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In the present study, a functionalized carboxymethyl cellulose-based adsorbent (PEI–PAM–CMC) was prepared via linking polyethyleneimine and polyacrylamide with carboxymethyl cellulose by epichlorohydrin. It possessed a sponge-like structure with a large number of micron-sized pores, which facilitated the mass transfer of Cr(VI). Under neutral conditions, Cr(VI) can be efficiently removed by the protonated PEI–PAM–CMC. The residual levels in the effluent were below 0.5 and 0.05 mg L−1 for 10 and 1 mg L−1 of Cr(VI), respectively. The adsorption data fitted well with the pseudo-second order kinetic model and Langmuir isotherm. Common ions including Cl−, H2PO4−, NO3−, K+, Na+, Ca2+, Mg2+ and Cr3+ had neglectable influence for Cr(VI) adsorption on the PEI–PAM–CMC except SO42−. Meanwhile, PEI–PAM–CMC showed good regeneration and reusability with a 7.5% decrease in the removal rate after ten adsorption/desorption cycles. XPS analysis and DFT calculation revealed that Cr(VI) uptake by the PEI–PAM–CMC was involved in electrostatic attraction and chemical binding. Electrostatics and induction were the main weak interaction between Cr(VI) and the adsorbent, and the major chemical adsorption sites were mainly distributed in the nitrogen groups. This research not only developed an efficient material for Cr(VI) removal but also provided a promising insight into an adsorption mechanism study. [ABSTRACT FROM AUTHOR]

Since graphene has been successfully exfoliated, two-dimensional (2D) materials constitute a vibrant research field and open vast perspectives in high-performance applications. Among them, bismuthene and 2D bismuth (Bi) are unique with superior properties to fabricate state-of-the-art energy saving, storage and conversion devices. The largest experimentally determined bulk gap, even larger than those of stanene and antimonene, allows 2D Bi to be the most promising candidate to construct room-temperature topological insulators. Moreover, 2D Bi exhibits cyclability for high-performance sodium-ion batteries, and the enlarged surface together with the good electrochemical activity renders it an efficient electrocatalyst for energy conversion. Also, the air-stability of 2D Bi is better than that of silicene, germanene, phosphorene and arsenene, which could enable more practical applications. This review aims to thoroughly explore the fundamentals of 2D Bi and its improved fabrication methods, in order to further bridge gaps between theoretical predictions and experimental achievements in its energy-related applications. We begin with an introduction of the status of 2D Bi in the 2D-material family, which is followed by descriptions of its intrinsic properties along with various fabrication methods. The vast implications of 2D Bi for high-performance devices can be envisioned to add a new pillar in energy sciences. In addition, in the context of recent pioneering studies on moiré superlattices of other 2D materials, we hope that the improved manipulation techniques of bismuthene, along with its unique properties, might even enable 2D Bi to play an important role in future energy-related twistronics. [ABSTRACT FROM AUTHOR]

Phosphorene, an emerging two-dimensional material, has received considerable attention due to its layer-controlled direct bandgap, high carrier mobility, negative Poisson's ratio and unique in-plane anisotropy. As cousins of phosphorene, 2D group-VA arsenene, antimonene and bismuthene have also garnered tremendous interest due to their intriguing structures and fascinating electronic properties. 2D group-VA family members are opening up brand-new opportunities for their multifunctional applications encompassing electronics, optoelectronics, topological spintronics, thermoelectrics, sensors, Li- or Na-batteries. In this review, we extensively explore the latest theoretical and experimental progress made in the fundamental properties, fabrications and applications of 2D group-VA materials, and offer perspectives and challenges for the future of this emerging field. [ABSTRACT FROM AUTHOR]

Two-dimensional carbon nitrides (CxNy) have gained significant attention in various fields including hydrogen energy development, environmental remediation, optoelectronic devices, and energy storage owing to their extensive surface area, abundant raw materials, high chemical stability, and distinctive physical and chemical characteristics. One effective approach to address the challenges of limited visible light utilization and elevated carrier recombination rates is to establish heterojunctions for CxNy-based single materials (e.g. C2N3, g-C3N4, C3N4, C4N3, C2N, and C3N). The carrier generation, migration, and recombination of heterojunctions with different band alignments have been analyzed starting from the application of CxNy with metal oxides, transition metal sulfides (selenides), conductive carbon, and Cx′Ny′ heterojunctions. Additionally, we have explored diverse strategies to enhance heterojunction performance from the perspective of carrier dynamics. In conclusion, we present some overarching observations and insights into the challenges and opportunities associated with the development of advanced CxNy-based heterojunctions. [ABSTRACT FROM AUTHOR]

Layered double hydroxide (LDH) is frequently used for phosphate removal in water, while a desirable LDH adsorbent should have sufficiently high adsorption capacity and selectivity. To enhance the removal performance and selectivity of phosphate by LDH, La-doped layered double hydroxide/biochar (La–MgAl–LDH/BC) was synthesized by using a co-precipitation method. Investigation results showed that lanthanum (La) metal loading can significantly enhance the phosphate adsorption performance of La–MgAl–LDH. Then, the introduction of La–MgAl–LDH into BC improved the adsorption capacity of phosphate by the adsorbent, which is 1.8 times that of pure La–MgAl–LDH. The optimum La to Al molar ratio was 0.2 : 0.8 in La–MgAl–LDH materials, and the La–MgAl–LDH to BC mass ratio was 9.3 : 10. Furthermore, both La–MgAl–LDH and La–MgAl–LDH/BC exhibited an enhanced ability to resist interference from co-existing anions (Cl−, SO42−, NO3− and CO32−) compared to LDH. For batch experiments, the kinetic results indicated that the adsorption process of phosphate by La–MgAl–LDH/BC follows a pseudo-second-order kinetics model, reaching equilibrium quickly within 1 h. Furthermore, film diffusion and intra-particle diffusion simultaneously took place. The maximum monolayer phosphate adsorption capacity of La–MgAl–LDH/BC could reach 249.3 mg PO43− g−1 (513.6 mg PO43− g−1, converting to an equivalent La–MgAl–LDH). After four cycles, La–MgAl–LDH/BC showed good reusability, and over 63.5% of phosphate uptake was retained with minimal metal leaching. Additionally, phosphate could be rapidly removed from actual water and simulated water at low concentrations. The electrostatic attraction, ligand exchange, ion exchange and Lewis acid action jointly facilitate the adsorption of phosphate. [ABSTRACT FROM AUTHOR]

Exhaustive research of phase engineering of two-dimensional molybdenum disulfide (2D-MoS2) is currently ongoing to develop numerous applications, including optoelectronic devices, spintronics, and new platforms for the study of unconventional quantum phenomena. Therefore, it is urgently needed to achieve phase-controlled synthesis of MoS2 with a high quality and large area. However, the metallic phase MoS2 (1T-MoS2) synthesized by conventional chemical vapor deposition (CVD) is randomly distributed in the semiconductor phase (2H-MoS2) domain, and the position-controlled synthesis of the phase is not achieved. In this study, we achieved the controlled synthesis of the 1T-MoS2 domain in the 2H main phase. Salt-assisted CVD was used to induce V-atom doping at the right time by controlling the concentration of vanadium ions. The synthesis benefitted from 1D vapor–liquid–solid (VLS) growth and 2D vapor–solid (VS) edge expansion. The results of the growth controlled by regulating the NaCl concentration showed that the 1T phase was located at the three vertex domains of the MoS2 triangle. The distribution domains of 1T phase MoS2 can be confirmed by Raman mapping, X-ray photoelectron spectroscopy, and transmission electron microscopy. Furthermore, we calculated the doping rate of V atoms in VLS and VS modes based on the two-dimensional diffusion model and observed that the doping rate of V atoms in the VLS mode was approximately three times higher than that in the VS mode, which was consistent with the experimental results. The controllable phase-domain synthesis of 2D-MoS2 is beneficial to the preparation of nano-electronic devices and provides a platform for the study of physicochemical properties. [ABSTRACT FROM AUTHOR]

The role of interfaces in facilitating the growth of conventional 1D nanostructures is well established. Apparently, the presence of interfaces is also decisive in the growth of 2D transition metal dichalcogenides, but their role remains ambiguous. Here, we show that the molten Na–Nb–O liquid precursor would create microscale vapor–liquid and liquid–solid interfaces, which determine the nucleation and growth of large single-crystal monolayer 2D metallic NbS2 by vapor–liquid–solid (VLS) method. We discover that reaction and growth are separated at the vapor–liquid interface and the liquid–solid interface, respectively, due to the insolubility between S and the liquid precursor. The vapor–liquid interface reaction reduces the concentration of NbSx monomers in droplets, thus effectively controlling the nucleation density. The liquid–solid interface lowers the diffusion barrier of NbS2 monomers, which increases the growth rate. We establish a 2D diffusion model and calculate and conclude that the growth rate in VLS mode is approximately 8 times that in vapor–solid (VS) mode, which is consistent with our experimental results. This finding reveals that two interfaces are the determining factors that control the nucleation and growth of large NbS2 single crystals, which will likely contribute to the development of the wafer-scale growth of 2D materials for further device applications. [ABSTRACT FROM AUTHOR]

Restacking of 2D nanomaterials is often deemed to be detrimental to their applications. In contrast to this common notion, here we demonstrate that tightly packed stacked MoS2 exhibits a higher electrocatalytic activity for hydrogen evolution than the more loosely stacked ones. [ABSTRACT FROM AUTHOR]