Fig. 3: Origin of the superior proton conductivity of m-H3Sb3P2O14 membranes.
From: Significant enhancement of proton conductivity in solid acid at the monolayer limit
a–d Cross-sectional SEM images of 1.0 nm-H3Sb3P2O14 (m-H3Sb3P2O14) membrane (a), 1.4 nm-H3Sb3P2O14 membrane (b), 3.1 nm-H3Sb3P2O14 membrane (c), and 8.6 nm-H3Sb3P2O14 membrane (d). e–h The corresponding azimuthal scan profiles for the (003) peak with the derived f values. The insets are the corresponding WAXS patterns for an incident Cu-Kα X-ray beam parallel to the membrane plane. i Proton conductivities at different temperatures for the above four membranes. Dashed lines are guides for the eye. j, k 1H spin-echo MAS NMR spectra (j) and 31P MAS NMR spectra (k) of bulk H3Sb3P2O14 (black line), m-H3Sb3P2O14 membrane (red line) and m-H3Sb3P2O14 nanosheets (blue line) at 100% RH and 30 °C. The insets in (j) are the zoom-in spectra ranging from 5 to 0 ppm. l Comparison of the proton conductivities of m-H3Sb3P2O14 membranes and H3Sb3P2O14 bulk pellets at RH ≤90% and 30 °C. Dashed lines are guides for the eye. Error bars represent standard deviations.
