The Performance Of 316L Stainless Steel As Direct Formic Acid Fuel Cell Bipolar Plate

As a new clean and high efficient energy technology,direct formic acid fuel cells?DFAFCs?have gained more and more attentions due to its fuel formic acid is non-toxic,non-flammable,good electrochemical oxidation performance and low Nafion membrane permeability.Researches on DFAFCs were mainly focus on the preparation of anode catalysts and catalyst carriers.However,the performance of the bipolar plate in strong corrosive formic acid were rarely reported.In this paper,the electrochemical behavior of 316 L stainless steel was investigated in simulated DFAFC environments.Interfacial Contact Resistance?ICR?was evaluated as an important parameter for bipolar plate in DFAFC before and after the potentiostatic polarization.To improve the electrochemical properties,we made surface modification of 316L stainless steel.The study and results are as follow:1.In simulated DFAFC anode environments?at 50?.0.05 mol/L H₂SO₄ + 2 ppm HF +x mol/L HCOOH,x= 2,5,10,15 mol/L?and cathode environments?at 50?,0.05 mol/L H₂SO₄ + 2 ppm HF purged air?,we make the electrochemical tests and measure the ICR.The results showed that the ICR of 316L stainless steel is about 550.2 mQ cm² and it is increased after electrochemical test.2.The niobium and niobium nitride alloying diffusion layers were respectively prepared on the surface of 316L stainless steel by the technology of plasma surface alloying.Both of the alloying diffusion layers are uniform in thickness,dense in microstructures without micropore and microcracks,and metallurgical bond with the 316L stainless steel substrate.In the simulated DFAFC environments,the niobium and niobium nitride alloying diffusion layers obviously improved the corrosion resistance,reduced the corrosion current density and interfacial contact resistance of 316L stainless steel and with good electrochemical stability.Compared with 316L stainless steel,the ICR of Nb-316L and Nb-N 316L are droped to 25.9 m?·cm² and 7.2 m?·cm².