Tri-functional carbon membrane for one-step uptake of low-concentration hydrogen to high purity

The uptake of hydrogen (H 2 ) from natural gas pipelines (CH 4 ) through membrane separation technology is an efficient avenue of obtaining H 2 resources. Carbon membranes have the potential to be an attractive option for energy-efficient gas separations in the next generation of membranes due to their precise molecular discrimination ability and easy scalability. Here, we report a carbon membrane composed of a mesoporous substrate, seed layer and sieving layer, achieving a one-step uptake with 55.3 × 10 -9 mol·m −2 ·s −1 Pa −1 permeance and a separation factor for H 2 /CH 4 of 359.1 by feeding hydrogen (20 vol%). As revealed by the kinetic diffusion experiment, H 2 is transported in mesoporous substrate via Knudsen flow, differing from the transition flow taken by CH 4 , thus H 2 diffusion rates exceed CH 4 by an order of magnitude, which substantially increased H 2 purity from 20 vol% to higher purity as gas mixtures passed through the substrate. Then, the H 2 passed through the seed layer and sieving layer, resulting in a final H 2 purity of ∼ 99 vol%, a sharp increase from the initial low concentration. This carbon membrane integrates three functions of capture, pre-separation and purification into one material and provides a new solution for the uptake of H 2 from CH 4 .