Effect of Cathode Stoichiometry on Local Performance of Proton Exchange Membrane Fuel Cell with Dead-Ended Anode

Abstract The cathode stoichiometry ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper S Subscript c a" display="inline" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">S</mml:mi> <mml:mi>ca</mml:mi> </mml:msub> </mml:math> ) is a key operational parameter that determines water-nitrogen management and durability of proton exchange membrane fuel cell with dead-ended anode (DEA-PEMFC). To clarify the role of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper S Subscript c a" display="inline" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">S</mml:mi> <mml:mi>ca</mml:mi> </mml:msub> </mml:math> in DEA-PEMFC performance, this study employed a combination of numerical simulation and experimental testing. The results indicate that increasing <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper S Subscript c a" display="inline" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">S</mml:mi> <mml:mi>ca</mml:mi> </mml:msub> </mml:math> to the range of 2–2.5 significantly enhances water purge on the cathode side, mitigates the transmembrane water concentration gradient between the anode and cathode, and reduces liquid water saturation at the anode flow channel outlet, thereby alleviating local hydrogen mass transport limitations. At the same time, the increased total airflow and pressure drop at the cathode intensify the permeation and accumulation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper N 2" display="inline" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">N</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:math> across the membrane to the anode, resulting in a decrease in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper H 2" display="inline" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">H</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:math> partial pressure at the anode outlet and suppression of local performance. During the initial startup, different <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper S Subscript c a" display="inline" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">S</mml:mi> <mml:mi>ca</mml:mi> </mml:msub> </mml:math> values exert little influence on the local current density distribution at the cathode. After 30 min of continuous operation, a moderate increase in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper S Subscript c a" display="inline" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">S</mml:mi> <mml:mi>ca</mml:mi> </mml:msub> </mml:math> mitigates the local current density decay in the outlet region, whereas an excessively high <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper S Subscript c a" display="inline" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">S</mml:mi> <mml:mi>ca</mml:mi> </mml:msub> </mml:math> reduces membrane water content and increases impedance. Therefore, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper S Subscript c a" display="inline" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">S</mml:mi> <mml:mi>ca</mml:mi> </mml:msub> </mml:math> must be carefully controlled to effectively optimize DEA-PEMFC performance.