Production of methanol from CO2 electroreduction at Cu2O and Cu2O/ZnO-based electrodes in aqueous solution

In this study, we examine the performance of Cu2O and Cu2O/ZnO surfaces in a filter-press electrochemical cell for the continuous electroreduction of CO2 into methanol. The electrodes are prepared by airbrushing the metal particles onto a porous carbon paper and then are electrochemically characterized by cyclic voltammetry analyses. Particular emphasis is placed on evaluating and comparing the methanol production and Faradaic efficiencies at different loadings of Cu2O particles (0.5, 1 and 1.8 mg cm−2), Cu2O/ZnO weight ratios (1:0.5, 1:1 and 1:2) and electrolyte flow rates (1, 2 and 3 ml min−1 cm−2). The electrodes including ZnO in their catalytic surface were stable after 5 h, in contrast with Cu2O-deposited carbon papers that present strong deactivation with time. The maximum methanol formation rate and Faradaic efficiency for Cu2O/ZnO (1:1)-based electrodes, at an applied potential of −1.3 V vs. Ag/AgCl, were r = 3.17 × 10−5 mol m−2 s−1 and FE = 17.7 %, respectively. Consequently, the use of Cu2O–ZnO mixtures may be of application for the continuous electrochemical formation of methanol, although further research is still required in order to develop highly active, selective and stable catalysts the electroreduction of CO2 to methanol.

Electrocatalytic reduction of CO2 to formate using particulate Sn electrodes: Effect of metal loading and particle size

The development of electrochemical processes for the conversion of CO2 into value-added products allows innovative carbon capture & utilization (CCU) instead of carbon capture & storage (CCS). In addition, coupling this conversion with renewable energy sources would make it possible to chemically store electricity from these intermittent renewable sources. The electroreduction of CO2 to formate in aqueous solution has been performed using Sn particles deposited over a carbon support. The effect of the particle size and Sn metal loading has been evaluated using cyclic voltammetry and chronoamperometry. The selected electrode has been tested on an experimental filter-press type cell system for continuous and single pass CO2 electroreduction to obtain formate as main product at ambient pressure and temperature. Experimental results show that using electrodes with 0.75 mg Sn cm−2, 150 nm Sn particles, and working at a current density of 90 mA cm−2, it is possible to achieve rates of formate production over 3.2 mmol m−2 s−1 and faradaic efficiencies around 70% for 90 min of continuous operation. These experimental conditions allow formate concentrations of about 1.5 g L−1 to be obtained on a continuous mode and with a single pass of catholyte through the cell.

Design of Activated Carbon/Activated Carbon Asymmetric Capacitors

Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors are optimized using the capacitance and the potential stability limits of the electrodes, with the reliability of the design largely depending on the accuracy and the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed. In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.

The physical chemistry of steel making,

The effect of deoxidation on the rate of ferrite formation in plain carbon steels by C. H. Herty, M. W. Lightner, and D. L. McBride.--The effect of deoxidation on grain size and grain growth in plain carbon steels, by C. H. Herty, D. L. McBride and S. O. Hough.--The effect of deoxidation on the aging of mild steels, by C. H. Herty and B. N. Daniloff.--Effect of deoxidation on the impact strength of carbon steels at low temperatures, by C. H. Herty and D. L. McBride.--The physical chemistry of steel-making. The control of iron oxide in the basic openhearth process, by C. H. Herty, and others.--The deoxidation of steel, by C. H. Herty.

Holley's steel reports.

Binder's title.

Directory of steel foundries in the United States, Canada, and Mexico, 1961-62.

"Producerh [i.e. Producers] of carbon, low and high alloy, heat and corrosion steel castings, high manganese castings, investment mold castings, shell mold castings, and tool steel castings are included."

Microstructure and grain boundary microanalysis of X70 pipeline steel

Grain boundaries (GBs), particularly ferrite: ferrite GBs, of X70 pipeline steel were characterized using analytical electron microscopy (AEM) in order to understand its intergranular stress corrosion cracking (IGSCC) mechanism(s). The microstructure consisted of ferrite (alpha), carbides at ferrite GBs, some pearlite and some small precipitates inside the ferrite grains. The precipitates containing Ti, Nb, V and N were identified as complex carbo-nitrides and designated as (Ti, Nb, WC, N). The GB carbides occurred (1) as carbides along ferrite GBs, (2) at triple points, and (3) at triple points and extending along the three ferrite GBs. The GB carbides were Mn rich, were sometimes also Si rich, contained no micro-alloying elements (Ti, Nb, V) and also contained no N. It was not possible to measure the GB carbon concentration due to surface hydrocarbon contamination despite plasma cleaning and glove bag transfer from the plasma cleaner to the electron microscope. Furthermore, there may not be enough X-ray signal from the small amount of carbon at the GBs to enable measurement using AEM. However, the microstructure does indicate that carbon does segregate to alpha : alpha GBs during microstructure development. This is particularly significant in relation to the strong evidence in the literature linking the segregation of carbon at GBs to IGSCC. It was possible to measure all other elements of interest. There was no segregation at alpha : alpha GBs, in particular no S, P and N, and also no segregation of the micro-alloying elements, Ti, Nb and V. (C) 2003 Kluwer Academic Publishers.

The effect of resin type on the sintering of freeformed maraging steel

The role of the resin type on the sintering of maraging steel with boron additions has been investigated. Two different resins were added to the steel mixture and their subsequent debinding was evaluated and sintering responses compared with that of a resin-free alloy. The two resins used, nylon and a mixture of phenolic resin and synthetic wax, possessed different debinding behaviour, with the latter causing significant carbon contamination of the parts. This caused the formation of a Ti-Mo carbide, depleting the matrix of these elements. Consequently, the microstructure consisted of the equilibrium Fe-Fe2B eutectic, as well as a Mo-rich boride. The liquid phase also appeared to contain significant amounts of carbon, which lowered the temperature at which the liquid formed, resulting in high density occurring at a much lower temperature. When nylon was used as the binder, a similar sintering response to the resin-free alloy was observed. (C) 2002 Published by Elsevier Science B.V.

Galvanic corrosion of magnesium alloy AZ91D in contact with an aluminium alloy, steel and zinc

An investigation was carried out into the galvanic corrosion of magnesium alloy AZ91D in contact with zinc, aluminium alloy A380 and 4150 steel. Specially designed test panels were used to measure galvanic currents under salt spray conditions. It was found that the distributions of the galvanic current densities on AZ91D and on the cathodes were different. An insulating spacer between the AZ91D anode and the cathodes could not eliminate galvanic corrosion. Steel was the worst cathode and aluminium the least aggressive to AZ91D. Corrosion products from the anode and cathodes appeared to be able to affect the galvanic corrosion process through an alkalisation, passivation, poisoning effect or shortcut effect. (C) 2003 Elsevier Ltd. All rights reserved.

Sintering of maraging steel with phosphorous additions

The aim Of this study was to develop a steel powder system for rapid tooling applications. The properties required are rapid densification, dimensional precision. high mechanical strength and corrosion resistance. To this end. the densification and microstructural development of a loose packed 200 grade maraging steel powder sintered with ferrophosphorous additions was examined. Liquid initially formed from a reaction of the Fe3P and carbon, which was a residue of the polymeric binder used to shape the powder compact. This liquid caused a burst of sintering which ceased as the liquid dissipated. On further heating, a phosphorous rich supersolidus liquid appeared at triple points and grain boundaries leading to rapid densification and a sintered density of 98%.

Atom probe field ion microscope measurements of carbon segregation at an a:a grain boundary and service failures by intergranular stress corrosion cracking

This work reports on a critical measurement to understand the intergranular stress corrosion cracking (IGSCC) of pipeline steels: the atom probe field ion microscope (APFIM) measurement of the carbon concentration at a grain boundary (GB). The APFIM measurement was related to the microstructure and to IGSCC observations. The APFIM indicated that the GB carbon concentration of X70 was similar to 10 at% or less, which correlated with a high resistance to IGSCC for X70. (C) 2005 Elsevier Ltd. All rights reserved.

Insights into hydrogen atom adsorption on and the electrochemical properties of nitrogen-substituted carbon materials

The nitrogen substitution in carbon materials is investigated theoretically using the density functional theory method. Our calculations show that nitrogen substitution decreases the hydrogen adsorption energy if hydrogen atoms are adsorbed on both nitrogen atoms and the neighboring carbon atoms. On the contrary, the hydrogen adsorption energy can be increased if hydrogen atoms are adsorbed only on the neighboring carbon atoms. The reason can be explained by the electronic structures analysis of N-substituted graphene sheets. Nitrogen substitution reduces the pi electron conjugation and increases the HOMO energy of a graphene sheet, and the nitrogen atom is not stable due to its 3-valent character. This raises an interesting research topic on the optimization of the N-substitution degree, and is important to many applications such as hydrogen storage and the tokamaks device. The electronic structure studies also explain well why nitrogen substitution increases the capacitance but decreases the electron conductivity of carbon electrodes as was experimentally observed in our experiments on the supercapacitor.

Synthesis of ordered nanoporous carbon and its application in Li-ion battery

Ordered nanoporous carbon (ONC) was comprehensively tested for the first time as electrode material in lithium-ion battery. Structure characterization shows the order nanoporous structure and tiny crystallite structure of as-synthesized ONC. The electrochemical properties of this carbon were studied by galvanostatic cycling and cyclic voltammetry. Of special interest is that ONC gave no peak on its positive sweep of the cyclic voltammetry, which was different from other known anode materials. Besides, X-ray photoelectron spectroscopy (XPS) and XRD were also used to investigate the electrochemical characteristics of ONC. (c) 2006 Elsevier Ltd. All rights reserved.

Erosion-corrosion of mild steel in hot caustic. Part I: NaOH solution

A novel apparatus, high-pressure/high-temperature nickel flow loop, was constructed to study the effect of the flow on the rate of erosion-corrosion of mild steel in hot caustic. It has been successfully used to measure the corrosion rate of 1020 steel in 2.75 M NaOH solution at a temperature of 160 degrees C and velocities of 0.32 and 2.5 m/s. In situ electrochemical methods were used to measure the corrosion rate such as the potentiodynamic sweep, the polarization resistance method, and electrochemical impedance spectroscopy (EIS). Also used were the weight-loss method and scanning electron microscopy (SEM). Eight electrodes/coupons were used to monitor the metal loss rate, four were placed at the low velocity section, while the other four were placed in the high velocity section. The first three coupons in each section were placed within the disturbed flow region, while the fourth was placed in a fully developed flow region. The corrosion rate of the coupons in the high velocity section was generally higher than that of the coupons in the low velocity section. One coupon in the disturbed flow region had a significantly higher corrosion rate than the others. (c) 2005 Elsevier Ltd. All rights reserved.

Erosion-corrosion of mild steel in hot caustic. Part II: The effect of acid cleaning

Corrosion rates of 1020 steel in 2.75 M NaOH solution at a temperature of 160 degrees C and velocities of 0.32 and 2.5 m/s were studied. The focus was on the effect of the acid cleaning which was performed by using strong, inhibited sulphuric acid in between the exposures to caustic. In situ electrochemical methods were used to measure the corrosion rate such as the potentiodynamic sweep and the polarization resistance method. Also used were the weight-loss method and scanning electron microscopy (SEM). Eight electrodes/coupons were used to monitor the metal loss rate, four were placed at the low velocity section, while the other four were placed in the high velocity section of a high temperature flow. The first three coupons in each section were placed within the disturbed flow region, while the fourth was placed in a fully developed flow region. During the exposure of mild steel to the inhibited acid, following the first caustic period, the corrosion rate increased significantly to between 3 and 10mm/y with a few electrodes experiencing as high as 50 mm/y. The second caustic period following the acidic period typically started with very high corrosion rates (20-80 mm/y). The length of this corrosion period was typically 2-3 h with a few exceptions when the high corrosion period lasted 7-10 h. Following the very high corrosion rates experienced at the beginning of the second caustic period, the corrosion rates were reduced sharply (as the corrosion potential increased) to nearly the same levels as those observed during the passive part of the first caustic period. (c) 2005 Elsevier Ltd. All rights reserved.