Composite Poly(norbornene) Anion Conducting Membranes for Achieving Durability, Water Management and High Power (3.4 W/cm²) in Hydrogen/Oxygen Alkaline Fuel Cells

Abstract

Alkaline fuel cells and electrolyzers are of interest because they have potential advantages over their acid counterparts. Highconductivity anion conducting membranes were analyzed and used in alkaline hydrogen/oxygen fuel cells. The membranes were composed of reinforced block copolymers of poly(norbornenes) with pendant quaternary ammonium head-groups. It was found that membranes with light cross-linking provided excellent mechanical stability and allowed very high ion exchange capacity polymers to be used without penalty of excessive water uptake and swelling. The optimum membrane and fuel cell operating conditions were able to achieve a peak power density of 3.4 W/cm 2 using hydrogen and oxygen. The performance increase was greater than expected from minimizing ohmic losses. Mechanical deformations within the membrane due to excess water uptake can disrupt full cell operation. Cells were also run for over 500 h under load with no change in the membrane resistance and minimal loss of operating voltage.

Achieving High‐Performance and 2000 h Stability in Anion Exchange Membrane Fuel Cells by Manipulating Ionomer Properties and Electrode Optimization

“…Experiential parameters for the DMA were set to 0.1% strain and a preload force of 0.01 N with a force track of 125%. [26] Electrode Fabrication Using GTXX Ionomers: GDEs were fabricated using a previously developed method [16,19] where a catalyst ink was made from the GTXX ionomers, DI H 2 O/isopropyl alcohol solvent, and Pt-based electrocatalysts. 40% Pt/C (Alfa Aesar HiSPEC 4000, Pt nominally 40 wt%, supported on Vulcan XC-72R carbon) was used at the cathode and 60% Pt-Ru/C (Alfa Aesar HiSPEC 10000, Pt nominally 40 wt%, and Ru, nominally 20 wt%, supported on Vulcan XC-72R carbon) was used at the anode.…”

“…Recently, Mandal et al, reported highly conductive crosslinked poly(norbonene) membranes (198 mS cm −1 ) that showed no significant ionic conductivity loss over 1000 h in 1 m KOH at 80 °C. [7] Huang et al, used similar materials in AEMFCs, enabling very high peak power density to be achieved (3.4 W cm −2 ) under H 2 /O 2 reacting gases, [26] which was recently improved to 3.5 W cm −2 by using thinner membranes. [27] In this study, three poly(norbornene) tetrablock copolymer ionomers with different IEC, molecular weight, dispersity, and water uptake were synthesized and fully characterized for their physical and electrochemical properties.…”

Quantifying and elucidating the effect of CO2 on the thermodynamics, kinetics and charge transport of AEMFCs

“…However, over the past two years, a significant increase in the peak power density has been observed, [5][6][7][8][9] with state-ofthe-art AEMFCs having the ability to achieve values over 3 W cm À2 operating on H 2 /O 2 gas feeds. 10 Also, the performance stability of AEMFCs has improved dramatically during this time, with multiple groups reporting 500+ hour stability at low degradation rates (5-10%). [11][12][13][14] Now that AEMFC performance and stability has been enhanced to the point where their future deployment in real applications can be seriously contemplated, it is now an important time in AEMFC development to begin to answer some of the other lingering issues that have to date been mostly put aside in the literature.…”

Improving the water management in anion-exchange membrane fuel cells via ultra-thin, directly deposited solid polymer electrolyte

“…Nonetheless, the highest AEMFC performances reported to date are based on this fabrication method. 3,22 DMD-10 shows a maximum power density of 800 mW cm À2 (compared to DMD-5 and DMD-3), which is likely a result of the thicker membrane, leading to increased ionic resistance (42 mOhm cm 2 @ 2000 mA cm À2 ) and an earlier onset of mass transport losses. The increased mass transport losses can most probably be ascribed to the reduced water back diffusion from the anode to the cathode side caused by the thicker membrane, 12,23 since all other fabrication and operation parameters were kept the same.…”

“…2 In particular in the past three years, the performance of AEMFCs has dramatically risen, surpassing 3 W cm À2 (under H 2 /O 2 conditions). 3 Although signicant progress has been made in the development of AEMFCs in the last decade, major challenges remain. 2 One issue is the sluggish HOR on the anode side, which, using platinum as a catalyst, is about two orders of magnitude slower than in acidic media.…”