Flow Field Plate Coating Stack for Conductive Corrosion Protection
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Solution Overview
Problem
Existing bipolar plates for fuel cells, electrolyzers, and redox flow cells face challenges in achieving high long-term stability, electrical conductivity, and cost-effectiveness while providing adequate corrosion protection for metallic substrates, particularly with the use of precious metals.
Innovation Solution
A layer system comprising an underlayer of titanium or titanium-niobium alloy, an intermediate layer of titanium nitride or carbide, and a top layer of indium-tin oxide with an indium content of 75-85% volume, optionally doped, applied via PVD or CVD processes, which serves as an adhesion promoter and corrosion barrier, enhancing mechanical protection and hydrogen barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal oxide protective coating is formed on a metallic substrate to provide corrosion protection, then corrosion resistance is improved, but electrical conductivity deteriorates
Solution Approach 1:
The coating is divided into multiple functional layers: a corrosion-resistant metal oxide layer (e.g., indium oxide, tin oxide) and a conductive intermediate layer (e.g., indium tin oxide with specific composition ratios). This segmentation allows each layer to optimize its specific function - the metal oxide provides corrosion protection while the conductive layer maintains electrical conductivity, resolving the contradiction between these two properties.
2Reliability
If precious metals are used in the coating to achieve high long-term stability and electrical conductivity, then reliability is improved, but cost increases
Solution Approach 1:
The patent replaces expensive precious metals (such as platinum, iridium) with cost-effective base metals like indium, tin, and their oxides. The coating system uses indium tin oxide (ITO) with specific indium content (40-85 wt%) combined with metal oxide layers to achieve the required long-term stability and electrical conductivity without relying on precious metals, significantly reducing material costs while maintaining performance.
3Loss of energy
If the indium content in the indium-tin oxide layer is increased to improve electrical conductivity, then electrical conductivity is improved, but corrosion resistance deteriorates
Solution Approach 1:
The coating system applies different composition ratios of indium and tin oxide in different layers to achieve local optimization. The indium tin oxide intermediate layer has higher indium content (60-85 wt%) to maximize electrical conductivity, while the outer metal oxide layer has lower indium content (10-40 wt%) and higher tin oxide content to provide superior corrosion resistance. This local quality variation resolves the contradiction between conductivity and corrosion 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 layer system achieves high electrical conductivity, long-term stability, and cost-effectiveness without using precious metals, providing excellent corrosion protection and mechanical durability for metallic substrates, thereby enhancing the performance and lifespan of bipolar plates.
Implementation Method 1
The layer system is preferably formed by a PVD or CVD process (PVD: Physical Vapour Deposition; CVD: Chemical Vapour Deposition)
Implementation Method 2
The layer system is preferably formed by a PVD or CVD process (PVD: Physical Vapour Deposition; CVD: Chemical Vapour Deposition)
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a layer system (1) for coating a metal substrate (2a) in order to form a flow field plate (2), the layer system comprising: - at least one cover layer (1a) made of metal oxide; - at least one intermediate layer (1b), which supports the cover layer (1a); and - a lower layer (1c), which supports the intermediate layer(s) (1b); wherein the cover layer (1a) is formed of indium tin oxide; wherein the indium tin oxide is optionally doped with at least one element from the group comprising carbon, nitrogen, boron, fluorine, hydrogen, silicon, titanium, tin and zirconium; wherein the at least one intermediate layer (1b) is formed of titanium nitride and/or titanium carbide and/or titanium carbonitride and/or titanium niobium nitride and/or titanium niobium carbide and/or titanium niobium carbonitrde and/or chromium nitride and/or chromium carbide and/or chromium carbonitride; and wherein the lower layer (1c) is formed of titanium or a titanium-niobium alloy or chromium. The invention also relates to a flow field plate having a layer system (1) of this type and to a fuel cell (10), electrolyzer or redox flow cell having a flow field plate (2, 2') of this type.