The use of expensive PGM catalysts for the OER and HER leads to high production costs of Polymer electrolyte water electrolysis (PEWE). Moving towards lower iridium oxide (IrOx) catalyst loadings for the anode side can severely affect performance and stability [1]. Recent studies revealed that the structure of the interface between the anodic porous transport layer (PTL) and the catalyst layer (CL) is a crucial factor limiting cell efficiency and contributes significantly to the performance and use of the CL. The coarse structure PTL can develop inactive zones of the catalyst layer, which happens when the catalyst layer is not “close” to the connecting titanium structure [2]. The situation becomes worse when the IrO2 catalyst loading is reduced, and the catalyst layers become thinner. Recent evidence has shown that having additional Microporous layers (MPL) can overcome some of these issues by maximizing catalyst utilization and increasing cell efficiency. However, at low Ir loadings, a thin protective Pt coating on MPL is needed to avoid formation of TiOx passivation layer on the MPL surface and increase surface conductivity [3].In this work, we attempt to replace the thin protective Pt coating by adding an additional layer of Ti or TiN on the existing MPL aiming when using low loadings of IrO2 (0.5 – 0.1 mgIr cm-2). Vacuum plasma spraying (VPS) technology was used to apply TiN on the surface of MPL, while Ti was spray-coated, and vacuum sintered to create a hierarchically structured 3-layer PTL. Electrochemical performances of both Ti and TiN coated MPLs were evaluated by polarization curves and Electrochemical Impedance Spectroscopy measurements. The results are compared with a Pt coated MPL reference.
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