Hydrogen Selective SiCH Inorganic–Organic Hybrid/γ-Al2O3 Composite Membranes

Solar hydrogen production via the photoelectrochemical water-splitting reaction is attractive as one of the environmental-friendly approaches for producing H2. Since the reaction simultaneously generates H2 and O2, this method requires immediate H2 recovery from the syngas including O2 under high-humidity conditions around 50 &deg
C. In this study, a supported mesoporous &gamma
Al2O3 membrane was modified with allyl-hydrido-polycarbosilane as a preceramic polymer and subsequently heat-treated in Ar to deliver a ternary SiCH organic&ndash
inorganic hybrid/&gamma
Al2O3 composite membrane. Relations between the polymer/hybrid conversion temperature, hydrophobicity, and H2 affinity of the polymer-derived SiCH hybrids were studied to functionalize the composite membranes as H2-selective under saturated water vapor partial pressure at 50 &deg
C. As a result, the composite membranes synthesized at temperatures as low as 300&ndash
500 &deg
C showed a H2 permeance of 1.0&ndash
4.3 &times
10&minus
7 mol m&minus
2 s&minus
1 Pa&minus
1 with a H2/N2 selectivity of 6.0&ndash
11.3 under a mixed H2-N2 (2:1) feed gas flow. Further modification by the 120 &deg
C-melt impregnation of low molecular weight polycarbosilane successfully improved the H2-permselectivity of the 500 &deg
C-synthesized composite membrane by maintaining the H2 permeance combined with improved H2/N2 selectivity as 3.5 &times
1 with 36. These results revealed a great potential of the polymer-derived SiCH hybrids as novel hydrophobic membranes for purification of solar hydrogen.