Hydrogen Separation by Natural Zeolite Composite Membranes: Single and Multicomponent Gas Transport

Hydrogen production technologies - Membrane based separation, storage and challenges

The production of hydrogen, its separation, and storage for use as a primary source of energy is an important component of the green energy economy of the world. Hydrogen is a potential non-carbon-based energy source, which is gradually replacing the dependency on fossil fuels. It is anticipated that as the alternative fuel since hydrogen can be produced from green and clean sources. The evolution of hydrogen from renewable and non-renewable sources by various technologies has now gained tremendous research and industrial interest. The most appropriate methods for hydrogen generation involve the direct conversion of solar energy, exploitation of solar and wind energy for the electrolysis of water, besides conversion of fuel and biomass. To produce cleaner hydrogen and its separation from the chemical impurities is crucial and several methods including photobiological, photoelectrochemical, electrochemical, photocatalytic, thermochemical, thermolysis, and steam gasification have been used. The diverse types of membranes along with the pressure gas swing adsorption technique is another technique used to separate hydrogen, but the storage of hydrogen in an inexpensive, safe, compact, and environmentally friendly manner is one of the major concerns contributing to the country's economy. Apart from the countless advantages, storage and handling of hydrogen is a serious concern. Owing to its high inflammability, enough safety measures should be adopted during its production and storage as a fuel. It is necessary to provide information regarding the production technologies, storage, and separation methods of hydrogen and the present review addresses these issues.

Etching gas-sieving nanopores in single-layer graphene with an angstrom precision for high-performance gas mixture separation

One of the bottlenecks in realizing the potential of atom-thick graphene membrane for gas sieving is the difficulty in incorporating nanopores in an otherwise impermeable graphene lattice, with an angstrom precision at a high-enough pore density. We realize this design by developing a synergistic, partially decoupled defect nucleation and pore expansion strategy using O₂ plasma and O₃ treatment. A high density (ca. 2.1 × 10¹² cm^-2) of H₂-sieving pores was achieved while limiting the percentage of CH₄-permeating pores to 13 to 22 parts per million. As a result, a record-high gas mixture separation performance was achieved (H₂ permeance, 1340 to 6045 gas permeation units; H₂/CH₄ separation factor, 15.6 to 25.1; H₂/C₃H₈ separation factor, 38.0 to 57.8). This highly scalable pore etching strategy will accelerate the development of single-layer graphene-based energy-efficient membranes.