Temperature controlled swelling of graphene oxide for switchable dehumidification membranes

Variation of water permeance and interlayer spacing of graphene oxide (GO) is traced with in-situ X-ray diffraction upon its heating/cooling in dry (-1000 Pa), humid (-100 % RH) air and liquid water. Reversible variation of GO interlayer distance ranging 8.3-7.2 a in dry air, 11-7.5 a in humid air and 13.9-12.4 a in liquid water is revealed in the temperature range of 25-80 degrees C. Accounting for GO layer thickness of -6 a it corresponds manifold alterations of slit width with temperature and water vapor pressure, resulting in over 3 orders of magnitude variation of membrane performance. A typical rise of the permeance of 300-500 % within the temperature range at constant humidity is contraposed to a miserable increase in the activation energy for H2O transport, revealing the decisive impact of slit sizes on GO performance. The effect is addressed to entropy-driven variation of water absorption heat with slit sizes in GO. Variation of interlayer spacing of -10 % was also exposed with thermal dissociation of GO groups and H+ migration to the interlayer space as supported by semiempirical calculations. Reversible structural changes in GO are successfully exploited for fabrication thermally switched membranes for dehumidification with initial permeance of -1.1 & sdot;10-6 mol m- 2 Pa- 1 & sdot;s- 1 and its variation over 50 % at supplied power of -500 W/m2.