Field-emission Microscopy Research Articles

Development of an Amorphous Nickel Boride/Manganese Molybdate Heterostructure as an Efficient Electrode Material for a High-Performance Asymmetric Supercapacitor.

The exploration of heterostructure materials with unique electronic properties is considered a desirable platform for fabricating electrode/surface interface relationships for constructing asymmetric supercapacitors (ASCs) with high energy density. In this work, a heterostructure based on amorphous nickel boride (NiXB) and crystalline square bar-like manganese molybdate (MnMoO4) was prepared by a simple synthesis strategy. The formation of the NiXB/MnMoO4 hybrid was confirmed by powder X-ray diffraction (p-XRD), field emission scanning electron microscopy (FE-SEM), field-emission transmission electron microscopy (FE-TEM), Brunauer-Emmett-Teller (BET), Raman, and X-ray photoelectron spectroscopy (XPS). In this hybrid system (NiXB/MnMoO4), the intact combination of NiXB and MnMoO4 leads to a large surface area with open porous channels and abundant crystalline/amorphous interfaces with a tunable electronic structure. This NiXB/MnMoO4 hybrid shows high specific capacitance (587.4 F g-1) at 1 A g-1, and it even retains a capacitance of 442.2 F g-1 at 10 A g-1, indicating superior electrochemical performance. The fabricated NiXB/MnMoO4 hybrid electrode also exhibited an excellent capacity retention of 124.4% (10000 cycles) and a Coulombic efficiency of 99.8% at a current density of 10 A g-1. In addition, the ASC device (NiXB/MnMoO4//activated carbon) achieved a specific capacitance of 104 F g-1 at 1 A g-1 and delivered a high energy density of 32.5 Wh.kg-1 with a power density of 750 W·kg-1. This exceptional electrochemical behavior is due to the ordered porous architecture and the strong synergistic effect of NiXB and MnMoO4, which enhances the accessibility and adsorption of OH- ions that improve electron transport. Moreover, the NiXB/MnMoO4//AC device exhibits excellent cyclic stability with a retention of 83.4% of the original capacitance after 10000 cycles, which is due to the heterojunction layer between NiXB and MnMoO4 that can improve the surface wettability without causing structural changes. Our results show that the metal boride/molybdate-based heterostructure is a new category of high-performance and promising material for the growth of advanced energy storage devices.

Emergence of chaos in a compartmentalized catalytic reaction nanosystem

In compartmentalized systems, chemical reactions may proceed in differing ways even in adjacent compartments. In compartmentalized nanosystems, the reaction behaviour may deviate from that observed on the macro- or mesoscale. In situ studies of processes in such nanosystems meet severe experimental challenges, often leaving the field to theoretical simulations. Here, a rhodium nanocrystal surface consisting of different nm-sized nanofacets is used as a model of a compartmentalized reaction nanosystem. Using field emission microscopy, different reaction modes are observed, including a transition to spatio-temporal chaos. The transitions between different modes are caused by variations of the hydrogen pressure modifying the strength of diffusive coupling between individual nanofacets. Microkinetic simulations, performed for a network of 52 coupled oscillators, reveal the origins of the different reaction modes. Since diffusive coupling is characteristic for many living and non-living compartmentalized systems, the current findings may be relevant for a wide class of reaction systems.

Analysis of the evolution law of oxide inclusions in U75V heavy rail steel during the LF–RH refining process

Abstract The number density, size and composition of inclusions in U75V heavy rail steel during ladle furnace (LF)–RH refining process were studied by an Aztec-Feature inclusion automatic software which equipped with a field emission microscope. The results showed that the MnO–SiO2–Al2O3-type inclusions were the main inclusions at LF start. The MnO–SiO2–Al2O3-type inclusions were transformed into the CaO–SiO2–Al2O3-type inclusions during the LF refining process because of the Ca and Al elements which were brought by ferroalloy. At the RH start stage, the main inclusions were CaO–SiO2–Al2O3-type inclusions with low melting temperature and CaO–MgO–Al2O3-type inclusions with high melting temperature in the sample. And, the CaO–MgO–Al2O3-type inclusions were obviously removed during RH vacuum treatment. The average compositions of CaO–SiO2–Al2O3-type inclusions had no obvious change from RH vacuum holding for 15 min, RH vacuum break to RH soft blowing.

Facile synthesis of pyrazolopyridine pharmaceuticals under mild conditions using an algin-functionalized silica-based magnetic nanocatalyst (Alg@SBA-15/Fe3O4).

Pyrazolopyridines are common scaffolds in various bioactive compounds, which have several therapeutic effects and unique pharmacological properties. In this study, we fabricated a novel environmentally friendly silica-based nanocomposite as a multifunctional catalytic system for the synthesis of pyrazolopyridine derivatives. This novel heterogeneous nanocomposite named Alg@SBA-15/Fe3O4 (Alg stands for alginic acid), was prepared in several steps. In this regard, SBA-15 was synthesized by the hydrothermal method. Next, it was magnetized by Fe3O4 nanoparticles via an in situ co-precipitation process. Then, SBA-15/Fe3O4 particles were functionalized with 3-minopropyltriethoxysilane (APTES). Afterward, Alg@SBA-15/Fe3O4 was obtained by a nucleophilic substitution reaction between SBA-15/Fe3O4-NH2 and an as-synthesized methyl-esterified alginic. Different analyses such as Fourier-transform infrared (FTIR), energy-dispersive X-ray (EDX) spectroscopy, field-emission scanning-electron microscopy (FESEM), vibrating-sample magnetometer (VSM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and BET (Brunauer-Emmett-Teller) have been used to confirm the structure of the fabricated catalyst. The magnetic properties of the Alg@SBA-15/Fe3O4 catalytic system imparted by Fe3O4 MNPs enable it to be conveniently isolated from the reaction mixture by using an external magnet. According to the obtained results, the prepared nanocatalyst has high thermal stability and it lost approximately 26% of its weight up to 800 °C. Interestingly, a small amount of prepared nanocatalyst (0.02 g) has shown excellent catalytic performance in the synthesis of pyrazolopyridine derivatives (90-97%) in a short reaction time (20-30 min) at room temperature which can be attributed to its porous structure and large surface area, and the presence of many acidic and basic functional groups. In general, it can be argued that the Alg@SBA-15/Fe3O4 nanocomposite deserves more attention due to its non-toxicity, ease of preparation, good recyclability, and its high catalytic efficiency.

Fungal Growth Physicochemical Properties Inhibition by Novel Zinc Oxide/ Glutinous Tapioca Starch Composite

Mango suffers from numerous diseases throughout its life due to fungal growth. Primarily, mango is infected with anthracnose, a disease caused by Collectotrichum gloeosporioides. In the present study, mango fruits were coated with zinc oxide (ZnO) and tapioca starch solution at different concentrations and stored at room temperature for a week. The growth of any black spots on the outer surface of the fruit peel was observed at two-day intervals. The mixed coating material, consisting of ZnO and tapioca starch, inhibited fungal growth. The field-emission scanning microscope (FESEM) results demonstrated that the nanoparticles were uniformly coated on the mango samples. Applying the ZnO coating also effectively maintained the quality attributes and extended the shelf life of the fruits. Consequently, the ZnO and starch coating could be an alternative safe coating technique of protecting mango fruits against anthracnose infection, hence prolonging the freshness and avoiding economic losses during transportation, marketing, and storage.

Synthesis of Bimetallic Ni-Co Phosphide Nanosheets for Electrochemical Non-Enzymatic H2O2 Sensing

NiCoP nanosheets (NSs) were successfully synthesized using the hydrothermal and high-temperature phosphorization process. The obtained NiCoP NSs were immobilized on a glassy carbon electrode (GCE) and used to construct a novel sensing platform for electrochemical non-enzymatic H2O2 sensing. Physicochemical characteristics of NiCoP NSs were obtained by field-emission scanning electron microscopy (FESEM), field-emission transmission electron microscope (FETEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In addition, the electrochemical properties of NiCoP NSs were obtained by cyclic voltammetry (CV) and chronoamperometry (CA) towards the non-enzymatic detection of H2O2. FESEM and FETEM images provided a morphological insight (the unique nanosheets morphology of NiCoP) that could expose more active sites to promote mass/charge transport at the electrode/electrolyte interface. XRD and XPS results also confirmed the crystalline nature of the NiCoP nanosheets and the coexistence of multiple transitional metal oxidation states in NiCoP nanosheets. These unique physicochemical characteristics had a degree of contribution to ensuring enhancement in the electrochemical behavior. As a result, the synthesized NiCoP NSs composed of intercalated nanosheets, as well as the synergistic interaction between bimetallic Ni/Co and P atoms exhibited excellent electrocatalytical activity towards H2O2 electroreduction at neutral medium. As the results showed, the electrochemical sensing based on NiCoP NSs displayed a linear range of 0.05~4 mM, a sensitivity of 225.7 μA mM-1 cm-2, a limit of detection (LOD) of 1.190 μM, and good selectivity. It was concluded that NiCoP NSs-based electrochemical sensing might open new opportunities for future construction of H2O2 sensing platforms.

One step synthesis of NiCo-LDH/CoNi2S4/rGO composite on Ni foam for asymmetric supercapacitor

The growth of NiCo-LDH/CoNi2S4/rGO composite on Ni foam was achieved with a simple one-step hydrothermal method. The obtained binder-free electrode (NiCo-LDH/CoNi2S4/rGO/Ni foam) was characterized with X-ray diffraction (XRD), field emission microscopy (FE-SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and galvanostastic charge/discharge (GCD). NiCo-LDH/CoNi2S4/rGO/Ni foam demonstrates a unique morphology with nanoparticles and nanowires mingled together, which endows the electrode large surface area as verified by the Brunauer–Emmett–Teller gas sorptometry measurement (BET). NiCo-LDH/CoNi2S4/rGO/Ni foam possesses excellent charge storage capabilities such as high areal capacitance, long cycling life and good rate performance. The asymmetric supercapacitor (ASC) with NiCo-LDH/CoNi2S4/rGO/Ni foam and activated carbon (AC) as positive and negative electrodes was assembled, characterized and successfully applied in practical applications, further confirming the great prospect of NiCo-LDH/CoNi2S4/rGO/Ni foam in energy storage.

Beam Trajectory Analysis of Vertically Aligned Carbon Nanotube Emitters with a Microchannel Plate

Vertically aligned carbon nanotubes (CNTs) are essential to studying high current density, low dispersion, and high brightness. Vertically aligned 14 × 14 CNT emitters are fabricated as an island by sputter coating, photolithography, and the plasma-enhanced chemical vapor deposition process. Scanning electron microscopy is used to analyze the morphology structures with an average height of 40 µm. The field emission microscopy image is captured on the microchannel plate (MCP). The role of the microchannel plate is to determine how the high-density electron beam spot is measured under the variation of voltage and exposure time. The MCP enhances the field emission current near the threshold voltage and protects the CNT from irreversible damage during the vacuum arc. The high-density electron beam spot is measured with an FWHM of 2.71 mm under the variation of the applied voltage and the exposure time, respectively, which corresponds to the real beam spot. This configuration produces the beam trajectory with low dispersion under the proper field emission, which could be applicable to high-resolution multi-beam electron microscopy and high-resolution X-ray imaging technology.

Self-Assembly 2D Ti3C2/g-C3N4 MXene Heterojunction for Highly Efficient Photocatalytic Degradation of Tetracycline in Visible Wavelength Range.

An ultrathin 2D Ti3C2/g-C3N4 MXene (2D-TC/CN) heterojunction was synthesized, using a facile self-assembly method; the perfect microscopic-morphology and the lattice structure presented in the sample with a 2 wt% content of Ti3C2 were observed by the field-emission scanning electron microscopy (SEM) and transmission electron microscope (TEM). The optimized sample (2-TC/CN) exhibited excellent performance in degrading the tetracycline (TC), and the degradation rate reached 93.93% in the conditions of 20 mg/L, 50 mL of tetracycline within 60 min. Except for the increased specific-surface area, investigated by UV-vis diffuse reflectance spectra (UV-vis DRS) and X-ray photoelectron microscopy (XPS) valence spectra, the significantly enhanced photocatalytic activity of the 2-TC/CN could also be ascribed to the formation of Ti-N bonds between Ti3C2 and g-C3N4 nanosheets, which reduced the width of the band gap through adjusting the position of the valence band, thus resulting in the broadened light-absorption. Furthermore, the facilitated electron transmission was also proved by time-resolved photoluminescence (TRPL) and electrochemical impedance spectroscopy (EIS), which is effective in improving the quantum efficiency of photo-generated electrons. In addition, the resulting radical-capture experiment suggested that superoxide radicals have the greatest influence on photodegradation performance, with the photodegradation rate of TC reducing from 93.16% to 32.08% after the capture of superoxide radicals, which can be attributed to the production of superoxide radicals only, by the 2-TC/CN composites with a high conduction-band value (-0.62 eV). These facilely designed 2D Ti3C2/g-C3N4 composites possess great application potential for the photodegradation of tetracycline and other antibiotics.

Impact of Graphene Nanofluid on Ionic Polarization in Reservoir Sandstone under Electric Double Layer

The improved oil recovery (IOR) is a way of enhancing the reservoir properties with the use of nanomaterials to detach the oil molecule from the trapped zone. The polarization effect on reservoir sandstone under an electric double layer is one of the major research interests. The nanoparticles agglomeration such as graphene nanofluid due to poor dispersion in reservoir zone can be a major challenge that can lead to low reservoir permeability are well elucidated. This study investigated the influence of graphene nanofluid on the ionic polarization under an electric double layer in reservoir sandstone. Saturated Berea sandstone was used to investigate the interaction of ionic species on reservoir sandstone with the aid of Field-emission microscopy (FESEM), Energy dispersive X-ray mapping (EDX), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectral analysis, and Core flooding experiment. This research gives information on the adsorption of ions within an electric double layer and its polarization mechanisms. It was revealed from the experimental result that ionic polarization occurs at 9.97 GHz with a 5.8nm wavelength shift which improves the mobility of the reservoir and in turn increases oil recovery factors. Graphene nanoparticles show a positive effect on both reservoir oil viscosity and stabilization characteristics of drilling fluids, wettability alteration, interfacial tension, and improving the emulsion Keywords: Nanomaterials, Sandstone, Electric double layer, Graphene

Mechanical compaction mechanisms in the input sediments of the Sumatra subduction complex – insights from microstructural analysis of cores from IODP Expedition 362

Abstract. The input sediments of the North Sumatra subduction zone margin, drilled during IODP Expedition 362, exhibit remarkable uniformity in composition and grain size over the entire thickness of the rapidly deposited Nicobar Fan succession (seafloor to 1500 m b.s.f.), providing a unique opportunity to study the micromechanisms of compaction. Samples were prepared from dried core samples (from Sites U1480 and U1481) by both Ar-ion cross-section polishing and broad ion beam cutting and imaged with a field-emission scanning electron microscope (SEM). The shallowest samples (seafloor to 28 m b.s.f.) display a sharp reduction in porosity from 80 % to 52 % due to collapse of large clay-domain surrounding matrix pores associated with rotation and realignment of clay platelets parallel to the bedding plane. The deeper succession (28 to 1500 m b.s.f.) exhibits less rapid reduction in porosity from 52 % to 30 % by the progressive collapse of silt-adjacent larger pores through bending as well as subsequent sliding and/or fracturing of clay particles. In addition, there is a correlated loss of porosity in the pores too small to be resolved by SEM. Clastic particles show no evidence of deformation or fracturing with increasing compaction. In the phyllosilicates, there is no evidence for pressure solution or recrystallization: thus, compaction proceeds by micromechanical processes. An increase in effective stress up to 18 MPa (∼ 1500 m b.s.f.) causes the development of a weakly aligned phyllosilicate fabric mainly defined by illite clay particles and mica grains, while the roundness of inter-particle pores decreases as the pores become more elongated. We propose that bending of the phyllosilicates by inter-particle slip may be the rate-controlling mechanism. Pore size distributions show that all pores within the compactional force chain deform, irrespective of size, with increasing compactional strain. This arises because the force chain driving pore collapse is localized primarily within the volumetrically dominant and weaker clay-rich domains; pores associated with packing around isolated silt particles enter into the force chain asynchronously and do not contribute preferentially to pore loss over the depth range studied.

High luminescent properties of Eu3+-doped CdSSe quantum dots within silicate glass for WLED

We have reported that a series concentration of Eu3+ doped CdSSe quantum dots (QDs) within silicate glass has good luminescent properties synthesized via conventional melt-quenching method. The crystal structure and photoluminescence (PL) properties were studied by a field-emission transmission electron microscope (TEM) and fluorescence spectrophotometer, respectively. The results of tests indicated that CdSSe QDs was formed within silicate glass and Eu3+ ions have been successfully doped into CdSSe crystals. Compared with the un-doped CdSSe QDs, the optical properties of Eu3+ doped CdSSe QDs enhanced effectively. After mounted with 395 nm light-emitting diodes (LEDs), the color temperature and color coordinates could be adjusted by turning content of Eu3+ ions. The energy transfer from CdSSe QDs to Eu3+ ions was confirmed by decay life. The main energy transfer mechanism is quadrupole-quadrupole interaction.

Solvent-Free Production by Extrusion of Bio-Based Poly(glycerol-co-diacids) Sheets for the Development of Biocompatible and Electroconductive Elastomer Composites.

Faced with growing global demand for new potent, bio-based, biocompatible elastomers, the present study reports the solvent-free production of 13 pure and derived poly(glycerol-co-diacid) composite sheets exclusively using itaconic acid, sebacic acid, and 2,5-furandicarboxylic acid (FDCA) with glycerol. Herein, modified melt polycondensation and Co(II)-catalyzed polytransesterification were employed to produce all exploitable prepolymers, enabling the easy and rapid manufacturing of elastomer sheets by extrusion. Most of our samples were loaded with 4 wt% of various additives such as natural polysaccharides, synthetic polymers, and/or 25 wt% sodium chloride as porogen agents. The removal of unreacted monomers and acidic short oligomers was carried out by means of washing with NaHCO3 aqueous solution, and pH monitoring was conducted until efficient sheet surface neutralization. For each sheet, their surface morphologies were observed by Field-emission microscopy, and DSC was used to confirm their amorphous nature and the impact of the introduction of every additive. The chemical constitution of the materials was monitored by FTIR. Then, cytotoxicity tests were performed for six of our most promising candidates. Finally, we achieved the production of two different types of extrusion-made PGS elastomers loaded with 10 wt% PANI particulates and 4 wt% microcrystalline cellulose for adding potential electroconductivity and stability to the material, respectively. In a preliminary experiment, we showed the effectiveness of these materials as performant, time-dependent electric pH sensors when immersed in a persistent HCl atmosphere.

Visible light responsive Cu-N/TiO2 nanoparticles for the photocatalytic degradation of bisphenol A.

Visible light active co-doped Cu-N/TiO2 photocatalyst was synthesized by the sol-gel method. The synthesized catalysts were characterized by X-ray diffraction (XRD), field-emission transmission electron microscope (FE-TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and UV-visible diffuse reflectance spectrophotometry (UV-vis DRS). The co-doping with Cu-N reduced the bandgap (∼2.83 eV) and extended the optical absorption range of TiO2 catalysts to the visible region. The incorporation of Cu and N on TiO2 lattice results in sub-conduction and valence band formation, which enhanced the photoactivity and electron-hole generation rate. The visible light activity of Cu-N/TiO2 was evaluated via photocatalytic degradation of bisphenol A (BPA) under blue LED illumination. The maximum BPA degradation of 42.7% was observed at 0.5 g L-1 catalyst dosage, initial pH of BPA solution = 8.2, and initial BPA concentration of 10 ppm. Further, a possible mechanism of photocatalytic degradation of BPA was also established.

Characterization of nanofiber composite membrane for high water flux and antibacterial properties

Nanostructured membranes are introduced as a new technology for water purification and treatment. In this work, a facile and simple route of alkaline treatment of polymeric and nanocomposite fiber membranes was developed using electrospinning technique. A blended polysulfone (PSF) and cellulose acetate (CA) polymers incorporated with (0.2 wt%, ZnO NPs), followed by immersion in 0.1 M NaOH solution was performed to enhance membrane surface properties. The membranes were characterized using field emission microscopy (FESEM), transmission electron microscopy (TEM), Fourier Transform Infrared (FTIR), mechanical strength, water contact angle (WCA), permeate flux, thermogravimetric analysis (TGA), and antimicrobial test. Interestingly, the proposed filtration membrane materials exhibited superhydrophilic property i.e. (WCA = 13° ± 3°) corresponding to (PSF/CA/ZnO NPs) membrane with highest water flux of 0.46 m3 m−2 h−1. Additionally, mechanical properties of the developed membranes showed that addition of ZnO NPs resulted in tensile strength of 0.29 MPa without treatment and 0.13 MPa after membrane treatment which is higher than that of pristine membrane tensile strength (0.11 MPa). The composite nanofibrous membrane displayed a strong antibacterial activity against E. coli, with a bacterial growth inhibition zone diameter of 10 ± 0.6 mm. The overall membrane river Nile water filtration resulted in slight decreasing water total dissolved ions (TDS), lower turbidity, and high-water flux. This facile membrane development route could facilitate not only the sustainable development of membrane technology but also achieve sustainable development goals (SDGs) for clean water and sanitation for drinking water purification and wastewater treatment.

Scanning anode field emission microscopy of a single Si emitter

Emitter tip radius nonuniformity results in exponential variations in emission current and a relatively low array utilization. Here, we provide a method of mapping the current and field-factor from a single emitter over a small area using a scanning anode field emission microscope. A dull W probe is used as the anode, and an array of emitters is fabricated on silicon (Si) wafers. We use a relatively wide spaced (100 μm pitch) emitter array with each emitter having an integrated Si pillar. Current-voltage characteristics are used to extract the field-factor and to experimentally demonstrate the mapping of the currents and field-factor of a single emitter. From emission spot sizes, the emission half-angles are measured to be <14° at anode voltages 2.5 kV and a minimum resolvable feature of 2–3 μm at 1.8 kV. We also determine the field-factor dependence with the distance between the anode and the emitter, where limiting the current becomes essential to prevent early burn-out of the emitter that could reduce the current. We also simulated the maximum currents tolerated by the pillar to assess the thermal effects on the emitter. Finite element modeling confirms the experimental trend in the field-factor with the distance between the anode and the emitter tip, resulting in a value of approximately 105 cm−1 for an emitter tip radius of 5 nm and an emitter-anode distance of 50 μm.

Electronic Processes at the Carbon-Covered (100) Collector Tungsten Surface.

We have performed density functional VASP calculations of a pure and of a carbon-covered (100) tungsten surface under the presence of an electric field E directed away from the surface. Our aim is to answer the question of an increased penetrability of electrons at the collector side of a nanometric tunnel diode when covered by carbon atoms, a purely quantum mechanical effect related to the value of the workfunction Φ. To obtain Φ at a non-zero electric field we have extrapolated back to the electrical surface the straight line representing the linear increase in the potential energy with distance outside the metal-vacuum interface. We have found that under the presence of E the workfunction Φ = Evac − EF of the (100) pure tungsten surface has a minor dependence on E. However, the carbon-covered tungsten (100) surface workfunction Φ(C − W) has a stronger E dependence. Φ(C − W) decreases continuously with the electric field. This decrease is ΔΦ = 0.08 eV when E = 1 V/nm. This ΔΦ is explained by our calculated changes with electric field of the electronic density of both pure and carbon-covered tungsten. The observed phenomena may be relevant to other surfaces of carbon-covered tungsten and may explain the reported collector dependence of current in Scanning Field Emission Microscopy.

Controlled Growth Interface of Charge Transfer Salts of Nickel-7,7,8,8-Tetracyanoquinodimethane on Surface of Graphdiyne

Controlled Growth Interface of Charge Transfer Salts of Nickel-7,7,8,8-Tetracyanoquinodimethane on Surface of Graphdiyne

Synthesis of nano‐coral tungsten carbide/carbon fibers as efficient catalysts for hydrogen evolution reaction

Tungsten-carbides (WxC) are cermet materials that exhibit different unique characteristics, such as supper strength, good thermal conductivity, and electrical conductivity as well as good catalytic activity. In this study, we report a facile and scalable process using the electrospinning technique to grow a unique structure which is nano-coral tungsten carbine (W2C) on carbon fibers. The crystallinity, structure, morphology, and chemical bonding of W2C are characterized by using different techniques, including X-ray diffraction (XRD), Raman spectra, field-emission scanning microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results confirm that the nano-coral structure of W2C is successfully prepared. Specifically, the diameter and length of nano-coral W2C are about 70 ~ 100 nm and 1 ~ 2 μm, respectively. Nano-coral W2C could be employed for electrocatalytic application including hydrogen evolution reaction (HER). Notably, nano-coral W2C shows the efficiency of electrocatalytic activity toward HER, with low Tafel slope of 79 mV.dec−1, high double-layer capacitance of 3.2 mF.cm−2, and exceptional stability under working conditions for 1000 cycles test. Therefore, this study presents an approach for the preparation of nano-coral W2C and demonstrates their potential as scalable and stable catalysts for the HER.

The effect of work function during electron spectroscopy measurements in Scanning Field-Emission Microscopy

Electron spectroscopy proves to be a handy tool in material science. Combination of electron spectroscopy and scanning probe microscopy is possible through Scanning Field Emission Microscopy (SFEM), where a metallic probe positioned close to the surface is used as an electron source. However, using this not too much technologically demanding technique, it looks like the compromise between the lateral resolution and spectroscopic clarity must be considered. Here, we demonstrate, using experimental and simulation data, that the spectroscopic information can be understood without the need to grossly deteriorate the potential spatial resolution of the microscope. We prepared a three-section sample with clean W(110), sub-monolayer Cs on W(110) and monolayer of Cs on W(110) on which electron energy loss spectra are obtained via Scanning Probe Energy Loss Spectroscopy (SPELS) measurements. To explain the detected spectra a new model describing SPELS measurements in a SFEM is developed which aids to uncover the origin of spectral features typically detected during experiments. Experimental and simulation data are in a mutual agreement and observed spectral features on different surfaces could be explained. This novel understanding of SPELS can solve the main issue previously related to this technique, and good spatial resolution can be accompanied by the understanding of the measured spectra.