Wearable electronics are some of the most promising technologies with the potential to transform many aspects of human life such as smart healthcare and intelligent communication. The design of self-powered fabrics with the ability to efficiently harvest energy from the ambient environment would not only be beneficial for their integration with textiles, but would also reduce the environmental impact of wearable technologies by eliminating their need for disposable batteries. Herein, inspired by classical Archimedean spirals, we report a metastructured fiber fabricated by scrolling followed by cold drawing of a bilayer thin film of an MXene and a solid polymer electrolyte. The obtained composite fibers with a typical spiral metastructure (SMFs) exhibit high efficiency for dispersing external stress, resulting in simultaneously high specific mechanical strength and toughness. Furthermore, the alternating layers of the MXene and polymer electrolyte form a unique, tandem ionic-electronic coupling device, enabling SMFs to generate electricity from diverse environmental parameters, such as mechanical vibrations, moisture gradients, and temperature differences. This work presents a design rule for assembling planar architectures into robust fibrous metastructures, and introduces the concept of ionic-electronic coupling fibers for efficient multimodal energy harvesting, which have great potential in the field of self-powered wearable electronics. In this work, a concept of ionic-electronic coupling fibers by integrating a 2D MXene and a polymer electrolyte to fabricate spiral metastructures is proposed to realize multimodal power generation from various sources simultaneously.

Developing efficient catalysts for the capture and direct conversion of CO2 into various chemicals is essential to alleviate CO2 emissions and minimize the negative environmental effects of fossil fuels. Combining density functional theory calculations and microkinetic analysis, we propose that single Bi atoms supported on V2CO2 MXenes (Bi@V2CO2) are promising single-atom catalysts (SAC) for CO2 hydrogenation. The catalytic performance of Bi SACs is ensured by the stable single-atom dispersion of Bi atoms on V2CO2 and enhanced adsorption of CO2. Of importance, Bi@V2CO2 exhibits remarkable selectivity toward the synthesis of formic acid (HCOOH), in which the main competing reaction, namely, the reverse water gas shift (RWGS) and the formation of CO, is strictly prohibited. In contrast to conventional Cu or In2O3 catalysts, CO2 hydrogenation exhibits a unique mechanism on Bi@V2CO2, in which the formic acid is directly generated via a concerted pathway. As a result, the formation of both intermediate HCOO and COOH is prevented, leading to high selectivity (nearly 100%) toward HCOOH on Bi@V2CO2. Moreover, analysis of the kinetic behavior suggests that the stabilization of HCOOH adsorption would be an effective approach to promote catalyst performance toward methanol synthesis.

Sulfur-terminated single sheet (ss-)MXene was recently achieved by delamination of multilayered van der Waals bonded (vdW)-MXenes Nb2CS2 and Ta2CS2 synthesized through solid-state synthesis, rather than via the traditional way of selectively etching A-layers from the corresponding MAX phase. Inspired by this, we perform a computational screening study of vdW-MXenes M(2)CCh(2) isotypical to Nb2CS2 and Ta2CS2, with M = Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Mo, or W and Ch = S, Se, or Te. The thermodynamic stability of each vdW-MXene M(2)CCh(2) is assessed, and the dynamical stability of both vdW- and ss-MXene is considered through phonon dispersions. We predict seven stable vdW-MXenes, out of which four have not been reported previously, and one, V2CSe2, incorporates a new transition metal element into this family of materials. Electronic properties are presented for the vdW- and ss-forms of the stable vdW-MXenes, suggesting that the materials are either metallic, semimetallic, or semiconducting. In previous experimental reports the vdW-MXene Nb2CS2 is synthesized by manipulation of the corresponding M(2)AX phase Nb2SC. Therefore, we also evaluate the thermodynamic stability of the corresponding M(2)AX phases, identifying 15 potentially stable phases. Six of these are experimentally reported, leaving nine new M(2)AX phases for future experimental investigation.

The creation of vacancies and/or pores into two-dimensional materials, like graphene and MXenes, has shown to increase their performance for sustainable applications. However, a simple and affordable method with controlled and tailorable vacancy concentration and/or pores size remains challenging. Herein, a simple and reproducible method is presented for controlled synthesis of Mo1.74CTz MXene with randomly distributed vacancies and pores, obtained from selective etching of both Ga and Cr in the Cr-alloyed MAX-phase like precursor Mo1.74Cr0.26Ga2C. Structural and compositional analysis of the 3D alloy show approximate to 13% Cr on the metal site, homogeneously distributed between different particles and within the atomic structure. After etching, it translates to Mo1.74CTz MXene, exhibiting defect-rich sheets. Notably, the incorporation of Cr facilitates a shorter etching time with an improved yield compared to Mo2CTz. The Mo1.74CTz MXene displays excellent electrochemical properties, almost doubling the capacitance values (1152 F cm(-3) and 297 F g(-1) at 2 mV s(-1) scan rate), compared to its pristine counterpart Mo2CTz. The presented method and obtained results suggest defect engineering of MXenes through precursor alloying as a pathway that can be generalized to other phases, to further improve their properties for various applications.

The optimization of magnetron sputter epitaxy (MSE) for the high -volume production of high -quality GaN films is increasingly important. This study concerns the influence of key MSE process parameters - including the partial pressure of process gas, target -to -substrate distance (TSD), and growth temperature (TG) - for the synthesis of GaN thin films using a liquid Ga target. It is observed that the effective Ga/N ratio on the substrate surface determines the film's growth behavior and affects material's composition and luminescence properties. A lower Ar/N2 partial pressure ratio substantially enhances the crystalline quality, evidenced by the reduction in peak width of x-ray rocking curves from approximately 1.25 degrees (N -rich regime) to 0.35 degrees (Ga-rich regime) and improved GaN bandgap emission. While target sputtered in a highly Ga-rich condition significantly reduces the GaN growth rate (R), primarily due to Ga desorption in nitrogen -limited condition at elevated TG. Ion mass spectrometry and rate monitor measurements demonstrate that the Ga/N ratio can be controlled by adjusting Ar/N2 pressure ratio in MSE process. A reduction in TSD from 9.3 cm to 7 cm resulted in an increased R from 541 nm/h to 731 nm/h, corroborated by Simulation of Metal Transport (SIMTRA) analysis. Temperature -dependent studies revealed that films grown above 900 degrees C exhibited flat surface with high crystalline quality.

Assembly of two-dimensional (2D) nanomaterials into well-organized architectures is pivotal for controlling their function and enhancing performance. As a promising class of 2D nanomaterials, MXenes have attracted significant interest for use in wearable electronics due to their unique electrical and mechanical properties. However, facile approaches for fabricating MXenes into macroscopic fibers with controllable structures are limited. In this study, we present a strategy for easily spinning MXene fibers by incorporating polyanions. The introduction of poly(acrylic acid) (PAA) into MXene colloids has been found to alter MXene aggregation behavior, resulting in a reduced concentration threshold for lyotropic liquid crystal phase. This modification also enhances the viscosity and shear sensitivity of MXene colloids. Consequently, we were able to draw continuous fibers directly from the gel of MXene aggregated with PAA. These fibers exhibit homogeneous diameter and high alignment of MXene nanosheets, attributed to the shear-induced long-range order of the liquid crystal phase. Furthermore, we demonstrate proof-of-concept applications of the ordered MXene fibers, including textile-based supercapacitor, sensor and electrical thermal management, highlighting their great potential applied in wearable electronics. This work provides a guideline for processing 2D materials into controllable hierarchical structures by regulating aggregation behavior through the addition of ionic polymers.

In this study, a simple thermal reduction process is used to synthesize a rGO-Ca2Fe2O5 (rGO-CFO) nanocomposite, with the morphological and optical characteristics of the CFO nanomaterial being modified by the rGO incorporation. The interface between rGO nanosheets and CFO nanoparticles facilitates efficient charge separation and resulting transfer of photogenerated charge carriers across the rGO nanosheets, demonstrated from photoluminescence and Mott-Schottky tests. Compared to CFO (2.1 eV), rGO-CFO has a reduced band gap energy of 1.9 eV. As synthesized nanocomposites were initially optimized and utilized for photodegradation of organic effluent Methylene blue (MB). An addition of 5 wt% rGO to the CFO demonstrated an improved photodegradation efficiency (97%) compared to bare CFO (72%). An active species trapping experiment was used to assess the MB photodegradation mechanism. The results demonstrate that hydroxyl radicals and holes are the major active species involved in photodegradation. The optimized composition (5rGO-CFO) was further tested for degradation of Bisphenol-A and Tetracycline (antibiotic). Altogether, these investigations show that the rGO-CFO is a highly efficient photocatalyst that can be used to remediate emerging contaminants in sunlight.

Near-stoichiometric chromium diboride films were subject to in situ annealing inside a scanning transmission electron microscope to access the thermal behavior of the film and embedded structural planar defects. Independent of films' stoichiometry, the planar defects were unaffected by the applied heat treatments. On the contrary, the interfaces between the boron-rich tissue phase and the CrB2 phase were reshaped in the overstoichometric CrB2 film. At high temperatures, diffusion of contact metal species (platinum) from the focused ion beam sample preparation was triggered, with subsequent migration onto the sample. This resulted in the formation of metal-rich regions as directly observed and characterized at the atomic level. We determined that platinum did not react with the diboride structure but is accommodated by various defects present in the film.

We report on a systematic study of the effect of pulse length (ton = 25 - 200 mu s), and peak target current density (JT,peak = 0.25 - 2.0 A /cm2) during HiPIMS deposition of AlB2-phase TiBx thin films from a TiB2 target at a pressure of pAr = 1.33 Pa (10 mTorr) and substrate temperature T-s = 500 C-degrees. All films are under-stoichiometric with B/Ti = 1.36-1.89, with the higher values corresponding to longer pulses and higher JT,peak values. While the deposition flux, including both ions and neutrals, in general increases with increasing ton and JT,peak, the Ti+ ion flux saturates, resulting in the higher B/Ti values under these conditions. Thus, the relative amount of Ti ionization, and the degree to which these ions are guided toward the substrate by magnetic fields, are main modulators determining the composition of TiBx thin films.

On-surface synthesis often proceeds under kinetic control due to the irreversibility of key reaction steps, rendering kinetic studies pivotal. The accurate quantification of reaction rates also bears potential for unveiling reaction mechanisms. Temperature-Programmed X-ray Photoelectron Spectroscopy (TP-XPS) has emerged as an analytical tool for kinetic studies with splendid chemical and sufficient temporal resolution. Here, we demonstrate that the common linear temperature ramps lead to fitting ambiguities. Moreover, pinpointing the reaction order remains intricate, although this key parameter entails information on atomistic mechanisms. Yet, TP-XPS experiments with a stepped temperature profile comprised of isothermal segments facilitate the direct quantification of rate constants from fitting time courses. Thereby, rate constants are obtained for a series of temperatures, which allows independent extraction of both activation energies and pre-exponentials from Arrhenius plots. By using two analogous doubly versus triply brominated aromatic model compounds, we found that their debromination on Ag(111) is best modeled by second-order kinetics and thus proceeds via the involvement of a second, non-obvious reactant. Accordingly, we propose that debromination is activated by surface supplied Ag adatoms. This hypothesis is supported by Density Functional Theory (DFT) calculations. We foresee auspicious prospects for this TP-XPS variant for further exploring the kinetics and mechanisms of on-surface reactions. The temporal evolution of the reactant concentrations as measured by XPS for different temperature profiles reveals that the debromination of organic molecules on Ag(111) is activated by Ag adatoms.

Aqueous zinc-ion batteries (AZIBs) based on vanadium oxides or sulfides are promising candidates for large-scale rechargeable energy storage due to their ease of fabrication, low cost, and high safety. However, the commercial application of vanadium-based electrode materials has been hindered by challenging problems such as poor cyclability and low-rate performance. To this regard, sophisticated nanostructure engineering technology is used to adeptly incorporate VS2 nanosheets into the MXene interlayers to create a stable 2D heterogeneous layered structure. The MXene nanosheets exhibit stable interactions with VS2 nanosheets, while intercalation between nanosheets effectively increases the interlayer spacing, further enhancing their stability in AZIBs. Benefiting from the heterogeneous layered structure with high conductivity, excellent electron/ion transport, and abundant reactive sites, the free-standing VS2/Ti(3)C(2)Tz composite film can be used as both the cathode and the anode of AZIBs. Specifically, the VS2/Ti3C2Tz cathode presents a high specific capacity of 285 mAh g(-1) at 0.2 A g(-1). Furthermore, the flexible Zn-metal free in-plane VS2/Ti3C2Tz//MnO2/CNT AZIBs deliver high operation voltage (2.0 V) and impressive long-term cycling stability (with a capacity retention of 97% after 5000 cycles) which outperforms almost all reported Vanadium-based electrodes for AZIBs. The effective modulation of the material structure through nanocomposite engineering effectively enhances the stability of VS2, which shows great potential in Zn2+ storage. This work will hasten and stimulate further development of such composite material in the direction of energy storage.

Aluminum (Al)-ion batteries have emerged as a potential alternative to conventional ion batteries that rely on less abundant and costly materials like lithium. Nonetheless, given the nascent stage of advancement in Al-ion batteries (AIBs), attaining electrode materials that can leverage both intercalation capacity and structural stability remains challenging. Herein, we demonstrate a C3N4-derived layered N,S heteroatom-doped carbon, obtained at different pyrolysis temperatures, as a cathode material for AIBs, encompassing the diffusion-controlled intercalation and surface-induced capacity with ultrahigh reversibility. The developed layered N,S-doped corbon (N,S-C) cathode, synthesized at 900 degrees C, delivers a specific capacity of 330 mAh g(-1) with a relatively high coulombic efficiency of similar to 85% after 500 cycles under a current density of 0.5 A g(-1). Owing to its reinforced adsorption capability and enlarged interlayer spacing by doping N and S heteroatoms, the N,S-C900 cathode demonstrates outstanding energy storage capacity with excellent rate performance (61 mAh g(-1) at 20 A g(-1)) and ultrahigh reversibility (90 mAh g(-1) at 5 A g(-1) after 10 000 cycles).

Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of center dot O-2(-) during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (similar to 56 mu mol g(-1) h(-1)) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.

Titanium diboride exhibits outstanding properties for hard and wear resistant coatings. However, efficient physical vapor deposition (PVD) processing through DC vacuum arc, with a deposition rate unreachable for any other PVD technique, is comparatively unexplored for TiB2 thin films due to challenges associated with the film synthesis process. In this work, we used an industrial scale arc plasma source having a plane cathode of 100 mm in diameter and a permanent magnet on its back side. We present analysis of the cathode surface, plasma generation/composition, as well as analysis of collected macroparticles. The cathode weight loss and the amount of generated macroparticles were measured as a function of process parameters (arc current and pressure, in both Ar and N2 gas). Plasma analysis shows average ion energies around 120 and 25 eV for Ti and B, respectively, and plasma ion composition of approximately 50 % Ti and 50 % B. The cathode weight loss was around 0.3-0.5 g/ min, of which at least 25 % is estimated to be macroparticles. Notably, the intensity of the macroparticle generation was reduced with an increase in N2 pressure. Altogether, the results show a stable and reproducible plasma generation process and a high potential for the use of the cathodic arc as an efficient and useful method for deposition of metal borides.

The synthesis of monolayer gold has so far been limited to free-standingseveral-atoms-thick layers, or monolayers confned on or inside templates.Here we report the exfoliation of single-atom-thick gold achieved throughwet-chemically etching away Ti3C2 from nanolaminated Ti3AuC2, initiallyformed by substituting Si in Ti3SiC2 with Au. Ti3SiC2 is a renown MAX phase,where M is a transition metal, A is a group A element, and X is C or N. Ourdeveloped synthetic route is by a facile, scalable and hydrofuoric acid-freemethod. The two-dimensional layers are termed goldene. Goldene layerswith roughly 9% lattice contraction compared to bulk gold are observedby electron microscopy. While ab initio molecular dynamics simulationsshow that two-dimensional goldene is inherently stable, experiments showsome curling and agglomeration, which can be mitigated by surfactants.X-ray photoelectron spectroscopy reveals an Au 4f binding energy increaseof 0.88 eV. Prospects for preparing goldene from other non-van der WaalsAu-intercalated phases, including developing etching schemes,are presented.

A desired prerequisite when performing a quantum mechanical calculation is to have an initial idea of the atomic positions within an approximate crystal structure. The atomic positions combined should result in a system located in, or close to, an energy minimum. Designing low-energy structures for large multi-component systems is, however, often a challenging task as the degrees of freedom are close to infinite. The low-energy basins of (M ' x M '' 1-x ) 3 AlB 4 material systems are herein explored by combining cluster expansion and crystal structure prediction methodologies with density functional theory calculations. Low-energy structures are specifically found at the (M ' 1/3 M '' 2/3 ) 3 AlB 4 composition, and this for multiple crystal symmetries. A subsequent high-throughput phase stability search was performed considering the identified low-energy structures at the (M ' 1/3 M '' 2/3 ) 3 AlB 4 composition where M ' and M '' were alloyed with Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, and Co for both ordered and disordered structures. Nine quaternary phases were predicted stable with five of these favoring structures with M -sites in the form of a simulated solid solution.

The hardness and fracture toughness of high-temperature wear-resistant transition metal aluminum nitride multilayer films depend largely on the constituting layer ' s structure, compositional modulation, morphology, and interface coherency. We present a study on 1-micron thick multilayered films consisting of stacked layers of TiN and Zr 0.37 Al 0.63 N 1.09 , each layer being 10 nm thick. The films were grown using ion-assisted reactive magnetron sputtering on MgO(001) and Si(001) at substrate temperatures ranging from ambient to 900 degrees C. By increasing growth temperature, we found that the ZrAlN layers transition from near amorphous to nanocrystalline wurtzite to decomposed c-ZrN and w-AlN domains. Concurrently, the TiN layers exhibit strong fiber texture, polycrystallinity, and epitaxial growth carried by the ZrN domains. Both hardness and fracture stress, evaluated by nanoindentation and micromechanical tests, increase with temperature from H=24 GPa M g O , 23 GPa Si to 36 GPa M g O , 30 GPa Si , and sigma F Si = 6.1-7.7 GPa, respectively. An improved fracture toughness of K IC =2.4-2.8 MPa root m is related to different toughening mechanisms for the various microstructures. The difference in hardness between the substrates is related to compressive stress due to the deposition conditions and thermal contraction. The superior fracture stress is attributed to dense multilayers, free from macroscopic defects due to ion-assisted growth. After being deposited at 200 degrees C, the multilayers remained thermally stable when vacuum annealed for 15 hours at 900 degrees C, with no significant change in phase composition or hardness. The improved hardness, toughness, and temperature stability of the otherwise brittle nitrides are promising for industrial applications.

2D titanium carbide (Ti3C2) MXenes have emerged as promising candidates for biomedical applications. However, the biological properties of these materials are poorly understood. Moreover, MXenes are prone to oxidation under ambient conditions. Here, we show that glutathione (GSH), a natural antioxidant present in millimolar concentrations in the cytosol of most cells, protects MXenes from oxidation in aqueous suspensions while preserving the biocompatibility of the material. Reactive molecular dynamics (RMD) simulations confirm that GSH protects MXenes. Moreover, we provide evidence of the intracellular biotransformation of Ti3C2 MXenes to the rutile form of TiO2, and we show that GSH tunes the transformation process, resulting in the secretion of pro -inflammatory interleukin (IL) -1b through a non -canonical, elastase-dependent pathway. These results are important because they shed new light on the biotransformation of Ti3C2 MXenes and its ramifications for cellular signaling.

MXenes are a family of two-dimensional (2D) materials typically formed by etching the A element from a parent MAX phase. Computational screening for other 3D precursors suitable for such exfoliation is challenging because of the intricate chemical processes involved. We present a theoretical approach for predicting 2D materials formed through chemical exfoliation under acidic conditions by identifying 3D materials amenable for selective etching. From a dataset of 66,643 3D materials, we identified 119 potentially exfoliable candidates, within several materials families. To corroborate the method, we chose a material distinctly different from MAX phases, in terms of structure and chemical composition, for experimental verification. We selectively etched Y from YRu2Si2, resulting in 2D Ru2SixOy. The high-throughput methodology suggests a vast chemical space of 2D materials from chemical exfoliation.

On-surface synthesis provides tools to prepare low-dimensional supramolecular structures. Traditionally, reactive radicals are a class of single-electron species, serving as exceptional electron-withdrawing groups. On metal surfaces, however, such species are affected by conduction band screening effects that may even quench their unpaired electron characteristics. As a result, radicals are expected to be less active, and reactions catalyzed by surface-stabilized radicals are rarely reported. Herein, we describe a class of inter-molecular radical transfer reactions on metal surfaces. With the assistance of aryl halide precursors, the coupling of terminal alkynes is steered from non-dehydrogenated to dehydrogenated products, resulting in alkynyl-Ag-alkynyl bonds. Dehalogenated molecules are fully passivated by detached hydrogen atoms. The reaction mechanism is unraveled by various surface-sensitive technologies and density functional theory calculations. Moreover, we reveal the universality of this mechanism on metal surfaces. Our studies enrich the on-surface synthesis toolbox and develop a pathway for producing low-dimensional organic materials. Radicals are expected to be inactive on metal surfaces. Here the authors describe general intermolecular radical transfer reactions on Ag and Cu surfaces and confirm the reaction mechanism by extensive control experiments.

On-surface reactions of terminal alkynes in ultrahigh vacuum have attracted widespread attention due to their high technological promise. However, employing different precursors and substrate materials often intricate reaction schemes appear far from being well-understood. Thus, recent investigations of alkyne coupling on noble metal surfaces suggest non-dehydrogenative scenarios, contradicting earlier reports. Herein, the study employs noncontact atomic force microscopy (nc-AFM) with high spatial resolution to conclusively characterize exemplary alkyne coupling products. Contrary to initial interpretations proposing dehydrogenative homocoupling on Ag(111), bond-resolved AFM imaging reveals the expression of enyne motifs. Based on complementary, extensive density functional theory calculations, the pertaining reaction mechanisms are explored. It is proposed that enyne formation initiates with a direct carbon-carbon coupling between two alkyne groups, followed by surface-assisted dehydrogenation-hydrogenation processes. Thereby consecutive steps of atomic hydrogen cleavage, surface migration and recombination to a different carbon atom enable bridging via carbon-carbon double bonding. The new results shed light on subtle, but crucial surface-mediated hydrogen transfer processes involved in the chemical bond formation, which are suggested to be of general relevance in on-surface synthesis. Terminal alkyne coupling on Ag(111) in ultrahigh vacuum is conclusively examined by bond-resolved atomic force microscopy and density functional theory modeling. The prevailing bonding motif is the enyne moiety, originating from a distinct surface-mediated dehydrogenation-hydrogenation reaction pathway. The findings highlight the important role of hydrogen transfer in the course of on-surface synthesis procedures. image

This investigation reports the influence of Ti-C and Ti-W cathode composition on an industrial-scale dc vacuum arc plasma source. Further, we analyze the influence of plasma generation and plasma properties on the resulting cathode surface after the operation and on basic film properties. The results are compared with previous work focused on Ti-Al and Ti-Si compound cathodes. For all Ti-X compound cathodes (X = W, C, Al, and Si), a direct correlation between plasma ion energy/charge and the cohesive energy of the cathode was demonstrated, with a small number of exceptions to a limited set of specific cathode compositions. Hence, the "velocity rule" and effects from different electron temperatures were suggested to be important for gaining a more detailed understanding of plasma properties. A discrepancy was found between the cathode and plasma ion composition, though the difference was reduced in a corresponding comparison between the cathode and the deposited film composition. A significant contribution of a flux of neutrals and/or macroparticles to the final film composition was, therefore, suggested. The effect of the melting point of the cathode phase composition on the intensity of macroparticle generation and the smoothness of the cathode surface operation was also investigated. The presented results contribute to the fundamental understanding of vacuum arc plasma generation and transport and are of importance for further development and applicability of Ti-based coatings from arc deposition.

Aqueous ammonium-ion batteries (AAIBs) are appealing due to their relatively low cost and good rate performance. In general, AAIBs are environmentally friendlier than their non-aqueous counterparts. However, it is still a challenge to achieve highly reversible AAIBs with decent voltages and energy/power densities. Herein, we report on a full-cell configuration using alpha-MoO3/Ti3C2Tz films as anodes, and (NH4)(x)MnO2/CNTs films as cathodes in a 1 M ammonium acetate (NH4Ac) electrolyte. At 2 V, the operating cell voltage, OCV, is one of the highest reported for AAIBs. A maximum energy density of similar to 32 Wh kg(-1) (similar to 54 Wh L-1) at 0.2 A g(-1) and a maximum power density of similar to 10 kW kg(-1) (similar to 17 kW L-1) at 10 A g(-1) are attained. When the full cells are cycled 2,000 times at 1 A g(-1) they retain similar to 73 % of their initial capacity. When cycling at 10 A g(-1), similar to 96 % of capacity is retained after 43,500 cycles. After 10 h, self-discharge reduces the OCV to similar to 72 % of its original value. This work provides a roadmap for developing high performance AAIBs with high voltages and high energy/power densities. Before this is possible it is imperative that the self-discharge rate be substantially reduced.

Functional 2D materials are interesting for a wide range of applications. The rapid growth of the MXene family is due to its compositional diversity, which, in turn, allows significant tuning of the properties, and hence their applicability. The properties are to a large extent dictated by surface terminations. In the present work, we demonstrate the influence of termination species (O, NH, N, S, F, Cl, Br, I) on the changes in electronic structure, work function, dynamical stability, and atomic charges and distances of MXenes (Ti2C, Nb2C, V2C, Mo2C, Ti3C2, and Nb4C3). Among these systems, the work function values were not previously reported for & SIM;60% of the systems, and most of the previously reported MXenes with semiconducting nature are here proven to be dynamically unstable. The results show that the work function generally decreases with a reduced electronegativity of the terminating species, which in turn is correlated to a reduced charge of both the metal and terminating species and an increased metal-termination distance. An exception to this trend is NH terminations, which display a significantly reduced work function due to an intrinsic dipole moment within the termination. Furthermore, the results suggest that halogen terminations improve the electrical conductivity of the materials.

More than a decade after the discovery of MXene, there has been a remarkable increase in research on synthesis, characterization, and applications of this growing family of two-dimensional (2D) carbides and nitrides. Today, these materials include one, two, or more transition metals arranged in chemically ordered or disordered structures of three, five, seven, or nine atomic layers, with a surface chemistry characterized by surface terminations. By combining M, X, and various surface terminations, it appears that a virtually endless number of MXenes is possible. However, for the design and discovery of structures and compositions beyond current MXenes, one needs suitable (stable) precursors, an assessment of viable pathways for 3D to 2D conversion, and utilization or development of corresponding synthesis techniques. Here, we present a critical and forward-looking review of the field of atomic scale design and synthesis of MXenes and their parent materials. We discuss theoretical methods for predicting MXene precursors and for assessing whether they are chemically exfoliable. We also summarize current experimental methods for realizing the predicted materials, listing all verified MXenes to date, and outline research directions that will improve the fundamental understanding of MXene processing, enabling atomic scale design of future 2D materials, for emerging technologies.

Out-of-plane chemically ordered transitionmetal boride(o-MAB) phases, Ta4M & DPRIME;SiB2 (M & DPRIME; = V, Cr), and a structurally equivalent disordered solidsolution MAB phase, Ta4MoSiB2, are synthesized.DFT calculations are used to examine the dynamic stability, elasticproperties, and electronic density states of the MAB phases. We report on the synthesis of computationally predictedout-of-planechemically ordered transition metal borides labeled o-MAB phases, Ta4M & DPRIME;SiB2 (M & DPRIME; =V, Cr), and a structurally equivalent disordered solid solution MABphase Ta4MoSiB2. The boride phases were preparedusing solid-state reaction sintering of the constituting elements.High-resolution scanning transmission electron microscopy along withRietveld refinement of the powder-X-ray diffraction patterns revealedthat the synthesized o-MAB phases Ta4CrSiB2 (98 wt % purity) and Ta4VSiB2 (81 wt% purity) possess chemical ordering with Ta preferentially residingin the 16l position and Cr and V in the 4c position, whereas Ta4MoSiB2 (46wt % purity) was concluded to form a disordered solid solution. Densityfunctional theory (DFT) calculations were used to investigate thedynamic stability, elastic properties, and electronic density statesfor the MAB phases, confirming the stability and suggesting the boridesbased on Cr and Mo to be stiffer than those based on V and Nb.

We report the synthesis of three out-of-plane chemically ordered quaternary transition metal borides (o-MAB phases) of the chemical formula M4CrSiB2 (M = Mo, W, Nb). The addition of these phases to the recently discovered o-MAB phase Ti4MoSiB2 shows that this is indeed a new family of chemically ordered atomic laminates. Furthermore, our results expand the attainable chemistry of the traditional M5SiB2 MAB phases to also include Cr. The crystal structure and chemical ordering of the produced materials were investigated using high-resolution scanning transmission electron microscopy and X-ray diffraction by applying Rietveld refinement. Additionally, calculations based on density functional theory were performed to investigate the Cr preference for occupying the minority 4c Wyckoff site, thereby inducing chemical order.

A desired prerequisite when performing a quantum mechanical calculation is to have an initial idea of the atomic positions within an approximate crystal structure. The atomic positions combined should result in a system located in, or close to, an energy minimum. However, designing low-energy structures may be a challenging task when prior knowledge is scarce, specifically for large multi-component systems where the degrees of freedom are close to infinite. In this paper, we propose a method for identification of low-energy crystal structures within multi-component systems by combining cluster expansion and crystal structure predictions with density-functional theory calculations. Crystal structure prediction searches are applied to the Mo2AlB2 and Sc2AlB2 ternary systems to identify candidate structures, which are subsequently used to explore the quaternary (pseudo-binary) (MoxSc1-x)(2)AlB2 system through the cluster expansion formalism utilizing the ground-state search approach. Furthermore, we show that utilizing low-energy structures found within the cluster expansion ground-state search as seed structures within crystal structure predictions of (MoxSc1-x)(2)AlB2 can significantly reduce the computational demands. With this combined approach, we not only correctly identified the recently discovered Mo(4/3)Sc(2/3)AlB(2)i-MAB phase, comprised of in-plane chemical ordering of Mo and Sc and with Al in a Kagome lattice, but also predict additional low-energy structures at various concentrations. This result demonstrates that combining crystal structure prediction with cluster expansion provides a path for identifying low-energy crystal structures in multi-component systems by employing the strengths from both frameworks.

The epitaxial growth of boron rich hexagonal zirconium diborides (h-ZrB2+delta) thin films on Si(111) substrates using the magnetron co-sputtering technique with elemental zirconium and boron is reported. The effect of process temperature (700-900 degrees C) on the compositions and epitaxy quality was investigated. The chemical composition of the films was found to have a higher boron to zirconium ratio than the ideal stoichiometric AlB2-type ZrB2 and was observed to be sensitive to process temperature. Films deposited at 700 degrees C exhibited intense diffraction peaks along the growth direction corresponding to (000l) of h-ZrB2 using both lab and synchrotron-based x-ray diffractograms. The thermal and compositional stability of the epitaxial h-ZrB2+delta film was further evaluated under a nitrogen-rich environment through isothermal annealing which showed a reduction in in-plane misorientation during thermal annealing. The relative stability of deviating compositions and the energetics of impurity incorporations were analyzed using density functional theory simulations, and the formation of native point defects or impurity incorporation in h-ZrB2 was found to be endothermic processes. Our experimental results showed that an epitaxial thin film of h-ZrB2+delta can be grown on Si(111) substrate using a magnetron co-sputtering technique at a relatively low processing temperature (700 degrees C) and has the potential to be used as a template for III-nitride growth on Si substrates.

Nanolaminated Mn2GaC epitaxial films crystallizing in the hexagonal structure belong to the family of MAX phase compounds and display complex magnetic interactions. While the critical temperature of the order-disorder transition is 507 K, at around 214 K this compound undergoes a first-order phase transition with the magnetic structure below the transition point not being fully resolved. Previous studies indicated a noncollinear spin arrangement, but a specific magnetic structure could not be defined. In this work we present the results of 69Ga, 71Ga, and 55Mn NMR experiments performed at 4.2 K in an external in-plane magnetic field up to 1 T. The in-depth analysis of the experimental results shows a helical magnetic structure consisting of the ferromagnetically coupled Mn-C-Mn slabs that are twisted across the Ga layer by 167.2 degrees with respect to the next Mn-C-Mn slab. As a result, the magnetic structure presents a spiral propagating along the out-of-plane direction (hexagonal c axis) with a pitch of around 14 lattice constants.

Heterojunction photocatalysts have recently emerged for use in degradation of organic pollutants, typically being suspended in effluent solution to degrade it. Post degradation, the catalyst must be removed from the treated solution, which consumes both energy and time. Moreover, the separation of nano catalysts from the treated solution is challenging. In the present work, we explore fabrication of immobilized TiO2-PEDOT:PSS hybrid heterojunction catalysts with the support of a PVA (polyvinyl alcohol) matrix. These photocatalytic films do not require any steps to separate the powdered catalyst from the treated water. While the PVA-based films are unstable in water, their stability could be significantly enhanced by heat treatment, enabling efficient removal of organic effluents like methylene blue (MB) and bisphenol-A (BPA) from the aqueous solution under simulated sunlight irradiation. Over 20 cycles, the heterojunction photocatalyst maintained high photocatalytic activity and showed excellent stability. Hence, an immobilization of the TiO2-PEDOT:PSS hybrid heterojunction is suggested to be beneficial from the viewpoint of reproducible and recyclable materials for simple and efficient wastewater treatment.

The sluggish kinetics associated with the oxygen evolution reaction (OER) limits the sustainability of fuel production and chemical synthesis. Developing catalysts based on Earth abundant elements with a reasonable strategy could solve the challenge. Here, we present a heterostructure built from CrOx and CuS whose interface gives rise to the advent of new functionalities in catalytic activity. Using X-ray photoelectron and absorption spectroscopies, we identified the multiple oxidation states and low coordination number of Cr metal in CrOx-CuS heterostructure. Benefitting from these features, CrOx-CuS generates oxygen gas through water splitting with a low over potential of 190 mV vs RHE at a current density of 10 mA cm-2. The catalyst shows no evident deactivation after a 36-hours operation in alkaline medium. The high catalytic activity, inspired by first principles calculations, and long-time durability make it one of the most effective OER electrocatalysts.

MXenes are two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides typically synthesized from layered MAX-phase precursors. With over 50 experimentally reported MXenes and a near-infinite number of possible chemistries, MXenes make up the fastest-growing family of 2D materials. They offer a wide range of properties, which can be altered by their chemistry (M, X) and the number of metal layers in the structure, ranging from two in M2XTx to five in M5X4T x . Only one M5X4 MXene, Mo4VC4, has been reported. Herein, we report the synthesis and characterization of two M(5)AX(4) mixed transition metal MAX phases, Ti2.5Ta2.5AlC4 and Ti2.675Nb2.325AlC4, and their successful topochemical transformation into Ti2.5Ta2.5C4T x and Ti2.675Nb2.325C4Tx MXenes. The resulting MXenes were delaminated into single-layer flakes, analyzed structurally, and characterized for their thermal and optical properties. This establishes a family of M(5)AX(4) MAX phases and their corresponding MXenes. These materials were experimentally produced based on guidance from theoretical predictions, leading to more exciting applications for MXenes.

MXene-based aqueous supercapacitors (SCs) have rapidly developed during the last decade because of their excellent cycling stability, fast charging capabilities, and environmental benignity. However, despite the prac-tical importance of mass loadings (MLs) and self-discharge (SD) rates, these two issues have, for the most part, been neglected by the MXene community. MXene-based devices with MLs > 10 mg cm(-2) are vital for the development of the next generation of SC devices. However, poor electrolyte accessibility to active materials and high electrical resistances at high MLs can reduce the specific capacitances significantly, leading to low energy/ power density devices. Most MXene SC papers do not report the SD, despite its great importance in terms of applications. SCs with high SD rates will have many fewer applications. In this review, we are focusing on the ML and SD challenges in MXene-based aqueous SCs. The strategies for constructing high-performance MXene-based aqueous SCs with high MLs and/or slow SD rates are summarized with key challenges and perspectives outlined. Moreover, this review also attempts to raise awareness in the MXene SC community of the importance of ML and SD for a large host of applications.

The MAX phases are a class of nanolaminated materials composed of an early transition-metal (M), an A-group element (A) and C, N, B and/or P (X). Progress in MAX phase research in recent years has increased their number from the original 50 or so, to more than 300 phases. Since half of the 342 MAX phases have been discovered after 2018, an overview of the progress made in the field is timely. Currently, 28 M elements, 28 A elements, and 6 X elements have been incorporated in the MAX phases, alloys included. We further categorize MAX phases based on the synthesis route used to make them; if made via a one-step approach in bottom-up synthesis or formed through elemental replacement reactions in top-down synthesis. This classification is also correlated to theoretical phase stability predictions, that in turn, can be used to identify novel synthesizable MAX phase compositions as well as to suggest suitable synthesis routes. Furthermore, using phase stability predictions we identify 182 new theoretically stable MAX phases awaiting experimental confirmation. Notably, as MAX phases are precursors for MXenes, the dramatically increased interest in the latter for a large host of potential applications renders the former even more valuable. © 2023 The Author(s)

Zero-field NMR investigations on the 69Ga, 71Ga, and 55Mn nuclei have been performed at 4.2 K on a 100 nm thick epitaxial Mn2GaC(0001) MAX phase film grown on a MgO(111) substrate. This nano-laminated structure consists of ferromagnetic Mn-C-Mn stacks interleaved with monolayers of gallium. A resolved quadrupolar structure of the observed gallium resonances is a fingerprint of a well-defined crystal field confirming high crystal quality. The nuclei of non-magnetic gallium atoms are shown to experience the transferred hyperfine magnetic field of 15.75 T (& PLUSMN;0.05 T), which is due to polarization of their 4s electron shell by the magnetic moments of manganese neighbors, evidencing the presence of an uncompensated ferromagnetic moment within the manganese sublattice. The average magnetic moment of manganese was found to be around 2 & mu;B, strongly contrasting with the reported remnant magnetization of only 0.3 & mu;B. Moreover, the 55Mn NMR spectrum in-dicates the presence of magnetically non-equivalent manganese sites within this structure. The observed features of the 69,71Ga and 55Mn NMR spectra cannot be reconciled with any of the hitherto proposed collinear ar-rangements of manganese moments and suggest their non-collinear arrangement across a gallium layer. Nevertheless a more advanced study is required to elucidate the detailed nature of magnetic structure in this material.

Belonging to the enyne family, enetriynes comprise a distinct electron-rich all-carbon bonding scheme. However, the lack of convenient synthesis protocols limits the associated application potential within, e.g., biochemistry and materials science. Herein we introduce a pathway for highly selective enetriyne formation via tetramerization of terminal alkynes on a Ag(100) surface. Taking advantage of a directing hydroxyl group, we steer molecular assembly and reaction processes on square lattices. Induced by O-2 exposure the terminal alkyne moieties deprotonate and organometallic bis-acetylide dimer arrays evolve. Upon subsequent thermal annealing tetrameric enetriyne-bridged compounds are generated in high yield, readily self-assembling into regular networks. We combine high-resolution scanning probe microscopy, X-ray photoelectron spectroscopy and density functional theory calculations to examine the structural features, bonding characteristics and the underlying reaction mechanism. Our study introduces an integrated strategy for the precise fabrication of functional enetriyne species, thus providing access to a distinct class of highly conjugated pi-system compounds. Enetriynes, which belong to the enyne family, are characterized by a distinct electron-rich carbon-bonding scheme. Here, the authors report the formation of enetriynes with high selectivity by tetramerization of terminal alkynes on Ag(100).

The factors controlling the top-down synthesis of MXenes, by selectively removing the A elements from parent MAX phases, is still under debate. In particular, understanding why some MAX phases can be used for creating MXenes, while others cannot, is of immense interest and would greatly support computational screening and identification of new two-dimensional materials that could also be created by chemical exfoliation. Here we computationally study the etching of MAX phases in hydrofluoric acid, considering the complete exfoliation process and competing processes during the initial steps of the synthesis. The results are compared to experiments and MAX phases successfully converted to MXenes, as well as so far unsuccessful attempts, including previously unpublished experimental data, rationalizing why some MAX phases are exfoliable while others are not. Our results provide an improved understanding of the synthesis of MXenes under acid conditions, anticipated to be vital for our ability to discover novel two-dimensional materials.

MAX/MAB phases are a series of non-van der Waals ternary layered ceramic materials with a hexagonal structure, rich in elemental composition and crystal structure, and embody physical properties of both ceramics and metals. They exhibit great potential for applications in extreme environments such as high temperature, strong corrosion, and irradiation. In recent years, two-dimensional (2D) materials derived from the MAX/MAB phase (MXene and MBene) have attracted enormous interest in the fields of materials physics and materials chemistry and become a new 2D van der Waals material after graphene and transition metal dichalcogenides. Therefore, structural modulation of MAX/MAB phase materials is essential for understanding the intrinsic properties of this broad class of layered ceramics and for investigating the functional properties of their derived structures. In this paper, we summarize new developments in MAX/MAB phases in recent years in terms of structural modulation, theoretical calculation, and fundamental application research and provide an outlook on the key challenges and prospects for the future development of these layered materials.

On-surface acetylenic homocoupling has been proposed to construct carbon nanostructures featuring sp hybrid-ization. However, the efficiency of linear acetylenic coupling is far from satisfactory, often resulting in undesired enyne products or cyclotrimerization products due to the lack of strategies to enhance chemical selectivity. Herein, we inspect the acetylenic homocou-pling reaction of polarized terminal alkynes (TAs) on Au(111) with bond-resolved scanning probe microscopy. The replacement of benzene with pyridine moieties significantly prohibits the cyclotrimerization pathway and facilitates the linear coupling to produce well-aligned N-doped graphdiyne nanowires. Combined with density functional theory calculations, we reveal that the pyridinic nitrogen modification substantially differentiates the coupling motifs at the initial C-C coupling stage (head-to-head vs head-to-tail), which is decisive for the preference of linear coupling over cyclotrimerization.

MXenes hold immense potential given their superior electrical properties. The practical adoption of these promising materials is, however, severely constrained by their oxidative susceptibility, leading to significant performance deterioration and lifespan limitations. Attempts to preserve MXenes have been limited, and it has not been possible thus far to reverse the materials performance. In this work, we show that subjecting oxidized micron or nanometer thickness dry MXene films-even those constructed from nanometer-order solution-dispersed oxidized flakes-to just one minute of 10 MHz nanoscale electromechanical vibration leads to considerable removal of its surface oxide layer, whilst preserving its structure and characteristics. Importantly, electrochemical performance is recovered close to that of their original state: the pseudocapacitance, which decreased by almost 50% due to its oxidation, reverses to approximately 98% of its original value, with good capacitance retention ( approximate to 93%) following 10,000 charge-discharge cycles at 10 A g(-1). These promising results allude to the exciting possibility for rejuvenating the material for reuse, therefore offering a more economical and sustainable route that improves its potential for practical translation. Despite their vast potential, the practical deployment of MXenes has been hampered by their tendency to be oxidized. Here, the authors show that simply vibrating MXene films in just a minute can remove the oxide layer formed and restore their electrochemical performance close to its original state.

Although perovskite light-emitting diodes (PeLEDs) have seen unprecedented development in device efficiency over the past decade, they suffer significantly from poor operational stability. This is especially true for blue PeLEDs, whose operational lifetime remains orders of magnitude behind their green and red counterparts. Here, we systematically investigate this efficiency-stability discrepancy in a series of green- to blue-emitting PeLEDs based on mixed Br/Cl-perovskites. We find that chloride incorporation, while having only a limited impact on efficiency, detrimentally affects device stability even in small amounts. Device lifetime drops exponentially with increasing Cl-content, accompanied by an increased rate of change in electrical properties during operation. We ascribe this phenomenon to an increased mobility of halogen ions in the mixed-halide lattice due to an increased chemically and structurally disordered landscape with reduced migration barriers. Our results indicate that the stability enhancement for PeLEDs might require different strategies from those used for improving efficiency.

MAX phases are a class of intrinsically nanolaminated materials, which combine features of metals and ceramics, owing to the alternating metallic and covalent bonding between atomic layers. Magnetic MAX phases have been known for a decade, but ferromagnetism at room temperature in this highly anisotropic system has been elusive, limiting their value as magnets in practice. Here, we show that a MAX phase with a strong ferromagnetic response is obtained by substituting Mn with Cr on the M-site in the well-known Mn2GaC. The ferromagnetic response is observed in (Mn1-xCrx)(2)GaC with 0.06 < x < 0.29 up to temperatures well exceeding room temperature (489 K). The strongest magnetization is achieved with x = 0.12, reaching a saturation moment of 1.25 mu B and a remanence of 0.67 mu(B) per M-atom at 3 K and maintaining 0.90 and 0.44 mu(B) per M-atom, respectively, at 300 K. This is the first experimental report of a significant ferromagnetic response in a MAX phase at room temperature. The results open the door to the use of MAX phases in a broad range of applications, from bulk magnets in power electronics to spintronic devices.(c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/).

This work was inspired by new experimental findings where we discovered a two-dimensional (2D) material comprised of titanium-oxide-based one-dimensional (1D) sub-nanometer filaments. Preliminary results suggest that the 2D material contains considerable amounts of carbon, C, in addition to titanium, Ti, and oxygen, O. The aim of this study is to investigate the low-energy, stable atomic forms of 2D titanium carbo-oxides as a function of C content. Via a combination of first-principles calculations and an effective structure sampling scheme, the stable configurations of C-substitutions are comprehensively searched by templating different 2D TiO2 polymorphs and considering a two O to one C replacement scheme. Among the searched stable configurations, a structure where the (101) planes of anatase bound the top and bottom surfaces with a chemical formula of TiC1/4O3/2 was of particularly low energy. Furthermore, the variations in the electronic band structure and chemical bonding environments caused by the high-content C substitution are investigated via additional calculations using a hybrid exchange-correlation functional.

The recent discovery of chemical ordering in quaternary borides offers new ways of exploring properties and functionalities of these laminated phases. Here, we have synthesized and investigated chemical ordering of the laminated Mo4MnSiB2 (T2) phase, thereby introducing a magnetic element into the family of materials coined o-MAB phases. By X-ray diffraction and scanning transmission electron microscopy, we provide evidence for out-of-plane chemical ordering of Mo and Mn, with Mo occupying the 16l site and Mn preferentially residing in the 4c site. Mn and B constitute quasi-two-dimensional layers in the laminated material. We have therefore also studied the magnetic properties by magnetometry, and no sign of long-range magnetic order is observed. An initial assessment of the magnetic ordering has been further studied by density functional theory (DFT) calculations, and while we find an antiferromagnetic configuration to be the most stable one, ferromagnetic ordering is very close in energy.

Supercapacitors based on two-dimensional MXene (Ti3C2Tz) have shown extraordinary performance in ultrathin electrodes with low mass loading, but usually there is a significant reduction in high-rate performance as the thickness increases, caused by increasing ion diffusion limitation. Further limitations include restacking of the nanosheets, which makes it challenging to realize the full potential of these electrode materials. Herein, we demonstrate the design of a vertically aligned MXene hydrogel composite, achieved by thermal-assisted self-assembled gelation, for high-rate energy storage. The highly interconnected MXene network in the hydrogel architecture provides very good electron transport properties, and its vertical ion channel structure facilitates rapid ion transport. The resulting hydrogel electrode show excellent performance in both aqueous and organic electrolytes with respect to high capacitance, stability, and high-rate capability for up to 300 mu m thick electrodes, which represents a significant step toward practical applications.

The combination of the ability to absorb most of the solar radiation and simultaneously suppress infrared re-radiation allows selective solar absorbers (SSAs) to maximize solar energy to heat conversion, which is critical to several advanced applications. The intrinsic spectral selective materials are rare in nature and only a few demonstrated complete solar absorption. Typically, intrinsic materials exhibit high performances when integrated into complex multilayered solar absorber systems due to their limited spectral selectivity and solar absorption. In this study, we propose CoSbx (2 < x < 3) as a new exceptionally efficient SSA. Here we demonstrate that the low bandgap nature of CoSbx endows broadband solar absorption (0.96) over the solar spectral range and simultaneous low emissivity (0.18) in the mid-infrared region, resulting in a remarkable intrinsic spectral solar selectivity of 5.3. Under 1 sun illumination, the heat concentrates on the surface of the CoSbx thin film, and an impressive temperature of 101.7 degrees C is reached, demonstrating the highest value among reported intrinsic SSAs. Furthermore, the CoSbx was tested for solar water evaporation achieving an evaporation rate of 1.4 kg m(-2) h(-1). This study could expand the use of narrow bandgap semiconductors as efficient intrinsic SSAs with high surface temperatures in solar applications.

We have computationally studied the formation mechanism of the biphenylene network via the intermolecular HF zipping, as well as identified key intermediates experimentally, on the Au(111) surface. We elucidate that the zipping process consists of a series of defluorinations, dehydrogenations, and C–C coupling reactions. The Au substrate not only serves as the active site for defluorination and dehydrogenation, but also forms C–Au bonds that stabilize the defluorinated and dehydrogenated phenylene radicals, leading to "standing" benzyne groups. Despite that the C–C coupling between the "standing" benzyne groups is identified as the rate-limiting step, the limiting barrier can be reduced by the adjacent chemisorbed benzyne groups. The theoretically proposed mechanism is further supported by scanning tunneling microscopy experiments, in which the key intermediate state containing chemisorbed benzyne groups can be observed. This study provides a comprehensive understanding towards the on-surface intermolecular HF zipping, anticipated to be instructive for its future applications.

Carbon-based hybrid nanostructures have shown to be promising candidates as cost-efficient and effective fillers for electromagnetic interference shielding and RF absorption. In this work, hybrids of graphene-augmented inorganic (alumina) nanofibers (GAIN) have been incorporated in epoxy resin to fabricate a multilayer struc-ture with tunable absorption. Highly aligned graphene augmented alumina nanofibers of 10 +/- 2 nm in diameter were produced with the help of a hot wall one-step catalyst-free chemical vapor deposition method at 1000 degrees C. Effective medium approximation has been used to calculate the intrinsic dielectric properties of GAIN nanofibers. The highest loss tangent of 0.4 has been achieved in a 5 mm thick composite containing 1 vol% of randomly oriented nanofibers. Furthermore, aligned graphene augmented nanofibers were embedded in an epoxy resin matrix to examine the effect of fiber alignment on the dielectric properties of the composite. Based on the ob-tained dielectric data, a superposed three-layer structure has been fabricated, offering an absorption of >90% in the entire X-band and an absorption peak of-25 dB at similar to 11 GHz. Several multilayer designs based on finite element method coupled with Monte Carlo simulations have been proposed to tune the absorption character-istics. This work demonstrates the potential of the hybrid nanofibers with a dual loss function for versatile design options in the area of RF absorption.