Superhydrophobic polycarbosilane membranes for purification of solar hydrogen

Superhydrophobic membranes composed of an organic-inorganic hybrid polymer, namely polycarbosilane (PCS) with Mw of 4-8.9 x 10(3), were formed on a mesoporous gamma-Al2O3-modified alpha-Al2O3 porous support. Under dry condition at 50 degrees C, the supported PCS membranes exhibited H-2 permeance of 1.1-1.6 x 10(-6) mol.m(2).s(1).Pa-1 and H-2/N-2 selectivity of 9.7-12.6 together with unique H-2/He selectivity of 1.4-1.6. Even under saturated humidity at 50 degrees C, H-2 permeance remained at 7.7 x 10(-8) mol(-1) m(2) s(1) Pa-1 with improved H-2/N-2 selectivity of 26. Moreover, when the measurements were performed using a H-2-N-2 (2:1) mixed feed gas as a simulated syngas produced by novel solar hydrogen production systems, the H-2 permeance almost unchanged, while the N-2 permeance was below the limit of detection. These results revealed a great potential of PCSs to develop novel H-2 selective membranes for purifying solar hydrogen under high-humidity conditions around 50 degrees C. Further study on the gas permeation behaviors of He, H-2 and N-2 suggested that the enhanced H-2/N-2 selectivity under the high humidity conditions could be explained by the synergistic effect of preferential H-2 permeation through the dense PCS network governed by the solid state diffusion mechanism and blockage of N-2 permeation through micropore channels within the PCS network by the permeate H2O-induced plugging at around the hetero interface between the superhydrophobic PCS and highly hydrophilic gamma-Al2O3.

Automated summary

The study demonstrated that superhydrophobic membranes made of polycarbosilane (PCS) showed excellent permeability and selectivity for purifying solar hydrogen under high-humidity conditions at around 50 degrees Celsius. The unique H-2 permeation behavior of PCS membranes could be attributed to the synergistic effect of preferential H-2 permeation and blockage of N-2 permeation through micropore channels within the PCS network.