Titanium Fuel Cell Separator Surface Layer for Low Contact Resistance
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Solution Overview
Problem
Titanium materials for solid polymer fuel cell separators face high initial contact resistance and increased resistance during power generation due to the formation of passivation films and elution of titanium ions, and existing methods using precious metals or electroconductive compounds are costly and affect recyclability.
Innovation Solution
A titanium material with a surface layer structure containing Ti compounds with C or N, covered by titanium oxide and/or metal Ti, where XPS analysis detects specific peak heights and ratios, and a method involving nitric acid treatment to form a stable oxide layer with low ion elution and high electroconductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation film forms on the titanium material surface during power generation, then corrosion resistance is improved, but contact resistance with carbon paper increases
Solution Approach 1:
The invention creates a surface layer with non-uniform composition and structure, where the outer layer contains titanium oxide and metal Ti for low contact resistance, while the inner layer contains Ti compounds with C or N for corrosion resistance. This local differentiation of properties resolves the contradiction between corrosion resistance and contact resistance.
Solution Approach 2:
The invention forms a composite surface layer structure consisting of multiple phases (titanium oxide, metal Ti, and Ti compounds with C or N) with different functional properties. The composite structure enables simultaneous achievement of low contact resistance (from metal Ti and titanium oxide) and high corrosion resistance (from inner layer Ti compounds).
2Object-affected harmful factors
If precious metals or electroconductive compounds are deposited on the titanium material surface, then contact resistance is reduced, but manufacturing cost increases
Solution Approach 1:
The invention uses a self-organizing surface treatment process where titanium ions are selectively removed and reprecipitated to form the desired surface layer structure. This self-organizing process eliminates the need for expensive precious metal deposits or complex external coating processes, thereby reducing manufacturing cost while achieving low contact resistance.
Solution Approach 2:
The invention replaces expensive precious metals (Au, Ag, Pt, Pd, Ru, Rh, Ir, Os) with abundant and inexpensive titanium-based compounds. The surface layer is formed from the titanium material itself through controlled ion removal and reprecipitation, eliminating the need for costly external coating materials.
3Object-affected harmful factors
If electroconductive compound particles are deposited on the titanium material surface, then contact resistance is reduced, but power generation ability declines due to metal ion elution
Solution Approach 1:
The invention converts the harmful effect of titanium ion elution (which normally causes contact resistance increase) into a beneficial process by controlling the elution and reprecipitation of titanium ions to form a low-resistance surface layer. The same ion transport mechanism that causes problems is harnessed to create the desired surface structure with low contact resistance and maintained power generation ability.
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 solution provides a titanium material with low initial and sustained contact resistance, reducing manufacturing costs and maintaining performance and recyclability, while suppressing the increase in contact resistance during fuel cell operation.
Implementation Method 1
immersing a titanium material in a nitric acid aqueous solution having a concentration of 15 to 59 mass% and a temperature of 40 to 120°C for 5 seconds to 120 minutes
Implementation Method 2
the Ti compound being covered by titanium oxide and/or metal Ti... high electroconductivity
Data Source
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AI summary
A titanium material for a solid polymer fuel cell separator having a low contact resistance and a method of production of the same, the titanium material having at its surface a surface layer structure in which particles of a Ti compound containing either C or N are dispersed, the particles of Ti compound being covered by titanium oxide and/or metal Ti, characterized in that, when analyzed from the surface by XPS, a Ti2p spectrum of TiO2 is detected, further, at a Ti2p spectral energy range of TiO and/or a Ti2p spectral energy range of metal Ti, a Ti maximum detection peak height is at least 3 times the standard deviations of the background at the respective spectral energy ranges, and at a C1s spectral energy range and N1s spectral energy range, a maximum detection peak height is less than 3 times the standard deviations of the background at the respective spectral energy ranges of C1s and N1s, are provided.