Towards Biohydrogen Separation Using Poly(Ionic Liquid)/Ionic Liquid Composite Membranes

Considering the high potential of hydrogen (H(2)) as a clean energy carrier, the implementation of high performance and cost-effective biohydrogen (bioH(2)) purification techniques is of vital importance, particularly in fuel cell applications. As membrane technology is a potentially energy-saving solution to obtain high-quality biohydrogen, the most promising poly(ionic liquid) (PIL)–ionic liquid (IL) composite membranes that had previously been studied by our group for CO(2)/N(2) separation, containing pyrrolidinium-based PILs with fluorinated or cyano-functionalized anions, were chosen as the starting point to explore the potential of PIL–IL membranes for CO(2)/H(2) separation. The CO(2) and H(2) permeation properties at the typical conditions of biohydrogen production (T = 308 K and 100 kPa of feed pressure) were measured and discussed. PIL–IL composites prepared with the [C(CN)(3)](−) anion showed higher CO(2)/H(2) selectivity than those containing the [NTf(2)](−) anion. All the membranes revealed CO(2)/H(2) separation performances above the upper bound for this specific separation, highlighting the composite incorporating 60 wt % of [C(2)mim][C(CN)(3)] IL.