Hydrogen Selective SiCH Inorganic–Organic Hybrid/γ-Al(2)O(3) Composite Membranes

Solar hydrogen production via the photoelectrochemical water-splitting reaction is attractive as one of the environmental-friendly approaches for producing H(2). Since the reaction simultaneously generates H(2) and O(2), this method requires immediate H(2) recovery from the syngas including O(2) under high-humidity conditions around 50 °C. In this study, a supported mesoporous γ-Al(2)O(3) membrane was modified with allyl-hydrido-polycarbosilane as a preceramic polymer and subsequently heat-treated in Ar to deliver a ternary SiCH organic–inorganic hybrid/γ-Al(2)O(3) composite membrane. Relations between the polymer/hybrid conversion temperature, hydrophobicity, and H(2) affinity of the polymer-derived SiCH hybrids were studied to functionalize the composite membranes as H(2)-selective under saturated water vapor partial pressure at 50 °C. As a result, the composite membranes synthesized at temperatures as low as 300–500 °C showed a H(2) permeance of 1.0–4.3 × 10(−7) mol m(−2) s(−1) Pa(−1) with a H(2)/N(2) selectivity of 6.0–11.3 under a mixed H(2)-N(2) (2:1) feed gas flow. Further modification by the 120 °C-melt impregnation of low molecular weight polycarbosilane successfully improved the H(2)-permselectivity of the 500 °C-synthesized composite membrane by maintaining the H(2) permeance combined with improved H(2)/N(2) selectivity as 3.5 × 10(−7) mol m(−2) s(−1) Pa(−1) with 36. These results revealed a great potential of the polymer-derived SiCH hybrids as novel hydrophobic membranes for purification of solar hydrogen.