Next-generation membrane cuts toluene crossover to boost hydrogen storage performance

A Korean research team has developed a new proton exchange membrane (PEM) that significantly enhances the performance of electrochemical hydrogen storage systems. The work was published as a cover article in the Journal of Materials Chemistry A.

Dr. Soonyong So of the Korea Research Institute of Chemical Technology (KRICT) and Professor Sang-Young Lee of Yonsei University have developed a next-generation PEM for LOHC-based electrochemical hydrogen storage using a hydrocarbon-based polymer called SPAES (sulfonated poly(arylene ether sulfone)).

This SPAES membrane reduces toluene permeability by over 60% compared to the commercially available perfluorinated PEM Nafion and improves the Faradaic efficiency of hydrogenation to 72.8%.

Liquid organic hydrogen carriers (LOHCs), such as toluene, are promising liquid compounds for storing and transporting hydrogen. Unlike compressed (over 100 bar) or liquefied (-252.9°C) hydrogen, LOHCs can be handled under milder conditions.

However, in electrochemical hydrogenation systems, a common issue is the undesired crossover of toluene through the membrane, which not only reduces efficiency but also contaminates the oxygen evolution reaction (OER) catalyst on the anode side.

To address these concerns, the research team designed a new hydrocarbon-based SPAES membrane with narrowed hydrophilic domains (approx. 2.1 nm), which serve as proton pathways in the membrane. These narrow domains drastically reduce the permeability of toluene molecules, decreasing their diffusivity by a factor of 20.

As a result, the toluene crossover was reduced by 60%, and the Faradaic efficiency increased from 68.4% (Nafion) to 72.8%. In long-term operation (48 hours), the voltage degradation rate decreased by 40%, from 1270 mV/h (Nafion) to 728 mV/h (SPAES). The membrane also showed strong chemical and mechanical stability, with minimal structural changes over extended use.

The researchers expect that this technology can pave the way for standalone, high-efficiency electrochemical hydrogen storage systems that can be commercialized around 2030.

Dr. So states that this research offers a solution to the performance bottlenecks of membrane technology in electrochemical hydrogen storage. KRICT President Youngkook Lee adds that the technology could be widely applied in eco-friendly energy systems such as hydrogen fuel cell vehicles and hydrogen power generation, thereby contributing to the hydrogen economy.