Porous Proton Exchange Membrane with High Stability and Low Hydrogen Permeability Realized by Dense Double Skin Layers Constructed with Amino tris (methylene phosphonic acid)

Abstract

Porous proton exchange membranes (PEMs) with abundant porous structures show enhanced phosphoric acid (PA) doping levels and proton transport capability. However, the high PA loss rate and serious hydrogen cross-over lead to poor membrane stability. Enhancing the stability of PA-doped porous PEMs is therefore crucial for obtaining high-performance proton exchange membrane fuel cells. Herein, a porous polybenzimidazole membrane with dense double skin layers is reported using amino tris (methylene phosphonic acid) (ATMP) constructed. This membrane effectively alleviates hydrogen permeation and PA loss in a water/anhydrous environment and exhibits enhanced stability. Surprisingly, as an organic proton conductor, ATMP has strong hydrogen bonding with PA, leading to the formation of more continuous proton transport channels. Due to the dense double skin layers protection and the synergistic mass transfer of ATMP and PA, the porous membrane shows excellent proton conductivity (0.112 S cm −1 ) and a H 2 -O 2 fuel cell peak power density of 0.98 W cm −2 at 160 °C. Moreover, it presents excellent fuel cell stability, with a voltage decay rate of only 5.46 µV h −1 . In addition, the porous membrane surpasses the traditional working temperature range, operating in the range of 80-220 °C. This study provides new insight into developing high-performance porous PEMs.

Construction of dense H-bond acceptors in the channels of covalent organic frameworks for proton conduction

“…These results suggested the successful synthesis via polycondensation. Additionally, solid-state 13 C cross-polarization/magic-angle spinning solid-state nuclear magnetic resonance (CP/MAS ssNMR) was also performed to further conrm the chemical structure of PyTTA-BMTP-COF (Fig. 2b, black curve and S1a †) and PyTTA-DHTA-COF (Fig.…”

“…Then, we further used 13 C solid-state NMR to investigate the binding sites aer the addition of H 3 PO 4 of PA@PyTTA-BMTP-COF (Fig. 2b, black curve) and PA@PyTTA-DHTA-COF (Fig.…”

“…[6][7][8][9][10][11] However, the most advanced PEMs (e.g., Naon) experience a plunge in conductivity at high temperature due to the low relative humidity (RH). 12,13 The operation of PEMs under high temperature or anhydrous conditions is a signicant technology that can provide high electrode catalytic efficiency. 14 However, the amorphous structure of mainstream polymer materials limits the exploration of the proton conduction mechanism.…”

Performance degradation and mitigation of high temperature polybenzimidazole-based polymer electrolyte membrane fuel cells

“…no crosslinking). 99 The test was conducted at 160 1C and 0.2 A cm À2 for periods of up to 13 000 h. The steady state operation was disturbed as little as possible with in-line diagnostics only via electrochemical impedance spectroscopy (EIS). The cell showed an average degradation rate of 0.5 mV h À1 within the first 9200 h and of 1.4 mV h À1 for the full test period of 13 000 h. The cell based on the reference membrane showed degradation rates of 2.6 mV h À1 and 4.6 mV h À1 within the respective time span.…”

“…The improved PA retention characteristics has also been observed for crosslinked PBI structures equipped with QA functionalities. 92 Strategies to mitigate the performance degradation due to the acid loss are discussed in a recent perspective, 93 and a few specific examples include use of intrinsically microporous polymers 94 or the incorporation of inorganic solid acids, 95 surface functionalized inorganic particles, 96 or clays 97 that contribute to immobilization of the excess PA. Other approaches make use of membranes containing graphene layers 98 or densified crosslinked layers 99 to contain the PA without compromising the through-plane proton conductivity.…”