Electrochemical behavior of niobium electrodeposited 316 stainless steel bipolar plate for PEMFC in choline chloride based ionic liquids

Abstract

Niobium was electrodeposited on 316 stainless steel bipolar plates of a fuel cell in water and air-stable choline chloride based ionic liquids. The electrochemical corruption property of bipolar plates in simulated PEMFC environment was investigated. It was showed that the plating film was distributed on the surface of 316 stainless steel like isolated islands with height less than 50 nm. The XPS, XRD results showed that a smooth and strong chemical inert film of NbO and Nb₂O₅ was formed on the surface of 316 stainless steel. In simulated cathodic condition, the corrosion potential of Nb coated stainless steel was improved by 244 mV, whilst in an anodic condition, it was improved by 105 mV. The current densities for the coated 316 stainless steel were decreased to 2.479 4 μA•cm^-2 from 14.810 μA•cm^-2 at -0.1 V and to 0.576 μA•cm^-2 from 13.417 μA/•cm^-2 at 0.6 V, respectively. It was implied that the niobium coating effectively decreased the corrosion rate. The results of the electrochemical tests indicated that the corrosion resistance of stainless steel was greatly improved after coated with niobium.

Keywords

stainless steel bipolar plates / niobium coating / choline chloride / ionic liquids / electro deposition / corrosion resistance / surface modification

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