The Electrocatalytic Performance of Rare Earth Ion Doped Co_(0.2)Ni_(0.8)-MOF-74 Catalyst for Nitrogen Reduction

We took Co_(0.2)Ni_(0.8)-MOF-74 with bimetallic synergistic effect as the basic material,and selected rare earth ions Ho,Gd,and Er with ion radii close to Co and Ni as the research objects for doping.The influence of rare earth ion doping amount and doping type on the eNRR performance of the catalyst was explored.The experimental results show that the ammonia yield rate and Faraday efficiency doped with Co_(0.2)Ni_(0.8)-MOF-0.5Ho are the highest,reaching 1.28×10^(-10)mol·s^(-1)·cm^(-2)/39.8%,which is higher than the1.12×10^(-10)mol·s^(-1)·cm^(-2)/32.2%of Co_(0.2)Ni_(0.8)-MOF-74,and is about 14.3%/23.7%higher than that without doping,respectively.And the stability of Co_(0.2)Ni_(0.8)-MOF-0.5 Ho is good(after 80 hours of continuous testing,the current density did not significantly decrease).This is mainly due to doping,which gives Co_(0.2)Ni_(0.8)-MOF-74 a larger specific surface area and catalytic active sites.The catalyst doped at the same time has more metal cation centers,which increases the electron density of the metal centers and enhances the corresponding eNRR performance.

Transition Metal Oxides/Chalcogenides for Electrochemical Oxygen Reduction into Hydrogen Peroxides

Electrochemical oxygen reduction reaction via the two-electron pathway(2e-ORR)is becoming a promising and sustainable approach to producing hydrogen peroxide(H_(2)O2)without significant carbon footprints.To achieve better performance,most of the recent progress and investigations have focused on developing novel carbon-based electrocatalysts.Nevertheless,the sophisticated preparations,decreased selectivity and undefined active sites of carbon-based catalysts have been generally acknowledged and criticized.To this end,transition metal oxides and chalcogenides have increasingly emerged for 2e-ORR,due to their catalytic stability and tunable microstructure.Here,the development of metal oxides and chalcogenides for O2-to-H_(2)O2 conversion is prospectively reviewed.By summarizing previous theoretical and experimental efforts,their diversity and outstanding catalytic activity are firstly provided.Meanwhile,the topological and chemical factors influencing 2e-ORR selectivity of the metal oxides/chalcogenides are systematically elucidated,including morphology,phase structures,doping and defects engineering.Thus,emphasizing the influence on the binding of ORR intermediates,the active sites and the underlying mechanism is highlighted.Finally,future opportunities and challenges in designing metal oxides/chalcogenides-based catalysts for H_(2)O2 electro-synthesis are outlined.The present review provides insights and fundamentals of metal oxides/chalcogenides as 2e-ORR catalysts,promoting their practical application in the energy-related industry.

Recovery of valuable metals from spent lithium ion batteries by smelting reduction process based on FeO-SiO_2-Al_2O_3 slag system

NA novel smelting reduction process based on FeO-SiO2-Al2O3 slag system for spent lithium ion batteries with Al cans was developed, while using copper slag as the only slag former. The feasibility of the process and the mechanism of copper loss in slag were investigated. 98.83% Co, 98.39% Ni and 93.57% Cu were recovered under the optimum conditions of slag former/battery mass ratio of 4.0：1, smelting temperature of 1723 K, and smelting mass ratio of time of 30 min. The FeO-SiO2-Al2O3 slag system for the smelting process is appropriate under the conditions of m（FeO）：m（SiO2）=0.58：1？1.03：1, and 17.19%？21.52% Al2O3 content. The obtained alloy was mainly composed of Fe-Co-Cu-Ni solid solution including small amounts of matte. The obtained slag mainly consisted of fayalite and hercynite. Meanwhile, the mechanism of copper loss is the mechanical entrainment from strip-like fayalite particles in the main form of copper sulfide and metallic copper.

Electrochemical reduction process of Co(Ⅱ) in citrate solution

Effects of citrate concentration and pH on the electrochemical reduction process of Co（Ⅱ） were investigated by cyclic voltammetry（CV） and electrochemical impedance spectroscopy（EIS）. The results show that Co（Ⅱ） is reduced into two species which are free Co2＋ and [Co（C6H607）] in the solution composed of 0.05 mol/L CoS04·5H2O, 0.20 mol/L Na2SO4 and 0-0.40 mol/L C6H5O7Na3·2H2O in the pH range of 3-9. The reduction behavior depends on the pH of the solution. Co（H） is mainly reduced into the form of free Co^2＋ at pH 3 and into the form of [Co（C6H6O7）] at the pH range of 4-6 in citrate solution. The [Co（C6H6O7）] is first reduced to an intermediate state and then to Co°. Adsorption of the intermediate state exists on the surface of the electrode. Co（Ⅱ） is difficult to be reduced in the solution with the pH above 7, because the existing Co（Ⅱ）-citrate complex species [Co（C6H5O7）]- and [Co（C6H4O7）]2- are more difficult to be reduced than the hydrogen ion.

Fe-Beta zeolite for selective catalytic reduction of NO_x with NH_3:Influence of Fe content

Fe doped Beta zeolite with different Fe contents were prepared by ion exchange by changing the volume or the concentration of a Fe salt solution. For a particular mass of Fe salt precursor, the concentration of the metal salt solution during ion exchange influenced the ion exchange capacity of Fe, and resulted in different activities of the Fe-Beta catalyst. Fe-Beta catalysts with the Fe contents of （2.6, 6.3 and 9） wt% were synthesized using different amounts of 0.02 mol/L Fe salt solution. These catalysts were studied by various characterization techniques and their NH3-SCR activities were evaluated. The Fe-Beta catalyst with the Fe content of 6.3 wt% exhibited the highest activity, with a temperature range of 202-616℃ where the NOx conversion was 〉 80%. The Fe content in Beta zeolite did not influence the structure of Beta zeolite and valence state of Fe. Compared with the Fe-Beta catalysts with low Fe content （2.6 wt%）, Fe-Beta catalysts with 6.3 wt% Fe content possessed more isolated Fe3. active sites which led to its higher NH3-SCR activity. A high capacity for NH3 and NO adsorption, and a high activity for NO oxidation also contributed to the high NH3-SCR activity of the Fe-Beta catalyst with 6.3 wt%. However, when the Fe content was further increased to 9.0 wt%, the amount of FexOy nanoparticles increased while the amount of isolated Fe3＋ active sites was unchanged, which promoted NH3 oxidation and decreased the NH3-SCR activity at high temperature.

Effect of Fe(Ⅲ) on the bromate reduction by humic substances in aqueous solution

Humic substances are ubiquitous redox-active organic compounds of environment. In this study, experiments were conducted to determine the reduction capacity of humic acid in the man-ix of bromate and Fe（Ⅲ） solutions and the role of Fe（Ⅲ） in this redox process. The results showed that the humic acid regenerated Fe（Ⅱ） and reduced bromate abiotically. The addition of Fe（Ⅲ） could accelerate the bromate reduction rate by forming humic acid-Fe（Ⅲ） complexes. Iron species acts as electron mediator and catalyst for the bromate reduction by humic acid, in which humic acid transfers electrons to the complexed Fe（Ⅲ） to form Fe（Ⅱ）, and the regenerated Fe（Ⅱ） donate the electrons to bromate. The kinetics study on bromate reduction further indicated that bromate reduction by humic acid-Fe（Ⅲ） complexes is pH dependent. The rate decreased by 2-fold with the increase in solution pH by one unit. The reduction capacity of Aldrich humic acid was observed to be lower than that of humic acid or natural organic matter of Suwanne River, indicating that such redox process is expected to occur in the environment.

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.

Mineral sulphide-lime reactions and effect of CaO/C mole ratio during carbothermic reduction of complex mineral sulphides

Mineral sulphide （MS）-lime （CaO） ion exchange reactions （MS ＋ CaO = MO ＋ CaS） and the effect of CaO/C mole ratio during carbothermic reduction （MS ＋ CaO ＋ C = M ＋ CaS ＋ CO（g）） were investigated for complex froth flotation mineral sulphide concentrates. Phases in the partially and fully reacted samples were characterised by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The primary phases during mineral sulphide-lime ion exchange reactions are Fe304, CaSO4 Cu2S, and CaS. A complex liquid phase of Ca2CuFeO3S forms during mineral sulphide-lime exchange reactions above 1173 K. The formation mechanisms of Ca2CuFeO3S liquid phase are determined by characterising the partially reacted samples. The reduction rate and extent of mineral sulphides in the presence of CaO and C increase with the increase in CaO/C ratio. The metallic phases are surrounded by the CaS rich phase at CaO/C 〉 1, but the metallic phases and CaS are found as separate phases at CaO/C 〈 1. Experimental results show that the stoichiometric ratio of carbon should be slightly higher than that of CaO. The reactions between CaO and gangue minerals （SiO2 and A1203） are only observed at CaO/C 〉 1 and the reacted samples are excessively sintered.

REDUCTION OF FERRIC IRON IN THE TITANIUM SULFATE SOLUTION BY THE ION EXCHANGE MEMBRANE PRIMARY CELL METHOD

In the production process of titanium dioxide with sulfuric acid, the contamination of the titanium sulfate solution (the ilmenite leaching solution) in the Fe 3+ reduction stage by iron scraps is a practical problem because it is difficult to guarantee the quality of the iron scraps. In this research, a new method, called the ion exchange membrane primary cell method, for reduction of Fe 3+ in the titanium sulfate solution has been advanced. The positive compartment of the primary cell consists of lead (copper) electrode and the titanium sulfate solution, and the negative compartment consists of iron electrode and acidic FeSO 4 solution. The anion ion exchange membrane is used as the diaphragm between two compartments. Fe 3+ in the titanium sulfate solution is reduced by the electric discharge of the primary cell. The effects of temperature, stirring strength of the solution and membrane area on the reduction rate have been investigated. The experimental result shows that the optimum current density can be higher than 100 A/m 2.

Electrochemical reduction mechanism of Zn^(2+)in molten NaCl-KCl eutectic

A process comprising selective chlorination and molten salt electrolysis was proposed to develop an efficient and environmental-friendly technology for zinc recovery from metallurgical dusts.The theoretical feasibility of this technology was firstly estimated based on thermodynamic fundamentals.Subsequently,the electrochemical behavior of Zn^(2+)on tungsten electrode was investigated in molten NaCl-KCl eutectic at 973 K by many electrochemical transient methods.The results showed that the reduction of Zn^(2+)on tungsten electrode was found to be a one-step process exchanging two electrons with the initial reduction potential of-0.74 V(vs Ag/AgCl),and the electrode process was considered as quasi-reversible and controlled by diffusion.The diffusion coefficient of Zn^(2+)ions in the melts was determined in the order of 10^(-5)cm^(2)/s.Finally,the electrolytic preparation of zinc was carried out by potentiostatic electrolysis in molten NaCl-KCl-ZnCl_(2)eutectic at-1.6 V(vs Ag/AgCl).Spheroidic granular metal with silver-white luster was attained after electrolysis for 9.5 h,and identified as pure Zn.The present study confirms that it is practically feasible to extract pure zinc metal by direct electrolysis of ZnCl_(2)in molten NaCl-KCl eutectic,and provides a valuable theoretical reference for the efficient recovery of zinc from metallurgical dusts.

Electroactive species study in the electrochemical reduction of CO_2 in KHCO_3 solution at elevated temperature

Photoelectrochemical and electrochemical reduction of CO_2 into organic chemicals is promising for directly or indirectly transforming solar energy into chemical energy for further utilization. However,research on the electroactive species in these processes has been rather limited. In this work, we investigated possible electroactive species(CO_2 or HCO_3~– ) involved in the electrochemical reduction of KHCO_3 at elevated temperatures without CO_2 bubbling. The results showed that CO, CH_4, and C_2H_4 were produced after electrochemical reduction of 3.0 mol/L KHCO_3 at elevated temperature on a Cu electrode even without CO_2 bubbling, although their faradaic efficiencies were low(< 6 %). Measurements for CO_2 generation from the decomposition of HCO_3~– showed that elevated temperature and high HCO_3~– concentration strongly promoted this process. These results suggested that the in-situ produced CO_2 from the decomposition of HCO_3~– was probably the electroactive species in the electrochemical reduction of HCO_3~– without CO_2 bubbling. Changes of the Gibbs free energy, rate constant, and activation energy of the decomposition of HCO_3~– into CO_2 were also investigated and calculated from the experimental data.

Evaluation of H2 Influence on the Evolution Mechanism of NOx Storage and Reduction over Pt–Ba–Ce/c-Al2O3 Catalysts

In this investigation, Pt–Ba–Ce/c-Al2O3 catalysts were prepared by incipient wetness impregnation and experiments were performed to evaluate the influence of H2 on the evolution mechanism of nitrogen oxides (NOx) storage and reduction (NSR). The physical and chemical properties of the Pt–Ba–Ce/c- Al2O3 catalysts were studied using a combination of characterization techniques, which showed that PtOx, CeO2, and BaCO3, whose peaks were observed in X-ray diffraction (XRD) spectra, dispersed well on the c-Al2O3, as shown by transmission electron microscope (TEM), and that the difference between Ce3+ and Ce4+, as detected by X-ray photoelectron spectroscopy (XPS), facilitated the migration of active oxygen over the catalyst. In the process of a complete NSR experiment, the NOx storage capability was greatly enhanced in the temperature range of 250–350℃, and reached a maximum value of 315.3μmol·gcat^-1 at 350℃, which was ascribed to the increase in NO2 yield. In a lean and rich cycling experiment, the results showed that NOx storage efficiency and conversion were increased when the time of H2 exposure (i.e., 30, 45, and 60 s) was extended. The maximum NOx conversion of the catalyst reached 83.5% when the duration of the lean and rich phases was 240 and 60 s, respectively. The results revealed that increasing the content of H2 by an appropriate amount was favorable to the NSR mechanism due to increased decomposition of nitrate or nitrite, and the refreshing of trapping sites for the next cycle of NSR.

Response Surface Optimization for Process Parameters of LiFePO_4/C Preparation by Carbothermal Reduction Technology

A statistically based optimization strategy is used to optimize the carbothermal reduction technology for the synthesis of LiFePO4/C using LiOH,FePO4 and sucrose as raw materials.The experimental data for fitting the response are collected by the central composite rotatable design(CCD).A second order model for the discharge ca-pacity of LiFePO4/C is expressed as a function of sintering temperature,sintering time and carbon content.The ef-fects of individual variables and their interactions are studied by a statistical analysis(ANOVA).The results show that the linear effects and the quadratic effects of sintering temperature,carbon content and the interactions among these variables are statistically significant,while those effects of sintering time are insignificant.Response surface plots for spatial representation of the model illustrate that the discharge capacity depends on sintering temperature and carbon content more than sintering time.The model obtained gives the optimized reaction parameters of sinter-ing temperature at 652.0 ℃,carbon content of 34.33 g?mol-1 and 8.48 h sintering time,corresponding to a dis-charge capacity of 150.8 mA·h·g-1.The confirmatory test with these optimum parameters gives the discharge ca-pacity of 147.2 and 105.1 mA·h·g-1 at 0.5 and 5 C,respectively.

Reduction behaviors of iron ore lump and pellets with H_2 -CO gas

The differences of reduction behaviors between iron ore lump and pellets were studied by conducting low temperature reduction degradation, static load reduction and droplet tests. These tests simulated the conditions of reduction temperature and hydrogen-containing gas in COREX. Due to its dense structure and low porosity compared with pellets, lump ore possesses poor reduction degradation index （RDI） and slower reduction rate in early and medium reaction stages ,showing signs of lower strength, lower softening and melting temperatures, as well as a wider melting zone and higher AP. That provides some basis to explain the phenomena of differential pressure rise,metallization decline and more sticking after the usage of lump ore in COREX plant.

Thermodynamic studies on gas-based reduction of vanadium titano-magnetite pellets

Numerous studies have focused on the reduction thermodynamics of ordinary iron ore;by contrast, the literature contains few thermodynamic studies on the gas-based reduction of vanadium titano-magnetite (VTM) in mixed atmospheres of H2, CO, H2O, CO2, and N2. In this paper, thermodynamic studies on the reduction of oxidized VTM pellets were systematically conducted in an atmosphere of a C–H–O system as a reducing agent. The results indicate that VTM of an equivalent valence state is more difficult to reduce than ordinary iron ore. A reduction equilibrium diagram using the C–H–O system as a reducing agent was obtained;it clearly describes the reduction process. Experiments were performed to investigate the effects of the reduction temperature, the gas composition, and two types of iron ores on the reduction of oxidized VTM pellets. The results show that the final reduction degree increases with increasing reduction temperature, increasing molar ratio of H2/(H2 + CO), and decreasing H2O, CO2, and N2 contents. In addition, the reduction processes under various conditions are discussed. All of the results of the reduction experiments are consistent with those of theoretical thermodynamic analysis. This study is expected to provide valuable thermodynamic theory on the industrial applications of VTM.

Fabrication of hierarchical ZnIn2S4@CNO nanosheets for photocatalytic hydrogen production and CO2 photoreduction

Photocatalytic H2 production and CO2 reduction have attracted considerable attention for clean energy development.In this work,we designed an efficient photocatalyst by integrating lamellar oxygen-doped carbon nitride(CNO)nanosheets into ZnIn2S4(ZIS)microflowers by a one-step hydrothermal method.A well-fitted 2D hierarchical hybrid heterostructure was fabricated.Under visible light irradiation,the ZIS@CNO composite with 40 wt%CNO(ZC 40%)showed the highest hydrogen evolution rate from water(188.4μmol·h-1),which was approximately 2.1 times higher than those of CNO and ZIS(88.6 and 90.2μmol·h-1,respectively).Furthermore,the selective CO production rates of ZC 40%(12.69μmol·h-1)were 2.2 and 14.0 times higher than those of ZIS(5.85μmol·h-1)and CNO(0.91μmol·h-1),respectively,and the CH4 production rate of ZC 40%was 1.18μmol·h-1.This enhanced photocatalytic activity of CNO@ZIS is due mainly to the formation of a heterostructure that can promote the transfer of photoinduced electrons and holes between CNO and ZIS,thereby efficiently avoiding recombination of electron-hole pairs.

CATHODIC REDUCTION OF METAL-CHLORIDE COORDINATION IONS

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Effect of Hydrogen Reduction of Silver Ions on the Performance and Structure of New Solid Polymer Electrolyte PEI/Pebax2533/AgBF4 Composite Membranes

In this paper, the effect of hydrogen reduction of silver ions on the performance and structure of new solid polymer electrolyte polyetherimide （PEI）/Pebax2533 （Polynylonl2/tetramethylene oxide block copolymer, PA12-PTMO）/AgBF4 composite membranes is investigated. For PEI/Pebax2533/AgBF4 composite membranesprepared with dillerent AgBF4 concentration, the permeances of propylene and ethylene increase with the increase of AgBF4 concentration due to the carrier-facilitated transport, resulting in a high selectivity. But for propyl- ene/propane mixture, the mixed-gas selectivity is lower than its ideal selectivity. The hydrogen reduction strongly influences the membrane performance, which causes the decrease of propylene permeance and the increase of pro-pane permeance. With the increase of hydrogen reduction time, the membranes show a clearly color change from white to brown, yielding a great selectivity loss. The data of X-ray diffraction and FT-IR prove that silver ions are reduced to Ago after hydrogen reduction, and aggregated on the surface of PEI/Pebax2533/AgBF4 composite mem- branes.

Drag reduction and shear resistance properties of ionomer and hydrogen bond systems based on lauryl methacrylate

Based on molecular dynamics simulation results, a lauryl methacrylate polymer with drag reduction and shear resistance properties was designed, and synthesized by emulsion polymerization using 2-vinyl pyridine and methyl methacrylate as the polar polymerization monomer. After ionization of lauryl methacrylate polymer, an ion-dipole interaction based drag reduction agent （DRA） was obtained. The existence of ion-dipole interaction was proven through characterization of the drag-reducing agent from its infrared （IR） spectrum. The pilot-scale reaction yield of the DRA under optimum conditions was investigated, and the drag reduction and shear resistance properties were measured. The results show that： l） The ion-dipole or hydrogen bonding interaction can form ladder-shaped chains, therefore the synthesized DRA has shear resistance properties; 2） The larger the molecular weight （MW） and more concentrated the distribution of MW, the better the drag reduction efficiency and the performance of the ionomer system was superior to that of the hydrogen bonding system; 3） With increasing shear frequency, the drag-reduction rates of both the DRAs decreased, and the drag reduction rate of the ionomer system decreased more slowly than of the corresponding hydrogen bonding system. From the point of view of drag reduction rate and shear resistance property, the ionomer system is more promising than the hydrogen bonding system

Electroreduction of Samarium Ion on Co and CuCathodes in Molten Chloride

The cyclic voltammetry was used to study the electrochemical reaction of Sm(III) in NaCl-KCl equimolar mixture on the Co and Cu cathodes. It is reasonable to presume that the reduction of Sm(III) to Sm(II) was realized on Co and Cu electrodes respectively at first step. Sm(II) was subject to the reduction and formed alloys with Co and Cu on the electrode surface.