Constructing Heterogeneous Metal Nodes in Metal–Organic Framework Lamellar Membranes for High Proton Conduction in Fuel Cells

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Abstract
Precisely defining proton transport channels and regulating the chemical microenvironment of proton carriers are critical for high-performance proton exchange membranes (PEMs). Beyond optimizing carrier type and density, modulation of electron density distribution offers an underexplored route to enhance intrinsic proton conductivity. Herein, a series of ZnM-BDC-COOH nanosheets are synthesized by partial substitution of Zn2+ with a second metal ion in Zn-BDC frameworks and subsequent -COOH modification. The optimized ZnCu-BDC-COOH achieves a high intrinsic proton conductivity of 361.5 mS cm-1 over 16 times that of the pristine Zn-BDC (22.2 mS cm-1) at 80 °C and 98% RH using comb electrodes. Density functional theory and molecular dynamics simulations reveal that the introduced Cu2+, with higher electronegativity, withdraws more electrons from adjacent -COOH groups and Zn ions, generating asymmetric electron cloud distribution within the O-H bonds and the heterogeneous Zn3CuO(COO)6 nodes. This electron asymmetry facilitates rapid H+ release and establishes a strong local potential gradient that lowers the proton transport barrier. The resulting ZnCu-BDC-COOH lamellar membrane achieves a peak power density of 0.92 W cm-2, outperforming Nafion-117 (0.28 W cm-2), and maintains good durability over 100 h of open-circuit voltage (OCV) under 80 °C and 100% RH in fuel cells.
Funding Information
  • China Postdoctoral Science Foundation (2025M771152)
  • National Natural Science Foundation of China (22375017)
  • National Natural Science Foundation of China (22478362)
  • National Natural Science Foundation of China (22502178)
  • the Project of Zhongyuan Critical Metals Laboratory (GJJSGFZD202401)
  • Key Research and Development Project of Henan Province (241111232200)
  • the Science and Technology Innovation Leading Talent Program of Henan Province (254200510048)
  • Joint Foundation for Science and Technology Research & Development Plan of Henan Province (232301420038)
  • Key Scientific and Technological Project of Henan Province (242102321032)

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