New Supramolecular Material Boosts Potential of Fuel Cells
Researchers at Northeast Normal University and Changchun University of Science and Technology have developed a novel proton-conducting material with promising implications for the advancement of proton exchange membrane fuel cells (PEMFCs). Their findings were recently published in the prestigious journal Angewandte Chemie International Edition.
The team, led by Professors Liu Bailin, Li Yangguang, and Zang Hongying, created the material – a BPN supramolecular cluster – using a simple aqueous self-assembly process. This new approach achieves a rare combination of high proton conductivity, low activation energy, and robust stability, addressing key limitations found in current PEMFC materials.
Proton conductors are essential components of PEMFCs, directly impacting their efficiency and longevity. Existing materials often struggle with optimizing proton transport at a molecular level due to micro-heterogeneity, and frequently fail to simultaneously deliver high performance across all critical areas. Materials like MOFs are sensitive to humidity, while ionicomer systems suffer from phase separation hindering proton flow. The researchers focused on overcoming these challenges by investigating how to “construct programmable proton transport paths and coordinate multiple performances” and “reveal the dynamic differences in local site proton transport.”
The breakthrough lies in the innovative combination of positively charged [BiO(OH)]⁺ bismuth oxide clusters and negatively charged [PWO]⁻ polyoxometalates (POM) thru self-assembly in water, resulting in a material with the chemical formula [BiO(OH)].[PWO][NO].[HO]. This pairing leverages the strengths of each component: bismuth oxide clusters enhance proton mobility, while POM stabilizes the proton transmission process, all supported by a dynamic hydrogen bond network.
Testing revealed notable improvements. The BPN material exhibited a proton conductivity of 0.12 S·cm⁻ at 90°C and 97% relative humidity – comparable to commercially available Nafion membranes. At 25°C, conductivity reached 5.6×10⁻ S·cm⁻. Furthermore, the material demonstrated exceptional stability, maintaining performance after 72 hours of continuous operation and resisting degradation after being immersed in water for 1,680 hours, with no detectable POM leakage. It also proved resistant to strong acids, oxidation, and high temperatures, with a low activation energy of 0.19 eV.
The material’s potential was further validated in a direct methanol fuel cell (DMFC). A composite membrane utilizing BPN and Nafion achieved an open-circuit voltage of 0.82 V and a maximum power density of 86 mW·cm⁻ under 80°C and 1 M methanol conditions – a 59.3% betterment over a DMFC using a pure Nafion membrane.
detailed mechanistic studies showed that Bi-O sites act as “fast channels” for proton transport. The addition of POM lowered the proton transfer energy barrier from 1.66 eV to 0.14 eV, with optimal performance observed when water adsorption reached 6.1 wt%.
This research introduces a promising “inorganic cluster unit + dynamic hydrogen bond network” design strategy, offering insights into local site proton transport and paving the way for more efficient, durable, and cost-effective PEMFCs for applications ranging from portable electronics to drones.
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