Enhanced proton conductivity promoted by self-assembly of aqueous 4-(1-ethyldecyl) benzenesulfonic lyotropic liquid crystal

Acidic lyotropic liquid crystals (LLCs) have an advantage in constructing continuous proton conduction pathways owing to the well-defined structures, but the contribution of LLC to proton conductivity is hard to determine for the water-dependent nature of LLC. An aqueous 4-(1-ethyldecyl) benzenesulfonic acid solution, exhibiting a lamellar LLC phase at low hydration levels and becoming a micellar solution at high hydration levels, is employed to investigate structure-dependent proton conductivity. Electrochemical impedance spectrum (EIS) characterization reveals that the proton conductivity reaches a maximum of 173 mS cm−1 in the LLC phase. Owing to the self-assembling, the degree of dissociation of -SO3H tends to stabilize at 0.26 with increasing hydration levels. An integrated rate constant Ki is derived to evaluate the effect of self-assembly on proton conductivity, which reaches 1.90 × 107 mS cm5 mol−2 in the LLC but decreases to 1.23 × 107 mS cm5 mol−2 in the micellar solution. The single fuel cell fabricated from the LLC supported membrane exhibits a peak power density of 23.7 mW cm−2, confirming the enhanced proton conductivity under actual working conditions. The results quantitatively unveil the effect of aqueous self-assembly on proton conduction and offer a guide for achieving high conductivities in hydrated electrolytes with well-defined architectures.