Strategies to Enhance the Activity and Durability of MEA for High Temperature PEMFC

Abstract

High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) using phosphoric acid (PA)-doped polybenzimidazole (PBI) membrane have advantages of enhanced electrode kinetics, improved carbon monoxide (CO) tolerance, and simplified water management [1], while poisoning of the catalysts by phosphate adsorption to deactivate them remains as an issue [2]. In addition, the deliquescence of PA (absorption of moisture when exposed to the humid atmosphere) resulted in the un-even distribution of PA [3], therefore deterioration in the MEA performance.To mitigate these issues, we have tried to optimize the structures of the commercial electrode and controlled the hydrophilicity of the electrode through additional deposition of very small amounts of Pt (anode) [4] or PtCu (cathode) using pulse electrodeposition. It was confirmed that the cell performance was improved by adjusting the hydrophilicity, improving the distribution of PA, and changing the formation of the triple phase boundary (TPB) of the catalyst layer. The performance loss due to the deliquescence of PA in the commercial PBI membrane when exposed to various humidity conditions was mitigated through an additional PA dosing method on the electrode [5].Apart from the activity, the durability of the modified MEAs exhibited different aspects. Various MEAs were fabricated by selectively combining the results of the pulse electrodeposition and PA dosing, and the durability tests for the MEAs were performed with repeated cycles of turning on (180°C) and turning off (room temperature). 40 cycles of repeated temperature variation deactivated most of the MEAs regardless of the modifications, while the amounts of the deterioration were the functions of the modification methods. Interestingly, the performance deterioration was more obvious in the observation of the peak powers while the change in the cell potential at low current density region (200 mA/cm2) was not substantial, implying the deterioration was greatly related to the mass transport management. The different behaviors in the durability according to the modification methods along with the materials characterization using electrochemical and spectroscopic analyses will be introduced at the conference.[1] I. I. Ponomarev, K. M. Skupov, A. V. Naumkin, V. G. Basu, O. M. Zhigalina, D. Y. Razorenov, I. I. Ponomarev, Y. A. Volkova, RSC Adv., 9 (2019) 257-267.[2] S. Kaserer, K. M. Caldwell, D. E. Ramaker, C. Roth, J. Phys. Chem. C, 117 (2013) 6210-6217.[3] S. Jahangiri, I. Aravi, L. I. Sanli, Y. Z. Menceloglu, E. Ozden-Yenigun, Polym. Advan. Technol., 29 (2018) 594-602.[4] D.-K. Kim, H. Kim, H. Park, S. Oh, S. H. Ahn, H.-J. Kim, S.-K. Kim, J. Power Sources, 438 (2019) 227022-227030.[5] H. Park, H. Kim, D.-K. Kim, W. J. Lee, I. Choi, H.-J. Kim S.-K. Kim, Int. J. Hydrogen Energy, (2019) DOI:10.1016/j.ijhydene.2020.03.039.