Fig 1.
(A) Chemical structure of KS. (B) An illustration of a three-monomer segment of KS. Possible intra- and inter-molecular hydrogen bonds as well as the hydrogen bonds between the water of hydration and the polar parts of the molecule form a continuous network comprised by hydrogen-bond chains. The sulfate group interacts with the hydrogen-bond network and forms an H3O+ (hydronium) ion.
Fig 2.
Proton conduction measurement of KS.
A) Palladium hydride(PdHx) electrode behavior. Under a VSD, PdHx source split into Pd, H+, and e−. Protons are injected into the KS, whereas electrons travel through external circuitry and are measured. B) TLM geometry. Varying the distance between source and drain (LSD) distinguishes between the fixed PdHx−KS interface contact resistance and the varying bulk resistance. C) Optical image of TLM geometry with hydrated KS on the surface. Scale bar, 500μm. D) Transient response to a 1V bias in KS at 75%, 90%, 90% H2 RH, in which the current under 90% with hydrogen is much higher than that under 90% RH without hydrogen. E) Deuterium current (black) at 90% D2 humidity is lower than proton current (red). F) The normalized resistance RLN as a function of LSD, A linear fit gives a bulk material proton conductivity of 0.50 ± 0.11 mS cm-1.
Table 1.
Room-temperature proton conductivities of Nafion and known biopolymers.