enabled through Zn doping: Mechanistic study considering modulation of Fe2+/Fe3+ ratio and oxygen vacancy

Barium hexaferrite (BaFe12O19) is an unexplored metal-oxide semiconductor with regard to ammonia (NH3) gas sensing. Herein, we have achieved substantial enhancement in response towards NH3 by virtue of Zn doping in BaFe12O19, synthesized via facile solid-state route. The improved response (Rgas/Rair) of Zn-doped BaFe12O19 towards 1 ppm NH3 was 7.36 at 250 °C which was ∼300% higher than pure BaFe12O19. Moreover, fast response/recovery time (2.66 s/35.25 s), good selectivity and long-term stability (100 days) towards NH3 has been achieved when Zn was incorporated. The lower limit of detection of Zn doped BaFe12O19 was estimated ∼150 ppb, that exceedingly favors lower concentration range of NH3 detection. Excellent sensing behavior of Zn-doped BaFe12O19 samples was attributed to modulation of Fe2+/Fe3+ ratio, oxygen vacancies and improved oxygen adsorbing ability as confirmed from X-ray photoelectron spectroscopy (XPS) study. Also, the improvement in sensing activity was validated through quenching of photoluminescence (PL) spectra in favor of electron-hole separation. The usefulness of developed Zn-doped BaFe12O19-based sensor for environmental air-quality surveillance and individualized health monitoring can be concluded through the sensor's notable resolution in detection of wide range (150 ppb - 100 ppm) of ammonia concentration.

The superior photocatalytic performance and DFT insights of S-scheme CuO@TiO2 heterojunction composites for simultaneous degradation of organics

The necessity to resolve the issue of rapid charge carrier recombination for boosting photocatalytic performance is a vigorous and challenging research field. To address this, the construction of a binary system of step-scheme (S-scheme) CuO@TiO2 heterostructure composite has been demonstrated through a facile solid-state route. The remarkably enhanced photocatalytic performance of CuO@TiO2, compared with single TiO2, which can consequence in the more efficient separation of photoinduced charge carriers, reduced the band gap of TiO2, improved the electrical transport performance, and improved the lifetimes, thus donating it with the much more powerful oxidation and reduction capability. A photocatalytic mechanism was proposed to explain the boosted photocatalytic performance of CuO@TiO2 on a complete analysis of physicochemical, DFT calculations, and electrochemical properties. In addition, this work focused on the investigation of the stability and recyclability of CuO@TiO2 in terms of efficiency and its physical origin using XRD, BET, and XPS. It is found that the removal efficiency diminishes 4.5% upon five recycling runs. The current study not only promoted our knowledge of the binary system of S-scheme CuO@TiO2 heterojunction composite photocatalyst but also shed new light on the design of heterostructure photocatalysts with high-performance and high stability.

CaSnO3 coupled g-C3N4 S-scheme heterostructure photocatalyst for efficient pollutant degradation

The perovskite CaSnO3/g-C3N4 heterostructure nanocomposite was successfully prepared via facile solid-state route. The properties of morphology, structural, optical, functional, elemental, surface, electrochemical and photocatalytic performances were investigated. The synthesised CaSnO3 (CS) nanoparticles were grafted on the g-C3N4 nanosheets and their photocatalytic performance were determined. The introduction of g-C3N4 possesses solid-solid intimately contacted interfaces with CS that provides more transport paths and effectively improve the separation of photogenerated electrons and holes (e−/h+). Thus, the formation of CaSnO3/g-C3N4 (CGN) heterostructures exhibits with tunable optical bandgap and suppresses the charge recombination process that leads to improve the photocatalytic efficiency. Compared with bare CS the CGN photocatalyst achieves 95% of degradation efficiency over methylene blue (MB) dye in 120 min of UV–visible light irradiation. The possible photocatalytic degradation mechanism was discussed. Furthermore, the CGN photocatalyst has been utilized for 4 repeated runs of experiments which shows good stability and reusability after the degradation experiments.

Layered 2H-MoTe2: A novel anode material for lithium-ion batteries

Transition metal dichalcogenides with well-developed two-dimensional layers and high structural stability provide superior Li+ storage property in lithium-ion batteries (LIBs). For this study, the MoTe2 polycrystalline powder sample is prepared using a facile solid-state route. Transmission electron microscopy (TEM) along with selected area diffraction (SAD) patterns, Field emission scanning electron microscopy (FE-SEM) combined with energy dispersive X-ray spectroscopy (EDX) have been performed to obtain crystallographic, morphological, and chemical information of the as-prepared MoTe2 powder. SAD patterns and the high-resolution transmission electron microscopy (HRTEM) study reveal the well-developed crystalline layered structure of the MoTe2 powder. The as-prepared MoTe2 electrode showed an initial specific discharge capacity of ~ 452 mAh g−1 versus lithium metal and a corresponding specific discharge capacity of ~ 279 mAh g−1 is achieved after 40 cycles at 1.0 A g−1 current density.

A facile synthesis of phosphorus doped Si/SiO2/C with high coulombic efficiency and good stability as an anode material for lithium ion batteries

Silicon (Si) has the drawbacks of large volume expansion and poor electronic conductivity to be overcome as the anode material for lithium ion batteries (LIBs). Herein, phosphorus (P) doped Si coated by dual layers of SiO2 and carbon (denoted as P-doped Si/SiO2/C) has been synthesized by a facile solid-state route. In that, commercial Si powder and polyvinyl butyral was used as raw material and carbon source, respectively. Importantly, the phosphoric acid was introduced as the doping agent, that also helped the formation of pure SiO2 coating layer rather than the mixture of SiO2 and less oxidized SiOx on surface of the Si material. The as-prepared P-doped Si/SiO2/C material exhibits an initial discharge capacity as high as 2860.3 mAh g−1 and an excellent inital coulombic efficiency of 86.7% at a current density of 200 mA g−1. After 150 cycles, charge capacity of 1389.8 mAh g−1 was retained, indicating the good cycle stability of P-doped Si/SiO2/C material, which is over three times higher than that of the Si/C material (449.2 mAh g−1) without phosphoric acid treatment. Additionally, a capacity enhancement of 25.7%, 40.7%, 79.1% 281.7% and 407.7% was achieved as compared to the Si/C material at the current densities of 100, 300, 600 1000 and 2000 mA g−1, respectively. The P-doping and SiO2 coating have played a significant role on the electrochemical performance by effectively improving the intrinsic electronic conductivity and further suppressing the volume expansion (~40%) of Si in charge-discharge tests respectively. It worth mentioning that the synthesis of P-doped Si/SiO2/C can be easily scaled up. Therefore, our work pave the way toward the industrilization of stable Si-based anode material with high capacity for LIBs.

Graphene reduction of P25 titania: Ti3+- doped titania/graphene nanohybrids for enhanced photocatalytic hydrogen production

Ti3+-doped titania has attracted great attention in recent years by its enhanced photocatalytic performance as compared to the conventional titania systems. In this work, solvothermally reduced hydroxy graphene (RHG), derived from fluorographite (FGT), is used to reduce commercially available P25 titania to produce Ti3+-doped, TiO2-x/RHG nanocomposites, via a facile solid-state route. These nanohybrids exhibit high performance towards photocatalytic hydrogen generation under broad-band irradiation, with a 3497 μmol/g/h hydrogen production rate, without the assistance of any noble metal co-catalyst. This enhanced rate can be attributed to the surface defects generated by Ti3+-doping as well as the ability of RHG to perform as a highly efficient scavenger for the photogenerated electrons. It is hypothesized that RHG could serve as one of the most suitable co-catalysts for the semiconductor-based photocatalysts.

Eutectic friction transfer lithography: a facile solid-state route for highly crystalline semiconducting polymers.

Herein, we report a solid-state lithography technique utilizing eutectic friction transfer lithography (EFTL). The EFTL technique employs eutectic pellets made of semiconducting polymers and volatile organic solid matrices. Using frictional heating and eutectic melting, various semiconducting polymer crystals were formed by a simple rubbing process under mild conditions. The strong anisotropic optical properties suggest that J-type packing is dominant in EFTL microwires because of the highly extended and planarized crystal structures.

CO2 hydrogenation to methanol over CuO[sbnd]ZnO[sbnd]TiO2[sbnd]ZrO2 catalyst prepared by a facile solid-state route: The significant influence of assistant complexing agents

A series of CuOZnOTiO2ZrO2 catalysts were prepared by a facile solid-state route, and the effects of adding citric acid or oxalic acid on the physicochemical properties and catalytic performance for CO2 hydrogenation to methanol were investigated. The catalysts were characterized by several techniques, including X-ray diffraction (XRD), N2 adsorption, transmission electron microscopy (TEM), reactive N2O adsorption, X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), temperature-programmed reduction with H2 (H2-TPR), and adsorption of CO2 followed by temperature programmed desorption (CO2-TPD). The results reveal that the addition of assistant complexing agents can improve the CuO dispersion in the catalysts and increase the metallic Cu surface area, and consequently greatly increase the CO2 conversion and methanol yield, with oxalic acid being a more effective assistant complexing agent than citric acid.

The Performance of CH3NH3PbI3 - Nanoparticles based – Perovskite Solar Cells Fabricated by Facile Powder press Technique

Here, we have introduced a facile solid-state route assisted method to prepare CH3NH3PbI3 perovskite nanoparticles (PNs) and together with a facile - powder press technique, for the deposition of prepared PNs - a solution cum vacuum-free route. The perovskite layer was prepared using different lead iodide (PbI2) precursor molar concentrations (0.5, 1, 1.5, 2 mmol) and the PbI2 concentration was found to have a significant impact on the structural, optical, morphological and electrical properties. The sample prepared using molar ratio PbI2: MAI at 1:3 shows the optimal bandgap value (∼1.51 eV), broader band edge peak at 755 nm and found have good optical property for photovoltaic (PV) applications. The J–V performance of the fabricated perovskite device with FTO/c-TiO2/mp-TiO2/Perovskite/CuI/ Cr/Pt-coated FTO counter electrode has been studied. The device fabricated using the concentration at PbI2:MAI 1:3 achieved a PCE of 3.9% and resulted in better long-term stability with deterioration in η and VOC by 27.87% and 29.23% after 15 days.

Potassium Intercalation into Sodium Metal Oxide and Polyanionic Hosts: Few Case Studies

Layered sodium metal oxide Na2Mn3O7 and mixed polyanion Na4Fe3(PO4)2P2O7 cathode materials were prepared by facile solid-state route and solution combustion synthesis respectively. The Na2Mn3O7 compound crystallized in triclinic structure with space group P-1, whereas Na4Fe3(PO4)2P2O7 assumed an orthorhombic structure with space group Pn21 a. Here, both these sodium-based materials are presented as intercalation hosts for K-ion batteries for the first time. An initial discharge capacity of 152 mAh g-1 was realized with a nominal voltage of 2.1 V vs K/K+ for Na2Mn3O7. The reversible K-ion (de) intercalation in Na4Fe3(PO4)2P2O7 was observed with high capacity of 116 mAh g-1 with average potential of 3.2 V vs K/K+ with fast rate capability and good cycling stability. These sodium-based materials act as robust insertion hosts for secondary potassium-ion batteries.

Effect of Titanium Substitution in a P2-Na2/3Co0.95Ti0.05O2 Cathode Material on the Structural and Electrochemical Properties.

Worries about lithium supplies have led to the development of research on sodium batteries. Sodium-ion batteries are regarded as the next generation of energy-storage devices thanks to the generous resources of sodium. In spite of that, structural changes in the electrode materials remain the main challenge of this storage technology. NaCoO2 has been widely investigated as a competitive candidate for LiCoO2. It has been found that the electrochemical cycling curves of this material present numerous potential steps as a result of electronic transitions and/or structural ordering. From this standpoint, this paper reports a novel cathode material, Na2/3Co0.95Ti0.05O2, where 5% of cobalt was replaced by titanium, prepared via a facile solid-state route. The sodiation/desodiation mechanism of this layered material was investigated. Na//Na2/3Co0.95Ti0.05O2 exhibits a first initial capacity of 119 mAh/g in the potential window 2-4.2 V with less potential jumps in the potential versus capacity curve compared to NaCoO2. Genuinely, the electrochemistry of this material demonstrated a reversibility upon the insertion/desinertion process with low polarization. In situ synchrotron investigations on Na2/3Co0.95Ti0.05O2 reveal the occurrence of reversible ordered phases. Ex situ magic-angle-spinning NMR disclosed different environments around sodium starting from the pristine state to the end of charge.

Direct Coal Liquefaction with Fe3O4 Nanocatalysts Prepared by a Simple Solid-State Method

Fe3O4 nanoparticles were prepared by a simple solid-state method under ambient conditions. The obtained nanoparticles, with small size and large surface area, were used as a catalyst for direct coal liquefaction (DCL). The results display that high conversion and oil yield were achieved with the nanocatalysts in direct liquefaction of two kinds of coals, i.e., Heishan coal and Dahuangshan coal. The effects of the temperature, initial H2 pressure, and holding time on conversion and product distribution have been investigated in the catalytic hydrogenation of Dahuangshan coal. The optimal reaction condition for DCL in which conversion and oil yield are 96.6 and 60.4 wt % was determined with Fe3O4 nanocatalysts. This facile solid-state route is beneficial for scale-up synthesis of iron-based catalysts with good performance for DCL.

Syntheses, crystal structures and magnetic properties of ternary rare-earth zirconium selenides, Ln2ZrSe5 (Ln = Ce–Nd)

Three new ternary rare-earth zirconium chalcogenides, Ce2ZrSe5 (1), Pr2ZrSe5 (2) and Nd2ZrSe5 (3), have been synthesized by a facile solid-state route with boron as the reducing reagent. They crystallize in the space group Pnma of the orthorhombic system, belonging to the U3Se5 structure type. Their 3-D structures are constructed by parallel polyanionic {[ZrSe5]6–}n chains and LnSe8 bicapped trigonal prisms. The magnetic susceptibilities' data indicate their antiferromagnetic-like behavior without magnetic order down to 2 K. The structural relationships among several similar structures are discussed, together with the lanthanide contraction in the Ln2ZrSe5 system.

Improved electrochemical properties of Li4Ti5O12–Li0.33La0.56TiO3 composite anodes prepared by a solid-state synthesis

Li4Ti5O12–Li0.33La0.56TiO3 composite anodes are successfully prepared by a facile solid state route. The structure, morphology and electrochemical performance of all samples are characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge–discharge tests, respectively. XRD reveals that the little La3+ ions enter into the lattice, and then make the crystal lattice of Li4Ti5O12 expand. SEM shows that all samples are composed of 1–2 μm primary particles with irregular shapes. CV and EIS imply that Li4Ti5O12–Li0.33La0.56TiO3 composites have lower polarization, larger lithium-ion diffusion coefficient and smaller charge transfer resistance corresponding to a much higher conductivity than those of Li4Ti5O12 corresponding to the extraction of Li+ ions. The improved electrochemical performance of Li4Ti5O12–Li0.33La0.56TiO3 composites can be attributed to the enhanced transfer kinetics of both the lithium ions and electrons. Particularly, Li4Ti5O12–Li0.33La0.56TiO3 (5 wt.%) composite shows a excellent high-rate capability and cycling stability. Therefore, the present Li4Ti5O12–Li0.33La0.56TiO3 (5 wt.%) composite anode is capable of large-scale applications, such as electric vehicles and hybrid electric vehicles, requiring high energy, long life and excellent safety.

Encapsulation of LiFePO4 by in-situ graphitized carbon cage towards enhanced low temperature performance as cathode materials for lithium ion batteries

The severe capacity decay of LiFePO4 at low temperatures (≤0°C) limits its wide applications as cathode materials for energy storage batteries. Creating comprehensive carbon network between particles with improved electronic conductivity is a well known solution to this problem. Here, a novel structured LiFePO4/C composite was prepared by a facile solid state route, in which nanosized LiFePO4 spheres were encapsulated by in-situ graphitized carbon cages. With the enhancement in electronic conductivity (2.15e−1Scm−1), the composite presented excellent rate performance at room temperature and remarkable capacity retention at −40°C, with charge transfer resistance much lower than commercial LiFePO4.