Electrochemical Properties of Niobium Modified AISI316L Stainless Steel Bipolar Plates for Direct Formic Acid Fuel Cell

To ameliorate the corrosion resistance and surface electrical conductivity of AISI316L stainless steel (316L SS) as bipolar plates for direct formic acid fuel cell (DFAFC), a niobium diffusion layer has been successfully prepared on 316L SS substrate via the plasma surface diffusion alloying (PSDA) technique. The niobium modified AISI316L stainless steel (Nb-316L SS) has a compact and successive niobium diffusion layer with a lower interfacial contact resistance (ICR) compared with bare 316L SS. The electrochemical behaviors of Nb-316L SS in simulated varied anode (0.05M H2SO4 + 2 ppm HF + xM formic acid (x = 2, 5, 10 and 15) solution at 50 °C) and cathode (0.05M H2SO4 + 2 ppm HF solution at 50 °C, bubbled with air) DFAFC environments are systematically studied. The results show that the corrosion resistance of 316L SS is distinctly bettered in both anode and cathode environments of DFAFC after the PSDA modification. After 4 h potentiostatic polarization tests, the ICR of bare and Nb-316L SS have increased at the clamping force of 140 N cm−2, but the increasing amplitude of the ICR for Nb-316L SS is much smaller than that of bare 316L SS.