Spinel Oxide Coating for SOFC Interconnect Cr Poisoning
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Solution Overview
Problem
Solid oxide fuel cells (SOFCs) with Cr-containing alloys face issues of Cr poisoning at the air electrode due to Cr scattering and oxidation, leading to increased electric resistance and reduced performance, particularly during high-temperature exposure and sintering processes.
Innovation Solution
A coating layer containing a spinel oxide composed of a first and second mono metal oxide is applied to the Cr-containing alloy, with specific equilibrium dissociated oxygen partial pressures, to stabilize the Cr oxide and prevent oxidation to Cr (VI), thereby reducing Cr poisoning and maintaining alloy performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Cr-containing alloy is used for the interconnect, then electron conductivity and oxidation resistance are improved, but Cr scattering toward the air electrode causes Cr poisoning and performance deterioration
Solution Approach 1:
A coating layer comprising a spinel oxide is introduced as an intermediary between the Cr-containing alloy and the air electrode. This coating layer acts as a barrier that prevents Cr scattering toward the air electrode while maintaining electron conductivity, thereby resolving the contradiction between using Cr-containing alloy for oxidation resistance and preventing Cr poisoning of the air electrode
2Strength
If sintering treatment is performed at high temperature (1000-1250°C) to minimize contact resistance, then bonding strength is improved, but Cr oxidation to Cr(VI) and evaporation causes Cr poisoning
Solution Approach 1:
The coating layer comprising a spinel oxide is formed on the Cr-containing alloy before the sintering treatment. This preliminary coating prevents Cr oxidation to Cr(VI) and subsequent evaporation during the high-temperature sintering process, allowing the sintering treatment to be performed at high temperature to achieve good bonding strength without Cr poisoning
3Object-affected harmful factors
If a mono metal oxide coating layer is formed to prevent Cr oxidation, then Cr poisoning is reduced, but electric resistance increases due to low conductivity of mono metal oxides
Solution Approach 1:
Instead of using a simple mono metal oxide coating layer, a composite coating layer comprising a spinel oxide is employed. The spinel oxide structure provides both the Cr oxidation prevention capability of metal oxides and maintains adequate electron conductivity, thereby resolving the contradiction between preventing Cr poisoning and maintaining electric conductivity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The spinel oxide coating effectively restricts Cr diffusion and oxidation, maintaining the performance and durability of the SOFC by preventing Cr poisoning and depletion, even under high-temperature operating conditions.
Implementation Method 1
restrict oxidation of Cr contained in the alloy into a hexavalent oxide which can easily scatter about
Implementation Method 2
Cr contained in the alloy tends to scatter about toward the air electrode
Implementation Method 3
forms on the alloy surface an n-type semiconductor coating layer obtained by doping a mono metal oxide with an impurity
Implementation Method 4
heat resistance of the alloy is attributable to a dense coating layer of chromia (Cr2O3) formed on the surface of this alloy
Data Source
AI summary
[OBJECT] In an SOFC cell comprising a Cr-containing alloy or the like and an air electrode bonded together, the invention is to provide a cell capable of effectively restricting occurrence of Cr poisoning of the air electrode and capable also of effectively restricting occurrence of oxidation deterioration due to Cr depletion in the alloy or the like.[SOLUTION] In a cell for a solid oxide fuel cell (SOFC) comprising a Cr (chrome)-containing alloy or oxide and an air electrode bonded together, wherein on the surface of the alloy or oxide, there is formed a coating layer containing a spinel oxide comprised of a first mono metal oxide and a second mono metal oxide, the first mono metal oxide having an equilibrium dissociated oxygen partial pressure at 750° C. ranging from 1.83×10−20 to 3.44×10−13 atm., the second mono metal oxide having a lower equilibrium dissociated oxygen partial pressure at 750° C. than the first mono metal oxide.