Study on electrode carbon corrosion of high temperature proton exchange membrane fuel cell

Abstract

Proton exchange membrane fuel cells (PEMFCs) allow producing the energy in clean and efficient way using hydrogen. They are being used in a variety of applications which characterize better performance. High temperature PEMFC (HT-PEMFC) technology is being developed as it exhibits advantages over low temperature PEMFC (LT-PEMFC). Though, the commercialization of HT-PEMFCs is still hampered because of performance degradation and limited life time. The performance of HT-membrane electrode assemblies (HT-MEAs) is affected because of various degradation mechanisms occurring during operation, like membrane thinning, phosphoric acid leaching, electrode carbon support corrosion, which causes the loss of electrochemically active surface area (ECSA) of platinum catalyst due to platinum particle agglomeration. The aim of this work is to study electrode carbon corrosion under accelerated stress test (AST) conditions. Carbon corrosion is influenced by temperature, relative humidity, open-circuit voltage (OCV), cell potential, start stop cycling and also fuel starvation. The influence of OCV and higher cell voltages on carbon corrosion is studied in phosphoric acid doped polybenzimidazole (PBI) based HT-MEA of 100 cm2 active area. The carbon corrosion is assessed using IR spectroscopy by detecting the carbon dioxide gas in cathode exhaust during 30 minutes operation at AST conditions. 63.55 µg.cm-2 of carbon is lost as carbon dioxide after the 1.2 V potential test. In-situ performance deterioration is observed using electrochemical methods like polarisation curves, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Impedance studies showed no change in membrane resistance whereas cathode polarisation losses increased after the AST. TEM analysis shows that the platinum particle size is increased after the operation at 1.2 V potential test. The ECSA of HT-MEA decreased over the time due to operation at various AST conditions which affected the fuel cell performance. The ECSA decreased from 20.06 m2.g-1 to 15.43 m2.g-1 of Pt after the 1.2 V applied potential test.