Electrode protective layers

Cofired thick Colired porous film electrode protection layer... 

Poisoning and thermal aging are the main reason why the lambda characteristic and dynamics of the sensor changes with lifetime [1, 31-33]. Plugging of the porous electrode protective layer by oil, ash, or silicon oxide favors the diffusion of hydrogen to the electrode, which leads to a lean shift in the static characteristic curve [31]. 

Kinetic stability of lithium and the lithiated carbons results from film formation which yields protective layers on lithium or on the surfaces of carbonaceous materials, able to conduct lithium ions and to prevent the electrolyte from continuously being reduced film formation at the Li/PC interphase by the reductive decomposition of PC or EC/DMC yielding alkyl-carbonates passivates lithium, in contrast to the situation with DEC where lithium is dissolved to form lithium ethylcarbonate [149]. EMC is superior to DMC as a single solvent, due to better surface film properties at the carbon electrode [151]. However, the quality of films can be increased further by using the mixed solvent EMC/EC, in contrast to the recently proposed solvent methyl propyl carbonate (MPC) which may be used as a single sol-... 

Protection layers between the titanium metal and the electrocatalytic coating, for example, of substoichiometric titanium oxides (see Ebonex above), increase the stability by shielding the metal, for example, to avoid the formation of insulating titanium dioxide layers on the metal [35]. The preparation of such electrodes with optimal properties usually needs the special know-how of commercial suppliers. 

A1 is thermodynamically unstable, with an oxidation potential at 1.39 V. Its stability in various applications comes from the formation of a native passivation film, which is composed of AI2O3 or oxyhydroxide and hydroxide.This protective layer, with a thickness of 50 nm, not only stabilizes A1 in various nonaqueous electrolytes at high potentials but also renders the A1 surface coating-friendly by enabling excellent adhesion of the electrode materials. It has been reported that with the native film intact A1 could maintain anodic stability up to 5.0 V even in Lilm-based electrolytes. Similar stability has also been observed with A1 pretreated at 480 °C in air, which remains corrosion-free in LiC104/EC/ DME up to 4.2 However, since mechanical... 

Zinc and zinc-coated products corrode rapidly in moisture present in the atmosphere. The corrosion process and its mechanism were studied in different media, nitrate [283], perchlorate [259], chloride ions [284], and in simulated acid rain [285]. This process was also investigated in alkaline solutions with various iron oxides or iron hydroxides [286] and in sulfuric acid with oxygen and Fe(III) ions [287]. In the solution with benzothia-zole (BTAH) [287], the protective layer of BTAH that formed on the electrode surface inhibited the Zn corrosion. 

Protective layer (A O- MgO) Measurement electrode (Pt) Solid electrolyte (Y203 Zr02) Reference electrode (Pt)... 

At the measurement electrode/solid electrolyte layer interface, the mass of Op gas which diffuses from the porous protective layer is equal to the mass of O2 which changes to oxygen ion plus the mass of CO gas which diffuses from the porous protective layer. (j), At the measurement electrode/solid electrolyte layer interface,... 

Fig. 8. Schematic of the procedure used for fabrication of nanoscale molecular-switch devices by imprint lithography [62]. (a) Deposition of a molecular film on Ti/Pt nanowires and their micron-scale connections to contact pads, (b) Blanket evaporation of a 7.5 nm Ti protective layer, (c) Imprinting of 10 nm Pt layers with a mold that was oriented perpendicular to the bottom electrodes and aligned to ensure that the top and bottom nanowires crossed, (d) Reactive ion etching with CF4 and O2 (4 1) to remove the blanket Ti protective layer.

The aforementioned requirements on surface stability are typical for all exposed areas of the metallic interconnect, as well as other metallic components in a SOFC stack (e.g., some designs use metallic frames to support the ceramic cell). In addition, the protection layer for the interconnect, or in particular the active areas that interface with electrodes and are in the path of electric current, must be electrically conductive. This conductivity requirement differentiates the interconnect protection layer from many traditional surface modifications as well as nonactive areas of interconnects and other components in SOFC stacks, where only surface stability is emphasized. While the electrical conductivity is usually dominated by their electronic conductivity, conductive oxides for protection layer applications often demonstrate a nonnegligible oxygen ion conductivity as well, which leads to scale growth beneath the protection layer. With this in mind, a high electrical conductivity is always desirable for the protection layers, along with low chromium cation and oxygen anion diffusivity. 

Coflred" thick film electrode and protection layer c. j O ... 

ZrtVCeramic Electrodes Raw Porous protective layer i i Insulation... 

The disadvantage of this diffusion barrier is that it slightly changes the gas composition at the electrode because of the different diffusion coefficients of the constituents of the raw exhaust gas. On average the rich gas components, especially the small H2, are faster than the bigger 02 or NOx molecules causing a lean shift that is typical for all sensors. The closer the exhaust gas is to equilibrium, the less lean shift is observed. Downstream of the catalytic converter the lean shift completely disappears. Furthermore, precatalytic layers in front of the electrode, or catalytic materials inside the protection layer, reduce the effect... 

A sensor sheet with a reference electrode exposed to the reference air duct and the outer measuring electrode covered with a porous protective layer. 

Porous protective layer Outer pumping electrode Pumping sheet ZrO Inner pumping electrode Diffusion barrier Nernst electrode Nernst shsetZrOr Reference electrode Air duct sheet ZrOa Insulation layer Heater... 

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