Abstract
AbstractTwo materials, polyaniline (PANI) and titanium nitride (TiN), used for bipolar plate (BPP) coatings have each shown promise in improving the corrosion resistance and contact resistance, respectively, of metallic bipolar plates. Polyaniline was shown to provide a barrier for the bipolar plate and to effectively lower the corrosion currents observed in ex situ corrosion tests. However, the interfacial contact resistance (ICR) between polyaniline coatings and gas diffusion layer (GDL) is high and results in high electrical losses. On the other hand, TiN is reported to achieve good conductivity and in some cases improved corrosion resistance.The two materials have also been investigated together in a composite coating and showed promising results, but the contact resistance of the coating was still too high for use in a commercial fuel cell. In this study, the application of an additional layer of TiN over the TiN‐polyaniline composite coating (a bilayer coating) is investigated. Composite bilayered PANI TiN coatings were deposited upon SS316L substrates. The optimized coating achieved U.S. Department of Energy (DoE) targets with potentiostatic corrosion currents of ∼0.024 μA cm−2 and ICR values of 11.2 mΩ cm2. PANI polymerization was confirmed, using Fourier‐transform infrared (FTIR) spectroscopy and TiN loadings were investigated with energy dispersive X‐ray (EDX) spectroscopy .
Highlights
Transportation accounts for 14% of all greenhouse gas emissions on the planet; new renewable technologies for use in the transportation sector are being investigated at ever increasing rates in the hope of stifling carbon emissions [1]
Polyaniline was coated onto the SS316L substrates via a 5 cycle cyclic voltammetry (CV)
A PANI-titanium nitride (TiN) composite bilayer was developed in a twostep electrochemical process and confirmed by energy dispersive X-ray (EDX) and Fourier-transform infrared (FTIR) studies
Summary
Transportation accounts for 14% of all greenhouse gas emissions on the planet; new renewable technologies for use in the transportation sector are being investigated at ever increasing rates in the hope of stifling carbon emissions [1]. A passive oxide layer forms on the surface of the stainless steel in the presence of oxygen, which offers additional corrosion protection in aggressive environments [13], and it causes the contact resistance to greatly increase, reducing the performance of the stack For this reason, coatings for metallic bipolar plates that provide an effective barrier to the harsh conditions have seen extensive research. This work looks to further development of polymer-metallic composite coatings, by optimizing a thin titanium nitride (TiN) polyaniline composite layer using low temperature plating solutions. This was modified to produce a bilayered coating with an electrodeposited surface layer of TiN. The aim here is to reduce the ICR achieved in literature to values within the DoE target while maintaining the reported corrosion resistance
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