Chemical Reduction of CO_2 to Different Products during Photo Catalytic Reaction on TiO_2 under Diverse Conditions:an Overview

The chemical reduction of CO2 remains a challenge with respect to the reversal of the oxidative degradation of any organic materials. The conversion of CO2 into useful substances is essential in developing alternative fuels and various raw materials for different industries. This also aids in preventing the continuous rise in tropospheric temperature due to the green house effect of CO2. In this article an overview of the growth taken place so far in the field of CO2 chemical reduction is pre- sented. The discussion comprises of photochemical methods for the development of different products, viz. CO, CH3OH and CH4, through chemical reduction of CO2. This includes the use of photo catalysts, mainly TiO2, and the role of a hole scavenger （such as 2-propanol） for this purpose.

Preparation of copper nanoparticles by chemical reduction method using potassium borohydride

High dispersive copper nanoparticles were prepared by chemical reduction method using potassium borohydride as reducing agent.The effects of reactant ratio,concentration of CuSO4,reaction temperature,and dispersant on the size of product and conversion rate were studied.The morphologies of copper nanoparticles were characterized by scanning electron microscopy.The results show that the optimum process conditions are as follows:the molar ratio of KBH4 to CuSO4 is 0.75(3:4),concentration of CuSO4 is 0.4 mol/L,reaction temperature is 30℃,and dispersant is n-butyl alcohol.The average particles size of copper powders with spherical shape gained is about 100 nm.

Microwave enhanced chemical reduction process for nitrite-containing wastewater treatment using sulfaminic acid

High-concentration nitrite-containing wastewater that presents extreme toxicity to human health and organisms is difficult to be treated using traditional biological process. In this study, a novel microwave-enhanced chemical reduction process （MECRP） using sulfarninic acid （SA） was proposed as a new manner to treat such type of wastewater. Based on lab-scale experiments, it was shown that 75%-80% nitrite （NO2-） could be removed within time as short as 4 min under 50 W microwave irradiation in pH range 5-10 when molar ratio of SA to nitrite （SA/NO2-） was 0.8. Pilot-scale investigations demonstrated that MECRP was able to achieve nitrite and chemical oxygen demand （COD） removal with efficiency up to 80% and 20%, respectively under operating conditions of SA concentration 80 kg/m3, SA/NO2- ratio 0.8, microwave power 3.4 kW, and stirring time 3 min. Five-day biological oxygen demand （BODs）/COD value of treated effluent after MECRP was increased from 0.05 to 0.36 （by 620%）, which clearly suggested a considerable improvement of biodegradability for subsequent biological treatment. This study provided a demonstration of using microwave irradiation to enhance reaction between SA and nitrite in a short time, in which nitrite in wastewater was completely converted into nitrogen gas without leaving any sludge and secondary pollutants.

Size-dependent melting properties of Sn nanoparticles by chemical reduction synthesis

Tin nanoparticles with different size distribution were synthesized using chemical reduction method by applying NaBH4 as reduction agent.The Sn nanoparticles smaller than 100 nm were less agglomerated and no obviously oxidized.The melting properties of these synthesized nanoparticles were studied by differential scanning calorimetry.The melting temperatures of Sn nanoparticles in diameter of 81,40,36 and 34 nm were 226.1,221.8,221.1 and 219.5？欲espectively.The size-dependent melting temperature and size-dependent latent heat of fusion have been observed.The size-dependent melting properties of tin nanoparticles in this study were also comparatively analyzed by employing different size-dependent theoretical melting models and the differences between these models were discussed.The results show that the experimental data are in accordance with the LSM model and SPI model,and the LSM model gives the better understanding for the melting property of the Sn nanoparticles.

Synthesis of Cu nanoparticles by chemical reduction method

Cu nanoparticles (CuNPs) have been synthesized through an easy route by chemical reduction at room temperature. The Cu^2+ ions were reduced and stabilized with sodium borohydride and polyvinylpyrrolidone, respectively. The effect of the variation of the reducing agent/precursor-salt (RA/PS) ratio on the size and morphology of the CuNPs was evaluated. The synthesized material was studied by ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The UV-Vis spectra showed a CuNPs plasmon peak at 569 nm and another peak belonging to Cu2O at 485 nm. XRD analysis showed the fcc-Cu phase with a small amount of fcc-Cu2O compound. SEM and TEM studies displayed that small semispherical CuNPs of approximately 7 nm were obtained at the RA/PS ratio of 2.6. The excess of polyvinylpyrrolidone stabilizer played an essential role in preventing CuNPs oxidation. On the other side, Cu2O polyhedral particles with larger sizes up to 150 nm were identified in the RA/PS ratio range of 2.0-1.84. In addition, Cu2O particles having star morphologies with quantum confinement at their tips were obtained at the RA/PS ratio of 1.66.

The Preparation of Nano Silver by Chemical Reduction Method

A silver nanostructures prepared by using chemical reduction method. The silver nanoparticles were prepared with diameters of about (20 nm). Numerous techniques had been used to study the optical, structural like the UV-Vis absorption spectrometer, Ttransmission Electron Microscopy (TEM), Field-Emission Scanning Electron microscope (FESEM), and X-ray diffraction (XRD). The practical results exhibited the absorption spectrum of the prepared nanoparticles at (357 nm), it was found that there is a relationship between the positions of the optical absorption peak and the size of the silver nanoparticles. The analysis of TEM results showed the presence of nanoparticles in the range (20 nm). The analyzing of XRD results explained the crystal structure for silver nanoparticles. It is found a cubic unit cell have a lattice constants (a = 4.0855 Å), with the Miller indices were (111), (002), (002), and (113).

Investigation of Fe-Ni-B and Fe-Cr-B Ultrafine Amorphous Alloy Powders Prepared by Chemical Reduction

Ultrafine amorphous alloy powders of spherical shape with diameters from 10 to 50nm for Fe-Ni-B and Fe-Cr-B were prepared by chemical reduction. The amorphous structure of two powders was identified by X-ray diffraction. The B concentrations for the two alloy systems did not change dramatically, as the preparation condition changed. An oxide film covered up the powders. The maximum magnetization decreased as increasing the content of Ni or Cr.

Fe3O4 and Fe Nanoparticles by Chemical Reduction of Fe(acac)3 by Ascorbic Acid: Role of Water

Nanoparticles of Fe3O4 and Fe are chemically synthesized by reduction of Fe(acac)3 using ascorbic acid in controlled condition. It was observed that addition of water during the chemical synthesis process yields Fe3O4 nanoparticles, whereas if the reaction is carried out in absence of water yields Fe nanoparticles—which get oxidized upon exposure to air atmosphere. Fe3O4 (15 ± 5 nm) and Fe/iron oxide nanoparticles (7 ± 1 nm) were successfully synthesized in the comparative study reported herewith. Mechanism for formation/synthesis of Fe3O4 and Fe/iron oxide nanoparticles is proposed herewith in which added water acts as an oxygen supplier. Physico-chemical characterization done by SEM, TEM, EDAX, and XPS supports the proposed mechanism.

Preparation of Monodispersed Copper Nanoparticles by an Environmentally Friendly Chemical Reduction

In this paper, highly dispersive nanosized copper particles with a mean particle size of less than 6 nm are prepared by an environmentally friendly chemical reduction method. Non-toxic L-ascorbic acid acts as both reducing agent and antioxidant in ethylene glycol in the absence of any other capping agent. Transmission electron microscopy （TEM） is used to characterize the size and morphology of Cu nanoparticles. The results of UV-Vis spectroscopy （UV-Vis）, energy dispersive spectroscopy （EDS） and high resolution TEM （HRTEM） illustrate that the resultant product is pure Cu nanocrystals. The size of Cu nanoparticles is remarkably impacted by the order of reagent addition, and the investigation reveals the reaction procedure of Cu^2＋ ions and L-ascorbic acid.

Growth-controlled synthesis of polymer-coated colloidal-gold nanoparticles using electrospray-based chemical reduction

In this study,the controlled nucleation and growth of gold nanoparticles(GNPs)were investigated using a self-repelled mist in a liquid chemical reaction environment.An electrospray-based chemical reduction method was conducted in the aqueous region and at room temperature to synthesize the polymeric-stabilized gold nanoparticles.The electrospray technique was used to atomize a hydrogen tetrachloraurate(III)(HAuCl4)precursor solution into electrostatically charged droplets.The atomized droplets were dispersed in an aqueous reaction bath containing L-ascorbic acid as a reducing agent and polyvinylpyrrolidone(PVP)as a stabilizer.The effect of the electrospray parameters,specifically the flow rate and electrospray droplet size,as well as the reaction conditions such as the concentration of reactants,pH,and stabilizer(PVP),were investigated.The mean diameter of the GNPs increased from around 4 to 9 nm with an increase in the electrospray flow rate,droplet size,and current passing through the electrospray jet.Spherical and monodispersed GNPs were synthesized at a relatively high flow rate of 2 mL/h and a moderate concentration of 2 mM of precursor solution.The smallest-sized GNP with a high monodispersity was obtained in the reaction bath at a high pH of 10.5 and in the presence of PVP.It is expected that continuous and mass production of the engineered GNPs and other noble metal nanoparticles could be established for scaling up nanoparticle production via the proposed electrospray-based chemical reduction method.

Absence of superconductivity in Nd0.8Sr0.2NiOx thin films without chemical reduction

The recently reported 9-15 K superconductivity in Nd0.8Sr0.2NiO2/SrTi03 heterostructures that were fabricated by a soft-chemical topotactic reduction approach based on precursor Nd0.8Sr0.2NiO3 thin films deposited on SrTiO3 substrates,has excited an immediate surge of research interest.To explore an alternative physical path instead of chemical reduction to realizing superconductivity in this compound,using pulsed laser deposition,we systematically fabricated 63 Nd0.8Sr0.2NiOx(NSNO)thin films at a wide range of oxygen partial pressures on various oxide substrates.Transport measurements did not find any signature of superconductivity in all the 63 thin-film samples.With the oxygen content reducing in the NSNO films by lowering the deposition oxygen pressure,the NSNO films are getting more resistive and finally become insulating.Furthermore,we tried to cap a 20-nm-thick amorphous LaAlO3 layer on a Nd0.8Sr0.2NiO3 thin film deposited at a high oxygen pressure of 20 Pa to create oxygen vacancies on its surface and did not succeed in obtaining higher conductivity either.Our experimental results together with the recent report on the absence of superconductivity in synthesized bulk Nd0.8Sr0.2NiO2 crystals suggest that the chemical reduction approach could be unique for yielding superconductivity in NSNO/SrTiO3 heterostructures.However,SrTiO3 substrates could be reduced to generate oxygen vacancies during the chemical reduction process as well,which may thus partially contribute to conductivity.

Effects of surface chemical properties of activated coke on selective catalytic reduction of NO with NH_3 over commercial coal-based activated coke

Surface chemical properties of typical commercial coal-based activated cokes were characterized by Xray photoelectron spectroscopy(XPS) and acid-base titration, and then the influence of surface chemical properties on catalytic performance of activated cokes of NO reduction with NH3 was investigated in a fixed-bed quartz micro reactor at 150 ℃. The results indicate that the selective catalytic reduction(SCR) activity of activated cokes with the increase of its surface acidic sites and oxygen content,obviously, a correlation between catalytic activity and surface acidic sites content by titration has higher linearity than catalytic activity and surface oxygen content by XPS. While basic sites content by acid-base titration have not correlation with SCR activity. It has been proposed that surface basic sites content measured by titration may not be on adjacent of acidic surface oxides and then cannot form of NO2-like species, thus the reaction of reduction of NO with NH3 have been retarded.

A Pioneering Approach to the Synthesis of Silver Nanoparticles

Our research introduces a groundbreaking chemical reduction method for synthesizing silver nanoparticles, marking a significant advancement in the field. The nanoparticles were meticulously characterized using various techniques, including optical analysis, structural analysis, transmission electron microscopy (TEM), and field-emission scanning electron microscope (FESEM). This thorough process instills confidence in the accuracy of our findings. The results unveiled that the silver nanoparticles had a diameter of less than 20 nm, a finding of great importance. The absorption spectrum decreased in the peak wavelength range (405 - 394 mm) with increasing concentrations of Ag nanoparticles in the range (1 - 5%). The XRD results indicated a cubic crystal structure for silver nanoparticles with the lattice constant (a = 4.0855 Å), and Miller indices were (111), (002), (002), and (113). The simulation on the XRD pattern showed a face center cubic phase with space group Fm-3m, providing valuable insights into the structure of the nanoparticles.

Synthesis and electrochemical performance of a novel nano sized Sn_2SbNi composite

Chemical reduction method was employed to prepare nano-sized Sn2SbNi alloy composites used as anode material for rechargeable lithium ion batteries.This strategy was adopted to combine the virtues of both active/inactive and active/active alloys to fabricate a Sn2SbNi alloy powder with two active components and one inactive component.The two active components can realize the high capacity feature of electrode and can make the volume change of electrode take place in a stepwise manner due to the different lithiation potentials of two active components,leading to a stable cycling performance.Sn2SbNi alloy provides a reversible specific capacity over 640 mA·h/g with an excellent cyclic ability.The Sn-Sb-Ni alloy composite material shows to be a good candidate anode material for the lithium ion batteries.

Comparison Between Electrolysis and Reduction for Treatment of Spent Electroless Nickel Plating Bath

There are lots of residual nickel and organic compounds in the spent electroless nickel plating bath. It not only wastes resource but also causes environmental pollution if the wastewater is discharged without treatment. In this paper, electrolytic method and reduction method for treating spent electroless nickel plating bath were compared. The factors studied included reaction time, pH, temperature, effectiveness and cost. It was found that the recovery rate of nickel by reduction was 99.9% under the condition ofpH 6, 50℃ for 10 min. The purity of reclaimed nickel was 66.1%. This treatment needed about 16 g NaBH4 for a liter spent solution, which cost RMB 64 Yuan. For electrolysis method, with pH 7.6, 80℃, 0.45 A （current intensity） for 2 h, the recovery rate reached 97.3%. The purity was 88.5% for the reclaimed nickel. Moreover, it was found that through electrolysis, the value of TOC （Total Organic Carbon） decreased from 114 to 3.08 g·L^-1 with removal rate of 97.3%. The main cost of electrolysis came from electric energy. It cost about 0.09 kWh （less than RMB 0.1 Yuan） per liter wastewater. Compared with reduction, electrolysis had more advantages, so the priority of selection should be given to the electrolysis method for the treatment of spent electroless nickel plating bath.

Effective exposure of nitrogen heteroatoms in 3D porous graphene framework for oxygen reduction reaction and lithium–sulfur batteries

The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,most of nitrogen heteroatoms are doped into the bulk phase of carbon without site selectivity, which significantly reduces the contacts of feedstocks with the active dopants in a conductive scaffold. Herein we proposed the chemical vapor deposition of a nitrogen-doped graphene skin on the 3D porous graphene framework and donated the carbon/carbon composite as surface N-doped grapheme（SNG）. In contrast with routine N-doped graphene framework（NGF） with bulk distribution of N heteroatoms, the SNG renders a high surface N content of 1.81 at%, enhanced electrical conductivity of 31 S cm^（-1）, a large surface area of 1531 m^2 g^（-1）, a low defect density with a low I_D/I_G ratio of 1.55 calculated from Raman spectrum, and a high oxidation peak of 532.7 ℃ in oxygen atmosphere. The selective distribution of N heteroatoms on the surface of SNG affords the effective exposure of active sites at the interfaces of the electrode/electrolyte, so that more N heteroatoms are able to contact with oxygen feedstocks in oxygen reduction reaction or serve as polysulfide anchoring sites to retard the shuttle of polysulfides in a lithium–sulfur battery. This work opens a fresh viewpoint on the manipulation of active site distribution in a conductive scaffolds for multi-electron redox reaction based energy conversion and storage.

Advances in Measures of Reducing Chemical Pesticides to Control Plant Diseases

In order to provide the technological support for further implementing measures of reducing chemical pesticide to control plant diseases,the research progress on non-chemical pesticide measures to control plant diseases are reviewed from the aspects of agricultural control,botanical pesticide control and microbial pesticide control,and the development prospects are proposed,including accelerating innovative research on botani-cal pesticide control such as Chinese herb extracts,and screening microbial pesticides from valuable bio-control bacteria or plant endophyte metabolites for commercial production and utilization.

Regulating composition and structure of coal-based graphene and its electrochemical characteristics

Coal,a carbon-rich mineral with plentiful reserves,serves not only as a fuel but also as a raw material,presenting lower pollution emissions in the latter use.From a materials chemistry standpoint,coal is a viable raw material for graphene production.This study develops a promising and sustainable method to convert coal into graphene,leveraging its unique macromolecular aromatic struc-ture and high carbon content.The investigation includes an analysis of the lateral size,morphology,and chemical composition of coal-derived graphene using techniques such as X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,and op-tical microscopy.Results confirm that coal can effectively replace natural graphite flakes in graphene production,with the derived graphene featuring three to six exfoliated layers and an oxygen content below 5.5%.While the graphene from coal shares a similar morphology to that derived from graphite,it exhibits more structural defects.Interestingly,the macroscopic size of the coal does not influence the microscopic composition and structure of the graphene.However,the thermal reduction method for oxidized graphene proves more effective at repairing structural defects than chemical reduction.Employing coal-derived graphene as a supercapacitor electrode demonstrates excellent cycling stability and ultra-high capacitance storage capacity.The H-CG-325 shows the highest dis-charge area-specific capacitance across various current densities.At an increased current density of 10 A/g,the H-CG-325 maintains 80.6%of its initial capacitance of 79 F/g observed at 1 A/g.Electrochemical tests reveal that coal-based graphene holds significant potential as a supercapacitor material,indicating promising applications in energy storage and conversion.

Size control and its mechanism of SnAg nanoparticles

Sn3.5Ag （mass fraction, %） nanoparticles were synthesized by an improved chemical reduction method at room temperature. 1,10-phenanthroline and sodium borohydride were selected as the surfactant and reducing agent, respectively. It was found that no obvious oxidation of the synthesized nanoparticles was traced by X-ray diffraction. In addition, the results show that the density of primary particles decreases with decreasing the addition rate of the reducing agent. Moreover, the slight particle agglomeration and slow secondary particle growth can result in small-sized nanoparticles. Meanwhile, the effect of surfactant concentration on the particle size can effectively be controlled when the reducing agent is added into the precursor at an appropriate rate. In summary, the capping effect caused by the surfactant molecules coordinating with the nanoclusters will restrict the growth of the nanoparticles. The larger the mass ratio of the surfactant to the precursor is, the smaller the particle size is.

Characterization and Microstructure of PLZT RAINBOW Ceramics

A new type of large-displacement actuating materials called RAINBOW (Reduced and Internally Biased Oxide Wafer) ceramics is fabricated by a chemical reduction of PLZT piezoelectric ceramics. It is found that PLZT is easily reduced and the thickness of reduced layer has a linear relationship with the reduction time. The optimal conditions for producing RAINBOW samples from PLZT are determined to be 950℃ for 1-1.5 hours. SEM micrograph shows that the RAINBOW ceramics are composed of reduced and unreduced layer obviously. And the reduced layer is transgranularly fractured while the unreduced ceramic is intergranularly fractured. Metallic lead and refractor oxides (PbO, ZrO_2, ZrTiO_4, etc.) are found in the reduced layer by XRD analyses, however, the crystal structure of PLZT is not found. The analysis of the reduction mechanism is in good accordance with experimental data.