Ultrahigh resistance of hexagonal boron nitride to mineral scale formation

Miracle in "White":Hexagonal Boron Nitride

The exploration of 2D materials has captured significant attention due to their unique performances, notably focusing on graphene and hexagonal boron nitride (h-BN). Characterized by closely resembling atomic structures arranged in a honeycomb lattice, both graphene and h-BN share comparable traits, including exceptional thermal conductivity, impressive carrier mobility, and robust pi-pi interactions with organic molecules. Notably, h-BN has been extensively examined for its exceptional electrical insulating properties, inert passivation capabilities, and provision of an ideal ultraflat surface devoid of dangling bonds. These distinct attributes, contrasting with those of h-BN, such as its conductive versus insulating behavior, active versus inert nature, and absence of dangling surface bonds versus absorbent tendencies, render it a compelling material with broad application potential. Moreover, the unity of such contradictions endows h-BN with intriguing possibilities for unique applications in specific contexts. This review aims to underscore these key attributes and elucidate the intriguing contradictions inherent in current investigations of h-BN, fostering significant insights into the understanding of material properties.

Solidophobic Surface for Electrochemical Extraction of High-Valued Mg(OH)2 Coupled with H2 Production from Seawater

A significant challenge in direct seawater electrolysis is the rapid deactivation of the cathode due to the large scaling of Mg(OH)2. Herein, we synthesized a Pt-coated highly disordered NiCu alloy (Pt-NiCu alloy) electrode with superior solidophobic behavior, enabling stable hydrogen generation (100 mA cm-2, >1000 h durability) and simultaneous production of Mg(OH)2 (>99.0% purity) in electrolyte enriched with Mg2+ and Ca2+. The unconventional solidophobic property primarily stems from the high surface energy of the NiCu alloy substrate, which facilitates the adsorption of surface water and thereby compels the bulk formation of Mg(OH)2 via homogeneous nucleation. The discovery of this solidophobic electrode will revolutionarily simplify the existing techniques for seawater electrolysis and increase the economic viability for seawater electrolysis.

More resilient polyester membranes for high-performance reverse osmosis desalination

Thin-film composite reverse osmosis membranes have remained the gold standard technology for desalination and water purification for nearly half a century. Polyamide films offer excellent water permeability and salt rejection but also suffer from poor chlorine resistance, high fouling propensity, and low boron rejection. We addressed these issues by molecularly designing a polyester thin-film composite reverse osmosis membrane using co-solvent-assisted interfacial polymerization to react 3,5-dihydroxy-4-methylbenzoic acid with trimesoyl chloride. This polyester membrane exhibits substantial water permeability, high rejection for sodium chloride and boron, and complete resistance toward chlorine. The ultrasmooth, low-energy surface of the membrane also prevents fouling and mineral scaling compared with polyamide membranes. These membranes could increasingly challenge polyamide membranes by further optimizing water-salt selectivity, offering a path to considerably reducing pretreatment steps in desalination.

Graphene Oxide Inhibits Calcium Carbonate Nucleation

Formation of minerals such as calcium carbonate often causes energy consumption and even safety risk increase due to the hindrance on heat/mass transfer. However, the current antiscalants are not efficient enough because of the poor understanding of the scale inhibition mechanisms. Here, we report an ultrahigh-performance antiscalant, graphene oxide (GO), which exhibits an outstanding nucleation inhibition effect far better than the current state-of-the-art antiscalants even on a subppm dosage. Our experiments reveal that the superior nucleation inhibition effect of GO is attributed to its limiting effect on the nucleation kinetics of ions and its ability to increase the nucleation barrier of calcium carbonate by altering the normal pathway of calcium carbonate polymorph formation. Further analysis indicates that the ion-limiting effect and the polymorph control ability of GO may stem from its oxygen functional group-rich surface chemistry and two-dimensional (2D) planar features, which endow GO with a Ca2+ binding ability and additional steric hindrance for CO32- diffusion, respectively.

Intrinsic and Strain-Dependent Properties of Suspended WSe2 Crystallites toward Next-Generation Nanoelectronics and Quantum-Enabled Sensors

Two-dimensional (2D) layered materials exhibit great potential for high-performance electronics, where knowledge of their thermal and phononic properties is critical toward understanding heat dissipation mechanisms, considered to be a major bottleneck for current generation nanoelectronic, optoelectronic, and quantum-scale devices. In this work, noncontact Raman spectroscopy was used to analyze thermal properties of suspended 2D WSe2 membranes to access the intrinsic properties. Here, the influence of electron-phonon interactions within the parent crystalline WSe2 membranes was deciphered through a comparative analysis of extrinsic substrate-supported WSe2, where heat dissipation mechanisms are intimately tied to the underlying substrate. Moreover, the excitonic states in WSe2 were analyzed by using temperature-dependent photoluminescence spectroscopy, where an enhancement in intensity of the localized excitons in suspended WSe2 was evident. Finally, phononic and electronic properties in suspended WSe2 were examined through nanoscale local strain engineering, where a uniaxial force was induced on the membrane using a Au-coated cantilever within an atomic force microscope. Through the fundamental analysis provided here with temperature and strain-dependent phononic and optoelectronic properties in suspended WSe2 nanosheets, the findings will inform the design of next-generation energy-efficient, high-performance devices based on WSe2 and other 2D materials, including for quantum applications.

Robust ceramic-based graphene membrane for challenging water treatment with enhanced fouling and scaling resistance

Membrane fouling and scaling are two challenges for efficient treatment of hypersaline wastewater, greatly hindering separation performance and operation stability of desalination membranes. In this work, we report a smooth ceramic-based graphene desalination membrane, exhibiting enhanced anti-fouling and anti-scaling ability and operational performance for efficient treatment of both synthetic and real industrial wastewaters, outperforming polypropylene (PP) membrane. For treatment of hypersaline waters containing organic or inorganic substance, we demonstrate that the graphene membrane exhibits more stable water flux and almost complete salt rejection (>99.9%) during constant operation. Enhanced anti-fouling and desalination performance of graphene membrane could be attributed to the lower attractive interaction force with foulant (-4.65 mJ m-2), lower surface roughness (Ra = 2.2 ± 0.1 nm) and higher affinity with water than PP membrane. Furthermore, an anti-scaling mechanism enabled by graphene membrane is evidenced, with a highlight on the roles of smooth graphene surface with lower roughness, less nucleation sites and lower binding force with scaling crystals. Importantly, even for industrial petrochemical wastewater, such a graphene membrane also exhibits relatively more stable water flux and promising oil and ions rejection during long-term operation, outperforming PP membrane. This study further confirms a promising practical application potential of robust ceramic-based graphene membrane for efficient treatment of more challenging hypersaline wastewater with complicated compositions, which is not feasible by conventional desalination membranes.