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Crystallization of DNL-6, a silicoaluminophosphate (SAPO) based molecular sieve with the RHO topology, was investigated under both the hydrothermal synthesis (HTS) and dry-gel conversion (DGC) conditions. Crystallization of DNL-6 under the HTS conditions is rather fast. But a combination of crystallization under the DGC conditions and reducing reaction temperature slow down the reactions, allowing for intermediates to be captured. Under the DGC conditions, DNL-6 crystallizes through a semi-crystalline layered phase. The nature of this intermediate is aluminophosphate (AlPO) rather than SAPO with most P atoms having a local environment of P(–O–Al)3(OH). The surfactant (cetyltrimethylammonium chloride) used for synthesis appears to be part of the layered intermediate. Si is directly incorporated in the DNL-6 framework via SM II mechanism when the semi-crystalline AlPO phase is transforming to DNL-6 with the assistance of a very small amount of water. Both the structure directing agent and the surfactant play a role in the formation of DNL-6, as they were found within the final synthesized products. SEM data show that hydrothermal synthesis produces a much more crystalline product. The facts that the semi-crystalline layered phase was also observed in the powder X-ray diffraction patterns of the solid samples obtained under the HTS conditions and that the evolution of the local structure around P and Al in the intermediate phases are similar imply that under the reaction conditions employed in the present study, the formation pathways of DNL-6 under the HTS and DGC conditions appear to have some similarities.

Thin-film photovoltaic cells using Cu

The hydrogen permeation behavior of X65 steel was studied in a simulated Canadian groundwater (NS4) using a Devanathan-Stachurski cell. In the absence of a palladium coating on the detection side of the steel membrane, the hydrogen permeation current was suppressed by the growth of an oxide film on the steel. When a palladium coating was applied it was necessary to first remove the air-formed oxide from the steel surface which would otherwise control the permeation behavior due to its low hydrogen diffusivity. On the charging side of the membrane the deposition of CaCO3 and Mg(OH)2 enhanced hydrogen absorption into the cell leading to an enhanced permeation current.

The deployment of electrolyzers that convert CO2 into chemicals and fuels requires appropriate integration with upstream carbon capture processes. To this end, the electrolytic conversion of aqueou...

Coatings and cathodic protection of pipelines can fail leading to exposure of underlying steel substrate to environmental conditions. In Canada, these conditions are typically alkaline and can contain dissolved sulfides. Sulfides are known to accelerate corrosion of steel, however, the corrosion behavior may differ if a preformed oxide or oxyhydroxide is present on the steel surface. This study investigates the change in corrosion behavior of steel in anoxic alkaline conditions that is directly exposed to sulfide or has a preformed surface oxide. The electrochemical response (corrosion potential and polarization resistance) were monitored for 90 d and 120 d, while simultaneously monitoring the film composition and morphology by Raman spectroscopy and scanning electron microscopy, respectively. In the absence of a preformed oxide the mackinawite film was able to undergo anoxic aging to greigite and pyrite whereas the electrodes with a preformed film had only mackinawite present on the surface. The interconversion of mackinawite to greigite and pyrite lead to a higher relative polarization resistance than the electrode with the preformed oxide.

The electrolysis of carbon capture solutions bypasses energy-intensive CO

This paper describes the conformational analysis of 1,2-dichloroethane adsorbed into three different metal-organic frameworks, MIL-53(Al), MIL-68(In), MIL-53-NH2(Al), by using FT-Raman spectroscopy in combination with powder XRD and TGA. For non-polar frameworks, the main guest-host interactions are van der Waal interactions between the C H bonds of 1,2-dichloroethane (DCE) and the π system of terephthalate ligands. The polar framework of MIL-53-NH2 is able to stabilize the gauche conformation of DCE at room temperature. The conformational enthalpy of each system was determined through variable temperature FT-Raman spectroscopy. Furthermore, the line-width of the Raman bands provides information regarding the molecular motion of the halocarbons at various temperatures inside the framework.

Electrochemical CO2 reduction offers a method to use renewable electricity to convert CO2 into CO and other carbon-based chemical building blocks. While nearly all studies rely on a CO2 feed, we show herein that aqueous bicarbonate solutions can also be electrochemically converted into CO gas at meaningful rates in a flow cell. We achieved this result in a flow cell containing a bipolar membrane (BPM) and a silver nanoparticle catalyst on a porous carbon support. Electrolysis upon a N2-saturated 3.0-M potassium bicarbonate electrolyte solution yields CO with a faradaic efficiency (F.E.CO) of 81% at 25 mA cm-2 and 37% at 100 mA cm-2. This output is comparable to the analogous experiment where the electrolyte is saturated with gaseous CO2 (faradaic efficiency for CO is 78% at 25 mA cm-2 and 35% at 100 mA cm-2). The H+ flux from the BPM is critical to this chemistry in that it reacts with the bicarbonate feed to generate CO2, which is then reduced to CO at the gas diffusion electrode. These results are important in that they show that the addition of gaseous CO2 to bicarbonate electrolytes is not necessary in order to obtain reduced carbon products with a flow cell architecture. This process offers a means of using electrolysis to bypass the thermally-intensive step of extracting CO2 from bicarbonate solutions generated in carbon capture schemes.

The influence of sulphide on the electrochemistry of carbon steel in neutral to slightly alkaline sulphide solutions was investigated using electrochemical and surface analytical techniques. Small concentrations of sulphide were found to promote anodic dissolution as FeII carbonate complexes and to destabilize FeIII oxides leading to the loss of passivity, especially at pH ≤ 9. The dominant phase formed was mackinawite, while reactions between FeIII and sulphide led to the formation of oxidized S species (elemental Sand sulphate), polysulfides, and pyrite.

Electrolyzers designed to convert CO2 into carbon products typically rely on a gaseous CO2 feedstock or CO2-saturated electrolyte. We show herein that aqueous HCO3- solutions can also be electrochemically converted into CO gas at meaningful rates in a flow cell containing a bipolar membrane (BPM) and a silver catalyst on a carbon support. Electrolysis upon a N2-saturated 3.0-M KHCO3 solution yields CO with a faradaic efficiency that is comparable to analogous experiment where the bicarbonate solution is saturated with gaseous CO2. This electrolytic process is made possible by reaction of protons, delivered by the BPM, with bicarbonate to form electrocatalytically active CO2. This reaction pathway offers the potential to use electrolysis to bypass the thermally-intensive step of extracting CO2 from HCO3- solutions generated in carbon capture schemes.

Pipelines are designed for a wide variety of applications. Their use in the energy sector for the transportation of crude oil, natural gas, and other petrochemical commodities is still regarded as the safest, fastest and most economical mode of product transmission and delivery. The degradation of the structural integrity of pipelines caused by corrosion has been an on-going problem. Depending on in-service use, different forms of corrosion can occur, with the deleterious effects depending on which type of corrosion is occurring, such as stress corrosion cracking (SCC) and hydrogen induced cracking (HIC) due to hydrogen embrittlement (HE). Further, the hydrogen may affect the protectiveness of any FeIII oxide present on the steel surface. This study investigates the effects of H absorption by X60, X65, X70 steels. A range of electrochemical techniques, such as monitoring the corrosion potential (Ecorr), polarization resistance (Rp) measurements, cyclic voltammetry (CV), and H permeation experiments (using the Devanathan-Stachurski (D-S) approach) have been used to investigate the effect of H on the steel and the oxides present on the steel surface. Surface analytical techniques such as X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used to determine the effect of H on the composition of the oxide and to identify the distribution of H trapping sites. The apparent diffusivity of H in X65 was found to depend on the composition of the solution on the reduction side of the D-S cell. The steady-state current measured in the oxidation cell was dependent on the solution composition in the reduction cell. The presence of calcium caused a sharp decrease of oxidation current, likely due to the quick formation of calcium carbonate deposits, whereas magnesium caused a gradual decrease in the observed oxidation current, which is likely due to the thickening of the magnesium hydroxide on the surface. The presence of both calcium and magnesium in the solution affects the amount of H that diffuses through the steel, likely by blocking adsorption sites on the steel surface. Blocked adsorption sites reduce the concentration of atomic hydrogen on the surface and lead to a decrease in the observed steady-state current. Thermal desorption data show that, in the X65 steel, a majority of the H trapped within the steel requires activation energy (Ea) of < 50 kJ/mol for its release, indicating that it is located in reversible trapping sites. SIMS data suggest that trapping occurs predominantly along grain boundaries, with the extent of H trapping at these sites possibly affecting the resistance of the surface FeIII oxides present. The RP values measured after cathodic charging for the pearlite-containing steel (X65) were lower than those obtained on the bainite-containing steel (X70). The presence of FeO on the steel surface after cathodic charging suggests partial oxide reduction, with this reduced oxide being more prominent on the X65 than on the X70 steel. Polarization resistance measurements were used to study the role of hydrogen on the passivity of the steel covered by iron oxides. It has been shown that at open circuit conditions the increase in RP value is slower when the steel has been charged with H. The phase of X70 being investigated was predominantly bainite, which is more resistive to hydrogen absorption. X70, after hydrogen charging, was found to have a lesser change in steady-state RP than did the X65. Further, the retardation of the resistance increase at open circuit was more prominent on the X65 than on the X70. XPS confirmed that more FeO was present on the X65 sample after charging than on the X65 after charging followed by potentiodynamic polarization experiments. All this suggests that, at open circuit conditions after the steel was charged with H, hydrogen being released from reversible trapping sites reduces the FeIII oxide to FeO. The reduction of FeIII to FeO, due to either the charging or release of atomic hydrogen trapped within the lattice, is likely causing a decrease in the resistance of the passive oxide.