Determining Substrate Oxygen Transport Resistance at Limiting Current Using Pore Network Modelling

Abstract

The polymer electrolyte membrane (PEM) fuel is a promising technology to supplant traditional, greenhouse gas emitting energy conversion devices. However, widespread commercial adoption of the PEM fuel cell is hindered by the high cost of the precious metals required for its catalyst (1). The amount of catalyst required in a PEM fuel cell can be reduced if the reactant (oxygen) is delivered more efficiently to the catalyst. Therefore, previous studies have sought to characterize the mechanisms affecting oxygen transport in PEM fuel cells (2)(3)(4)(5). In past studies, the oxygen transport resistance of a PEM fuel cell was measured at limiting current, and this value was further decomposed into contributions from individual PEM fuel components using empirical modelling. By resolving each PEM fuel cell component’s contribution to oxygen transport resistance, an informed approach can be undertaken to design next generation components with enhanced oxygen transport capabilities.In this study, we employed pore network modelling to quantify the oxygen transport resistance arising from the presence of liquid water within the substrate region of the gas diffusion layer (GDL). First, we captured the operando liquid water distribution within a PEM fuel cell operating at limiting current using synchrotron X-ray radiography. Next, we used a combination of invasion percolation and an in-house water invasion inlet selection algorithm to partially saturate the representative pore network of the substrate and to reproduce the mean water saturation. Finally, we obtained substrate oxygen transport resistance values by performing transport simulations on the partially saturated pore network and compare our findings with the experimental observations. References X. X. Wang, M. T. Swihart, and G. Wu, Nature catalysis, 2, 7 (2019).D. R. Baker, D. A. Caulk, K. C. Neyerlin, and M. W. Murphy, J. Electrochem. Soc., 156, B991 (2009).T. Reshtenko, J. St-Pierre, J. Electrochem. Soc., 161, F1089 (2014)D. Muirhead, R. Banerjee, M. G. George, N. Ge, P. Shrestha, H. Liu, J. Lee, A. Bazylak, Electrochimica Acta, 274 (2018).N. Ge, P. Shrestha, M. Balakrishnan, D. Ouellette, A. K. C. Wong, H. Liu, C. H. Lee, J. K. Lee, A. Bazylak, Electrochimica acta, 328 (2019).