Pressure-Induced Enhancement of Proton Conduction across MOF Grain Boundaries

Abstract

The proton exchange membrane is the core of a fuel cell, with its performance limited by proton transport efficiency. Metalorganic frameworks (MOFs) have shown promise as proton conductors due to their adjustable porosity, but the grain boundaries of polycrystalline MOFs impede proton transport. This study innovatively applies external pressure to UiO-66-SO3H to shorten the grain boundary distance, thus reducing its resistance.The pressurized sample exhibited tightly packed bulks and reduced grain boundaries, achieving a maximum proton conductivity of 1.13×10 -2 S cm -1 at 80 ℃ and 100% RH, which is about 3 orders of magnitude higher than the unpressurized sample (3.5×10 -5 S cm -1 ). Due to the shortened grain boundary distance, sulfonic acid groups form a denser hydrogen-bonding network throughout the bulk and grain boundaries, facilitating proton conduction. This study offers a new approach to optimizing the proton conduction performance of polycrystalline MOFs via physical regulation, and provides significant reference value for addressing grain boundary-induced conduction bottlenecks in fuel cells.