ELECTROCHEMICAL CODEPOSITION OF MOLYBDENUM AND SELENIUM

The electrodeposition of the Mo-Se thin films from sulfate solution containing Na2MoO4 and H2SeO3 was studied. The process of deposition were conducted under potentiostatic condition on copper electrode. The effect of different potential, pH and time of deposition were examined. The deposits were characterized by X-ray diffraction, X-ray fluorescence and scanning electron microscopy

The Mechanism of Phase Transfer Synthesis of Silver Nanoparticles Using a Fatty Amine as Extractant/Phase Transfer Agent

The paper presents the research results on synthesizing silver nanoparticles in aqueous solutions and their extraction into the organic phase. Studies have shown that it is best to perform the extraction process using n-hexane > cyclohexane > toluene > chloroform > ethyl acetate. The results show a correlation between the dielectric constant of the organic phase and its ability to extract nanoparticles. The lower the dielectric constant is, the higher the extractability. The hydrodynamic radius of the silver nanoparticles changes after transfer to the organic phase, depending greatly on the organic phase used. The extraction mechanism is complex and multi-step. As the first step, the Ag nanoparticles are transferred to the phase boundary. As the second step, the octadecylamine (ODA) molecules adsorb on the silver nanoparticles (AgNPs) surface. The change in particle shape was also noted. This suggests that the interfacial processes are more complex than previously reported. Below the initial concentration of ODA 2 × 10−4 M, the formation of a third phase has been observed. In a one-stage experiment, the concentration of silver nanoparticles after transferring to the organic phase was increased 500 times in about 10 s. The role of the concentration of ODA, therefore, is not only a measure of the extraction efficiency and productivity but functions as an enabler to maintain favorable biphasic processing, which underlines the role of the solvent again

The mechanism of phase transfer synthesis of silver nanoparticles using a fatty amine as extractant/phase transfer agent

The paper presents the research results on synthesizing silver nanoparticles in aqueous solutions and their extraction into the organic phase. Studies have shown that it is best to perform the extraction process using n-hexane > cyclohexane > toluene > chloroform > ethyl acetate. The results show a correlation between the dielectric constant of the organic phase and its ability to extract nanoparticles. The lower the dielectric constant is, the higher the extractability. The hydrodynamic radius of the silver nanoparticles changes after transfer to the organic phase, depending greatly on the organic phase used. The extraction mechanism is complex and multi-step. As the first step, the Ag nanoparticles are transferred to the phase boundary. As the second step, the octadecylamine (ODA) molecules adsorb on the silver nanoparticles (AgNPs) surface. The change in particle shape was also noted. This suggests that the interfacial processes are more complex than previously reported. Below the initial concentration of ODA 2 × 10−4 M, the formation of a third phase has been observed. In a one-stage experiment, the concentration of silver nanoparticles after transferring to the organic phase was increased 500 times in about 10 s. The role of the concentration of ODA, therefore, is not only a measure of the extraction efficiency and productivity but functions as an enabler to maintain favorable biphasic processing, which underlines the role of the solvent again

Influence of the Applied External Magnetic Field on the Deposition of Ni–Cu Alloys

Ni–Cu alloys are suitable candidates as catalysts in hydrogen evolution reaction. Because of the different magnetic properties of Ni and Cu, the influence of an applied external magnetic field on the synthesis Ni–Cu alloys was studied. The coatings were prepared with visible changes in their appearance. The differences between the observed regions were studied in terms of morphology and chemical composition. In addition, the overall chemical and phase compositions were determined using X-ray fluorescence and X-ray diffraction methods, respectively. The catalytic activity was measured in 1 M NaOH using linear sweep voltammetry. The contact angle was determined using contour analysis. All samples were hydrophilic. Hydrogen evolution started at different times depending on the area on the surface. It started earliest on the coating obtained in parallel to the electrode magnetic field at 250 mT. We found that when the Lorenz force is maximal, Cu deposition is preferred because of the enhancement of mass transport

Synthesis of Co–Fe 1D Nanocone Array Electrodes Using Aluminum Oxide Template

Porous anodic alumina oxide (AAO) obtained via two-step anodization is a material commonly used as a template for fabricating 1D nanostructures. In this work, copper and cobalt-iron 1D nanocones were obtained by an electrodeposition method using AAO templates. The templates were produced using two-step anodization in H2C2O4. The Co–Fe nanostructures are characterized by homogeneous pore distribution. The electrocatalytic activity of the produced nanomaterials was determined in 1 M NaOH using the linear sweep voltammetry (LSV) and chronopotentiometry (CP) methods. These materials can be used as catalysts in the water-splitting reaction. The sample’s active surface area was calculated and compared with bulk materials

The Mechanism of Phase Transfer Synthesis of Silver Nanoparticles Using a Fatty Amine as Extractant/Phase Transfer Agent

The paper presents the research results on synthesizing silver nanoparticles in aqueous solutions and their extraction into the organic phase. Studies have shown that it is best to perform the extraction process using n-hexane > cyclohexane > toluene > chloroform > ethyl acetate. The results show a correlation between the dielectric constant of the organic phase and its ability to extract nanoparticles. The lower the dielectric constant is, the higher the extractability. The hydrodynamic radius of the silver nanoparticles changes after transfer to the organic phase, depending greatly on the organic phase used. The extraction mechanism is complex and multi-step. As the first step, the Ag nanoparticles are transferred to the phase boundary. As the second step, the octadecylamine (ODA) molecules adsorb on the silver nanoparticles (AgNPs) surface. The change in particle shape was also noted. This suggests that the interfacial processes are more complex than previously reported. Below the initial concentration of ODA 2 × 10−4 M, the formation of a third phase has been observed. In a one-stage experiment, the concentration of silver nanoparticles after transferring to the organic phase was increased 500 times in about 10 s. The role of the concentration of ODA, therefore, is not only a measure of the extraction efficiency and productivity but functions as an enabler to maintain favorable biphasic processing, which underlines the role of the solvent again

Zero waste, Single Step Methods of Fabrication of Reduced Graphene Oxide Decorated with Gold Nanoparticles

This paper reports a novel approach to the use of carbon, in the form of reduced graphene oxide, as a reducing agent for Au(III) chloride complex ions. This approach allows fabrication of a composite material Au@GOr in a single-step process. The reduction of Au(III) complex ions was performed using high pressure, 50 bar, and high temperature, 250◦C, reactor. The average diameter of obtained gold nanoparticles was below 3 nm. The advantage of the reduced graphene oxide as the reducing agent is its high surface area. This accelerates the reaction rate significantly. The greenness and sustainability of the process are assessed by green chemistry metrics and circularity indicators recently applied for the first time to a nanomaterial synthesis. As a key green metrics, atom economy (AE) measures the degree of the incorporation of reactant atoms into the final product and in the case of the research presented scoring 99%

Ru–Co alloy coatings electrodeposited on a MAX phase substrate as efficient catalysts for the hydrogen evolution reaction

This study investigates the structure, electrochemical behavior and hydrogen evolution reaction (HER) performance of electrodeposited Ru–Co alloy coatings. The alloys were prepared from a 0.75 M Co2+ + 0.025 M Ru3+ solution at various potentials ranging from −0.5 to −1.2 V vs. SCE. Results reveal that the Ru and Co deposition processes are interdependent. The deposition of nobler Ru from the mixed metal solution reaches pure diffusion control already at −0.7 V compared to −1.0 V from a single Ru bath. On the other hand, Co deposition is significantly facilitated in the presence of Ru in the solution. Consequently, as the deposition potential changes from −0.6 to −1.0 V, Ru–Co solid solution coatings characterized by a distinct globular morphology are formed, with their Co content increasing from 22.1/7.4 to 70.2/86.1 wt% for the Cu/Ti2AlC MAX phase substrate applied. The alloy catalysts are found to show much better HER activity and stability in alkaline than in acidic solutions. The best Ru–Co@Ti2AlC sample, electrodeposited at −0.6 V, requires an overpotential of only −95 mV to deliver a current density of −100 mA cm−2 in 1 M KOH, thus outperforming most Ru–Co-based HER electrocatalysts reported to date

One-Step Synthesis of Pt–Pd@ACF Catalyst in the Microreactor System for the Hydrogen Evolution Reaction

Currently, new technologies for catalyst synthesis for the production of green energy are being sought. Platinum-based materials are of particular interest due to their unique catalytic properties. In this work, a one-step synthesis of a bimetallic Pt–Pd@ACF (ACF = activated carbon fibers) catalyst in the microreactor system was demonstrated. For this purpose, a glass microreactor was applied, and synthesized catalysts were analyzed using the following techniques: spectrophotometry, TEM, SEM, DLS, XRD, and MP-AES (microwave plasma atomic emission spectroscopy). The obtained results showed that the process of catalyst deposition on ACF as a catalyst carrier is more efficient in the microreactor system compared to the analogous process carried out in a batch reactor. Moreover, the composition of the catalyst can be slightly changed with the flow rate. It contained 32% of Pt and 68% of Pd for a flow rate of 5 mL/min and 33% of Pt and 67% of Pd for the lowest flow rate, i.e., 1 mL/min. While the amount of catalyst deposited on ACF can be adjusted by using the flow rate in the order from the lowest to the highest. The catalytic properties of the catalyst were tested for the hydrogen evolution reaction (HER). The catalytic performance of the synthesized material was directly related to its amount on the carbon surface. The highest catalytic activity was observed for the catalyst synthesized at a flow rate of 5.0 mL/min, and the registered current for HER achieved −25 mA at a potential of −0.28 V

Zero waste, single step methods of fabrication of reduced graphene oxide decorated with gold nanoparticles

This paper reports a novel approach to the use of carbon, in the form of reduced graphene oxide, as a reducing agent for Au(III) chloride complex ions. This approach allows fabrication of a composite material Au@GOr in a single-step process. The reduction of Au(III) complex ions was performed using high pressure, 50 bar, and high temperature, 250°C, reactor. The average diameter of obtained gold nanoparticles was below 3 nm. The advantage of the reduced graphene oxide as the reducing agent is its high surface area. This accelerates the reaction rate significantly. The greenness and sustainability of the process are assessed by green chemistry metrics and circularity indicators recently applied for the first time to a nanomaterial synthesis. As a key green metrics, atom economy (AE) measures the degree of the incorporation of reactant atoms into the final product and in the case of the research presented scoring 99%