Northeast Normal University/Changchun University of Science and Technology Team Develops POM-Based Supramolecular Assemblies to Break Through the Bottleneck of High-Efficiency Fuel Cells

Recently, a collaborative team led by Professors Liu Bailin, Li Yangguang, and Zang Hongying from Northeast Normal University and Changchun University of Science and Technology published significant research findings in the international top journal Angewandte Chemie International Edition. The study synthesized BPN supramolecular cluster proton conductors through an aqueous self-assembly strategy, achieving a synergy of "high conductivity-low activation energy-strong stability," providing a modular new approach for the design of next-generation PEMFC key materials.

Proton conductors are the "core skeleton" of PEMFCs, and their performance directly determines the battery's energy conversion efficiency and service life. Current research has two major limitations: first, it overlooks the micro-heterogeneity of local proton transport, making it difficult to optimize the conduction path at the molecular level; second, traditional materials cannot balance the "three performances," with MOF-based proton conductors being highly sensitive to humidity and ionic omer systems' proton channels constrained by phase separation. The team tackled two key scientific questions: "how to construct programmable proton transport paths and coordinate multiple performances" and "how to reveal the dynamic differences in local site proton transport."

The innovation of this research lies in the first-time combination of [Bi₆O₅(OH)₃]⁵⁺ bismuth oxide clusters and [PW₁₂O₄₀]³⁻ polyoxometalates (POM) through aqueous self-assembly, forming BPN supramolecular cluster materials (chemical formula: [Bi₆O₅(OH)₃]₂.₂₄[PW₁₂O₄₀][NO₃]₂.₄[H₃O]₅.₈). This design utilizes the synergistic effect of "bismuth oxide clusters enhancing proton mobility + POM stabilizing the transmission transition state," coupled with a dynamic hydrogen bond network, to overcome the performance limitations of traditional homogeneous materials.

The core research results highlight three major breakthroughs: In terms of structural characteristics, BPN forms a hierarchically ordered structure through "charge-assisted hydrogen bonding + electrostatic complementarity." MD simulations show that bismuth oxide clusters are arranged around POM in a face-centered cubic mode, similar to fluorite crystal stacking, with XAS and NMR verifying the mixed valence state of W⁵⁺/W⁶⁺ and strong hydrogen bonding. In terms of performance, at 90°C and 97% RH, the proton conductivity reaches 0.12 S·cm⁻¹, comparable to commercial Nafion membranes, and at 25°C, it is 5.6×10⁻³ S·cm⁻¹. The performance remains stable after 72 hours of continuous operation, with an activation energy as low as 0.19 eV, and it can withstand strong acids, oxidation, and high temperatures, with no POM leakage after soaking in water for 1,680 hours. In terms of application, a DMFC assembled with a BPN-Nafion composite membrane, under 80°C and 1 M methanol conditions, achieves an open-circuit voltage of 0.82 V and a maximum power density of 86 mW·cm⁻², representing a 59.3% improvement over pure Nafion membranes.

Mechanism studies reveal that Bi-O sites serve as "fast channels" for protons, and the introduction of POM reduces the proton transfer energy barrier from 1.66 eV to 0.14 eV, with the optimal transmission efficiency when the water molecule adsorption amount reaches 6.1 wt%. The "inorganic cluster unit + dynamic hydrogen bond network" design strategy proposed by the study not only reveals the mechanism of local site proton transport heterogeneity, but also provides key material support for clean energy devices in scenarios such as portable electronics and drones, promoting the development of PEMFC towards higher efficiency, longer lifespan, and lower cost.