Numerical study of triple-phase boundary length in high-temperature proton exchange membrane fuel cell

Catalyst layer (CL) is the most important component in the high-temperature proton exchange membrane fuel cell (HT-PEMFC), as it offers reaction sites for hydrogen oxidation reaction (HOR) and oxygen reduction reactions (ORR). As the electrochemical reactions take place at gas/electron/proton interface, the length of this triple-phase boundary (TPB) in the CL governs the rate of electrochemical reactions. As the TPB in the HT-PEMFC has not been studied yet, a numerical non-isothermal 3D model and a percolation micro model were developed in this work to investigate the effect of CLs' properties on both the TPB length and cell performance. The volume fractions, particle size, and particle size ratio of ionomer and Pt/C were selected for optimization. The results show that peak current density could be achieved at an ionomer volume fraction of 52%. Further improvement of cell performance requires smaller particle size and smaller particle size ratio of ionomer. Novelty statement: A three-dimensional non-isothermal model of HT-PEMFC was developed. By adopting the percolation model, length of triple phase boundary of HT-PEMFC was successfully quantified. The particle parameters including the particle size and ionomer volume fraction can be optimized to increase the length of triple phase boundary, thus achieving higher cell performance.