Designing multifunctional CoOx layers for efficient and stable electrochemical energy conversion

Disordered and porous metal oxides are promising as earth-abundant and cost-effective alternatives to noble-metal electrocatalysts. Herein, we leverage non-saturated oxidation in plasma-enhanced atomic layer deposition to tune structural, mechanical, and optical properties of biphasic CoOx thin films, thereby tailoring their catalytic activities and chemical stabilities. To optimize the resulting film properties, we systematically vary the oxygen plasma power and exposure time in the deposition process. We find that short exposure times and low plasma powers incompletely oxidize the cobaltocene precursor to Co(OH)2 and result in the incorporation of carbon impurities. These Co(OH)2 films are highly porous and catalytically active, but their electrochemical stability is impacted by poor adhesion to the substrate. In contrast, long exposure times and high plasma powers completely oxidize the precursor to form Co3O4, reduce the carbon impurity incorporation, and improve the film crystallinity. While the resulting Co3O4 films are highly stable under electrochemical conditions, they are characterized by low oxygen evolution reaction activities. To overcome these competing properties, we applied the established relation between deposition parameters and functional film properties to design bilayer films exhibiting simultaneously improved electrochemical performance and chemical stability. The resulting biphasic films combine a highly active Co(OH)2 surface with a stable Co3O4 interface layer. In addition, these coatings exhibit minimal light absorption, thus rendering them well suited as protective catalytic layers on semiconductor light absorbers for application in photoelectrochemical devices.

Особенности роста слоев в напряженных сверхрешетках InAs/GaSb

The paper presents the results of a study of factors affecting the thickness of transition (interface) layers in stressed InAs/GaSb superlattices during growth by MOCVD method. It is shown that the thicknesses of the interface layers between InAs and GaSb are practically independent of the growth temperature. The thickness of the interface layers is influenced by the direction of switching the layer growth. The smallest thickness of 1.2-1.4 nm of the interface layer InAs/GaSb was obtained for the direction of growth switching from GaSb to InAs.

Establishment of Silane/GO Multistage Hybrid Interface Layer to Improve Interfacial and Mechanical Properties of Carbon Fiber Reinforced Poly (phthalazinone ether ketone) Thermoplastic Composites

This study focused on the faint interface bonding between carbon fiber (CF) and poly(phthalazinone ether ketone) (PPEK) thermoplastic, a multistage hybrid interface layer was constructed via the condensation reaction of N-[3-(Trimethoxysilyl)propyl]-N,N,N-trimethylammonium chloride (KHN+) and the electrostatic adsorption of graphene oxide (GO). The influence of the contents of GO (0.2 wt%, 0.4 wt%, 0.6 wt%) on the interfacial properties of composites was explored. FTIR, Raman spectra, XPS tests indicated the successful preparation of CF-KHN+-GO reinforcements. The multistage hybrid interface layer significantly increased fiber surface roughness without surface microstructure destruction. Simultaneously, polarity and wettability are remarkably improved as evidenced by the dynamic contact angle experiment. The interlaminar shear strength (ILSS) and flexural strength of the CF/PPEK composites with 0.4 wt% GO (CF-KHN+-4GO) were 74.57 and 1508 MPa, which was 25.2% and 23.5% higher than that of untreated CF/PPEK composite, respectively. Dynamic mechanical analysis proved that CF/GO/PPEK composites have excellent high-temperature mechanical properties. This study furnishes an unsophisticated and valid strategy to build an interface transition layer with a strong binding force, which would offer a new train of thought in preparing high-performing structural composites.

Surface Transport Properties of Pb-Intercalated Graphene

Intercalation experiments on epitaxial graphene are attracting a lot of attention at present as a tool to further boost the electronic properties of 2D graphene. In this work, we studied the intercalation of Pb using buffer layers on 6H-SiC(0001) by means of electron diffraction, scanning tunneling microscopy, photoelectron spectroscopy and in situ surface transport. Large-area intercalation of a few Pb monolayers succeeded via surface defects. The intercalated Pb forms a characteristic striped phase and leads to formation of almost charge neutral graphene in proximity to a Pb layer. The Pb intercalated layer consists of 2 ML and shows a strong structural corrugation. The epitaxial heterostructure provides an extremely high conductivity of σ=100 mS/□. However, at low temperatures (70 K), we found a metal-insulator transition that we assign to the formation of minigaps in epitaxial graphene, possibly induced by a static distortion of graphene following the corrugation of the interface layer.

Smart Crude Desalter Monitoring System Using Capacitance Based Technology

Saudi Aramco operates several electrostatic coalescers for bulk emulsion separation and crude desalting. One of the major challenges in operating electrostatic coalescers is the potential buildup of tight emulsions and a rag layer at the interface layer, which causes short-circuiting of the electrostatic grids which increases the risk excessive carryover of water with the crude. Conventional liquid level instrumentation cannot measure the thickness of emulsion layers since the level taps are at the clean oil and water layers. Consequently, the buildup of emulsions is normally not detected by operators. A capacitance-based emulsion detection system was installed at one of the electrostatic coalescers of a Saudi Aramco facility. The system is comprised of multiple probes installed at various elevations in the vessel. Each probe measures the capacitance of the liquid in which it is immersed in. The data is then transmitted to the DCS, where an algorithm computes the oil/water content. Saudi Aramco developed an enhanced predictive alarm logic and advisory tool using the measured capacitance data so that operations may take preemptive measures to prevent upsets from occurring. The alarm system was tested over an extended period of time and it has shown that it can accurately detect the buildup of emulsions prior to an upset in the electrostatic coalescer. What is unique about the system is that it utilizes a combination of absolute capacitance measurements and capacitance variations in the algorithm. Emulsion buildups are detected by the alarm system hours before a potential upset, providing operators ample time to take preemptive measures such as increasing the demulsifier injection rate, desludging the vessel or lowering the interface level. The system significantly reduced the number of electrostatic coalescer upsets at the facility and crude quality was enhanced. Upon inspection of the probes during shutdowns, no buildup of deposits, which impacts capacitance readings, were found on the probes since a flushing system was installed. The alarm system has been utilized for four years with no major issues. Utilizing the capacitance probes to develop an algorithm for an alarm system is a novel technique to detect emulsion layer buildup hours prior to a potential electrostatic grid upset. Large-scale deployment is more economical as it is more cost-effective than radioactive profilers and is logistically easier to manage.