A research team from the Qingdao Institute of Bioenergy and Bioprocess Technology of the Chinese Academy of Sciences, along with collaborators, has introduced a novel membrane design that mimics biological protein channels to enhance proton transport for efficient energy harvesting. This study was published in the Journal of the American Chemical Society.
Proton transport is fundamental to many biological processes and energy conversion methods. Inspired by the ClC-ec1 antiporter found in Escherichia coli, which facilitates the movement of chloride (Cl⁻) and protons, the researchers developed a hybrid membrane composed of covalent organic frameworks (COFs) integrated with aramid nanofibers (ANFs). This ANF/COF composite forms a robust hydrogen-bonding network and features amide groups that selectively bind to Cl⁻ ions, significantly lowering the energy barrier for proton conduction.
In acidic environments, adding just 0.1% Cl⁻ ions (relative to protons) increased the membrane's proton permeation rate threefold, reaching 9.8 mol m⁻² h⁻¹. This enhancement was not observed with other anions like NO₃⁻ or SO₄²⁻, emphasizing the unique role of Cl⁻. The system's proton hopping mechanism, validated through spectroscopy and density functional theory (DFT) calculations, demonstrates that Cl⁻ binding stretches ANF chains, improves hydrogen-bond networks, and enables efficient migration of H⁺ ions.
Importantly, the membrane's performance translates into real-world applications. Under simulated acidic wastewater conditions, the ANF/COF membrane achieved an output power density of 434.8 W m⁻²-one of the highest reported to date for osmotic energy generation. It also showed structural stability over 9,000 minutes (~150 hours) of operation in highly acidic media.
"This work exemplifies how mimicking nature can address real environmental and energy challenges," said co-corresponding author Prof. ZHU Ying from Beihang University. "Our membrane not only enhances proton transport efficiency but also opens the door to converting industrial waste acid into electricity."
This study highlights a novel Cl⁻-assisted proton transport paradigm, providing a blueprint for next-generation membranes in energy and environmental applications.
