Irreversible thermodynamics-driven optimization of proton exchange membrane fuel cell with gradient-structured cathode catalyst layers

Gradient electrode design has been a key tool for reducing the cost and increasing the efficiency of proton exchange membrane fuel cell (PEMFC). However, due to challenges in balancing the trade-off between efficiency and uniformity, this technique still has not been widely applied. To address this challenge, a one-dimensional, two-phase, non-isothermal PEMFC model is constructed, and multi-physical field distributions inside the cell are investigated under different ionomer and Pt gradient distributions. Furthermore, within the framework of nonequilibrium thermodynamics, an evaluation metric dealing with the trade-off between efficiency and nonuniformity is proposed. Results demonstrate that the reverse ionomer gradient distribution significantly improves the cell output power by 6.2 %, while the forward distribution of the ionomer notably reduces the output power by 23.7 %. An increase in Pt loading near the membrane side results in a 1.7 % power improvement, and also reduces temperature nonuniformity under high current density. Moreover, the proposed evaluation metric can effectively assess the “gain” and “cost” of different gradient electrode designs, based on which two optimal design regions for the ionomer and Pt gradient distributions are identified. All these facilitate the integration of thermodynamic and electrochemical principles to guide the design of gradient electrodes for PEMFC.