Structural engineering of transition-metal nitrides for surfaceenhanced Raman scattering chips

Noble-metal-free surface-enhanced Raman scattering(SERS)substrates have attracted great attention for their abundant sources,good signal uniformity,superior biocompatibility,and high chemical stability.However,the lack of controllable synthesis and fabrication of noble-metal-free substrates with high SERS activity impedes their practical applications.Herein,we propose a general strategy to fabricate a series of planar transition-metal nitride(TMN)SERS chips via an ambient temperature sputtering deposition route.For the first time,tungsten nitride(WN)and tantalum nitride(TaN)are used as SERS materials.These planar TMN chips show remarkable Raman enhancement factors(EFs)with~105 owing to efficient photoinduced charge transfer process between TMN chips and probe molecules.Further,structural engineering of these TMN chips is used to improve their SERS activity.Benefiting from the synergistic effect of charge transfer process and electric field enhancement by constructing a nanocavity structure,the Raman EF of WN nanocavity chips could be greatly improved to~1.29×10^(7),which is an order of magnitude higher than that of planar chips.Moreover,we also design the WN/monolayer MoS2 heterostructure chips.With the increase of surface electron density on the upper WN and more exciton resonance transitions in the heterostructure,a~1.94×10^(7)level EF and a 5×10^(-10)M level detection limit could be achieved.Our results provide important guidance for the structural design of ultrasensitive noble-metal-free SERS chips.

Theoretical insights into the structures and fundamental properties of pnictogen nitrides

Recent experimental advancements reported a chemical reaction between antimony and nitrogen under high temperature and high pressure,yielding crystalline antimony nitride(Sb_(3)N_(5))with an orthorhombic structure.Motivated by this statement,we calculate the stability,elastic properties,electronic properties and energy density of the Cmc2_(1) structure for pnictogen nitrides X_(3)N_(5)(X=P,As,Sb,and Bi)using first-principles calculations combined with particle swarm optimization algorithms.Calculations of formation enthalpies,elastic constants and phonon spectra show that P_(3)N_(5),As_(3)N_(5) and Sb_(3)N_(5) are thermodynamically,mechanically and kinetically stable at 35 GPa,whereas Bi_(3)N_(5) is mechanically and kinetically stable but thermodynamically unstable.The computed electronic density of states shows strong covalent bonding between the N atoms and the phosphorus group atoms in the four compounds,confirmed by the calculated electronic localization function.We also calculate the energy densities for Sb_(3)N_(5) and find it to be a potentially high-energy-density material.

Insight into structure evolution of carbon nitrides and its energy conversion as luminescence

A series of carbon nitride(CN)materials represented by graphitic carbon nitride(g-C_(3)N_(4))have been widely used in bioimaging,biosensing,and other fields in recent years due to their nontoxicity,low cost,and high luminescent quantum efficiency.What is more attractive is that the luminescent properties such as wavelength and intensity can be regulated by controlling the structure at the molecular level.Hence,it is time to summarize the related research on CN structural evolution and make a prospect on future developments.In this review,we first summarize the research history and multiple structural evolution of CN.Then,the progress of improving the luminescence performance of CN through structural evolution was discussed.Significantly,the relationship between CN structure evolution and energy conversion in the forms of photoluminescence,chemiluminescence,and electrochemiluminescence was reviewed.Finally,key challenges and opportunities such as nanoscale dispersion strategy,luminous efficiency improving methods,standardization evaluation,and macroscopic preparation of CN are highlighted.

Pulsed laser interference patterning of transition-metal carbides for stable alkaline water electrolysis kinetics

We investigated the role of metal atomization and solvent decomposition into reductive species and carbon clusters in the phase formation of transition-metal carbides(TMCs;namely,Co_(3)C,Fe_(3)C,TiC,and MoC)by pulsed laser ablation of Co,Fe,Ti,and Mo metals in acetone.The interaction between carbon s-p-orbitals and metal d-orbitals causes a redistribution of valence structure through charge transfer,leading to the formation of surface defects as observed by X-ray photoelectron spectroscopy.These defects influence the evolved TMCs,making them effective for hydrogen and oxygen evolution reactions(HER and OER)in an alkaline medium.Co_(3)C with more oxygen affinity promoted CoO(OH)intermediates,and the electrochemical surface oxidation to Co_(3)O_(4)was captured via in situ/operando electrochemical Raman probes,increasing the number of active sites for OER activity.MoC with more d-vacancies exhibits strong hydrogen binding,promoting HER kinetics,whereas Fe_(3)C and TiC with more defect states to trap charge carriers may hinder both OER and HER activities.The results show that the assembled membrane-less electrolyzer with Co_(3)C∥Co_(3)C and MoC∥MoC electrodes requires~2.01 and 1.99 V,respectively,to deliver a 10 mA cm−2 with excellent electrochemical and structural stability.In addition,the ascertained pulsed laser synthesis mechanism and unit-cell packing relations will open up sustainable pathways for obtaining highly stable electrocatalysts for electrolyzers.

Recent advances of transition-metal metaphosphates for efficient electrocatalytic water splitting

Sustainable production of H2 through electrochemical water splitting is of great importance in the foreseeable future.Transition-metal metaphosphates(TMMPs)have a three-dimensional(3D)open-framework structure and a high content of P(which exists as PO3-),and therefore have been recognized as highly efficient catalysts for oxygen evolution reaction(OER)and the bottleneck of electrochemical water splitting.Furthermore,TMMPs can also contribute to hydrogen evolution reaction(HER)in alkaline and neutral media by facilitating water dissociation,and thus,overall water splitting can be achieved using this kind of material.In this timely review,we summarize the recent advances in the synthesis of TMMPs and their applications in OER and HER.We present a brief introduction of the structure and synthetic strategies of TMMPs in the first two parts.Then,we review the latest progress made in research on TMMPs as OER,HER,and overall water-splitting electrocatalysts.In this part,the intrinsic activity of TMMPs as well as the current strategy for improving the catalytic activity will be discussed systematically.Finally,we present the future opportunities and the remaining challenges for the application of TMMPs in the electrocatalysis field.

Flexible and Robust Functionalized Boron Nitride/Poly(p‑Phenylene Benzobisoxazole)Nanocomposite Paper with High Thermal Conductivity and Outstanding Electrical Insulation

With the rapid development of 5G information technology,thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent.In this work,“high-temperature solid-phase&diazonium salt decomposition”method is carried out to prepare benzidine-functionalized boron nitride(m-BN).Subsequently,m-BN/poly(pphenylene benzobisoxazole)nanofiber(PNF)nanocomposite paper with nacremimetic layered structures is prepared via sol–gel film transformation approach.The obtained m-BN/PNF nanocomposite paper with 50 wt%m-BN presents excellent thermal conductivity,incredible electrical insulation,outstanding mechanical properties and thermal stability,due to the construction of extensive hydrogen bonds andπ–πinteractions between m-BN and PNF,and stable nacre-mimetic layered structures.Itsλ∥andλ_(⊥)are 9.68 and 0.84 W m^(-1)K^(-1),and the volume resistivity and breakdown strength are as high as 2.3×10^(15)Ωcm and 324.2 kV mm^(-1),respectively.Besides,it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640°C,showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment.

Development and Application of Multi-phase Nitrides Bonded Silicon Carbide Lintel Blocks for Dry Quenching Furnaces

Multi-phase nitrides bonded silicon carbide lintel blocks were prepared using industrial SiC(SiC≥98 mass%,3-0.5,≤0.5 and≤0.044 mm),Si powder(Si≥98 mass%,≤0.044 mm),and SiO2 micropowder(SiO2≥96 mass%,d50=0.15 pm)as raw materials,and calcium lignosulfonate as the additive,batching,mixing,and molding on a vibration pressure molding machine,drying and then firing at 1420℃for 10 h in high-purity N2.The apparent porosity,the bulk density,the cold modulus of rupture,the hot modulus of rupture,and the linear expansion coefficient of the samples were tested.The phase composition and the microstructure of the samples at different nitriding depths(50,100,and 150 mm)were analyzed by XRD and SEM.The field application effects of the blocks were studied.The results show that:(1)the multi-phase nitrides bonded silicon carbide refractories can dynamically adjust their own phase composition and minimize structural and thermal stresses,improving the service life of key parts of dry quenching furnaces;(2)calcium lignosulfonate can improve the nitriding micro-environment of multi-phase nitrides bonded silicon carbide lintel blocks,successfully increasing the effective nitriding thickness of the blocks to 300 mm;(3)Sinosteel LI RR provides a unique concept in the design of materials and block types as well as the stable and scientific overall structure,promoting the industrialization process of dry quenching furnaces with long service life in China.

Recension of boron nitride phase diagram based on high-pressure and high-temperature experiments

Cubic boron nitride and hexagonal boron nitride are the two predominant crystalline structures of boron nitride.They can interconvert under varying pressure and temperature conditions.However,this transformation requires overcoming significant potential barriers in dynamics,which poses great difficulty in determining the c-BN/h-BN phase boundary.This study used high-pressure in situ differential thermal measurements to ascertain the temperature of h-BN/c-BN conversion within the commonly used pressure range(3-6 GPa)for the industrial synthesis of c-BN to constrain the P-T phase boundary of h-BN/c-BN in the pressure-temperature range as much as possible.Based on the analysis of the experimental data,it is determined that the relationship between pressure and temperature conforms to the following equation:P=a+1/bT.Here,P denotes the pressure(GPa)and T is the temperature(K).The coefficients are a=-3.8±0.8 GPa and b=229.8±17.1 GPa/K.These findings call into question existing high-pressure and high-temperature phase diagrams of boron nitride,which seem to overstate the phase boundary temperature between c-BN and h-BN.The BN phase diagram obtained from this study can provide critical temperature and pressure condition guidance for the industrial synthesis of c-BN,thus optimizing synthesis efficiency and product performance.

Tuning the crystallinity of titanium nitride on copper-embedded carbon nanofiber interlayers for accelerated electrochemical kinetics in lithium-sulfur batteries

The development of lithium-sulfur(Li-S)batteries is hindered by the disadvantages of shuttling of polysulfides and the sluggish redox kinetics of the conversion of sulfur species during discharge and charge.Herein,the crystallinities of a titanium nitride(TiN)film on copper-embedded carbon nanofibers(Cu-CNFs)are regulated and the nanofibers are used as interlayers to resolve the aforementioned crucial issues.A low-crystalline TiN-coated Cu-CNF(L-TiN-Cu-CNF)interlayer is compared with its highly crystalline counterpart(H-TiN-Cu-CNFs).It is demonstrated that the L-TiN coating not only strengthens the chemical adsorption toward polysulfides but also greatly accelerates the electrochemical conversion of polysulfides.Due to robust carbon frameworks and enhanced kinetics,impressive highrate performance at 2 C(913 mAh g^(-1)based on sulfur)as well as remarkable cyclic stability up to 300 cycles(626 mAh g^(-1))with capacity retention of 46.5%is realized for L-TiN-Cu-CNF interlayer-configured Li-S batteries.Even under high loading(3.8 mg cm^(-2))of sulfur and relatively lean electrolyte(10μL electrolyte per milligram sulfur)conditions,the Li-S battery equipped with L-TiN-Cu-CNF interlayers delivers a high capacity of 1144 mAh g^(-1)with cathodic capacity of 4.25 mAh cm^(-2)at 0.1 C,providing a potential pathway toward the design of multifunctional interlayers for highly efficient Li-S batteries.

3D-printable Boron Nitride/Polyacrylic Hydrogel Composites with High Thermal Conductivities

Polyacrylic acid(PAA)hydrogel composites with different hexagonal boron nitride(h-BN)fillers were synthesized and successfully 3D-printed while their thermal conductivity was systematically studied.With the content of h-BN increasing from 0.1 wt%to 0.3 wt%,the thermal conductivity of the 3D-printed composites has been improved.Moreover,through the shear force given by the 3D printer,a complete thermal conductivity path is obtained inside the hydrogel,which significantly improves the thermal conductivity of the h-BN hydrogel composites.The maximum thermal conductivity is 0.8808 W/(m·K),leading to a thermal conductive enhancement of 1000%,compared with the thermal conductivity of pure PAA hydrogels.This study shows that using h-BN fillers can effectively and significantly improve the thermal conductivity of hydrogelbased materials while its 3D-printable ability has been maintained.

Boron Nitride-Integrated Lithium Batteries:Exploring Innovations in Longevity and Performance

The current global warming,coupled with the growing demand for energy in our daily lives,necessitates the development of more efficient and reliable energy storage devices.Lithium batteries(LBs)are at the forefront of emerging power sources addressing these challenges.Recent studies have shown that integrating hexagonal boron nitride(h-BN)nanomaterials into LBs enhances the safety,longevity,and electrochemical performance of all LB components,including electrodes,electrolytes,and separators,thereby suggesting their potential value in advancing eco-friendly energy solutions.This review provides an overview of the most recent applications of h-BN nanomaterials in LBs.It begins with an informative introduction to h-BN nanomaterials and their relevant properties in the context of LB applications.Subsequently,it addresses the challenges posed by h-BN and discusses existing strategies to overcome these limitations,offering valuable insights into the potential of BN nanomaterials.The review then proceeds to outline the functions of h-BN in LB components,emphasizing the molecular-level mechanisms responsible for performance improvements.Finally,the review concludes by presenting the current challenges and prospects of integrating h-BN nanomaterials into battery research.

Nanoscale cathodoluminescence spectroscopy probing the nitride quantum wells in an electron microscope

To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and spectroscopy was used to measure the luminescence of In_(0.15)Ga_(0.85)N five-period multiquantum wells.The lattice-composition-energy relationship was established with the help of energy-dispersive x-ray spectroscopy,and the bandgaps of In_(0.15)Ga_(0.85)N and GaN in multiple quantum wells were extracted by electron energy loss spectroscopy to understand the features of cathodoluminescence spectra.The luminescence differences between different periods of multiquantum wells and the effects of defects such as composition fluctuation and dislocations on the luminescence of multiple quantum wells were revealed.Our study establishing the direct relationship between the atomic structure of In_(x)Ga_(1-x)N multiquantum wells and photoelectric properties provides useful information for nitride applications.

Effect of trace oxygen on plasma nitriding of titanium foil

Titanium nitride films are prepared by plasma enhanced chemical vapor deposition method on titanium foil using N_(2) as precursor. In order to evaluate the effect of oxygen on the growth of titanium nitride films, a small amount of O_(2) is introduced into the preparation process. The study indicates that trace O_(2) addition into the reaction chamber gives rise to significant changes on the color and micro-morphology of the foil, featuring dense and long nano-wires. The as-synthesized nanostructures are characterized by various methods and identified as TiN, Ti_(2) N, and TiO_(2) respectively. Moreover, the experiment results show that oxide nanowire has a high degree of crystallinity and the nitrides present specific orientation relationships with the titanium matrix.

Strong metal–support interaction boosts the electrocatalytic hydrogen evolution capability of Ru nanoparticles supported on titanium nitride

Ruthenium(Ru)has been regarded as one of the most promising alternatives to substitute Pt for catalyzing alkaline hydrogen evolution reaction(HER),owing to its inherent high activity and being the cheapest platinum-group metal.Herein,based on the idea of strong metal–support interaction(SMSI)regulation,Ru/TiN catalysts with different degrees of TiN overlayer over Ru nanoparticles were fabricated,which were applied to the alkaline electrolytic water.Characterizations reveal that the TiN overlayer would gradually encapsulate the Ru nanoparticles and induce more electron transfer from Ru nanoparticles to TiN support by the Ru–N–Ti bond as the SMSI degree increased.Further study shows that the exposed Ru–TiN interfaces greatly promote the H_(2) desorption capacity.Thus,the Ru/TiN-300 with a moderate SMSI degree exhibits excellent HER performance,with an overpotential of 38 mV at 10 mA cm^(−2).Also,due to the encapsulation role of TiN overlayer on Ru nanoparticles,it displays super long-term stability with a very slight potential change after 24 h.This study provides a deep insight into the influence of the SMSI effect between Ru and TiN on HER and offers a novel approach for preparing efficient and stable HER electrocatalysts through SMSI engineering.

Synthesis of boron nitride nanorod and its performance as a metalfree catalyst for oxidative desulfurization of diesel fuel

In order to reduce the sulfur compounds in diesel fuel,boron nitride(BN)has been used as a novel metal-free catalyst in the present research.This nanocatalyst was synthesized via template-free approach followed by heating treatment at 900℃ in nitrogen atmosphere that the characteristics of the sample were identified by the X-ray diffraction,Fourier-transform infrared spectroscopy,Raman spectroscopy,field emission scanning electron microscopy,transmission electron microscopy,atomic force microscopy,and N2 adsorption-desorption isotherms.The results of structural and morphological analysis represented that BN has been successfully synthesized.The efficacy of the main operating parameters on the process was studied by using response surface methodology based on the Box-Behnken design method.The prepared catalyst showed high efficiency in oxidative desulfurization of diesel fuel with initial sulfur content of 8040 mg·kg^(-1)S.From statistical analysis,a significant quadratic model was obtained to predict the sulfur removal as a function of efficient parameters.The maximum efficiency of 72.4%was achieved under optimized conditions at oxidant/sulfur molar ratio of 10.2,temperature of 71℃,reaction time of 113 min,and catalyst dosage of 0.36 g.Also,the reusability of the BN was studied,and the result showed little reduction in activity of the catalyst after 10 times regeneration.Moreover,a plausible mechanism was proposed for oxidation of sulfur compounds on the surface of the catalyst.The present study shows that BN materials can be selected as promising metal-free catalysts for desulfurization process.

Advances in Polymeric Carbon Nitride Photocatalysts for Enhanced CO_(2)Reduction

Photocatalysis has emerged as a promising alternative for converting and utilizing CO_(2).Polymeric carbon nitride(PCN),typically synthesized through the one-step thermal polycondensation of nitrogen-rich precursors,has shown considerable promise due to its adjustable band structure and inherent safety.Over the past five years,significant literature in this field has identified five primary methods for modifying PCN:morphology modulation,element doping,defect induction,co-catalyst loading,and heterojunction construction.A detailed discussion on how each modification method influences light absorption,charge separation,and surface reaction efficiencies in photocatalysis is provided.Based on these findings,several future directions for the development of PCN-based materials are proposed,such as designing tailored PCN structures for specific photocatalytic reactions and using theoretical calculations to verify and correct results from current characterization methods.Despite the challenges associated with the large-scale synthesis of PCN materials with controllable structures and satisfactory performance,this work offers valuable insights for advancing photocatalytic PCN-based systems for large-scale solar fuel production.

Coaxial Wet Spinning of Boron Nitride Nanosheet‑Based Composite Fibers with Enhanced Thermal Conductivity and Mechanical Strength

Hexagonal boron nitride nanosheets(BNNSs)exhibit remarkable thermal and dielectric properties.However,their self-assembly and alignment in macroscopic forms remain challenging due to the chemical inertness of boron nitride,thereby limiting their performance in applications such as thermal management.In this study,we present a coaxial wet spinning approach for the fabrication of BNNSs/polymer composite fibers with high nanosheet orientation.The composite fibers were prepared using a superacid-based solvent system and showed a layered structure comprising an aramid core and an aramid/BNNSs sheath.Notably,the coaxial fibers exhibited significantly higher BNNSs alignment compared to uniaxial aramid/BNNSs fibers,primarily due to the additional compressive forces exerted at the core-sheath interface during the hot drawing process.With a BNNSs loading of 60 wt%,the resulting coaxial fibers showed exceptional properties,including an ultrahigh Herman orientation parameter of 0.81,thermal conductivity of 17.2 W m^(-1)K^(-1),and tensile strength of 192.5 MPa.These results surpassed those of uniaxial fibers and previously reported BNNSs composite fibers,making them highly suitable for applications such as wearable thermal management textiles.Our findings present a promising strategy for fabricating high-performance composite fibers based on BNNSs.

Hollow Ni Mo-based nitride heterojunction with super-hydrophilic/aerophobic surface for efficient urea-assisted hydrogen production

Hydrogen evolution reaction(HER)and urea oxidation reaction(UOR)are key reactions of the watercycling associated catalytic process/device.The design of catalysts with a super-hydrophilic/aerophobic structure and optimized electron distribution holds great promise.Here,we have designed a threedimensional(3D)hollow Ni/NiMoN hierarchical structure with arrayed-sheet surface based on a onepot hydrothermal route for efficient urea-assisted HER based on a simple hydrothermal process.The Ni/NiMoN catalyst exhibits super-hydrophilic/aerophobic properties with a small droplet contact angle of 6.07°and an underwater bubble contact angle of 155.7°,thus facilitating an escape of bubbles from the electrodes.Density functional theory calculations and X-ray photoelectron spectroscopy results indicate the optimized electronic structure at the interface of Ni and NiMoN,which can promote the adsorption/desorption of reactants and intermediates.The virtues combining with a large specific surface area endow Ni/NiMoN with efficient catalytic activity of low potentials of 25 mV for HER and 1.33 V for UOR at10 mA cm^(-2).The coupled HER and UOR system demonstrates a low cell voltage of 1.42 V at 10 mA cm^(-2),which is approximately 209 mV lower than water electrolysis.

Hybrid 2D/3D Graphitic Carbon Nitride-Based High-Temperature Position-Sensitive Detector

Ultraviolet position-sensitive detectors(PSDs)are expected to undergo harsh environments,such as high temperatures,for a wide variety of applications in military,civilian,and aerospace.However,no report on relevant PSDs operating at high temperatures can be found up to now.Herein,we design a new 2D/3D graphitic carbon nitride(g-C_(3)N_(4))/gallium nitride(GaN)hybrid heterojunction to construct the ultraviolet high-temperature-resistant PSD.The g-C_(3)N_(4)/GaN PSD exhibits a high position sensitivity of 355 mV mm^(-1),a rise/fall response time of 1.7/2.3 ms,and a nonlinearity of 0.5%at room temperature.The ultralow formation energy of-0.917 eV atom^(-1)has been obtained via the thermodynamic phase stability calculations,which endows g-C_(3)N_(4)with robust stability against heat.By merits of the strong built-in electric field of the 2D/3D hybrid heterojunction and robust thermo-stability of g-C_(3)N_(4),the g-C_(3)N_(4)/GaN PSD delivers an excellent position sensitivity and angle detection nonlinearity of 315 mV mm^(-1)and 1.4%,respectively,with high repeatability at a high temperature up to 700 K,outperforming most of the other counterparts and even commercial silicon-based devices.This work unveils the high-temperature PSD,and pioneers a new path to constructing g-C_(3)N_(4)-based harsh-environment-tolerant optoelectronic devices.

Microwave-Assisted Confining Growth and Liquid Exfoliation of sp^(3)-Hybrid Carbon Nitride Nano/Micro-Crystals

As one promising carbon-based material,sp^(3)-hybrid carbon nitride has been predicted with various novel physicochemical properties.However,the synthesis of sp^(3)-hybrid carbon nitride is still limited by the nanaoscale,low crystallinity,complex source,and expensive instruments.Herein,we have presented a facile approach to the sp^(3)-hybrid carbon nitride nano/micro-crystals with microwave-assisted confining growth and liquid exfoliation.Actually,the carbon nitride nano/micro-crystals can spontaneously emerge and grow in the microwave-assisted polymerization of citric acid and urea,and the liquid exfoliation can break the bulk disorder polymer to retrieve the highly crystalline carbon nitride nano/micro-crystals.The obtained carbon nitride nano/micro-crystals present superior blue light absorption strength and surprising photoluminescence quantum yields of 57.96%in ethanol and 18.05%in solid state.The experimental characterizations and density functional theory calculations reveal that the interface-trapped localized exciton may contribute to the excellent intrinsic light emission capability of carbon nitride nano/micro-crystals and the interparticle staggered stacking will prevent the aggregation-caused-quenching partially.Finally,the carbon nitride nano/micro-crystals are demonstrated to be potentially useful as the phosphor medium in light-emitting-diode for interrupting blue light-induced eye damage.This work paves new light on the synthesis strategy of sp^(3)-hybrid carbon nitride materials and thus may push forward the development of multiple carbon nitride research.