Abstract
Cost reduction and high efficiency are the mayor challenges for sustainable H2 production via proton exchange membrane (PEM) electrolysis. Titanium-based components such as bipolar plates (BPP) have the largest contribution to the capital cost. This work proposes the use of stainless steel BPPs coated with Nb and Ti by magnetron sputtering physical vapor deposition (PVD) and vacuum plasma spraying (VPS), respectively. The physical properties of the coatings are thoroughly characterized by scanning electron, atomic force microscopies (SEM, AFM); and X-ray diffraction, photoelectron spectroscopies (XRD, XPS). The Ti coating (50 μm) protects the stainless steel substrate against corrosion, while a 50-fold thinner layer of Nb decreases the contact resistance by almost one order of magnitude. The Nb/Ti-coated stainless steel bipolar BPPs endure the harsh environment of the anode for more than 1000 h of operation under nominal conditions, showing a potential use in PEM electrolyzers for large-scale H2 production from renewables.
Highlights
In 1973, Russell and coworkers introduced solid polymer electrolyte (SPE) electrolysis for the production of hydrogen from water splitting[1]
We report the development of a non-precious metal based, corrosion resistant and highly conductive coating of Nb/Ti for stainless steel bipolar plates
In our previous reports we demonstrated that the Pt/Ti coatings on stainless steel bipolar plates (BPP) are suitable for both anode and cathode, achieving a performance comparable to the reference cell[22]
Summary
In 1973, Russell and coworkers introduced solid polymer electrolyte (SPE) ( known as proton exchange membrane; PEM) electrolysis for the production of hydrogen from water splitting[1]. The electrical properties and contact between the interconnectors, namely bipolar plates (BPP) or current collectors (CC), and the electrodes can be improved as well by using precious metal coatings[14,15,16] or by optimizing other functional properties[17,18,19] These coatings are quite expensive due to chemical processing, cleaning and etching procedures (e.g. dimensional stable anodes, DSA); and the use of large amount of expansive and scarce metals such as Ir and Pt. The second approach aims to reduce the specific hydrogen production costs by decreasing CAPEX. We report the development of a non-precious metal based, corrosion resistant and highly conductive coating of Nb/Ti for stainless steel bipolar plates It allows reducing the production costs of bipolar plates, lowering the amount of titanium in general, and decreasing the interface contact resistance (ICR). A systematic physical and electrochemical characterization of the coating was carried out and the study was finalized with a 1000 h durability test in a high-end commercial PEM electrolyzer stack without showing any degradation
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