Effect Of Reduction Time Research Articles

The coexistence of highly dispersed Pt2+ and Pt0 co-catalysts on chemically oxidized g–C3N4 via metal-support interaction: The effect of reduction time on Pt species and hydrogen evolution of Pt/g-C3N4 photocatalysts

Platinum (Pt) cocatalyst greatly enhances the photoactivity of the graphitic carbon nitride (g-C3N4) photocatalyst for photocatalytic H2 evolution where the Pt properties are critical to determine the photocatalytic activity. In this study, highly dispersed Pt was successfully loaded onto chemically oxidized g–C3N4 (OCN) via a hydrogen reduction process over different reduction time. OCN photocatalysts containing highly dispersed Pt2+/Pt0 exhibited outstanding charge separation efficiency and photocatalytic performance. Symmetrical –CO groups on the OCN surface specifically interacted with atomic Pt2+, and the Pt2+ atoms were stably reduced to Pt0 atoms along with the generation of –OH groups over time. The coexistence of Pt0 and Pt2+ promoted superior photocatalytic performance because the photoinduced charge transfer was facilitated by the Pt0 atoms, which was evidenced by the DFT calculation and the EIS, PL, and photocurrent response results. Consequently, after the 24 h reduction, the highly stable and active Pt2+/Pt0 atoms were effectively distributed over OCN, resulting in the highest HER activity at 4091.3 µmol g−1 h−1.

Enhancing polyamide fabric performance through green reduction of graphene oxide for superior ultraviolet protection and electrical conductivity

AbstractIn this study, a polyamide warp‐knitted fabric was treated with a graphene oxide (GO) aqueous dispersion using a laboratory‐type Jigger dyeing machine. Subsequently, the GO underwent a chemical reduction process, employing rosehip extract powder as a nature‐based reducing agent. The effect of reduction time (12 and 24 h) was investigated. The study involved an examination of the surface morphology, colour coordinates, and colour difference of both the GO coated and reduced graphene oxide (RGO) coated fabrics. Additionally, the colour fastness against rubbing was assessed. Furthermore, electrical resistivity measurements were conducted on the GO‐coated polyamide‐6,6 fabric both before and after the reduction process. The ultraviolet (UV) transmittance and ultraviolet protection factor (UPF) of both GO‐coated and reduced fabrics were determined. The study also explored the effect of the washing process on colour properties, electrical resistivity, and UPF. Notably, the lowest electrical surface resistivity and the highest UPF rating were obtained as 1.20 × 102 kΩ/sq and 50+ after the reduction process. Additionally, after the washing process, the electrical surface resistivity increased, while the UPF rating remained 50+, indicating excellent UV protection.

Recovery of Metals from Copper Smelting Slag Using Coke and Biochar

With the purpose of recovering the metal values, in this study the copper slag was reduced by coke and biochar at 1250 °C in an argon gas atmosphere using the isothermal reduction/drop quenching technique. The phase compositions of metal, matte, and slag were determined using electron probe microanalysis (EPMA). The effects of reduction time and amount of reductant were investigated. The distribution of elements between metal/matte and slag was ascertained based on the elemental concentrations determined by EPMA. It was found that copper concentration in slag can be effectively decreased to approximately 0.4–0.6 wt% within 5 min by coke and biochar. Copper and nickel can also be successfully recovered into the copper alloy phase once settling has been accomplished.Graphical

Modulating Co reduction degree and Fischer-Tropsch synthesis performance by reducing cobalt silicate at different conditions

It is always hard to reduce Co2SiO4 to active Co0 on supported Co-based catalyst for Fischer-Tropsch synthesis (FTS). Here, amorphous Co2SiO4 material was prepared by in-situ doping TMOS during synthesis of ZIF-67, which was then reduced at different temperature and time to obtain ReX-2h (X = 400, 450, 500, 550, 600) and Re500-Yh (Y = 2, 4, 8) catalysts. The effects of reduction temperature and time on Co reduction degree and FTS performance were investigated. Results indicated that the ReX-2h and Re500-Yh catalysts exhibited low CH4 selectivity due to no obvious Co microcrystal found. The reduction degree of ReX-2h increased with reduction temperature, which led to enhanced FTS activity. However, both Re550-2h and Re600-2h exhibited poorer stability than Re500-2h, so the effects of reduction time on Re500-Yh were done. The reduction degree and FTS activity of Re500-Yh were also promoted with extending reduction time. The Re500-8h exhibited higher FTS activity with good stability.

A novel process for recovering aluminum and silicon from fly ash in cryolite molten salt

The recovery and utilization of by-product coal fly ash (CFA) in high-value-added thermal power plants is of great significance. This research focused on producing high-value-added Al–Si master alloy by aluminothermic reduction with coal fly ash as the raw material. The effects of reduction time and reducing agent amount on thermal reduction products were investigated using the single factor method. X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) results showed that Al, Si, and a small amount of Fe were the main components of the alloy. With an increase in reaction time, the mass fraction of Si in the product increased from 4.41% to 9.93%. Besides, the molten salt after thermal reduction was recovered by the electrochemical reduction process. The results showed that a longer electrolysis time is more conducive to improving the recovery of Si and Al. The results of cyclic voltammetry and electrodeposition showed that Si would be reduced in a multi-step process. Combined with thermal reduction and electrochemical secondary recovery process, the comprehensive recovery of Al and Si in fly ash could reach 87.33% and 84.02%, respectively.

Interfacial Characterization of Polypyrrole/AuNP Composites towards Electrocatalysis of Ascorbic Acid Oxidation

Polypyrrole (PPy) is an interesting conducting polymer due to its good environmental stability, high conductivity, and biocompatibility. The association between PPy and metallic nanoparticles has been widely studied since it enhances electrochemical properties. In this context, gold ions are reduced to gold nanoparticles (AuNPs) directly on the polymer surface as PPy can be oxidized to an overoxidized state. This work proposes the PPy electrochemical synthesis followed by the direct reduction of gold on its surface in a fast reaction. The modified electrodes were characterized by electronic microscopic and infrared spectroscopy. The effect of reduction time on the electrochemical properties was evaluated by the electrocatalytic properties of the obtained material from the oxidation of ascorbic acid (AA) and electrochemical impedance spectroscopy studies. The presence of AuNPs improved the AA electrocatalysis by reducing oxidation potential and lowering charge transfer resistance. EIS data were fitted using a transmission line model. The results indicated an increase in the electronic transport of the polymeric film in the presence of AuNPs. However, PPy overoxidation occurs when the AuNPs’ deposition is higher than 30 s. In PPy/AuNPs 15 s, smaller and less agglomerated particles were formed with fewer PPy overoxidized, confirming the observed electrocatalytic behavior.

Synergetic valorization of basic oxygen furnace slag and stone coal: Metal recovery and preparation of glass-ceramics.

A synergetic valorization method was proposed to convert the basic oxygen furnace (BOF) slag and stone coal into ferroalloy and glass-ceramic in this work. Effects of reduction time, temperature, and the mass ratio of BOF slag to stone coal on the reduction were studied. The reduction mechanism was investigated by in-situ observation and dissolution experiments. The effect of sintering temperature on the properties of glass-ceramics prepared from the final slag was further studied. The in-situ observation results indicate that the reduction reactions occurred mainly in the temperature range of 1673-1793K. The reduction ratio of oxides and size of metal droplets can be improved by increasing reduction time, temperature, and decreasing stone coal addition. The recovered ferroalloys consisted of Fe, Mn, P, and V, which has the potential of returning to the steelmaking process or extracting vanadium. The modified final slag was suitable material for preparing glass-ceramic. Wollastonite-based glass-ceramic with a maximum bending strength of 95.83MPa was prepared, which could be applied as abrasion-resistant and building decoration materials. Therefore, the present technological route can convert two kinds of industrial solid waste into two kinds of cleaner products and achieve the target of "zero waste".

Synthesis of Ti(C, N, O) ceramic from rutile at low temperature by CH4-H2-N2 gas mixture

Titanium carbides, oxides, nitrides, and carbonitrides possess many special and excellent properties. But the high production cost caused by the traditional carbothermic reduction process severely limits the wide applications. In this study, a novel synthesis process has been proposed by reducing and carbonitriding TiO2 with a CH4-H2-N2 gas mixture at low temperatures. The synthesis of Ti(C, N, O), reaction mechanism, and the composition of the product have been investigated. Thermodynamic analysis indicated that TiO2 could be ultimately reduced and carbonitrided to Ti(C, N, O) by CH4-H2-N2 gas mixture. Based on the predictions of thermodynamics, the effects of reduction time, temperature, and gas composition have been studied experimentally. The obtained results indicated that increasing reduction temperature and introduction of N2 are beneficial to the synthesis of Ti(C, N, O). Finally, the optimum reaction conditions have been obtained. The density functional theory (DFT) results further demonstrated the reaction mechanism. This work provides a new approach to prepare metallic carbonitrides from their oxides.

Improved Catalytic Activity of the High-Temperature Water Gas Shift Reaction on Metal-Exsolved La0.9Ni0.05Fe0.95O3 by Controlling Reduction Time

The catalyst exsolved from nickel-doped perovskite oxide, La0.9Ni0.05Fe0.95O3, has been proven to be effective for gas-phase reactions. To obtain the optimum amount of exsolved nanoparticles from the parent perovskite oxide, control of the reduction treatment condition is vital. Here, the effect of reduction time on the exsolved nanoparticle distribution, and thus the catalytic activity of the high-temperature water gas shift reaction (WGSR), was investigated. Upon conducting a wide range of characterizations, we assumed that the exsolution process might be a two-step process. Firstly, the surface oxygen is extracted. Secondly, due to the unstable perovskite structure, the Ni ions in the bulk La0.9Ni0.05Fe0.95O3 continuously diffuse toward the surface and, as the reduction progresses, more nuclei are generated to form a greater number of nanoparticles. This assumption is proven by the fact that, with an increase in the exsolution treatment time, the population of exsolution nanoparticles increases. Moreover, as the reduction time increases, the high-temperature WGSR activity also increases. The temperature-programmed measurements suggest that the exsolved nanoparticles are the active reaction sites. We believe that this study is helpful for understanding exsolution behavior during reduction treatment and, thus, developing a perovskite exsolution catalyst for the WGSR.

Time-intended effect on electrochemical performance of hydrothermally reduced graphene oxide nanosheets: Design and study of solid-state symmetric supercapacitor

Self-organized porous sheet-like assemblies have attracted extensive attention for the development of flexible high-performance electrodes. This work demonstrates the facile synthesis and effects of reduction time on the electrochemical performance of porous sheet-like assemblies of reduced graphene oxide (rGO) on carbon cloth. An rGO porous assembly with a reduction time of 4 h exhibited a superior specific capacitance of 456 F/g at a scan rate of 5 mV/s and 223 F/g at a current density of 1 mA/cm2, with ~ 93.9% initial capacity retention over 2000 cycles. A solid-state symmetric supercapacitor device constructed of a rGO4//rGO4 porous assembly achieved a specific capacitance of 45.86 F/g at a scan rate of 5 mV/s and yielded an energy density of 1.27 Wh/kg and specific power of 833.3 W/kg in a PVA-H2SO4 gel polymer electrolyte. Furthermore, the flexible solid-state symmetric device provides outstanding cyclic stability with a 95.3% retention of its initial capacity over 2000 cycles. Thus, electrodes constructed of rGO porous sheets show great potential for flexible and transparent solid-state symmetric energy storage devices.

Direct reduction of copper slag-carbon composite pellets by coal and biochar

ABSTRACT As a renewable resource of reducer, biochar prepared by pine sawdust is proposed for direct reduction of copper slag in this paper. Combined with thermodynamic analysis, effects of reduction time, temperature and CaO addition ratio on solid copper slag reduction characteristics are discussed. The oxides of iron in copper slag are Fe3O4 and 2FeO·SiO2. The reduction processes were carried out step by step for Fe3O4 and 2FeO·SiO2, respectively: Fe3O4 → FeO → Fe and 2FeO·SiO2 → Fe. The porous structure of biochar exhibits higher reduction reactivity and reaction rate than that of coal. CaO reduced the Gibbs free energy of reduction reactions and facilitated the reduction of 2FeO·SiO2 with C and CO. When CaO was added, separation reaction of FeO and SiO2 took place and α-SiO2 and β-SiO2 were produced. When the addition ratio of CaO is above 0.3, CaO·SiO2 and 2CaO·SiO2 are produced. The reduction process of copper slag was established as follows: (a) dehydration and fast pyrolysis; (b) reduction of iron oxides by C and CO; and (c) sweating metallic iron outflows from cracks in pellet. Besides, direct reduction reaction mechanism and transport process of Cu are established based on reduction experiments, XRD and SEM-EDS analysis.

The synthesis of magnetically exchange coupled CoFe2O4/CoFe2 composites through low temperature CaH2 reduction

CoFe2O4 sub-micron particles were synthesized through a hydrothermal method. The as-synthesized CoFe2O4 particles were then mixed with CaH2 and heated at 180 °C for reduction. In three parallel experiments, the reduction time was controlled to be 10, 20 and 30 h, respectively. The effects of reduction time on the particle morphology and magnetic properties were investigated. The results showed that the reduction time did not affect the morphology of CoFe2O4 under 180 °C, indicating that these particles had a good thermal stability at reduction temperature. The XRD patterns showed that long reduction time resulted in a stronger peak of CoFe2. The magnetic hysteresis loops of reduced products showed that magnetic exchange coupling was presented when the reduction time was 10 h. Further extended reduction time resulted in the kinks in the magnetic hysteresis loop, and magnetic decoupling.

Effect of reduction time on the structure and properties of porous graphene

Porous graphene with nanoscaled pores on the sheets was prepared by a carbon thermal reduction method, in which the molybdenum oxide nanoparticles generated from the thermal decomposition of molybdate were used as the etching reagent, and the pores were formed on the surface of the reduced graphene oxide under the conditions of 650 °C and a nitrogen atmosphere. The morphology of pores on the graphene sheets may affect their potential applications in various fields, especially in the enhancement of mass transfer. Previous studies have shown that the reduction temperature and the amount of metal oxide are the key factors affecting the morphology of porous graphene, but in fact the reduction time is a more important affecting factor according to the present study. The results of SEM/TEM showed that a disordered large sheet-like structure with wrinkles was obtained at 120 min in the carbon-thermal reaction. The structural integrity of the PG was further destroyed after the reaction time of 140 min, in which the edge exhibited slightly crush and significant fold. The PG exhibited a hollow rod-like structure at the reaction time of 180 min. FTIR, Raman, XRD, and XPS studies were performed to characterize the morphology of porous graphene prepared at different reduction times.

Two-stage reduction for the preparation of ferronickel alloy from nickel laterite ore with low Co and high MgO contents

The preparation of ferronickel alloy from the nickel laterite ore with low Co and high MgO contents was studied by using a pre-reduction–smelting method. The effects of reduction time, calcination temperature, quantity of reductant and calcium oxide (CaO), and pellet diameter on the reduction ratio of Fe and on the pellet strength were investigated. The results show that, for a roasting temperature >800 °C, a roasting time >30 min, 1.5wt% added anthracite coal, 5wt% added CaO, and a pellet size of ~10 mm, the reduction ratio of Fe exceeds 70% and the compressive strength of the pellets exceeds 10 kg per pellet. Reduction smelting experiments were performed by varying the smelting time, temperature, quantity of reductant and CaO, and reduction ratio of Fe in the pellets. Optimal conditions for the reduction smelting process are as follows: smelting time, 30–45 min; smelting temperature, 1550°C; quantity of reductant, 4wt%–5wt%; and quantity of CaO, 5wt%; leading to an Fe reduction ratio of 75% in the pellets. In addition, the mineral composition of the raw ore and that during the reduction process were investigated by process mineralogy.

Effect of reduction time on third order optical nonlinearity of reduced graphene oxide

We report the influence of reduction time on structural, linear and nonlinear optical properties of reduced graphene oxide (rGO) thin films synthesized by spin coating method. We observed that the structural, linear and nonlinear optical properties can be tuned with reduction time in GO is due to the increased structural ordering because of the restoration of sp2 carbon atoms with the time of reduction. The nonlinear absorption studies by open aperture Z-scan technique exhibited a saturable absorption. The nonlinear refraction studies showed the self de focusing nature of rGO by closed aperture Z scan technique. The nonlinear absorption coefficient and saturation intensity varies with the time for reduction of GO which is attributed to the depletion of valence band and the conduction band filling effect. Our results emphasize duration for reduction of GO dependent optical nonlinearity of rGO thin films to a great extent and explore its applications Q switched mode locking laser systems for generating ultra short laser pulses and in optical sensors. The rGO coated films were characterized by X-Ray diffraction method (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV–Vis absorption spectroscopy (UV–Vis), Photoluminescence (PL) and Scanning electron microscope (SEM) measurements.

Green Synthesis of Silver Nanoparticles and Study of Their Antimicrobial Properties

One of the major disadvantages of polymers when used in food-contact applications is that they are very susceptible to microbial attack. On the other hand, silver nanoparticles have received increased attention as novel antimicrobial agents. Therefore, the introduction of silver nanoparticles into conventional polymers results in new materials with improved properties. In this investigation, colloidal silver nanoparticles using an environmentally friendly procedure were synthesized. An aqueous solution of AgNO3 was used as a silver precursor with ‘green’ reducing agents either different types of honey, or β-d-glucose. In the first case, different pH values, as well as the addition of poly(ethylene glycol), PEG were studied, while in the latter, the effect of reduction time in the presence of PEG with various average molecular weights was examined. Properties of the nanoparticles were measured using X-Ray diffraction, UV–Vis and FTIR spectroscopy. Using honey it seems that spherical particles are produced with the smaller average particle size obtained at pH 8.5. Use of honey has the advantage of being a natural product, although its main drawback is that its composition varies and it cannot be predefined to result in reproducible results. Use of β-d-glucose results in stable silver nanoparticles with small average particle size after 24 h reduction. The addition of low molecular weight PEG seems to be beneficial in the production of stable nanoparticles. Finally, the antimicrobial activity of the nanoparticles produced was investigated at different concentrations on both Gram positive and negative bacteria, such as Bacillus cereus, Bacillus subtilis, Escherichia coli and Staphylococcus aureus.

One-Step Hydrothermal Reduction and Functionalization of Graphene Oxide with a Modified Diethylene Triamine

Graphene oxide (GO) was prepared by modified Hummer’s method, and reduced by solvothermal method using ethanol as the solvent and modified diethylene triamine (amine curing agent 593) as reducing agent and modifier. The effect of reduction time and temperature on the structure and conductive property of reduced graphene oxide (593-rGO) was investigated by SEM, FT-IR and XRD. The results show that the graphene modified by 593 is obviously improved in dispersibility and sedimentation stability in dichloromethane, as well as in conductivity. The optimal reduction processing is that the mass ratio of GO to 593 is 2:1, the reduction time and temperature is 6 h and 160°C, respectively.

Influence factors on activity of Ru–Zn catalysts in selective hydrogenation of benzene

Selective hydrogenation of benzene is an atom economic green route to produce cyclohexene. The control of Zn species is the key to the catalytic performance of Ru–Zn catalysts. The influences of ZnO crystals on selective hydrogenation of benzene were explored. A series of Ru–Zn catalysts with different Zn contents and ZnO morphologies were prepared by changing the amount of NaOH in the co-precipitation process. The catalysts were characterized by N2 physisorption, X-ray powder diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), scanning electron microscope (SEM), temperature-programmed reduction (H2-TPR) and Malvern laser particle size analyzer. It is found that with increasing the amount of NaOH, the Zn content first increased then decreased, and the ZnO crystals changed from relatively thicker pyramidal-shaped crystals to slimmer needle-shaped crystals. The catalyst had the highest Zn content (22.1%) and strongest interaction between ZnO crystals and Ru particles at pH10.6 of the solution after reduction. As a result, it had the lowest activity. The activity of Ru–Zn catalysts is affected by both the Zn content and the interaction between ZnO crystals and Ru particles. The effect of reduction time was also investigated. Prolonging the reduction time caused no significant growth of ZnO crystals but the aggregation of catalyst particles and growth of Ru nanocrystals, thus resulting in the decrease of catalytic activity.

The Effect of Reduction Time and Size Distribution of Mixed Iron Ore with Coconut Shell Charcoal on the Percentage of Metallization by using a Rotary Kiln

The Effect of Reduction Time and Size Distribution of Mixed Iron Ore with Coconut Shell Charcoal on the Percentage of Metallization by using a Rotary Kiln

Effects of reduction time on the structural, electrical and thermal properties of synthesized reduced graphene oxide nanosheets

The reduction of graphene oxide (GO) nanosheet is a promising route to produce a stable colloidal dispersion of reduced graphene oxide (RGO) nanosheets in a large scale. The production of RGO nanosheet is one of the important topics in nanotechnology disciplines due to its contribution in various applications, such as the platinum catalyst support in direct methanol fuel cell. Therefore, in this paper, the RGO nanosheets were prepared via highly efficient chemical reduction reaction of exfoliated GO nanosheets using sodium oxalate (Na2C2O4) as the reducing agent. Extensive characterizations have been conducted in terms of structural, thermal stability and electrical conductivity properties by means of high-resolution transmission microscopy, the Fourier transform infrared spectroscopy, UV–visible spectroscopy, 13C NMR and four-point probe conductivity measurement. The results indicate that most of oxygen-containing functional groups from GO nanosheets have been removed and the RGO-3 possess greater thermal stability compared to GO nanosheets. The prepared RGO-3 shows the highest electrical conductivity at room temperature which is ∼2.0 × 103 S cm−1. Based on these analyses, the plausible mechanism of reduction of GO to RGO by sodium oxalate is well proposed.