Fuel Cell Interconnect Alloying for Chromium Oxidation Control
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Solution Overview
Problem
Chromium-based alloys used in solid oxide fuel cell stacks degrade due to chromium oxidation, leading to increased ohmic resistance and cathode poisoning, which affects the electrochemical activity and performance of the fuel cells.
Innovation Solution
Incorporating transition metals like Co, Cu, Mn, Ni, or V into the chromium-based alloys to form a chromium-transition metal oxide spinel interfacial layer, which reduces chromium evaporation and increases electrical conductivity, and applying a protective oxide coating on the air side to minimize chromium oxide growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromium-based alloys are used in solid oxide fuel cell stacks, then the interconnects can provide electrical connection and gas flow channels, but chromium oxidation occurs leading to increased ohmic resistance and cathode poisoning
Solution Approach 1:
A protective coating layer comprising manganese oxide and/or cobalt oxide is applied over the air side of the interconnect body, acting as an intermediary barrier between the chromium-based alloy and the oxidizing environment. This coating prevents direct oxidation of chromium while allowing the interconnect to maintain its electrical connection and gas flow functions
Solution Approach 2:
The interconnect structure is designed as a composite system comprising the chromium-based alloy interconnect body combined with a protective oxide coating layer. This composite structure combines the electrical conductivity and mechanical strength of the Cr-Fe alloy with the oxidation resistance of the manganese oxide and/or cobalt oxide coating
2Reliability
If chromium reacts with oxygen to form chromia, then a protective oxide layer is formed, but this leads to degradation of the SOFC stack through increased ohmic resistance and cathode poisoning
Solution Approach 1:
The protective coating of manganese oxide and/or cobalt oxide serves as an intermediary layer that controls the oxidation process. It allows formation of a stable oxide barrier without releasing chromium species that would cause cathode poisoning, thus protecting against both oxidation and its harmful effects
Solution Approach 2:
The invention converts the potential harm of chromium oxidation into a benefit by controlling the oxidation to form a protective manganese oxide and/or cobalt oxide layer instead of harmful chromia. The oxidation reaction is redirected to form a beneficial protective coating that prevents cathode poisoning while maintaining low ohmic resistance
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 chromium-transition metal oxide spinel interfacial layer significantly reduces chromium evaporation and ohmic resistance, enhancing the long-term performance and stability of the fuel cell stack by promoting higher electrical conductivity and suppressing chromium poisoning.
Implementation Method 1
chromium in the CrFe or CrFeY alloys react with oxygen and form chromia
Implementation Method 2
chromium evaporation
Implementation Method 3
compressing an interconnect powder to form an interconnect
Implementation Method 4
sintering the interconnect
Data Source
AI summary
A method of making an interconnect for a fuel cell stack includes compressing an interconnect powder to form an interconnect, the interconnect power containing Cr, Fe and at least one transition metal selected from Co, Cu, Mn, Ni, or V pre-alloyed with at least one of the Cr and the Fe, and sintering the interconnect.