Partial Reduction Process Research Articles

Investigating the influence of oxygen-functionalized graphene nanosheets as an efficient multifunctional material for supercapacitor and electrocatalytic water splitting applications

Graphene oxide (GO) has received great research attention to develop its efficiency in electrochemical applications, particularly supercapacitor (SC) and water splitting systems. However, the presence of various oxygen moieties in GO drastically reduces the utilization of the material for commercial usages. In this work, we demonstrate the use of different sources to reduce graphene oxide (GO) nanosheets. The partially reduced GO not only improves the electronic conductivity but also boosts the interaction between the sp2- and sp3-hybridized carbon atoms. Benefiting from the partial reduction process, RGO is applied for the SC test in the three-electrode system and reveals a specific capacitance of 151.1 F g−1 at 1 A g−1 with a long cycle life. Furthermore, the asymmetric solid-state device can also be constructed from an M-GO cathode with an activated carbon anode, which displays a specific capacitance of 54.4 F g−1 at 1 A g−1, with a maximum energy density of 19.3 W h kg−1. Besides, the electrochemical water splitting performance of the partially reduced GO in KOH solution was also explored, confirming the effectiveness of the reduction process. This work highlights the successful preparation of RGO nanosheets, which may open a new route to constructing high-performance energy storage and conversion devices.

Oxygen Vacancy-Rich NiCo2O4 on Carbon Framework with Controlled Pore Architectures as Efficient Bifunctional Electrocatalysts for Zn-Air Batteries

Transition metal oxides are considered alternative electrocatalysts for ZAB owing to their multiple oxidation states. However, they have limitations such as low electrical conductivity and the deficiency of reactive sites. In this study, to overcome these shortcomings and improve electrocatalytic activity, oxygen vacancies and porous architectures were introduced through a partial reduction process and a porous carbon framework. Open porous carbon microspheres with uniformly loaded NiCo2O4 nanosheets and oxygen vacancies (V-NCO/OPC) displayed enhanced electrocatalytic performance with a low Tafel slope (68 mV dec-1) in the oxygen reduction reaction (ORR) and a low overpotential (402 mV) at 10 mA cm–2 in the oxygen evolution reaction (OER). The combined effect of the oxygen vacancies and porous architecture can offer sufficient active sites, modify the electronic structure of the metal oxide surface, and facilitate mass transport, enhancing the electrocatalytic properties of V-NCO/OPC. Furthermore, when applied for ZAB, V-NCO/OPC demonstrated better electrochemical performance including discharge power density (154.9 mW cm-2) at the current density of 175.9 mA cm-2, low voltage gap (0.85 V) at the initial cycle, and long-term (250 h) cycle stability at the current density of 10 mA cm−2 than those of noble-metal electrocatalysts.

Oxygen vacancies-rich NiCo2O4-4x nanowires assembled on porous carbon derived from cigarette ash: A competitive candidate for hydrogen evolution reaction and supercapacitor

NiCo2O4 has aroused intense interest for hydrogen evolution reaction (HER) and supercapacitor (SCs). Nevertheless, the poor electric conductivity and insufficient electroactive sites hinder its commercial application. In this work, oxygen vacancies-rich NiCo2O4-4x nanowires assembled on porous carbon derived from discarded cigarette ash (named as Ov-NCO/PC-Y) are achieved via hydrothermal treatment combined with partial reduction process. The rich oxygen vacancies could offer remarkable conductivity, rapid ions transport rates, and rich electroactive sites. The introduction of phosphate ions is favorable for weakening the activation energy of their redox reactions, and therefore greatly promoting their surface reactivity and electrochemical reaction reversibility. Moreover, the interconnected 3D porous network structure of porous carbon (PC) could offer large surface area and short transport channel of ions/electrons. In virtue of intrinsic characteristic and structural advantage, Ov-NCO/PC-0.1 can be regarded as an effective HER catalyst with a low overpotential of 135.9 mV to reach 10 mA/cm2. Furthermore, Ov-NCO/PC-0.1 demonstrates superior specific capacitance of 1002.2 F/g, and Ov-NCO/PC-0.1//AC-based aqueous asymmetrical supercapacitor delivers the energy density of 32.7 Wh/kg at the power density of 160.2 W/kg. Moreover, the specific capacitances of Ov-NCO/PC-0.1//AC-based aqueous asymmetrical supercapacitor nearly keep unchanged after 3500 cycles. Overall, these findings shed fundamental insight on constructing high-performance bifunctional transition metal oxides for optimizing electrochemical energy conversion and storage.

Enrichment of Phosphorus from Iron Ore to Dicalcium-silicate Phase by Partial Reduction

Due to the low quality of available iron ore, it is necessary to develop a new technology to produce high quality steel from ore containing a high concentration of phosphorous. In this study, we propose a new process for producing low-P steel by concentrating P in the dicalcium silicate phase through a partial reduction process. High-P iron ore was mixed with varying quantities of CaO and graphite and heated at 1573 K in an Ar atmosphere, and the obtained product was analyzed by electron probe microanalysis. It was found that in the reduced product mixture that was obtained under specific conditions of high basicity and a lower amount of added carbon, more than 95% of P was concentrated in the dicalcium silicate phase, and the P content in metallic iron was sufficiently low.

Experimental Design and Response Surface Methodology Applied to Graphene Oxide Reduction for Adsorption of Triazine Herbicides.

In this work, pristine graphene oxide and its thermally reduced derivatives, rGO, were tested for the removal of triazines (atraton, prometryn, and atrazine) from water. The reduction process was optimized by means of design of experiments (DOE) coupled with response surface methodology (RSM), relying on the adsorption efficiency of the material. The optimal reduction conditions were calculated at a temperature of 110 °C maintained for 24 h; the mildest and simplest reduction protocol was chosen, as it allows in-air heat treatment with a common laboratory oven. The rGO samples were characterized before use, confirming a partial reduction process that, leaving intact most of the oxygenated functionalities on the graphene skeleton, may still allow favorable adsorption of pollutants through both hydrogen bonds and π–π interactions, which result from a large conjugated polyaromatic system. Triazine analyses were performed by high-performance liquid chromatography (HPLC); the data obtained from the adsorption isotherms were fitted with the Langmuir and Freundlich models, highlighting a slightly different adsorption behavior of atraton and prometryn compared with atrazine. Model outcomes were also used to support the hypotheses about the adsorption process.

Defect-rich Fe-doped Co3O4 derived from bimetallic-organic framework as an enhanced electrocatalyst for oxygen evolution reaction

Herein, oxygen-deficient Fe-doped Co3O4 polyhedral nanoparticles derived from FeCo‐based bimetal–organic frameworks are prepared for the electrocatalytic oxygen evolution reaction (OER) via a facile self‐templating strategy. A well-defined rhombic dodecahedral structure with abundant oxygen vacancies was constructed based on the coprecipitation, carbonization, oxidation, and partial reduction process. The proposed synthetic method is effective for fabricating a bimetallic hierarchical structure with a rough surface and a moderately controlled electronic structure, which significantly facilitates charge and mass transfer and appropriately exposes the active sites for efficient electrocatalysis. Subsequently, the as-obtained defect-rich Fe-doped Co3O4 nanoparticles was found to be a superior OER electrocatalyst, with a small overpotential of 318 mV required for a current density of 10 mA cm−2, a low Tafel slope of 76.8 mV dec−1, a turnover frequency of 0.1553 s−1 at an overpotential of 370 mV, and outstanding long-term durability in 1.0 M KOH. The proposed strategy will offer a new approach in the design and development of electrochemically active non-noble materials as advanced catalysts for various energy storage and conversion applications.

Investigation on microwave absorption characteristics of ternary MWCNTs/CoFe2O4/FeCo nanocomposite coated with conductive PEDOT-Polyaniline Co-polymers

In this study, ternary MWCNTs/CoFe2O4/FeCo nanocomposite coated with conductive PEDOT-polyaniline (PA@MW/F/C) co-polymers were synthesized by microwave-assisted sol-gel followed in-situ polymerization methods. The phases, crystal structures, morphologies, magnetic and electromagnetic features of the as-prepared samples were identified via XRD, SEM, XPS, VSM, and VNA respectively. Absorption characteristics were investigated in the frequency (12–18 GHz) Ku band. XRD, VSM and SEM analysis confirmed the partial reduction process of CoFe2O4 and successfully decorated magneto-dielectric particles with co-polymers. By measuring electromagnetic features of the samples, it was found that coating magneto-dielectric particles with conductive co-polymers improved the permittivity and dielectric constant, accordingly affecting the impedance matching characteristic and attenuation constant performance. Moreover, exchange coupling behavior was found significant impacts on the microwave absorption properties. PA@MW/F/C coated nanocomposite revealed the maximum reflection loss of −90 dB at 13.8 GHz with 4 GHz effective bandwidth and 1.5 mm thickness. Due to the enhanced interfacial polarization, impedance matching and exchange coupling effects of the as-prepared nanocomposite, it owns excellent microwave absorption properties, which can be applied as an absorber with distinguishing features (strong absorption, thin thickness, and broadest effective bandwidth).

Synthesis of porous nitrogen-doped graphene decorated by γ-Fe2O3 nanorings for enhancing microwave absorbing performance

Excellent wave absorbers are key materials for reducing electromagnetic radiation pollution. In this work, novel γ-Fe2O3 nanoring/porous nitrogen-doped graphene (γ-Fe2O3 NR/PNG) composites with varying mass ratios were successfully synthesized as lightweight absorbers using a two-step solvothermal method in combination with a partial reduction process. The diameter of the uniform γ-Fe2O3 NRs is approximately 150 nm with a shell thickness of approximately 50 nm. The uniform γ-Fe2O3 NRs are dispersed onto PNG sheets. Compared with pure γ-Fe2O3 NRs and PNG, all γ-Fe2O3 NR/PNG composites exhibit better microwave absorbing performance, among which a γ-Fe2O3 NR/PNG composite with a 4:1 mass ratio of γ-Fe2O3 NR:PNG shows the best absorption over a broad bandwidth for its special nanoring and porous structure and excellent impedance matching. The minimum reflection loss (RLmin) reaches −40.18 dB at 7.80 GHz with a thickness of 2.5 mm; the absorption bandwidth (RL < −10 dB) is 3.41 GHz. Moreover, the composite also reveals a good absorption for microwaves in the low frequency range. At 3.38 GHz, RLmin reaches −32.69 dB with a thickness of 5.5 mm. This work provides guidance for designing absorbers that are lightweight, wideband with strong absorption.

Flash spark plasma sintering of 3YSZ

Flash SPS (FSPS) consolidation of 3YSZ cold pressed pellets was investigated. The results show that FSPS allows ultra-rapid consolidation of 3YSZ samples in 30–90 s under an applied electric field. The DC field induces electrochemical blackening. The partial reduction process starts from the cathode (-) and propagates toward the anode (+). This phenomenon, not previously discussed in FSPS literature, induces the development of internal temperature gradients resulting in a polarity dependent grain size/densification.

Preparation of metal catalyst component doped perovskite catalyst particle for steam reforming process by chemical solution deposition with partial reduction

Co-doped LaAlO3 nanoparticles with partial reduction were applied as a catalyst to ethanol steam reforming. Co-doped LaAlO3 nanoparticles were prepared using chemical solution deposition. The Co component was generated on the nanoparticle surface by a partial reduction process. The estimated H2 yield of the ethanol steam reforming process was changed by altering the reduction conditions, although the surface areas of the reduced nanoparticles were almost equal. The highest H2 yield was attained at 948 K reduction temperature. The calculated H2 yield and the conversion ratio were, respectively, 78% and 99%. Reaction bi-products during steam reforming were measured to elucidate the change of the H2 yield with the reduction temperature.

Band-gap engineering and comparative investigation of Ti2Nb10O29 photocatalysts obtained by Various synthetic routes

Ti2Nb10O29 photocatalysts were successfully synthesized by three different methods. Ti2Nb10O29 fabricated by the solvothermal method (ST-TNO) exhibited unique microspheres compared to the larger irregular particles observed for the samples annealed in air (Air-TNO) and Ar (Ar-TNO). X-ray Photoelectron Spectroscopy (XPS) results revealed that a partial reduction process from Ti4+ into Ti3+ occurs in Ar-TNO, because of the introduction of oxygen defects. Ar-TNO exhibited visible-light absorption with a band gap of 2.85 eV, while the absorption edges of Air-TNO and ST-TNO were approximately 400 nm. Under UV light irradiation (λ < 420 nm), Ar-TNO exhibited a photocatalytic activity 2.1 times greater than that of Air-TNO, corresponding to the highest activity. The results indicated that the preparation method is crucial for determining the band gap and photocatalytic activity of semiconductors. Moreover, the novel semiconductor photocatalyst can be further applied for constructing the heterojunction and designing the band structure.

Characterization and magnetic exchange observation for CoFe2O4–CoFe2 nanocomposite microfibers

The magnetic hard-soft CoFe2O4–CoFe2 nanocomposite microfibers have been synthesized by the sol–gel and partial reduction process, where CoFe2O4 ferrite is the hard phase with a grain size range from 43 to 62 nm and CoFe2 alloy the soft phase with grain sizes around 30 nm. These nanocomposite microfibers exhibit the magnetization behavior like a single phase magnetic material, and the magnetic exchange coupling effects are observed between the hard and soft phases. The specific saturation magnetization of CoFe2O4–CoFe2 nanocomposite microfibers shows an increase tendency with the increasing weight fraction of CoFe2, while the coercivity is consequently reduced. The nanocomposite microfibers have a maximum remanence 51.7 Am2/kg when the phase contents of CoFe2 around 28 wt% and CoFe2O4 about 72 wt%.

Preparation of Integrated Oxygen Permeable Membranes with a Porous Layer by Partial Reduction Process

An oxygen permeable membrane based on mixed oxide-ion and electronic conduction is a promising material for hydrogen production from methane at high temperatures. To increase an oxygen permeation flux, decreasing in thickness is required. In this study, integrated oxygen permeable membranes supported on a porous layer was prepared by partial reduction of dense composite materials. The dense samples of (ZrO 2 -3 mol%Y 2 O 3 )-x vol%NiFe 2 O 4 (x = 33,40,50) were prepared by sintering at 1400°C under air for 5 h. The one side of the sample was reduced at a temperature range of 800 to 1000°C under Ar-5%H 2 . The microstructure and oxygen flux density were analyzed by using a scanning electron microscopy and a quadrupole mass spectroscopy, respectively. An integrated oxygen permeable membrane of (ZrO 2 -3 mol%Y 2 O 3 )-50 vol%NiFe 2 O 4 having a dense layer of 200 μm and a porous layer of 300 μm was successfully prepared. The oxygen flux density of the membrane was found to be 4.3―7.4 x 10 ―7 mol·cm ―2 ·s ― 1 .

Influence of Sm 2O 3 on the crystallization and luminescence properties of boroaluminosilicate glasses

Sm 2O 3-doped SiO 2–B 2O 3–Al 2O 3–BaO glasses were prepared by melting method in order to study the influence of Sm 2O 3 on the crystallization behavior and luminescence properties. Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy were used to characterize the rare earth glasses and the crystalline phases after heat-treatment. The course of phase separation and devitrification of the glasses were also investigated. The results show that the thermal stability of the glasses decreases with the increase of content of Sm 2O 3. The crystalline phase changed from SmAl 2.07(B 4O 10)O 0.6 to SmBO 3. Divalent Sm 2+ ions were detected in the crystallization product after heat-treatment. The valence transformation from Sm 3+ to Sm 2+ in the crystal suggests the samarium atoms entering the barium sites. The charge carried in vacancy defect induced by the substitution led to the partial reduction process. The reduction of Sm 3+ ions was promoted by the increasing of Sm 2O 3 content or the extending of heat-treated holding time in boroaluminosilicate glass.

Partial reduction of pyrroles: application to natural product synthesis

The partial reduction of N-Boc pyrroles has been explored giving stereoselective routes to disubstituted pyrrolines in good yields and with excellent diastereoselectivities. A novel methodology has been developed to carry out reductive aldol reactions on 2-substituted N-Boc pyrroles; use of aldehydes under reductive aldol conditions gave the anti aldol product in good selectivity. This chemistry was used as the key transformation in a synthesis of omuralide, which was achieved in 13 steps and 14% overall yield. We also report a methodology for selectively forming either cis or trans 2,5-disubstituted pyrrolines via a partial reduction of an electron-deficient N-Boc pyrrole. The trans pyrroline formed using this route was utilized in the syntheses of the polyhydroxylated pyrrolizidine natural products hyacinthacine A1 and 1-epiaustraline. Further investigation has led to the development of routes to enantiopure substituted pyrroline compounds. This has been achieved via a chiral protonation approach using easily accessible chiral acids, such as ephedrine and oxazolidinones, to quench enolates formed during the partial reduction process. Alternatively, enzymatic desymmetrization of symmetrical diol compounds formed from the partial reduction products of substituted pyrroles is also reported. This leads to formation of both enantiomers of 2,2- and 2,5-disubstituted N-Boc pyrrolines in excellent ee and yields.

Blast Furnace Ironmaking System Using Partially Reduced Iron Ore Reduced by an Energy Source with Low Carbon Content

It is possible to improve the productivity and flexibility of the blast furnace operation and also to substitute energy sources in the pig iron production processes by combining the partial reduction process using low carbon content energy sources such as natural gas with the blast furnace process. In this case, the blast furnace process conducts the final reduction and melting of the partially reduced iron ore produced in the partial reduction process. The production rate of the partially reduced iron ore is much higher than that of the fully reduced iron one, because the reduction rate tends to decrease remarkably as the reduction degree rises. As for the technological problems of using the partially reduced ore in the blast furnace process, the deadman temperature might decrease if a large amount of fine iron ore that has been partially reduced is injected. However, if the appropriate amount is used, the reducing agent rate may lower, and productivity can be improved without decreasing the deadman temperature. This method not only reduces energy consumption in the existing blast furnace ironmaking process, but also reduces the energy consumption related to carbon dioxide emission in the total hot metal production processes, including the partial reduction process.

Metal Oxide Composites for Lithium-Ion Battery Anodes Synthesized by the Partial Reduction Process

A thermochemical process based on the partial reduction of mixed oxides is used to create ultrafine metal-ceramic composites for Li-ion battery electrodes. Mixed oxides containing a more noble metal selected to be capable of alloying with lithium at potentials useful as a Li-ion battery anode are partially reduced to form electrochemically active metal-ceramic composites. Experiments show the differences in microstructure obtained in systems with slow oxygen diffusion and fast oxygen diffusion distorted fluorite), and microphase separation rutile). Materials are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and scanning transmission electron microscopy, and electrochemical tests are presented. Reversible charge capacities of 200-350 mAh/g (1100-2200 mAh/cm3) have been obtained in experiments to date. © 2002 The Electrochemical Society. All rights reserved.

Transformations of 3,4-Disubstituted Pyridines under Dissolving Metal Conditions - Partial Reduction followed by Radical Cyclisation

The reductive alkylation of 3,4-disubstituted pyridines is reported using either sodium in ammonia or ammonia free conditions (Na, naphthalene, THF). This partial reduction process works cleanly and efficiently giving good yields of highly functionalised dihydropyridine templates. Radical cyclisation reactions were performed on these dihydropyridines and gave fused 2- and 3-ring heterocycles with defined stereochemistry.

Coloration effect of pulsed laser on WO 3

When laser pulses irradiate the surface of the sample WO3, an interesting coloration effect is obtained. Only by one pulse of XeCl laser irradiation (wavelength: 308 nm, pulse duration: 36 ns, output power: 100 mJ/pulse), a significant color change appears. X-ray photoelectron spectroscopy (XPS) shows that a partial reduction process of WO3 occurs and conduction band electrons appears. X-ray diffraction pattern indicates that the lattice parameters of the colored samples are increased. A molten layer can be seen in scanning electron microscopy (SEM) image. It may be concluded that the coloration effect of pulsed laser undergoes a process different from that of electro- or photo-chromism, and may be attributed to thermochromism and substoichiometric WO3 is formed. The coloration process is characterized by its high speed and stability.