Electrophoretic Deposition of Titanium Nitride Onto 316 Stainless Steel As a Bipolar Plate for Fuel Cell Application

Abstract

The polymer electrolyte membrane fuel cell(PEMFC) is being considered as a clean source of power for the application of future energy owing to its high-power density, lower operating temperature than other fuel cells, and environment-friendliness [1]. For commercialization, the cost of bipolar plates (BPs) is a crucial factor among cell components, which comprises a high percentage of the total volume, weight, and the cost [2]. Graphite BPs is widely used due to high chemical stability and low surface contact resistance, but brittleness and machining cost are the critical concerns [3]. Stainless steel is commonly utilized an alternative material due to their high strength and chemical stability, low gas permeability. However, stainless steel suffers corrosion during PEMFC operation. Such corrosion deteriorates cell performance by dissolution of the metal ion into gas diffusion layer and increased interfacial contact resistance(ICR) of the formation of the passivation film [4]. Titanium nitride(TiN) can be one of the promising protective coating material in PEMFC due to the excellent durability, chemical stability, as well as good electrical conductivity. Various methods such as CVD [5], PVD [6], and sputtering [7] have been investigated to fabricate TiN films. In this study, we explore electrophoretic deposition (EPD) of TiN layers. It is known that EPD provides simple, versatile, easy adjustment of coating thickness and cost-effective method to fabricate homogeneous coatings onto complex shape as well as a porous substrate [8]. TiN powders were coated successfully onto a 316 stainless steel by EPD. The different particle size of TiN including 20nm, 80nm and 800nm TiN powders was used to investigate morphology of coating layers, EPD kinetics and mechanism. In addition, two kinds of additives, PDADMAC and PEI were used to obtain a uniform suspension and EPD mechanism. Although both additives cationic polymers, different polymeric structure and molecular weight would influence condition of suspensions and potentially properties of coating layers. The morphologies and structure of TiN coated surface were analyzed by SEM and XRD. The potentiodynamic and potentiostatic electrochemical tests were conducted to measure the corrosion resistance for the applicability of EPD of TiN as a protective layer of bipolar plate in PEMFC.