High-temperature (120-200 ℃) proton exchange membrane fuel cells (HT-PEMFCs) based on a phosphoric acid (PA)-doped polybenzimidazole (PBI) membrane electrolyte are considered as an alternative fuel cell, because it has higher reaction kinetics for oxygen reduction reaction (ORR), more simplified water management and improved carbon monoxide (CO) tolerance than that of the lower-temperature proton exchange membrane fuel cell (LT-PEMFC, below 80 ℃) [1-4]. Meanwhile, the larger temperature gradient between inside of fuel cell stacks and outside of environmental temperature makes it easy for thermal management [5]. Different with LT-PEMFCs, the proton conductivity of HT-PEMFCs primarily rely on phosphoric acid molecules through Grotthuss mechanism [6]. A problem that comes with this is PA loss into gas diffusion layer and even bipolar plate, which results in fuel gas mass transport polarization loss and bipolar plate corrosion, having an extremely serious impact on the performance and durability of HT-PEMFCs [7].

In this study, nitrogen doped reduced electrochemically exfoliated graphene oxide and carbon black supported platinum (Pt/NrEGO₂-CB₃) has been prepared to solve these problems. On the one hand, the nitrogen doping could control the Pt nanoparticles size to an average of 4.88 ± 1.79 nm and prevent its growth through the strong interaction between Pt and N bonds, which lead to an increase of the electrochemical surface area (ECSA) from 61.41 m² g^-1 in commercial Pt/C to 73.92 m² g^-1 in Pt/NrEGO₂-CB₃. On the other hand, after 100 hours steady-state operation, the membrane electrode assembly (MEA) with Pt/NrEGO₂-CB₃ on both anode and cathode shows the mass power density of 1.652 W mg_Pt^-1 with a decay rate of 0.01 mV h^-1, which is 3 times higher than that of commercial Pt/C.

Reference

[1] P. Kallem, N. Yanar, H. Choi. Nanofiber-based proton exchange membranes: Development of aligned electrospun nanofibers for polymer electrolyte fuel cell applications. ACS Sustainable Chemistry & Engineering. 2018. 7(2): 1808-1825.

[2] J. Lobato, H. Zamora, J. Plaza, P. Cañizares, M.A. Rodrigo. Enhancement of high temperature PEMFC stability using catalysts based on Pt supported on SiC based materials. Applied Catalysis B: Environmental. 2016. 198: 516-524.

[3] H. Su, Q. Xu, J. Chong, H. Li, C. Sita, S. Pasupathi. Eliminating micro-porous layer from gas diffusion electrode for use in high temperature polymer electrolyte membrane fuel cell. Journal of Power Sources. 2017. 341: 302-308.

[4] Y. Hu, Y. Jiang, J.O. Jensen, L.N. Cleemann, Q. Li. Catalyst evaluation for oxygen reduction reaction in concentrated phosphoric acid at elevated temperatures. Journal of Power Sources. 2018. 375: 77-81.

[5] F.J. Pinar, P. Cañizares, M.A. Rodrigo, D. Úbeda, J. Lobato. Long-term testing of a high-temperature proton exchange membrane fuel cell short stack operated with improved polybenzimidazole-based composite membranes. Journal of Power Sources. 2015. 274: 177-185.

[6] M.A. Haque, A.B. Sulong, K.S. Loh, E.H. Majlan, T. Husaini, R.E. Rosli. Acid doped polybenzimidazoles based membrane electrode assembly for high temperature proton exchange membrane fuel cell: A review. International Journal of Hydrogen Energy. 2017. 42(14): 9156-9179.

[7] G. Liu, H. Zhang, J. Hu, Y. Zhai, D. Xu, Z.-g. Shao. Studies of performance degradation of a high temperature PEMFC based on H3PO4-doped PBI. Journal of Power Sources. 2006. 162(1): 547-552.