Chromium nitride films on stainless steel as bipolar plate for proton exchange membrane fuel cell

Abstract

Abstract A series of chromium nitride films are prepared on stainless steel substrates by pulsed bias arc ion plating (PBAIP) at different N 2 flow rate as bipolar plates for proton exchange membrane fuel cell (PEMFC). The film chemical composition and phase structure are characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD). The characterization results indicate that the nitrogen content of deposited films varies from 0.28 to 0.50, and the phase structure changes from mixtures of Cr + Cr 2 N, pure Cr 2 N through Cr 2 N + CrN, to pure CrN. The interfacial contact resistance between samples and carbon paper is measured by Wang's method, and a minimum value of 5.8 mΩ cm 2 is obtained under 1.2 MPa compaction force. The anticorrosion property is examined by potentiodynamic test in the simulated corrosive circumstance of the PEMFC under 25 °C, and the lowest corrosive current density of 5.9 × 10 −7 A cm −2 is obtained at 0.6 V (vs. SCE). Stainless steel substrates coated by the film with lowest contact resistance are chosen as the bipolar plates to assemble cells. An average voltage value of 0.62 V is achieved at 500 mA cm −2 , which is close to that of the cell with Ag-plated bipolar plates.