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

Electrochemical alcohols oxidation mediated by N-hydroxyphthalimide on nickel foam surface

Alcohol to aldehyde conversion is a critical reaction in the industry. Herein, a new electrochemical method is introduced that converts 1 mmol of alcohols to aldehydes and ketones in the presence of N-hydroxyphthalimide (NHPI, 20 mol%) as a mediator; this conversion is achieved after 8.5 h at room temperature using a piece of Ni foam (1.0 cm2) and without adding an extra-base or a need for high temperature. Using this method, 10 mmol (1.08 g) of benzyl alcohol was also successfully oxidized to benzaldehyde (91%) without any by-products. This method was also used to oxidize other alcohols with high yield and selectivity. In the absence of a mediator, the surface of the nickel foam provided oxidation products at the lower yield. After the reaction was complete, nickel foam (anode) was characterized by a combination of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and spectroelectrochemistry, which pointed to the formation of nickel oxide on the surface of the electrode. On the other hand, using other electrodes such as Pt, Cu, Fe, and graphite resulted in a low yield for the alcohol to aldehyde conversion

challenges for biomimetic water oxidation

Herein, we report the synthesis, characterization, crystal structure, density functional theory calculations, and water-oxidizing activity of a pivalate Mn–Ca cluster. All of the manganese atoms in the cluster are Mn(IV) ions and have a distorted MnO6 octahedral geometry. Three Mn(IV) ions together with a Ca(II) ion and four-oxido groups form a cubic Mn3CaO4 unit which is similar to the Mn3CaO4 cluster in the water-oxidizing complex of Photosystem II. Using scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, extended X-ray absorption spectroscopy, chronoamperometry, and electrochemical methods, a conversion into nano-sized Mn-oxide is observed for the cluster in the water-oxidation reaction

Investigation of corrosion inhibitory process of marine Vibrio neocaledonicus sp bacterium for carbon steel

The present work explains the corrosion inhibitory process of Vibrio neocaledonicus sp. bacterium for carbon steel. The first and significant inhibitory effect was obtained after 45 min of exposing carbon steel in the bacterial solution due to the adsorption of organic macromolecules on the surfaces and decrease in dissolved oxygen concentration. After that, biofilm covered the surfaces homogenously and thickened by exposure time; so the corrosion inhibitory effect increased by exposure time. EDS results detected the oxygen amount decreased in the presence of bacterium by expousre time due to biofilm formation and hindering the oxygen diffusion on the metal surfaces. (C) 2015 Elsevier Ltd. All rights reserved

Exopolysaccharide produced by Vibrio neocaledonicus sp as a green corrosion inhibitor: Production and structural characterization

Exopolysaccharide produced by Vibrio neocaledonicus sp as a green corrosion inhibitor: Production and structural characterizatio

Exopolysaccharide produced by Vibrio neocaledonicus sp as a green corrosion inhibitor: Production and structural characterization

An exopolysaccharide substances produced by Vibrio neocaledonicus sp. was introduced as a novel green inhibitor against the corrosion of carbon steel in artificial seawater and acidic media. The produced extracellular polymeric substance (EPS) is heterogeneous with composition of polysaccharides, nucleic acids and protein and average molecular weight of 29,572 Da. Adsorption of EPS on the metal surfaces and formation of Fe-EPS complexes acted as a barrier to prevent the oxygen penetration and hindered anodic and cathodic reactions. The inhibitory effect increases with increasing EPS concentration and exposure time. The highest corrosion inhibitory effect (95.1%) was observed for 10 g/L of EPS after 5 days of exposure in seawater. This is the highest inhibitory effect ever been reported by EPSs. While, the optimum concentration of EPS with the highest inhibition efficiency in 1 N H2SO4 was 1000 ppm. The influence of different parameters, such as initial pH, growth phase, various nitrogen and carbon sources on the production of EPS and its corrosion inhibitory effect were also investigated. According to results, the optimum culture medium for EPS production is contained artificial seawater including 5% mannitol as carbon source and 0.1% (NH4)(2)SO4 as nitrogen source at pH= 8. This medium could produce 22.24 g/L EPS during 3 days' incubation at 30 degrees C. The corrosion inhibitory efficiency of obtained EPS was 95.97%. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology

Influences of Ag and In Alloying on Microstructure and Mechanical Properties of Sn-58Bi Solder

Ag (2.0 wt.%) and In (1.5 wt.%) were alloyed into Sn-58Bi eutectic solder, and the individual and combined influences of Ag and In on the microstructure, microhardness, and impact toughness of the SnBi solder were investigated. The results reveal that the microstructures of the SnBiAg, SnBiIn, and SnBiAgIn alloyed solders are coarser than that of the SnBi eutectic solder. Fine Ag3Sn particles are formed in the SnBiAg and SnBiAgIn solders, while small regions of In-rich phases appear in the SnBiIn and SnBiAgIn solders. The microhardness of the three alloyed solders are higher than the SnBi solder, and the Sn-rich phases in the alloyed solders show higher nanohardness, while the nanohardness of the Bi-rich phases with Ag and In addition changes little. The impact toughness of the SnBiAg, SnBiIn, and SnBiAgIn solders are observed to be higher than the SnBi solder, especially in the case of the SnBiAgIn solder. The improvement in ductility of the Sn-rich phase induced by the In solution, and the strengthening effect from the Ag3Sn particles are predicated to be the reason for the increase in impact toughness. The fracture surfaces demonstrate that plastic deformation of the SnBiAgIn solder during the impact process is more obvious. Overall, the combined addition of Ag and In can increase the microhardness and impact toughness of SnBi eutectic solder

Introducing a novel bacterium, Vibrio neocaledonicus sp., with the highest corrosion inhibition efficiency

Degradation of metals due to corrosion causes serious economic problems throughout the world, and different corrosion protection techniques are being used to extend the service life of metallic structures. It has been suggested that some microorganisms can inhibit electrochemical corrosion of metals. Here we isolated a new marine inhibitory bacterium, Vibrio neocatedonicus sp., and EIS results showed that the corrosion resistance of carbon steel increased by more than sixty fold in the presence of this bacterium. This is the highest corrosion inhibitory effect reported for bacteria and is comparable with some industrial coatings such as electroless Ni. This bacterium affected corrosion by the formation of an inhibitory layer on the metal surface in the first hours of attachment, with the consumption of oxygen by electron transport proteins. Extracellular polymeric substances produced by this bacterium also have a corrosion inhibitory effect. Thus we propose a new, natural, non-toxic, and cost-effective system for controlling corrosion processes using this bacterium or extracellular polymeric substances produced by this bacterium. (C) 2014 Elsevier B.V. All rights reserved

Exopolysaccharide produced by Vibrio neocaledonicus sp as a green corrosion inhibitor: Production and structural characterization

An exopolysaccharide substances produced by Vibrio neocaledonicus sp. was introduced as a novel green inhibitor against the corrosion of carbon steel in artificial seawater and acidic media. The produced extracellular polymeric substance (EPS) is heterogeneous with composition of polysaccharides, nucleic acids and protein and average molecular weight of 29,572 Da. Adsorption of EPS on the metal surfaces and formation of Fe-EPS complexes acted as a barrier to prevent the oxygen penetration and hindered anodic and cathodic reactions. The inhibitory effect increases with increasing EPS concentration and exposure time. The highest corrosion inhibitory effect (95.1%) was observed for 10 g/L of EPS after 5 days of exposure in seawater. This is the highest inhibitory effect ever been reported by EPSs. While, the optimum concentration of EPS with the highest inhibition efficiency in 1 N H2SO4 was 1000 ppm. The influence of different parameters, such as initial pH, growth phase, various nitrogen and carbon sources on the production of EPS and its corrosion inhibitory effect were also investigated. According to results, the optimum culture medium for EPS production is contained artificial seawater including 5% mannitol as carbon source and 0.1% (NH4)(2)SO4 as nitrogen source at pH= 8. This medium could produce 22.24 g/L EPS during 3 days' incubation at 30 degrees C. The corrosion inhibitory efficiency of obtained EPS was 95.97%. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology

Transient Soldering Reaction Mechanisms of SnCu Solder on CuNi Nano Conducting Layer and Fracture Behavior of the Joint Interfaces

Soldering can be used in the connection of thin film solar cells, while the soldering quality is difficult to control as the conducting layer on the solar cells is nano-sized and can be consumed within a few seconds. In this study, the microstructure and fracture behavior of the Sn-0.7wt.%Cu/Cu-30wt.%Ni joint interfaces were investigated. The use of CuNi conducting layer deposited on the Al/Si film with about 150 nm thickness and a soldering time of a few seconds were investigated. The results reveal that dense rod-like (Cu,Ni)(6)Sn-5 grains with a diameter of 100-200 nm are formed at the edge of the joint interface, which gradually transform into coarsely and loosely distributed rod-like (Cu,Ni)(6)Sn-5 grains from the edge to the inner of the solder joint. The CuNi layer is completely consumed at the inner region, and the diameter of the (Cu,Ni)(6)Sn-5 grain were constant at about 1 mu m. With longer soldering time, the width of the transition region between the fine and coarse (Cu,Ni)(6)Sn-5 grains decrease sharply from a few hundred micrometers to about 10 mu m, and the coarse rod-like (Cu,Ni)(6)Sn-5 grains distribute throughout all the joint interface. Tensile fracture of the Cu/SnCu/CuNi solder joints occurs around the (Cu,Ni)(6)Sn-5/CuNi interface at the edge and along the solder/Al or Al/Si interfaces at the inner region. The longer reaction time results in exhaustion of the CuNi layer, weakening of the bonding between the Al/Si/SnO2 films, and decreased joint strength from over 40 MPa to lower than 35 MPa