There is a global push to develop a range of hydrogen technologies for timely adoption of the hydrogen economy. This is critical in view of the depleting oil reserves and looming transport fuel shortage, global warming, and increasing pollution. Molecular hydrogen (H 2 ) can be generated by a number of renewable and fossil-fuel-based resources. However, given the high cost of H 2 generation by renewable energy at this stage, fossil or carbon fuels are likely to meet the short-to medium-term demand for hydrogen. In view of this, effective technologies are required for the separation of H 2 from a gas feed (by-products of coal or bio-mass gasification plants, or gases from fossil fuel partial oxidation or reforming) consisting mainly of H 2 and CO 2 with small quantities of other gases such as CH 4 , CO, H 2 O, and traces of sulphur compounds. Several technologies are under development for hydrogen separation. One such technology is based on ion transport membranes, which conduct protons or both protons and electrons. Although these materials have been considered for other applications, such as gas sensors, fuel cells and water electrolysis, the interest in their use as gas separation membranes has developed only recently. In this paper, various classes of proton-conducting materials have been reviewed with specific emphasis on their potential use as H 2 separation membranes in the industrial processes of coal gasification, natural gas reforming, methanol reforming and the watergas shift (WGS) reaction. Key material requirements for their use in these applications have been discussed.

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Hydrogen separation membrane devices are attracting increasing interest for the industrial production of hydrogen. Metal membranes, in particular, are promising due to their resilience to the demands of a typical hydrogen purification process. However, the use of too much Pd within the membranes limits their wide-scale industrial use due to excessive costs. The present article reviews the design, preparation, operation, and critical performance features of novel non-Pd-based alloys. The theory behind the permeation of hydrogen through metal membranes is presented as well as the materials and methods central to their design and improvement. Crystalline, amorphous, and thin layer metal membranes are contrasted, while the advanced experimental techniques and mechanical tests for their characterization are discussed. The review considers the design of novel metal membranes from first principles and assesses catalytic and protective surface layers which may enhance their hydrogen separation capabilities.

Future fossil fuel power generation is likely to include technologies which increase process efficiency and reduce its impact on the environment, for example, CO 2 sequestration. Some of the key technologies identified for clean coal and natural gas combustion to produce power or hydrogen or both include O 2 generation/separation, H 2 and CO 2 separation. Hydrogen is considered as a potentially excellent substitute for transport fuels due to the concern over dwindling oil reserves and global warming. This paper discusses various separation processes that may be used in the industrial production of hydrogen from fossil fuels, with an emphasis on membrane separation technologies. Membrane separation has the advantage over other separation methods in that it is simple and potentially less energy intensive. Depending on the particular separation process utilised, however, the membrane materials can differ substantially. The materials used for H 2 , O 2 and CO 2 separation are discussed and the major similarities and differences between the membranes highlighted. Critical design aspects of the membrane such as multiple phase design, nano-structure control, the need for surface layers and fabrication processes are also reviewed as they represent the areas where most research and development effort is likely to be directed in the future. r