[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Transition metal carbides and nitrides (MXenes), a family of two-dimensional (2D) inorganic compounds, are materials composed of a few atomic layers of transition metal carbides, nitrides, or carbonitrides. Ti3C2, the first 2D layered MXene, was isolated in 2011. This material, which is a layered bulk material analogous to graphite, was derived from its 3D phase, Ti3AlC2 MAX. Since then, material scientists have either determined or predicted the stable phases of >200 different MXenes based on combinations of various transition metals such as Ti, Mo, V, Cr, and their alloys with C and N. Extensive experimental and theoretical studies have shown their exciting potential for energy conversion and electrochemical storage. To this end, we comprehensively summarize the current advances in MXene research. We begin by reviewing the structure types and morphologies and their fabrication routes. The review then discusses the mechanical, electrical, optical, and electrochemical properties of MXenes. The focus then turns to their exciting potential in energy storage and conversion. Energy storage applications include electrodes in rechargeable lithium- and sodium-ion batteries, lithium-sulfur batteries, and supercapacitors. In terms of energy conversion, photocatalytic fuel production, such as hydrogen evolution from water splitting, and carbon dioxide reduction are presented. The potential of MXenes for the photocatalytic degradation of organic pollutants in water, such as dye waste, is also addressed, along with their promise as catalysts for ammonium synthesis from nitrogen. Finally, their application potential is summarized.

Applications of 2D MXenes in energy conversion and storage systems

2D MXenes: Electromagnetic property for microwave absorption and electromagnetic interference shielding

Recent advances in metal-organic framework membranes for water treatment: A review.

Traditional ways of producing drinking water from groundwater, water recycling and water conservation are not sufficient. Seawater desalination would close the gap but the main technology used is thermally driven multi-flash distillation, which is energy consuming and not sustainable. Stacking two-dimensional (2D) nanomaterials into lamellar membranes is a promising technique in the pursuit of both high selectivity and permeance in water desalination. However, 2D membranes tend to swell in water, and increasing their stability in aqueous solution is still challenging. Here, we report non-swelling, MXene membranes prepared by the intercalation of Al3+ ions. Swelling is prevented by strong interactions between Al3+ and oxygen functional groups terminating at the MXene surface. These membranes show excellent non-swelling stability in aqueous solutions up to 400 h and possess high rejection of NaCl (~89.5–99.6%) with fast water fluxes (~1.1–8.5 l m−2 h−1). Such membranes can be easily fabricated by simple filtration and ion-intercalating methods, which holds promise for their scalability. Two-dimensional lamellar membranes for water purification are promising but suffer from swelling that reduces their ion sieving performance in water. This study reports easy-to-fabricate, non-swelling MXene membranes prepared by the intercalation of Al3+ ions that could be scalable.

Effective ion sieving with Ti 3 C 2 T x MXene membranes for production of drinking water from seawater

Ion transport is crucial for biological systems and membrane-based technology. Atomic-thick two-dimensional materials, especially graphene oxide (GO), have emerged as ideal building blocks for developing synthetic membranes for ion transport. However, the exclusion of small ions in a pressured filtration process remains a challenge for GO membranes. Here we report manipulation of membrane surface charge to control ion transport through GO membranes. The highly charged GO membrane surface repels high-valent co-ions owing to its high interaction energy barrier while concomitantly restraining permeation of electrostatically attracted low-valent counter-ions based on balancing overall solution charge. The deliberately regulated surface-charged GO membranes demonstrate remarkable enhancement of ion rejection with intrinsically high water permeance that exceeds the performance limits of state-of-the-art nanofiltration membranes. This facile and scalable surface charge control approach opens opportunities in selective ion transport for the fields of water transport, biomimetic ion channels and biosensors, ion batteries and energy conversions.

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Controllable ion transport by surface-charged graphene oxide membrane

2D MXene Nanofilms with Tunable Gas Transport Channels

Recent innovations highlight the great potential of two-dimensional graphene oxide (GO) films in water-related applications. However, undesirable water-induced effects, such as the redispersion and peeling of stacked GO laminates, greatly limit their performance and impact their practical application. It remains a great challenge to stabilize GO membranes in water. A molecular bridge strategy is reported in which an interlaminar short-chain molecular bridge generates a robust GO laminate that resists the tendency to swell. Furthermore, an interfacial long-chain molecular bridge adheres the GO laminate to a porous substrate to increase the mechanical strength of the membrane. By rationally creating and tuning the molecular bridges, the stabilized GO membranes can exhibit outstanding durability in harsh operating conditions, such as cross-flow, high-pressure, and long-term filtration. This general and scalable stabilizing approach for GO membranes provides new opportunities for reliable two-dimensional laminar films used in aqueous environments.

Molecular Bridges Stabilize Graphene Oxide Membranes in Water

3D nanoporous crystals enabled 2D channels in graphene membrane with enhanced water purification performance

Graphene oxide (GO)-polyether block amide (PEBA) mixed matrix membranes were fabricated and the effects of GO lateral size on membranes morphologies, microstructures, physicochemical properties, and gas separation performances were systematically investigated. By varying the GO lateral sizes (100–200 nm, 1–2 μm, and 5–10 μm), the polymer chains mobility, as well as the length of the gas channels could be effectively manipulated. Among the as-prepared membranes, a GO-PEBA mixed matrix membrane (GO-M-PEBA) containing 0.1 wt % medium-lateral sized (1–2 μm) GO sheets showed the highest CO2 permeation performance (CO2 permeability of 110 Barrer and CO2/N2 mixed gas selectivity of 80), which transcends the Robeson upper bound. Also, this GO-PEBA mixed matrix membrane exhibited high stability during long-term operation testing. Optimized by GO lateral size, the developed GO-PEBA mixed matrix membrane shows promising potential for industrial implementation of efficient CO2 capture. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2843–2852, 2016

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Mengchen Zhang

Papers

Controllable ion transport by surface-charged graphene oxide membrane

2D MXene Nanofilms with Tunable Gas Transport Channels

Molecular Bridges Stabilize Graphene Oxide Membranes in Water

3D nanoporous crystals enabled 2D channels in graphene membrane with enhanced water purification performance

Size effects of graphene oxide on mixed matrix membranes for CO2 separation