Supramolecular hydrogen-bonded organic networks grown on cellulose fibers for efficient proton conduction

The development of new proton-conducting materials through a convenient and low-cost method is crucial in fuel cell technology. Supramolecular hydrogen-bonded organic networks (SHONs) are constructed by self-assembly of multi-component organic molecules through hydrogen bond interactions, in which the intermolecular hydrogen bond bridge constructed by Brønsted acid–base pairs and water molecules can accelerate the process of protonation and deprotonation for efficient proton conduction. The particle state and hydrophilicity of SHONs directly affect the grain boundary conductivity and the stability of the hydrogen bond network, which play a decisive role in the proton conduction. In this study, cellulose fibers were used as carrier to induce the in-situ growth of SHONs, constructed by melamine and 1,2-ethanedisulfonic acid, to prepare composite paper for a promising proton exchange membrane. Cellulose fibers exhibited significant regulation on the particle state and hydrophilicity of SHONs. Scanning electron microscopy and surface area analysis showed that the introduction of cellulose fiber changed the particle state of SHONs. Compared with pure SHONs, SHONs grown in-situ on cellulose fibers exhibited a smaller particle size and a more continuous arrangement, which was beneficial to improve the grain boundary conductivity. Contact angle measurements proved that the introduction of cellulose fibers improved the hydrophilicity of SHONs. This contributed to improving the stability of the hydrogen bond networks and the smoothness of the proton conduction channel. The regulation effect of cellulose fibers on SHONs improved the proton conduction efficiency of SHONs. The formed composite paper with SHONs grown in-situ on cellulose fibers exhibited a proton conduction value of up to 6.46 × 10–2 S cm−1 at 75 °C and 85% RH. This work provides a novel strategy for preparing highly efficient proton conducting composite paper for potential application in proton-exchange membrane fuel cells.