Robabeh Bagheri

Nanolayered manganese oxides: insights from inorganic electrochemistry

Nanolayered Mn oxides are among the important Mn-based catalysts for water oxidation. Mn(II), (III) and (IV) ions are present in the structure, and, thus, the electrochemistry of the solid is very complicated. Herein, the cyclic voltammetry of nanolayered Mn oxides in the presence of LiClO4 at pH = 6.3, under different conditions, was studied using scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy, X-ray diffraction and visible spectroelectrochemistry. The scan rates, calcination temperatures and the range of the cyclic voltammetry have very important effects on the electrochemistry of nanolayered Mn oxides. The effect of the use of D2O instead of H2O on the electrochemistry of nanolayered Mn oxides was also considered. Such nanolayered Mn oxides were reported as water-oxidizing catalysts in the presence of cerium(IV) ammonium nitrate. As a next step, we studied the cyclic voltammetry of nanolayered Mn oxides under acidic conditions and in the presence of cerium(IV) ammonium nitrate.

Corrosion Protection Properties of PPy-ND Composite Coating: Sonoelectrochemical Synthesis and Design of Experiment

AbstractIn this research, the nanocomposite coatings comprising the polypyrrole-nanodiamond, PPy-ND, on St-12 steel electrodes were electro-synthesized using in situ polymerization process under ultrasonic irradiation. The corrosion protection performance and morphology characterization of prepared coatings were investigated by electrochemical methods and scanning electron microscopy, SEM, respectively. Also, the experimental design was employed to determine the best values considering the effective parameters such as the concentration of nanoparticles, the applied current density and synthesis time to achieve the most protective films. A response surface methodology, RSM, involving a central composite design, CCD, was applied to the modeling and optimization of the PPy-ND nanocomposite deposition. Pareto graphic analysis of the parameters indicated that the applied current density and some of the interactions were effective on the response. The electrochemical results proved that the embedment of diamond nanoparticle, DNP, improves the corrosion resistance of PPy coatings significantly. Therefore, desirable correlation exists between predicted data and experimental results.

Nanosized silver bromide: an efficient catalyst for alcohol oxidation in the presence of a multinuclear silver complex

Upon investigating a silver-based complex for the alcohol oxidation reaction, we found AgBr as a new and efficient catalyst for the reaction in the presence of oxone (2KHSO5·KHSO4·K2SO4). The catalyst was characterized by scanning electron microscopy, energy dispersive spectrometry, transmission electron microscopy, dynamic light scattering, X-ray diffraction, chronoamperometry, X-ray photoelectron spectroscopy, and liquid chromatography-electrospray ionization mass spectrometry. We propose that nanosized silver bromide can be used as a catalyst for the oxidation of alcohol to aldehyde in the presence of oxone (2KHSO5·KHSO4·K2SO4) as an oxidant.

Template free growth of robustly stable nanophotonic structures: broadband light superabsorbers

Producing stable ultra-wideband light absorbers by a simple method is challenging for various applications such as solar energy harvesting, thermal regulation and suppression of stray light. Nanostructured refractory materials possess exceptional features enabling them to manipulate incident photons at the subwavelength scale and withstand against severe conditions. Here, we report a sputtering technique-based route to fabricate robustly stable TiAlN black absorbing coatings with a vertically aligned columnar structure, as a unique approach to produce large area metamaterials. The fabrication process is simple, free of any sophisticated patterning approach, substrate-independent, viable and scalable. Robust stability in adverse environments is an exceptional feature of these superabsorbers. Broadband (200–2500 nm) absorption of 89% is achieved from a single TiAlN layer and is increased to 95% after grading with thin anti-reflecting layers. The proposed sputtering based fabrication process would open a new platform to design, prepare and integrate nanophotonic structures, having applications in energy, electronic and optical sectors.

Water oxidation by a manganese-potassium cluster: Mn oxide as a kinetically dominant “true” catalyst for water oxidation

Nature uses an Mn cluster for water oxidation, and thus, water oxidation using Mn clusters is interesting when used in artificial water-splitting systems. An important question is whether an Mn cluster is a true catalyst for water oxidation or not. Herein, an Mn–K cluster was investigated for electrochemical water oxidation to find the true and the kinetically dominant catalyst using X-ray absorption spectroscopy, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electrochemical methods. The experiments showed that conversion into nanosized Mn oxide occurred for the cluster, and the nanosized Mn oxides are the true catalyst for water oxidation.

The application of a nickel(II) Schiff base complex in water oxidation: the importance of nanosized materials

Herein, the role of Ni oxide in the electrocatalytic water oxidation of a nickel(II) Schiff base (N,N′-bis (salicylidene)ethylenediamino nickel(II)) is investigated using scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, nuclear magnetic resonance spectroscopy, extended X-ray absorption fine structure, X-ray absorption near edge structure, chronoamperometry, electrochemical methods and theoretical calculations. Although Ni oxide does not have a pure, simple and crystalline structure, the experiments showed that Ni oxide at a pH of 11 is a water-oxidizing catalyst on the surface of a fluorine-doped tin oxide electrode. At pH 3 or 7, no clear water oxidation or NiOx formation was detected. Below this low pH, a solid with high carbon content was detected, which is not a water-oxidizing catalyst. A metal oxide-based mechanism for water oxidation in the presence of a metal complex has not been considered using theoretical calculations. Herein, our theoretical calculations indicated that after the oxidation of the Ni(II) complex, all Ni equatorial bonds in the oxidation state of III were weakened. This effect may cause the decomposition of the intermediate to NiOx. This study could be very promising for the design and synthesis of new, efficient and stable catalysts.

Pomegranate (Punica granatum) Peel Extract as a Green Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution

The inhibition effect of pomegranate peel extract (PPE) on the corrosion of mild steel in hydrochloric acid (HCl) solution was investigated. The polarization, mass loss, and electrochemical impendence techniques were used to evaluate the corrosion inhibition performance of the pomegranate peel extract. The results revealed that PPE acts as a corrosion inhibitor in HCl solution. The inhibition efficiency increased with the increase of extract concentration. The inhibition action was attributed to the adsorption of the chemical compounds present in the extract solution, on mild steel surface.