Understanding Carbon Corrosion Damage to Fuel Cell Electrodes: Towards Reversal Invincible

Abstract

Polymer electrolyte membrane fuel cells (PEMFCs) have the advantage of low carbon dioxide emission and high efficiency over internal combustion engines in automobile applications1. However, durability of PEMFCs is one of the major obstacles for a wide range of applications. One such durability issue is the cell reversal caused by hydrogen starvation. It results in severe carbon support corrosion in the anode catalyst layer and dramatically decreases the fuel cell performances2. Material-based solutions to increasing the cell’s tolerance to reversal are preferable since it will not increase the system control complexity. Effective material-based solutions include using more corrosion-resistant carbon supports3 and adding water electrolysis catalysts to promote the oxygen evolution reaction (OER) over carbon corrosion4,5. However, these current solutions are still not resilient enough to guarantee long-term durability of PEMFCs under extreme hydrogen starvation conditions. This present work has examined different anode configurations and their effectiveness in preventing cell performance degradation during hydrogen starvation events. Three different anode structures are studied and compared, including i) a conventional Pt/C gas diffusion electrode (GDE), ii) an anode made of platinum (Pt) black and gas diffusion layer (GDL), and iii) an anode made of Pt black, a thin titanium (Ti) protection layer (10 μm in thickness), and a GDL. Figure 1a shows the change in cell voltage of PEMFCs when hydrogen was cut off while keeping a constant current density of 0.2 A/cm2. During reversals, the Pt/C GDE anode and the anode made of Pt black and a GDL experienced a sudden voltage drop within 5 min which was attributed to severe carbon corrosion damage. In contrast, the cell with Ti protection layer between the Pt black and the GDL was stable for 60 min of reversal without a large voltage drop. As shown in Figire 1b, the cell voltage of the fuel cell with an anode made of Pt black, a Ti protection layer, and a GDL decreased less than 10 % even after the accumulated voltage reversal time of 240 min. Thus the anode with Ti protection layer is much more effective compared with the common reversal tolerant anode approach of adding OER catalyst (i.e., 50 wt% IrO2) to the anode5. Both hydrogen starvation tests and post-reversal electrochemical characterizations demonstrate that using a carbon-free anode with a corrosion-resistant barrier layer is highly effective in preventing cell reversal damage over long periods of time. Figure 1