Abstract
Hydrogen (H2) is an industrial gas that has showcased its importance in several well-known processes such as ammonia, methanol and steel productions, as well as in petrochemical industries. Besides, there is a growing interest in H2 production and purification owing to the global efforts to minimize the emission of greenhouse gases. Nevertheless, H2 which is produced synthetically is expected to contain other impurities and unreacted substituents (e.g., carbon dioxide, CO2; nitrogen, N2 and methane, CH4), such that subsequent purification steps are typically required for practical applications. In this context, membrane-based separation has attracted a vast amount of interest due to its desirable advantages over conventional separation processes, such as the ease of operation, low energy consumption and small plant footprint. Efforts have also been made for the development of high-performance membranes that can overcome the limitations of conventional polymer membranes. In particular, the studies on graphene-based membranes have been actively conducted most recently, showcasing outstanding H2-separation performances. This review focuses on the recent progress and potential challenges in graphene-based membranes for H2 purification.
Highlights
Hydrogen (H2 ) is an important industrial gas that is heavily utilized in the petrochemical industries.For instance, H2 is involved in the hydrodesulfurization process, which removes sulfur from natural gas [1,2] for subsequent petroleum refining process
Efforts in improving the gas separation performance have been made by employing molecular sieves such as zeolites, metal-organic frameworks (MOFs) and microporous organic polymers (MOPs) as membrane materials
Apart from this, the effectiveness of graphene in composite membranes can be quantified with the evaluation of the filler enhancement index (Findex )
Summary
Hydrogen (H2 ) is an important industrial gas that is heavily utilized in the petrochemical industries. Efforts in improving the gas separation performance have been made by employing molecular sieves such as zeolites, metal-organic frameworks (MOFs) and microporous organic polymers (MOPs) as membrane materials These membranes suffer from limited scalability and poor mechanical stability [33,34]. Various two-dimensional (2D) materials such as MXene [35,36], transition metal dichalcogenides (e.g., MoS2 -TMD) [37], layered double hydroxides (NiAl-CO3 -LDH) [38], MOF-based nanosheets [39], covalent organic framework (COF)-based nanosheets [40], graphene [41] and carbon nitrides [42] have been developed and studied for potential applications in many fields Their uniquely high aspect ratios (atomically thin) allow such materials to be assembled into ultrathin membranes exhibiting a high permeation flux [43]. Properties of polar molecules (presence of net force under uniform electric field). (b) Presence of net force under nonuniform electric field. (c) Helium (He) and water vapor (H2O) is included in the table as a reference
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