Novel Two-polymer Membrane Boosts Hydrogen Fuel Cell Performance

Scientists have designed a highly conductive hydrogen fuel cell ion-exchange membrane using two readily available polymer materials

Fuel cells are an attractive sustainable energy source due to their eco-friendly by-product, water. However, existing fuel cells are either expensive or low performance. Now, scientists from Korea have designed a robust and highly conductive fuel cell ion-exchange membrane using two readily available polymer materials and a unique technique, opening doors to fuel cells that are both cheap and high performing, bringing us closer to realising a hydrogen economy.

A considerable portion of the efforts to realize a sustainable world has gone into developing hydrogen fuel cells so that a hydrogen economy can be achieved. Fuel cells have distinctive advantages: high energy-conversion efficiencies (up to 70 percent) and a clean by-product, water. 

In the past decade, anion exchange membrane fuel cells (AEMFC), which convert chemical energy to electrical energy via the transport of negatively charged ions (anions) through a membrane, have received attention due to their low-cost and relative environment friendliness compared to other types of fuel cells. But while inexpensive, AEMFCs suffer from several major drawbacks such as low ion conductivity, low chemical stability of the membrane, and an overall lower performance rate than its counterparts. Now, in a study published in the Journal of Materials Chemistry A, scientists from Korea report a novel membrane that is both thin and strong and takes care of these drawbacks.

To develop their membrane, the scientists used a novel method: they chemically bonded two commercially available polymers, poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) without using a cross-linking agent. 

Professor Tae-Hyun Kim from the Incheon National University, who led the study, explains, “a previous study made a similar attempt to fabricate anion exchange membranes (AEMs) by cross-linking PPO and SEBS with diamine as a cross-linking agent. While the AEMs displayed excellent mechanical stability, the use of diamine could have led to different reactions other than those between PPO and SEBS, which made it difficult to control the properties of the resultant membrane. 

“Therefore, in our study, we cross-linked PPO and SEBS without any cross-linking agent to ensure that only PPO and SEBS react with each other.” 

The strategy used by Prof. Kim’s team also involved adding a compound called triazole to PPO to increase the membrane’s ion conductivity.

Membranes fabricated using this method were up to 10 µm thin and had excellent mechanical strength, chemical stability, and conductivity at even 95 percent room humidity. Together, these conferred a high overall performance to the membrane and to the corresponding fuel cell on which the scientists tested their membrane. When operated at 60°C, this fuel cell exhibited stable performance for 300 hours with a maximum power density surpassing those of existing commercial AEMs and matching cutting-edge ones.

Excited about the future prospects of this novel promising AEM, Prof. Kim said, “the polymer electrolyte membranes in our study can be applied not only to fuel cells that generate energy, but also to water electrolysis technology that produces hydrogen. Therefore, I believe this research will play a vital role in revitalising the domestic hydrogen economy.”