Correlation of Changes in Electrochemical and Structural Parameters due to Voltage Cycling Induced Degradation in PEM Fuel Cells

Abstract

Membrane electrode assemblies were degraded by voltage cycling in hydrogen/air atmosphere. The impact of degradation on fuel cell performance was measured by various electrochemical characterization techniques. Loss of electrochemically active surface area was correlated to kinetic voltage losses at low current density as well as losses at high current density due to oxygen transport limitations. It was found that the oxygen transport resistance scales proportionally to the inverse of normalized platinum surface area. The change in the catalyst layer structural properties due to voltage cycling was visualized by electron microscopy. A new method of calculating changes in platinum loading of degraded samples by transmission electron microscopy is presented and shows redistribution of platinum in the catalyst layer due to platinum dissolution.

Temperature control strategy for polymer electrolyte fuel cells

“…[2][3][4][5][6][7] Though the fuel cell industry continues to rise, the commercialization of PEFCs is still limited, which is partly due to its stability issue. 8,9 The operating temperature greatly affects the stability and performance of the PEFC system. 10 For example, higher operation temperature helps to improve the velocity of the protons passing through the membrane and enhance the electrochemical kinetics, thus leading to a better system performance.…”

“…where m O 2 , k up, ca , k down, ca , P ca, u , P ca , P ca, d , and M O 2 are oxygen mass, cathode inlet mass flow rate coefficient, cathode outlet mass flow rate coefficient, cathode inlet pressure, cathode pressure, cathode outlet pressure, and molar mass of oxygen, respectively. The calculation of stack temperature T in Equation (A.2) is based on the thermal model from Equations (1) to (8).…”

“…The entire controlling process would keep circulating until the controlling objective is achieved. In detail, the thermodynamic model described in Equations (1) to (8) is rewritten to the state space form. The MPC will use this state space model to predict future behaviour of the system and calculate a control output by solving an optimization problem.…”

“…Though the fuel cell industry continues to rise, the commercialization of PEFCs is still limited, which is partly due to its stability issue . The operating temperature greatly affects the stability and performance of the PEFC system .…”

Analysis of HT-PEM MEAs’ Long-Term Stabilities

“…Furthermore, it can be observed that the drying cracks in the catalyst layer widened significantly in the course of the experiment as shown in Figure 8a,b). The chosen test conditions seem to indicate structural changes in the CL [30] for both MEA types (see Figures 6 and 7). Similar observations were made by Pokhrel at al.…”