Metal Ratio Research Articles

MOFs derived N doped CuNix@C dual metallic core-shell electrocatalysts for CO2 electrocatalytic reduction

Electroreduction CO2 to produce high-value-added multi-carbon products is an ideal way to mitigate the greenhouse effect. However, designing efficient, inexpensive electrocatalysts is a technical bottleneck. In this work, a series of CuNix @N-C core-shell catalysts were prepared by high-temperature carbonization method using MOF as a precursor. The selectivity of the multi-carbon products was optimized by adjusting the Cu and Ni metal ratio in the precursor. Besides, the outer layer of graphite promoted the adsorption capacity of CO2 and prevented the agglomeration of metal particles. As a result, CuNi2 @N-C exhibited superior electrocatalytic performance at − 0.97 V vs. RHE. The Faradaic efficiencies of ethanol and acetone were 27.38% and 25.96%, respectively. Moreover, the CuNi2 @N-C could operate stably for 10 h even at 200 mA·cm−2. This work provides an effective strategy for designing high performance Cu-based electrocatalysts.

Metal ratios as possible biomarkers for amyotrophic lateral sclerosis

Metal ratios as possible biomarkers for amyotrophic lateral sclerosis

The Use of Rapid Precipitation to Synthesise Multivariate UiO-66 Metal–Organic Frameworks for Photocatalysis

A rapid synthesis method is used to form multivariate metal–organic frameworks (MTV-MOFs) with the UiO-66 structure, where precipitation occurs upon mixing solutions of ligands and metal salts at temperatures less than 60 °C. The materials include mixtures of metals and ligands, Ce/Zr-UiO-66(1,4-NDC/BDC), Ce/Zr-UiO-66(1,4-NDC/2,6-NDC), Ce/Zr-UiO-66(1,4-NDC), Ce/Ti-UiO-66(1,4-NDC), and Ce/Ti-UiO-66(BDC-NH2) (NDC = naphthalene dicarboxylate, BDC = benzene-1,4-dicarboxylate, BDC-NH2 = 2-amino-benzene-1,4-dicarboxylate). Phase purity was determined by powder X-ray diffraction (PXRD), with a broadening of the profile indicative of nanoscale crystallites, verified by scanning electron microscopy (SEM). The molar ratio of metals and organic ligands in Ce/Zr-UiO-66(1,4-NDC/2,6-NDC) was confirmed by X-ray fluorescence (XRF) and solution 1H nuclear magnetic resonance (NMR) after digestion, respectively. Analysis of the adsorption of dyes by the MTV-MOFs showed that a pseudo-first-order model accounts for the kinetics. The effectiveness of photocatalytic degradation of two cationic (methylene blue and rhodamine B) and two anionic (Congo red and Alizarin Red S (AR)) dyes was studied under UV and visible light. The most effective photocatalytic degradation was found between 1 and 15 min towards both cationic and anionic dyes by Ce/Zr-UiO-66(1,4-NDC/2,6-NDC). Measurements of recyclability and photostability showed retention of crystallinity after five cycles of use and exposure to light for 17 h, as confirmed by PXRD.

Direct Synthesis of Mixed-Metal Paddle-Wheel Metal-Organic Frameworks with Controlled Metal Ratios under Ambient Conditions.

Currently, synthesizing mixed-metal metal-organic frameworks (MM-MOFs) in a single step remains a challenge due to the varying reactivities of different metal cations. This often results in the formation of mixtures of monometallic MOFs or MM-MOFs with nonstoichiometric metal ratios. A promising approach to overcoming this issue is the controlled precursor method, which uses prebuilt polynuclear complexes with structures similar to the secondary building units (SBUs) of the desired MOFs. In this study, we report that metal acetates can serve as natural prebuilt SBUs, enabling the controlled synthesis of MBDs ([M2(BDC)2DABCO]n, M = metal, BDC = 1,4-benzenedicarboxylic acid, DABCO = 1,4-diazabicyclo[2,2,2]octane) under ambient conditions. By exploiting the fact that metal acetates readily form soluble paddle-wheel dimers similar to the SBUs of MBDs, we achieve the direct synthesis of mixed-metal MBDs at room temperature. The metal ratios (Zn, Co, and Ni) in the resulting MBDs are controllable, and the production yields exceed 90%. The use of metal acetates facilitates the fast and uniform nucleation of MBDs, regardless of the metal cations involved. This similarity in nucleation rates leads to the formation of bimetallic and trimetallic MBDs with predefined metal ratios and homogeneous metal distribution while maintaining the quality of the MOFs. Importantly, this strategy offers an efficient pathway for synthesizing mixed metal MBDs using stoichiometric amounts of metal salts without toxic additives, high energy consumption, and complex synthesis steps.

Transient 3D hydrodynamic model of a blast furnace main trough

A transient 3D CFD model is solved to investigate the features of the complex flow in a blast furnace trough. Hot metal, slag, and air are considered as different phases of the flow. The influence of various taphole stream conditions on the hydrodynamics in the trough is examined, such as different slag-hot metal ratios, taphole diameters, and stream velocities. The special case of a dry trough during its first tapping is also addressed. Attention is devoted to the characterization of the wall shear stress, closely related to mechanical erosion, and to the evolution of the interfaces separating the fluid phases. Intricate flow patterns, characterized by large recirculations and return currents of both slag and hot metal, are observed. The simultaneous tapping of slag and hot metal leads to distinct flow features, deviating from the initial stage, when only hot metal is drained, as well as lower shear stress values, up to 31% less with increasing slag content in the taphole stream. Slag and hot metal levels in the trough evolve rapidly to quasi-steady states. Although the influence of the taphole stream velocity and diameter have a modest impact on the free surface dynamics, variations in the taphole slag fraction lead to significant fluctuations in the depth of slag and hot metal pools in the trough. The height of the slag-iron free surface can increase by up to 40% relative to its initial level, while the variation in the slag pool depth approaches 30%. These changes in the interface positions carry potential implications for refractory wear, as they suggest a substantial shift of the slag-hot metal line during each tapping.

Supervirial hot phase in Milky Way circumgalactic medium: further evidences

ABSTRACT Recent discoveries of a supervirial hot phase of the Milky Way circumgalactic medium (CGM) have launched new questions regarding the multiphase structure of the CGM around the Galaxy. We use 1.05 Ms of archival Chandra/high-energy transmission grating observations to characterize highly ionized metal absorption at z = 0 along the line of sight of the quasar NGC 3783. We detect two distinct temperature phases with T$_1 = 5.83^{+0.15}_{-0.07}$ K, warm–hot virial temperature, and T$_2=6.61^{+0.12}_{-0.06}$ K, hot supervirial temperature. The supervirial hot phase coexisting with the warm–hot virial phase has been detected in absorption along only two other sightlines and in one stacking analysis. There is scatter in temperature of the hot as well as warm–hot gas. Similar to previous observations, we detect supersolar abundance ratios of metals in the hot phase, with a Ne/O ratio 2σ above solar mixtures. These new detections continue the mystery of the mechanism behind the supervirial hot phase, but provide evidence that this is a true property of the CGM rather than an isolated observation. The supervirial CGM could hold the key to understanding the physical and chemical history of the Milky Way.

Synergistic effect of ZnMgAl-hydrotalcite nanomaterials electrocatalysts on high efficiency electrocatalytic reduction of CO2 to CO

The excessive consumption of fossil fuels causes the increasing concentration of carbon dioxide (CO2) in the atmosphere. How to convert CO2 into various organic compounds and chemical fuels to promote the carbon cycle has become a hot issue in the forefront of science and technology in the world. In this paper, ZnMgAl-hydrotalcite (ZnxMg3-xAl-LDH, x=0, 1, 1.5, 2, 3) with different molar ratios of Zn, Mg and Al was prepared by hydrothermal synthesis method. Research results indicate that Zn1.5Mg1.5Al1-LDH with a molar ratio of n(Zn2+): n(Mg2+): n(Al3+) =1.5:1.5:1 on the layer of hydrotalcite has more appropriate metal ratio and arrangement, leading to the strongest synergistic effect among metals and demonstrating relatively optimal electrochemical performance. The Faraday efficiency of CO (FECO) preparation by CO2RR was up to 91.8% (-1.4V vs. RHE), which control the consumption within 9hours to less than 15%. The spin polarization density functional theory (DFT) method was used for calculation and structural analysis with the help of DMol3 module of Materials Studio. The results show that Zn1.5Mg1.5Al1-LDH has the lowest energy barrier of various reactions, the theoretical calculation results are consistent with the experimental results. Zn1.5Mg1.5Al1-LDH designed in this work has good catalytic activity and can be used for efficient electrocatalytic CO2 reduction to produce CO, realizing the resource utilization of CO2, and helping to improve the environmental problems caused by excessive CO2 emission. It provides a promising strategy for the environmental sciences to mitigate the effects of CO2.

Flexible and sewable electrode based on Ni-Co@PANI-salphen composite-coated on textiles for wearable supercapacitor

Flexible electrodes with high deformability and energy density are critical for electronic textiles. The key factor for achieving high-performance supercapacitors with superior power and energy density is the evaluation of materials that exhibit exceptional capacitive performance. Herein, we have prepared Ni-Co nanoparticles at the surface of polyaniline-salphen (Ni-Co@PS). Then, followed by casting Ni-Co@PS on a conductive carbon cloth (CC) as a substrate through a facile in-situ polymerization strategy. The morphologies of Ni-Co@PS composite were characterized by different methods such as FE-SEM, XPS, XRD, BET, and electrochemical methods. This nanocomposite showed high tolerability and a large surface area with excellent behavior as a new nanomaterial for supercapacitor application. Thus, the optimum composite designed with a metal ratio (nickel–cobalt 3:1 w/w) satisfactorily possesses a specific capacitance of up to 549.994 C g−1 (1447.2 F g−1) under 0.5 A g−1 and long-term cyclic stability featuring capacity retention of 95.9% after 5000 cycles at a current density of 9.0 A g−1. The Ni-Co@PS-CC, is a material with great potential as an electrode in asymmetric wearable supercapacitor (AWSC) apparatus, demonstrating a remarkable specific capacity of 70.01, and accompanied by an energy density of 23.46 Wh k g−1 at a power density of 800 W k g−1.

Mechanical responses of architected boron carbide-aluminum lattice composites fabricated via reactive metallic infiltration of hierarchical pore structures

The incorporation of micro and nanoscale constituents in a hierarchical order improves mechanical properties of bulk structures while inducing controlled deformation. However, these features have seldomly been applied to the fabrication of cermet materials due to manufacturing constraints. Overcoming previous limitations, boron carbide cermets with embedded aluminum lattices were produced using a combination of additive manufacturing and gelcasting techniques. Kelvin cell and octet truss scaffolds were printed, cast and burned out so the negative volume could be infiltrated with metal to form an architected cermet. Computed microtomography scans reveal full aluminum infiltration of the volume with high fidelity to the target architecture. Equibiaxial flexural tests showed localized crack propagation in lattice-reinforced cermets and that samples with imbedded architecture required nearly double the energy for complete failure. Overall, the addition of an internal aluminum lattice limits abrupt fracture of the composite and provides a method for tuning its mechanical response with architected ratios of metal to ceramic.

Regiochemical Switching in Ir-Catalyzed C-H Borylation by Altering Ligand Loadings of N,B-Type Diboron Species.

Traditional reaction conditions in Ir-catalyzed C-H borylation consist of a 2:1 ligand to Ir metal ratio, affording C(sp2)-H borylation at the least sterically hindered position. We found that lowering the ligand to metal ratio of a N,B-type diboron (BB) preligand in respect to the IrI precatalyst to 0.5:1 affords the chelate controlled ortho product. Switching from steric-directed to chelate-directed products is shown for various substituted arenes and (hetero)arenes containing Lewis-basic functionalities. This work offers the first example of obtaining complementary regioisomers as the major product by altering the ligand loading in CHB.

Fabrication and mechanism of La/Al bimetallic organic frameworks for phosphate removal

Lanthanum (La) is constantly used in phosphorus removal due to its high affinity with phosphate. Herein, a novel La/Al bimetallic organic framework was developed to improve the usage efficiency of La species. The effects of metal ratio, pH value and competitive anions were investigated, through which the adsorption mechanism was further explained. Results showed that when the doped La:Al ratio was 1:3, the absorbent (La1Al3-BTC) achieved the most excellent adsorption capacity of 210.3 mg P·g−1 and usage efficiency (P/metal ratio = 1.09). La1Al3-BTC can adapt to the wide pH range and multitudinous coexisting ions in real water, and its adsorption process was in accordance with Langmuir and pseudo-second-order models. Surface morphology of materials transformed from rod-like crystal to amorphous structure as the increase of Al doping. La replaced some Al atoms and embedded in Al-BTC skeleton. The specific surface area raised from 9.27 m2·g−1 of La-BTC to 257.01 m2·g−1 of La1Al3-BTC. The main mechanism for the adsorption of phosphate was the inner-sphere complexation occurred in the La active sites. Electron migration between different metals enhanced the adsorption process. Density-function theory (DFT) calculation well matched the experimental phenomenon. Overall, the development of La1Al3-BTC presented new potential applications for enhanced phosphorus removal and provided new insights for the design of La-based adsorbents.

Thermal plasma-driven looping for metal scrap processing with hydrogen

In the present research, a novel process was proposed and assessed using an equilibrium thermochemical modelling study to evaluate the performance of a combined disruptive technology of thermal plasma and thermochemical looping to utilise hydrogen for iron reduction processing. The study was aimed at conducting a high-level power performance assessment of the process by integrating a built-in power block with a focus on a novel equilibrium thermal plasma technology for reducing iron scrap particles. The effect of thermal plasma operating parameters such as temperature (1000 °C < T < 1800 °C) and hydrogen-to-iron ratio in the feed stream to the thermal plasma reactor (0 < H2/metal < 20) on the performance of the system was numerically investigated using Aspen coupled with Matlab. Also, the self-sustaining factor was evaluated coupled with a quantitative analysis of the sustainability and lifecycle of the process aiming at better understanding the impact of the proposed system on the environment. Results showed that the system is crucially sensitive to the ratio of H2/metal such that the overall power demand of the reactor can change in a way that the dominant regime of the plasma can change from endothermic (partial reduction of iron) to exothermic (complete reduction, combustion of iron) once the hydrogen to metal ratio exceeds ∼ 2.5. It was also identified that an increase in the temperature of the combustor decreased the power demand for the thermal plasma reactor. Similarly, with increasing the temperature, a ramp-up in the self-sustaining factor was observed reaching 0.8 showing that 80 % of the energy of the auxiliaries can be maintained using the built-in heat recovery and power block. The thermal efficiency of the system was also a strong function of the H2/metal ratio reaching ∼ 0.4 at the H2/metal ratio of ∼ 2.5 reflecting the fact that the proposed process efficiency is within the state-of-the-art power production systems. The sustainability assessments showed that the process offers a high circular economy capability of the process with above-the-average lifetime and Material Circularity Indicator values.

Enhanced photodegradation of 3-nitro-1, 2, 4-triazol-5-one by FeCuO bimetallic catalyst supported on mesoporous carbon nitride

3-Nitro-1,2,4-triazol-5-one (NTO) is one high energy and insensitive single explosive that has been applied in insensitive ammunition in recent years. However, the high deposition of NTO after detonation and the challenge of wasterwater treatment during its productive process are the key concerns of the environmental issue and safe manufacture. The catalytic performance of the traditional Fe-based catalysts for the decontaminating wastewater owing to the high stability of the triazole ring of NTO. To address this problem, FeCuO/mpg-C3N4 was prepared by depositing Fe-Cu oxides on mesoporous carbon nitride (mpg-C3N4) as the catalysts of photo Fenton process. After optimizing the metal ratio and screening the reaction condition, FeCuO/mpg-C3N4(5:5, 6%) exhibited the unprecedent k value of 0.10669 min−1 (96.4% degradation after 30 min) in the photo degradation of NTO (λ > 400 nm; 1000 mg/L FeCuO/mpg-C3N4; 40 mg/L NTO) and maintained high catalytic activity after 2 cycles (k1 =0.09491 min−1, k2 =0.08607 min−1). By characterizing thoroughly the catalysts, the synergetic effect of Fe-Cu bimetallic oxide and the contribution of the carbon nitride in the photo Fenton process have been evidenced, which presents an efficient, environmentally friendly, and cost-effective approach for treating NTO wastewater, offering a novel method and concept for addressing other challenging-to-degrade organic pollutant wastewaters.

Oxidation behavior of novel ultra-high temperature hafnium-zirconium carbonitrides: Effect of nitrogen and metal ratios

In this work, the effect of nitrogen and the Hf/Zr ratio on the oxidation resistance of hafnium-zirconium carbides and carbonitrides have been investigated. According to thermogravimetric investigations, carbonitride samples containing 50 and 20 at% Zr exhibit the smallest weight gains of 15.5 and 11.5 %, respectively. The isothermal exposure of the samples at 1200 °C revealed that the incorporation of nitrogen into the lattice of hafnium-zirconium carbides results in a decrease in the oxidation rate by 2–3.5 times, depending on the Zr content. The hafnium-zirconium carbonitride (Hf0.8Zr0.2)C0.5N0.3 has shown to possess the highest level of oxidation resistance.

Heavy Metals in Urban Soils of the Volga Federal District: a Conjugate Analysis of Official Data

Based on a conjugated analysis of the official data of Roshydromet on the content of priority heavy metals (Cd, Pb, Zn, Cu, Ni) in the soils of 23 cities of the Volga Federal District, as well as Rosstat data on the socio-economic indicators of these settlements, the ecological and geochemical characteristics of urbanozems (Urbic Technosols) and with the help of multivariate statistical analyzes (cluster and factorial), possible relationships between soil pollution parameters and urban features of cities were revealed. For the soils of most cities in the region with average socioeconomic indicators, admissible levels of accumulation of Cd, Pb, Zn, and Cu have been established, which, in terms of concentrations, are close to the average abundance of urban soils in Russia. In small and medium-sized cities of the Republic of Bashkortostan, exceedances of APC Ni in soils are recorded, which reflects the presence of a regional geochemical anomaly of natural and anthropogenic nature in the eastern part of the Volga Federal District, but no correlations between nickel pollution and socio-economic indicators of settlements are revealed. The moderately hazardous level of complex pollution in urbanozems with dominant accumulation of Cd and significantly lower concentration ratios of other heavy metals (Belebey, Davlekanovo, Dzerzhinsk) shows no correlation with the demographic indicators of settlements. The more complex profile of soil pollution (Cd–Zn in Penza or Cu–Cd–Zn in Mednogorsk) shows lower values of the total fertility rate and higher values of the mortality rate (compared with the average regional indicators). In general, using the example of the cities of the Volga Federal District, it is shown that the gradients of increasing concentrations in soils of Cd, Pb, Zn, Cu and the total pollution index Zc are codirectional with an increase in the general mortality rate of the population.

Prospects of Using Ruthenium within the Composition of Three-Way Palladium–Rhodium Catalysts

The possibility of using ruthenium within the composition of palladium-rhodium catalysts used to neutralize the exhaust gases of vehicles with gasoline engines was investigated. Thermolysis of the supported precursor in oxidizing and reducing media leads to the formation of samples with different initial catalytic activity. Stability of trimetallic systems is compared under conditions of prompt thermal aging with reference samples of similar chemical composition, but obtained by mechanical mixing of monometallic catalysts. The obtained results allow one to conclude that the alloy nanoparticles are more stable, and the thermolysis of the precursor in the reducing medium contributes to a higher initial activity of the catalyst in the oxidation of CO. According to the X-ray photoelectron spectroscopy method, the high thermal stability of trimetallic catalysts is due to the constant ratio of metals on the surface of the support during the catalytic reaction.

Effect of metal ratios on oxygen evolution reaction activity in binary hydroxide electrocatalysts

Effect of metal ratios on oxygen evolution reaction activity in binary hydroxide electrocatalysts

Molybdenum-Ruthenium-Carbon Solid-Solution Alloy Nanoparticles: Can They Be Pseudo-Technetium Carbide?

Technetium (Tc), atomic number 43, is an element that humans cannot freely use even in the 21st century because Tc is radioactive and has no stable isotope. In this report, we present molybdenum-ruthenium-carbon solid-solution alloy (MoxRu1-xCy) nanoparticles (NPs) that are expected to have an electronic structure similar to that of technetium carbide (TcCy). MoxRu1-xCy NPs were synthesized by annealing under a helium/hydrogen atmosphere following thermal decomposition of metal precursors. The obtained NPs had a solid-solution structure in the whole composition range. MoxRu1-xCy with a cubic structure (down to 30 atom % Mo in the metal ratio) showed a superconducting state, and the transition temperature (Tc) increased with increasing Mo composition. The continuous change in Tc across that of TcCy indicates the continuous control of the electronic structure by solid-solution alloying, leading to pseudo-TcCy. Density functional theory calculations indicated that the synthesized Mo0.53Ru0.47C0.41 has a similar electronic structure to TcC0.41.

Efficiently catalyzing photo-oxidation of water by surface engineering of bismuth vanadate with nickel molybdenum oxide coverages

Bismuth vanadate with suitable band edges is one of the efficient photocatalysts for water oxidation. Establishing heterojunction can improve electron diffusion lengths and photocatalytic ability of BiVO4. In this work, nickel molybdenum oxide (Ni–Mo–O) and BiVO4 heterojunction is established by the hydrothermal process with different nickel to molybdenum precursor ratios. The Ni–Mo–O/BiVO4 electrode is applied as photoanodes for water oxidation. The growth mechanism of Ni–Mo–O on BiVO4 surface is proposed. The Ni–Mo–O deposition amount is optimized regarding to light absorbance and charger transportation. The largest photocurrent density of 1.72 mA/cm2 at 1.23 VRHE is obtained for the optimal NiMoO4/BiVO4 electrode (NM12) in the electrolyte without hole scavenger, while the pure BiVO4 electrode only shows a photocurrent density of 0.90 mA/cm2. The NM12 electrode even presented an impressive photocurrent density of 5.39 mA/cm2 at 1.23 VRHE in the electrolyte with the hole scavenger, owing to the abundant active sites and higher light absorbance as well as the favorable synergistic effects from its suitable Ni to Mo ratio. The NM12 electrode also shows excellent long-term stability with the photocurrent retention of 83% after illumination for 6500 s. This work opens a blueprint for establishing a novel heterojunction with the adjustable metal ratio and coverage on BiVO4.

Mixed matrix membrane based on PEBAX® filled with layered double hydroxides

The effect of incorporating layered double hydroxide (LDH) nanoparticles containing different molar ratios of metals on the thermal, mechanical, and gas permeation properties of membranes based on PEBAX® was evaluated. The three nanoparticles were synthesized using molar x-ratios (x = Al/(Mg + Al)) equal to 0.20, 0.25 and 0.33. The dispersed nanoparticles changed thermal resistance, improved mechanical properties and CO2/CH4 separation performance of MMM when compared to the membranes of neat PEBAX®. The addition of 2 % of LDH in PEBAX® 1657 promoted an increase of about 17 % in the elastic modulus and 10 % in the stress at break. The best result of permeation tests (1657–0.33–5 % MMM at 0.5 bar), shows increase CO2 permeability by 44 % and CO2/CH4 selectivity by 115 % as compared to the neat material. Gas permeation results showed that LDH with more anions favors the facilitated transport of CO2.