Multi-objective optimization of graded catalyst layer to improve performance and current density uniformity of a PEMFC

Abstract

The optimal use of compositions (platinum and ionomer) in cathode catalyst layers (CCLs) is essential to enhance the performance and improve the current density uniformity of proton exchange membrane fuel cells (PEMFCs). This paper presents a numerical study of graded CCL for a PEMFC. A one-dimensional, two-phase, non-isothermal model is developed, and the concept of the high power range (HPR) is defined. The effects of operating voltage and composition gradients across the catalyst layer thickness on output performance and current density distribution are investigated within the HPR. The results show an intense conflict between the output performance and current density uniformity, and only when biasing ionomer toward the membrane and operating in the higher spectrum of the HPR could improve them simultaneously. Otherwise, the improvement of one indicator means the deterioration of another. Finally, with the consideration of the interaction between the operating voltage and the gradients of platinum and ionomer, a multi-objective optimization is conducted to improve the aforementioned two indicators. Compared to the base case, the current density uniformity and the output performance were improved by 71.4% and 5.26%, respectively, which provides a solution to achieve higher performance and more uniform current density.