Formation Of Metal Oxides Research Articles

Spectroscopic characterization and XRD of some new metal complexes with dithranol in presence of 8-hydroxyquinoline

IN THE PRESENT work, dithranol (Dithr) reacts with Ni(II), Zn(II), Zr(IV), La(III), and Th(IV) in presence of heterocyclic ligand 8-hydroxyquinoline (8HQ) in acetone forming new mixed ligand complexes. The structures of the synthesized complexes were characterized by conventional techniques including melting point, molar conductivity, magnetic properties, elemental analyses, infrared, ultraviolet-visible, 1H nuclear magnetic resonance, and X-ray powder diffraction (XRD) spectra, as well as thermogravimetric (TG) and differential thermogravimetric (DTG) analyses. The molar conductance values of the metal complexes in dimethyl sulphoxide (DMSO) indicated that the complexes were found to be electrolytes with different ratios. The magnetic susceptibility measurements for Ni(II) complex is 3.1 BM with distorted octahedral geometry. TG/DTG studies confirmed the chemical formula for these complexes and established the thermal decomposition processes ended with the formation of metal oxide contaminated with carbon atom. The infrared spectra of the complexes showed shift for ν(O-H) and ν(C=N) in all complexes, which indicated the coordination of oxygen atom of phenolic group and nitrogen atom of pyridine ring of 8HQ with metal ions. X-ray powder diffraction analysis of the compounds showed that Dithr, 8HQ, and their metal complexes display crystalline peaks except Zr(IV) and La(III) complexes.

Surface and bulk phase analysis of the tribolayer of nanocrystalline diamond films sliding against steel balls

Low friction coefficient of nanocrystalline diamond (NCD) films deposited on steel alloys was observed in high-vacuum at high-temperature (HV HT) tribological conditions. High wear resistance of the film was observed in high-vacuum at room temperature (HV RT) condition. However, high friction and low wear resistance of the films were measured in ambient atmosphere at room temperature (AA RT) conditions and this was associated to the formation of metal-oxide (Fe2O3 and Fe3O4) layer in the sliding interfaces. Micro-Raman spectra of wear tracks of deformed films and ball scars showed the formation of a carbonaceous bulk tribolayer and this was the main reason for the improved frictional properties in the HV HT conditions. Bulk form of such tribolayer was absent on the ball scar in AA RT condition. The Fe2O3 peak was absent in HV HT which could be one of the important reasons for the low friction coefficient in this conditions. A comprehensive analysis of X-ray photoelectron spectroscopy showed limited oxidation of NCD films and the elimination of contaminated surface layer in HV HT condition which was correlated as a major cause for low friction.

Activity calculation and phase transformation predication for heavy metals with slag activity calculation model during using electroplating sludge in production of bricks

Electroplating sludge is usually regarded as the hazardous waste because of the considerable amount of heavy metals. The vitrification process or firing clay bricks mixing of electroplating sludge is an alternative way to disposal it. The reaction behaviors of heavy metals in electroplating sludge at high temperature are closely associated with the leachability of heavy metals from fired products. In this work, an available thermodynamic model, slag activity calculation model, was used to examine the reaction behaviors and predicate the phase transformation of heavy metals under different conditions. CaO would preferably combine with SiO2 and form CaSiO3 at 1100–1500 K. Most of Cr, Zn and Cu would exist in a form of oxides and spinel phases. Cr would be preferably incorporated into ZnO·Cr2O3 and CaO·Cr2O3 rather than CuO·Cr2O3 except metal oxide; Zn would be preferably incorporated into ZnO·Cr2O3 and ZnO·Fe2O3 rather than 2ZuO·SiO2 and ZnO·Al2O3; Cu would be preferably incorporated into CuO·Al2O3 and CuO·Fe2O3 rather than CuO·Cr2O3. Elevating the basicity facilitated Zn to transform into ZnO·Al2O3, ZnO·Fe2O3 and CuO·Fe2O3, while hindered Zn and Cu being incorporating into 2ZnO·SiO2 and CuO·Cr2O3. Increasing the amount of Fe2O3 in system suppressed the formation of heavy metal oxides (i.e. Cr2O3, ZnO and CuO) and spinel species containing Cr, while promoted the formation of spinel species containing Fe, especially for ZnO·Fe2O3 and CuO·Fe2O3. This work can provide some useful information for reaction behaviors and phase transformation of heavy metals during heating solid waste containing heavy metals.

Atmospheric-pressure plasma oxidation of aluminum for large-area electronics

We developed an atmospheric pressure plasma (APP) process for forming metal oxides and self-assembled monolayers (SAMs) without a vacuum process. SAMs are frequently utilized for surface modification. In particular, a combination of aluminum oxide (AlOx) and alkylphosphonic acid is used as the gate dielectric in flexible electronics, with a low operating voltage of 2 V because of its simple fabrication process at room temperature in air. However, when using a combination of SAMs and AlOx as the gate dielectric, it is necessary to form a metal oxide with sufficient thickness using a vacuum plasma process to reduce the leakage current, which is not suitable for use in flexible large-area electronics. In this study, we resolved this problem by utilizing an APP process and substrate heating instead of the vacuum plasma process. Heating a substrate above 100 °C forms a sufficient AlOx layer. The leakage current of plasma-processed AlOx with SAMs was reduced by three orders of magnitude compared to that of natural AlOx with SAMs. X-ray photoelectron spectroscopy revealed a time dependence of the thickness of AlOx. An exposure time of 100 s was sufficient to form an AlOx layer with a thickness of 4 nm. An organic transistor with this APP treatment of AlOx and SAMs showed a mobility of 1.4 cm2/V s and an on/off ratio of 104 within 2 V. We also fabricated an inverter and a ring oscillator circuit with an inverter gain of more than 300 and an oscillation frequency of 40 Hz.

ELECTROCHEMICAL SYNTHESIS OF POROUS CRYSTALLINE TANTAL OXIDE

Self-organization of nanoscale structures during electrochemical processing is most pronounced during the formation of porous anodic metal oxides (aluminum, titanium, tungsten, niobium, tantalum). These oxides contain arrays oriented perpendicular to the pore substrate. A distinctive feature of these films is a high degree of orderliness in the arrangement of pores and the possibility of controlled variation of the pore diameter in a wide range (from 10 to 150 nm). In this work, the features of the electrochemical formation of nanoporous oxide coatings on tantalum in acid-fluoride and organic electrolytes are investigated. Tantalum foil with a thickness of 0.1 mm and a purity of 99.99 % was used as a working electrode. For the formation of tantalum oxides, 1 M H2SO4 solutions with the addition of HF (0.1 M; 0.25 M; 0.5 M; 1 M) and an organic electrolyte were used: EG + 5.5 М H2O + 0.05 М H3PO4 + 0.8 М NH4F, EG + 5.5 М H2O + 0.05 М H3PO4 + 0.8 М NaF. Polarization studies were carried out on a P-45X potentiostat. in potentiodynamic mode. The reference electrode is saturated silver chloride. The magnitudes of the potentials are given relative to the normal hydrogen electrode. The morphology of the obtained coatings was studied using scanning electron microscopy using a JSM-7001F microscope. It is shown that the use of fluoride ion activator and electrolytes of different nature allows at the initial stage of anodizing to provide conditions for the formation of a crystalline anodic oxide film with different surface morphology. By varying the anodizing regime on tantalum, it is possible to synthesize porous films of amorphous or crystalline types. To obtain a crystalline porous oxide of tantalum with a developed surface, it is advisable to use an organic aprotic electrolyte composition: EG + 5.5 М H2O + 0.05 М H3PO4 + 0.8 М NH4F.

Synthesis, structural characterization, and thermal properties of monomeric (Mn, Co, Ni, and Zn) and polymeric (Cd) complexes of thiocyanates with benzyl carbazate as an ancillary ligand

Five complexes [M(NCS)2(bc)2] M = Mn (1), Co (2), Ni (3), Zn (4), and [Cd(NCS)2(bc)]n (5), (bc) = benzyl carbazate (benzyl hydrazinecarboxylate), have been synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structures of all five complexes have been confirmed by X-ray structural analysis. These results confirm that 1–4 are isotypes, and all four are centrosymmetric, with two mutually trans N,O chelating (bc) ligands in equatorial positions and a pair of trans-thiocyanate anions in the axial positions. The cadmium complex (5) is a coordination polymer. The asymmetric unit contains a square planar CdN2OS core, in which the (bc) ligand adopts an N, O bidentate coordination mode together with N and S bound thiocyanato anions. Polymer expansion increases the coordination number to six with the N and S bound thiocyanate ligands linking two adjacent complexes. This expansion results in double layers of cadmium octahedra propagating along the c axis direction. The thermal analyses of these compounds show endothermic decomposition processes to give respective metal thiocyanates as intermediates. For the Mn, Co, Ni, and Zn compounds these intermediates decompose exothermically to form metal oxides, whereas the Cd complex forms cadmium sulfide as the end product.

Pd-based Catalysts by Colloid Synthesis Using Different Reducing Reagents for Complete Oxidation of Methane

Here, without using any organic stabilizer, via two-steps process, Pd-based catalysts supported on La-modified Al2O3 by a new colloid synthesis method using different reducing reagents were prepared. It was found that the reducibility and structure of reducer controlled the rate of nucleation and growth of Pd in its precursor solution supported on the modified Al2O3. The surface OH groups of alumina can stabilize the formed Pd nanoparticles and enhance Pd dispersion. The catalyst obtained by using the mild reducing reagent, ethylene glycol, had the highest dispersion (32.6%) and largest active metal surface area. This catalyst showed the best catalytic performance among the five as-synthesized catalysts for removing pollutants in a simulated natural gas vehicles (NGVs) exhaust. Compare to its counterpart by common impregnation method, the light-off temperature over the catalyst by colloid synthesis method can be significantly decreased by 39 °C for CH4 and 27 °C for NO, respectively. The study may provide a general method to control the formation of metal (oxide) nanoparticles for heterogeneous catalysis, especially for emission abatement of NGVs.

Innovative N2-selective metallic membranes for the potential use of CO2 capture

The permeability of nitrogen in Group V metal membranes having an approximate thickness of 40 μm was determined for the first time at conditions of relatively low temperature (400–600 °C) and pressure (300–600 kPa). Vanadium, niobium and tantalum membranes were investigated to evaluate the permeation characteristics towards nitrogen permeation. Analogous to the hydrogen transport mechanism through palladium-based membranes, the nitrogen permeating flux through the metallic membranes was determined to take place through a solution-diffusion mechanism. In particular, at 400 °C, the nitrogen permeability was found to be 1.15 × 10-12, 1.05 × 10-12, and 6.54 × 10-13 mol/(m s Pa0.5) for vanadium, niobium and tantalum, respectively.The optimal nitrogen partial pressure exponent value was found to be 0.5 for all the membranes investigated. The nitrogen permeability for the vanadium membrane was described by an Arrhenius-type relation where the pre-exponential factor and apparent activation energy for this correlation were 3.55 × 10-15 mol/(m s Pa0.5) and 31.8 kJ/mol, respectively. For niobium and tantalum membranes, it was not possible to perform any permeation tests due to cracks, which formed at temperatures higher than 500 °C.SEM and EDS analyses revealed the formation of metal oxides on the surface of V, Nb, Ta membranes, which may benefit the transport of nitrogen through the membrane as it may aid in preserving the structured nature of the bulk phase thereby preventing the formation of defects and/or grain migration at high temperature. Although the nitrogen permeability through metallic membranes is low and metal oxides form on the surface, this work describes the performance of metallic membranes toward nitrogen permeation, and it can be considered as the benchmark for future work related to this field.

High temperature oxidation behavior of thermally sprayed alumina—titania coatings on nickel based superalloys

In this paper, high temperature oxidation behavior has been studied on thermally sprayed nickel based superalloys. Alumina—titania powder was deposited on Hastelloy and Inconel 718 using atmospheric plasma spray process. Investigations were carried out at 1000 °C for fifty hours under cyclic process. From the experimental results, the corrosion kinetics has been calculated from mass change per unit area. The tested samples were subjected to metallurgical characterization studies using SEM, EDS and XRD analysis. It has been confirmed that the presence of iron has highly influenced in the formation of metal oxide (FeO) scale on exposed surface with nickel and chromium. The repeated thermal cycle has influenced iron oxide to spall thermal coatings on prolonged exposure. It was due to the intermediate oxide scale that has grown between the coatings and substrate on Inconel 718. The metallurgical reactions were studied and reported in detail.

Crystallization, non-isothermal kinetics and structural analysis of nanocrystalline multiferroic bismuth ferrite (BiFeO3) synthesized by combustion method

The synthesis of bismuth ferrite (BiFeO3) in the nanocrystalline form is described in the present work with the help of self-combustion technique with DL-malic acid as fuel to obtain single-phase BiFeO3 nanopowders. The crystallization behavior for the formation of BiFeO3 was confirmed from the obtained powder diffraction pattern (p-XRD) and thermogravimetric analysis with simultaneous differential thermal analysis. Thermal measurements were carried out in the nitrogen atmosphere to determine the crystallization kinetics through various heating rates from simultaneous thermogravimetric–differential thermal (TG–DTA) analysis curve. The activation energies for the formation of BiFeO3 metal oxides formation were found to be around 124 kJ mol−1 and 113 kJ mol−1 from the phenomenological Johnson–Mehl–Avrami equation or in short JMA. The growth mechanism along three dimensions was observed for all heating rates. The formation of single-phase BFO in nanocrystalline nature was confirmed through microstructural investigations by the use of transmission electron microscopic analysis. The selected area electron diffraction pattern of nanostructure bismuth ferrite for the sample calcinated at 800 °C reveals the diffraction miller indices planes {104} and doublet peaks of {110}, {202} which is in good agreement with that of the present powder XRD pattern. The magnetization for the synthesized samples calcinated indicates that there exists the magnetic order and existence of room-temperature magnetic saturation for the multiferroic BiFeO3.

THE EFFECT OF CRUDE OILS ON THE METALLIC CORROSION AND THE STABILITY OF METALS IN A CORROSIVE ENVIRONMENT

Crude oil is a supreme earth resource that essential in most of industrial applications while having some adverse effects in the crude oil refining process regarding metals such as the corrosion. According to the general definition usually the corrosion is the formation of metal oxides, sulfides, hydroxides or any compound related with carboxylic group. In the environment of crude oils the corrosion is highly depended on the sulfur, organic acids, mercaptans and salts composed in crude oils and also the chemical compositions of such metals. In the current research it was expected to investigate the relative effects of corrosive properties on the rate of corrosion in seven selected types of metals which are frequently used in the Sri Lankan crude oil refining industry and the stability of those metals against the effect of both Murban and Das Blend crude oils regarding the composition and properties. Corrosive properties of both crude oils were determined using in order to XRF analyzer, titration methods and salt analyzer also the chemical compositions of each metal was determined by XRF detector. Batches of equal sized metal coupons from seven types of metal were dipped in crude oils separately and their corrosion rates were determined after 15, 30 and 45 days while observing through an optical microscope. The metallic concentration in each crude oil sample was tested by AAS. The initial and the hardness after the corrosion were tested in each metal coupon. According to the observed results Das Blend was ahead regarding sulfur content, mercaptans content and acidity even though higher corrosion rates were shown by four types of metals in Murban than the corrosion rate in Das Blend. The slight reductions in the hardness were found in each metal coupon and some significant metallic concentrations were found in both crude oils regarding some metals forever. Article DOI: https://dx.doi.org/10.20319/mijst.2019.51.5972 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Doping Effect of Indium on Zinc-tin Oxide Thin-Film Transistor Using Electrohydrodynamic Jet Spray Technology

The effect of indium doping on zinc-tin oxide thin-film transistor was investigated using electrohydrodynamic (EHD) jet spray technology. EHD jet spray is a new and unique drop-on-demand patterning technology for printed electronics. After optimizing process parameters, the EHD jet spraying conditions were determined to be a voltage of 4.5 kV, a syringe speed of 0.032 μm/s, spraying time of 10 s, and a substrate temperature of 50 ℃. Indium doping increased metal-oxide formation in the thin-film, as confirmed by XPS. In addition, improved TFT electrical properties were obtained compared with non-doped TFTs by using EHD jet spray. A 0.1 M In-doped ZTO TFT showed a mobility of 7.40 cm2/V s, a threshold voltage of -3.4 V, an on-to-off current ratio of 1.87 × 106, and a sub-threshold slope of 1.2 V/dec. Improved hysteresis behavior of the TFT was also achieved by indium doping. Key words: EHD jet, spray, ZTO TFT, Indium doping

High-performance low voltage operation of indium zinc tin oxide thin film transistors using chemically derived sodium β-alumina dielectric

We present high performance, low voltage (≤ 3 V) operation of thin film transistors (TFTs) with indium zinc tin oxide (IZTO: In4Sn4ZnO15)-semiconductor. The film of IZTO was fabricated via low-temperature (200 °C) solution combustion processing without incorporating an external fuel. As 2-methoxyethanol is a widely used organic solvent due to its high dissolution capability, serve the purpose of both the solvent and the fuel. On quantification from the balanced redox reaction, 0.3% of 2-methoxyethanol assisted for the action of fuel and helped in the formation of metal oxide, and the rest (99.7%) served the purpose of being dissolution medium. The balanced redox chemistry yielded a significant fraction of (56.5%) metal oxide at 200 °C confirmed via high-resolution oxygen 1s spectrum. Further, the chemically derived thin film of sodium β-alumina with a dielectric constant of ~ 21, while annealing at 350 °C incorporated in the TFT for the realization of low voltage operation. The performance assessment is systematically carried out both silicon dioxide (SiO2) and sodium β-alumina and found that the TFTs with SiO2 and IZTO exhibited a saturation mobility (µsat), Ion/Ioff ratio and the threshold voltage (Vth) of 0.50 ± 0.02 cm2 V−1 s−1, 1.25 × 104 and 6.6 ± 0.79 V respectively. While changing the dielectric to sodium β-alumina presented a µsat, Ion/Ioff ratio and Vth of 4.21 ± 0.18 cm2 V−1 s−1, 1.4 × 102 and 0.47 ± 0.08 V respectively.

Structural characterization, thermal investigation and biological activity of metal complexes containing Schiff Base ligand (Z)‐3‐(1‐((4,6‐dimethyl‐1H‐pyrazolo[3,4‐b] pyridin‐3‐yl)imino)ethyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one

A new series of metal complexes containing Co(II), Pd(II), Fe(III) chloride and Cu(II) salts (chloride, bromide, sulphate and perchlorate) have been prepared with Schiff base ligand (HL). The synthesized compounds were elucidated using elemental analyses, spectral techniques, molar conductance, magnetic measurements and thermogravimetric studies. The analytical data established (1 M:1 L) stoichiometry for complexes (1), (2), (4), (6) and (7) as well as (1 M:2 L) and (2 M:3 L) stoichiometry for complexes (5) and (3), respectively. As a result, the ligand HL coordinates in complexes (1), (2), (4), (6) as a monobasic tridentate ONN moiety via the oxygen atom of the deprotonated phenolic OH, the nitrogen atoms of the azomethine and the imine group in pyrazolopyridine ring. While, it behaves as a neutral bidentate in complexes (3,7), chelates via oxygen and nitrogen atoms of enolic OH and azomethine groups. Also, in complex (5) Cu2+ ion binds via NO sits of two ligand molecules in its monobasic and neutral forms. The magnetic moment and electronic spectral data proposed octahedral structure for complexes (2, 3 and 7) as well as triagonal bipyramidal and square pyramidal geometry for complexes (1 and 4), while, chelates (5) and (6) possess square planar geometry. TG/DTG studies confirmed the chemical formula for these complexes and established the thermal decomposition processes ended with the formation of metal or metal oxides contaminated with carbon residue. An axial electron spin resonance spectra were suggested for Cu(II) complexes pointing to 2B1g as a ground state with hyperfine structure for complex (4). In vitro antibacterial and antioxidant activities were performed for HL ligand and its metal complexes. The biological studies indicate that complex (3) has better antibacterial activity compared to the ligand and the other complexes.

Fabrication and characterization of inverted organic PTB7:PC70BM solar cells using Hf-In-ZnO as electron transport layer

In this study, we report the use of Hafnium-Indium-Zinc-Oxide (HIZO) as electron transport layer (ETL) in inverted organic solar cells (iOSCs) using a bulk heterojunction of Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) as active layer. The absorption spectrum and performance parameters obtained are compared to those obtained for similar iOSCs where the ETL was poly [(9,9-bis (30- (N,N-dimethylamino) propyl) -2,7-fluorene) -alt-2,7- (9,9-dioctylfluorene)] (PFN). Initially, devices showed the S-shaped current–voltage curve that has been modeled using a three-diode equivalent circuit model. This phenomenon can be removed by repeating electrical sweep-cycles under illumination. The degradation under nitrogen atmosphere and under encapsulation was also analyzed and compared with the degradation of the iOSCs using PFN. It was observed that the degradation of encapsulated HIZO-iOSC was twice slower than that of PFN-iOSCs. This increase in stability can be attributed to the Hf atoms, which have a stronger thermodynamic tendency to form metal oxides, suppressing the dissociation of HIZO.

Basics of the Metallic Corrosion in Crude Oils

Corrosion is an often-used term regarding the ferrous metals also the general phenomenon of the formation of metal oxides, sulfides, hydroxides or any certain compound on the metal surface itself. There were found the effect of corrosive compounds in crude oils on the metallic corrosion in most of researches up to certain stage. In the current research it was expected to speculate the effect of sulfur, mercaptans, organic acids and salts in both Murban and Das Blend crude oils on the corrosion rates of seven different types of ferrous metals and variations of the hardness of such metals. The corrosive properties of both crude oils were determined by the standard methods and instruments. The chemical compositions of metals were detected by XRF detector. A batch of similar sized metal coupons was prepared, and those metal coupons were immersed in both crude oils separately. The rates of corrosion of those metal coupons were determined by the weight loss method after 15, 30 and 45 days from the immersion also both initial hardness and hardness after corroded of each metal coupon were tested by Vicker’s hardness tester. The corroded surfaces were observed by the optical microscope also the ferrous concentration and copper concentration of each crude oil sample were measured by the atomic absorption spectroscopy (AAS) after exposed to metals. There were found relatively lower corrosion rates from stainless steels than other metals, higher corrosion rates of four types of metals in Murban crude oil although it was composed lower amount of sulfur, mercaptans, organic acids and higher amount of salts than Das Blend, higher ferrous concentrations in crude oil samples which were exposed to carbon steels than other crude oil samples whereas high concentrations of copper in crude oil samples relevant to the Monel metal and eventually it was a slight reduction of the initial hardness of each metal coupon due to the corrosion.

Facile Green Synthesis of SnO2 NPs Using Vitex altissima (L.) Leaves Extracts: Characterization and Evaluation of Antibacterial and Anticancer Properties

An eco-friendly approach is introduced for the synthesis of SnO2 nanoparticles using the Vitex altissima L. plant extract. Bioinspired mediated synthesis of nanoparticles have been suggested as a very simple, inexpensive, non-toxic and environmental manner. The presence of biomolecules in V. altissima induced the metal salts to form metal oxides. The prepared SnO2 NPs were characterized by XRD, UV–Vis, FT-IR, SEM and TEM Techniques. The PXRD patterns revealed that SnO2 nanoparticles exhibits tetragonal structure and its average crystallite size of SnO2 NPs is found in the range of ~ 10 to 20 nm. The UV–visible absorption spectrum of SnO2 nanoparticles showed absorption band at 257 nm and its band gap was found to be 4.18 eV. FTIR spectrum of green synthesized SnO2 NPs shows the band at 534.22 cm−1 which indicates O–Sn–O stretching vibration modes. The morphological features of SnO2 nanoparticles were fundamentally dependent up on concentration of V. altissima leaves extract. Green synthesized SnO2 nanoparticles exhibit significant antibacterial activity against pathogenic bacterial strains by agar well diffusion method. Furthermore, the SnO2 NPs shows significant cytotoxic effect on MCF-7 cancerous cell line. This result indicates that, V. altissima leaves extract acts as a reducing agent for the formations of SnO2 NPs with effective biological properties.

Cyclic voltammetry growth and characterization of Sn-Ag alloys of different nanomorphologies and compositions for efficient hydrogen evolution in alkaline solutions.

Electrodeposition of silver, tin and their alloys from different aqueous electrolytes suffer from various environmental issues and deposits are affected by H2 evolution and metal oxide formation. In this work, these metals and their alloys are electrodeposited by cyclic voltammetry utilizing ionic liquids based on C5H14ClNO (choline chloride) that permits deposit properties control. Both Ag and Sn concentrations in the ionic liquid were varied from 0.01 to 0.15 mol L−1. Methionine effect on the reduction potential of Sn and Ag was studied. Different techniques were applied to explore the structures, morphologies, and electrochemical (EC) activities of the deposits. A single Ag3Sn phase with orthorhombic packed structure was observed for all alloys, whereas the preferred growth orientation was varied from (202) to (112) depending on Ag%. Also, the dislocation density is decreased by increasing Ag content. EDX spectra showed only Ag and Sn signals indicating the high purity of the Sn–Ag alloys. The deposit from Sn-rich liquid showed rougher and larger agglomerates at the surface than that formed from the Ag-rich liquids with or without methionine. The electrochemical activities of the deposits toward the H2 evolution reaction (HER) were investigated through electrochemical polarization (ECP) measurements and EC impedance spectroscopies (EISs). The Sn–Ag alloys possess higher performance, as a catalyst for HER using alkaline solution, than Ag or Sn electrodes. The highest rate of HER was recorded for Sn–35% Ag and Sn–97% Ag deposits, which correlated strongly to the microstructure and surface morphology. The ECP results were confirmed by EIS investigations. The measured impedance values are close-fitting to a hypothetical model for the electrode/electrolyte interface.

Characterization and adsorptive behaviour of snail shell-rice husk (SS-RH) calcined particles (CPs) towards cationic dye

In this study, a low-cost composite adsorbent was prepared from snail shell and rice husk (SS-RH) through calcination for brilliant green dye (BGD) adsorption from aqueous solution. Six two-parameter and three three-parameter isotherm models were used to fit the experimental data by both linear and non-linear regression methods using ten error functions. Linear and non-linear regression analysis coupled with linear and non-linear fit error functions all revealed Langmuir and Sip as two- and three-parameter isotherm models well-fitted for BGD uptake from aqueous solution using calcined particles (CPs) of SS-RH. Chi-square (χ2) error function proved to be the best applicable predictive error function for the two-parameter isotherm study while sum of absolute error (EABS), hybrid functional error (HYBRID) and normalized standard deviation (NSD) are the best error functions for non-linear Redlich-Peterson, Sips and Toth three-parameter isotherm models respectively. Irregular surface texture was observed for the calcined particles of SS-RH as revealed by SEM with BGD filling the opening pores after adsorption. FTIR revealed shift in spectrum broad peaks after adsorption. EDS exhibited active mixed metal oxides formation before adsorption with the observance of weight percent change after adsorption.

Carbon supported PdM (M = Fe, Co) electrocatalysts for formic acid oxidation. Influence of the Fe and Co precursors

Pd and PdM (M = Fe or Co) nanostructured electrocatalysts were synthesized by the impregnation method and supported on carbon black Vulcan XC-72R for the formic acid oxidation reaction, FAOR, in acid medium. Nitrates or chlorides were used as Fe and Co precursors to study the counter ion role on the physicochemical features and electrochemical performance of the electrocatalysts. TEM analysis showed that PdM was deposited on the carbon material with a particle size around 2–3 nm. From XRD, peaks associated with the fcc palladium planes were observed along with evidence of PdM alloy formation, particularly when the nitrate salts were used as metal precursors. Furthermore, XPS analyses indicated that nitrates promote the metal oxide formation to a greater extent than chlorides, mainly for Pd. PdCo electrocatalyst obtained from nitrates exhibited the highest performance for FAOR with a steady state current density of 451 and 313 μA cm−2 at 200 and 400 mV respectively, which is in both cases, 3 times larger than that developed for a commercial Pd/C catalyst.