Scanning Transmission Electron Microscopy Energy Dispersive Spectroscopy Research Articles

Water-dispersible colloids facilitate the release of potentially toxic elements from contaminated soil under simulated long-term acid rain

The release behaviors of potentially toxic elements (PTEs) associated with water-dispersible colloids (WDCs) in contaminated soils are of considerable public concern. However, little information is available on the size distribution and elemental composition of WDCs and their effects on the release of PTEs in contaminated soils under long-term acid rain. Here, a quantitative accelerated aging leaching test was conducted to evaluate the long-term release risks of PTEs from four contaminated agricultural soil types exposed to acid rain. Asymmetric flow field-flow fractionation (AF4), scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) and ultrafiltration were used to clarify the size distribution and elemental composition of WDCs containing PTEs. Solution dynamics of successive leaching indicate high release potential for As, Cd, and Pb depending on soil properties under long-term (∼65 years) acid rain. Both ultrafiltration and AF4 analysis show that As in leachate was mainly in the “truly dissolved” fraction, while Pb, Cu, Cd and Fe were predominantly in the colloidal fraction and their percentages increased with increasing extraction time by acid rain. AF4-UV-ICP-MS and STEM-EDS reveal that nanoparticles at 1–7 nm most likely composed of organic matter (OM)-Fe/Al(/Si) oxides composite were the main carriers of Pb, Cu, As and Cd. Lead was also verified in Fe-oxide colloids at 34–450 nm in the first extracts but disappeared in the tenth extracts. This indicates that WDC-bearing PTEs become smaller as leaching proceeds. The study indicates the quantitative description and size-resolved understanding of WDC- and nanoparticle-bound PTEs in leachates of contaminated soils subjected to long-term acid rain.

Deformation twinning in Ti48.9Zr32.0Nb12.6Ta6.5 medium entropy alloy

Abstract The {112} β deformation twinning has never been confirmed in refractory high or medium entropy alloys (HEAs or MEAs) at room temperature. Here a Ti48.9Zr32.0Nb12.6Ta6.5 MEA shows {112} β twins was designed based on the d-electron alloy design method learned from β Ti alloys. The solution-treated (ST) samples show equiaxed grains, single β phase, homogenous chemical composition and good tensile properties. Transmission electron microscopy (TEM) investigation shows that the ST samples is free of athermal ω phase. Following TEM results revealed abundant dislocations and their structures such as jogs, loops, cross-slips and slip bands in the deformed samples. The {112} β twins were observed in the fractured samples, with interfacial ω phase on the twin boundary. Elemental segregation has not been detected in the twinned region by scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) mapping. The interaction between dislocations and twins was revealed by low-angle annular dark field (LAADF), thus twins in addition to the dislocation jogs, loops, cross-slips and slip bands, contribute to the work hardening in the present MEA. Deformation twinning in HEAs and MEAs has been discussed and twins can be expected in these alloys when the effects of their constituent elements were carefully considered. In particular, the present strategy of starting from β Ti alloys can be applied to design refractory HEAs and MEAs with desirable deformation microstructures.

Failure Analysis and Defects Characterization of Polymer Electrolyte Membrane Fuel Cells after Relative Humidity Cycling

Water content in the proton exchange membrane fuel cell (PEMFC) changes due to the spatiotemporal interplay of temperature, humidity, and electrochemical reactions. The humidity fluctuations result in membrane swelling and shrinking, and consequently, in-plane tensile stress development that causes mechanical failures [1,2]. In this study, commercial catalyst coated membranes (CCMs) were tested, under a relative humidity (RH) cycling accelerated stress test (AST), between oversaturated and fully-dry states. After the failure of the membrane, a conventional bubble jig test was performed on the membrane electrode assemblies (MEAs) to identify the defective regions. For further understanding of the morphology around the defects and the associated failure mechanism, the identified failure regions were examined using scanning electron microscopy (SEM) cross-section imaging and X-ray computed tomography (XCT) to be referenced with the beginning of life (BOL) sample [3]. The failed regions showed a wide range of defects, from small pinholes to fully-ruptured CCMs, in various forms and patches. There was good conformity between the size of the bubble obtained from the bubble jig test and the morphology of the defects in the images. Further, possible microstructural changes, i.e. porosity and ionomer distribution of the RH cycled catalyst layers were evaluated for the first time by scanning-transmission electron microscopy- energy dispersive spectroscopy (STEM-EDS) analysis along with an in-house developed quantitative method [3,4]. The STEM-EDS mapping revealed a changed ionomer distribution as well as a decrease in the catalyst layer porosity with respect to the BOL sample. The novel analysis approach revealed additional mechanisms of MEA degradation in the RH cycled MEAs, beside the membrane failure modes. To further explain the failure mechanisms, the nuclear magnetic resonance (NMR) was used to investigate the perfluorosulfonic acid (PFSA) chain and structure changes due to the RH cycling and differentiate any mechanical defect from chemical alteration of the chains in the membrane [5]. The NMR spectrum showed irregular broadening of the 19F peaks, which can be correlated to the mechanical changes in the fluorine chains of the membrane. Complementary characterization techniques such as Fourier transform infra-red spectroscopy (FTIR) and Raman spectroscopy analyses results will be shown for the catalyst layer to further explain the failure modes. Consequently, a comprehensive characterization methodology was developed for better understanding of the failure mode from the RH cycling AST.Keywords: RH cycling, Failure Analysis, Polymer Electrolyte Membrane, Fuel Cell Durability.

Failure Analysis and Defects Characterization of Polymer Electrolyte Membrane Fuel Cells after Relative Humidity Cycling

Commercial catalyst coated membrane (CCM) was tested under a relative humidity (RH) cycling accelerated stress test (AST). The morphology around the failed regions, identified by the bubble jig test, were examined by scanning electron microscopy (SEM), scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS), and X-ray computed tomography (XCT) and compared with beginning of life (BOL) sample. The SEM images showed the defects in forms of catalyst layer (CL) and membrane cracks, delamination, and bulging along with CL thickness alterations. The XCT scans confirmed the presence of circular and volcano-shape defects protruded throughout the CCM, as well as MPL irregularities. Defects were correlated to the morphology of the microporous layer (MPL), suggesting that MPL structure may affect the degradation of CCMs. The STEM-EDS microstructural evaluations and analysis revealed changes in the CL porosity with respect to the BOL, confirming the thickness changes and defect formation observed in SEM and XCT.

Controllable Vacancy Redistributions in Embedded Thin Films Under Concentrated Electric Fields

The redistribution and accumulation of oxygen vacancies under electric field underpins both the functionality and degradation of electrical and electrochemical devices comprising oxide layers. Interfacial accumulations of oxygen vacancies form defect dipoles, significantly reduce the breakdown strength, increase the breakdown path area, yet facilitates charge transfer reactions. Confinement of both oxygen vacancy redistributions and their mobility remains critical to preserving function in oxide systems.Here we study one of the most important, yet random transport processes: the redistribution of oxygen vacancies in binary oxides under high local electric fields. The ability to identify or predefine the shape, size, and location of vacancy distributions is critical to controlling interfacial properties of functional oxides. We achieved superior uniformity in HfO2 films by embedding highly-ordered metal nanoisland (NI) arrays to act as electric field concentrators. Embedded films exhibit significant reduction in operating voltages while displaying enhanced uniformity of resistance states. This behavior is attributed to the concentration of electric fields along Pt and Ti NIs and their interactions with the surrounding oxide film matrix environment, which induce separate and distinct filamentary formation mechanisms that affect the stability. A comparison of the density and distribution of the oxygen vacancies responsible driving filament dynamics is made via combined electrostatic force microscopy (EFM) and conductive atomic force microscopy (c-AFM) studies. Finally, the morphological evolution of conducting vacancy filaments is enabled by three-dimensional (3-D) c-AFM nanotomography and cross-sectional scanning transmission electron microscopy – energy dispersive spectroscopy (STEM-EDS) to provide direct correlations of nanoisland-oxide interactions with overall switching performance. The application of these exciting results to other vacancy-mediated electronic and electrochemical processes will also be discussed.

Legacy of multiple heavy metal(loid)s contamination and ecological risks in farmland soils from a historical artisanal zinc smelting area

Farmland soil contamination of heavy metal(loid)s (HM) derived from smelting activities is a global concern, owing to its potential threat for human health through food chain. This study aims to evaluate total contents and bioavailability of HMs (Pb, Zn, Tl, Cd, Cu, As, Ag, Co, Cr and Ni) in farmland soils distributed over ten different villages from a former artisanal zinc smelting area in the northwest Guizhou province, China. The results showed that most of the studied soils still exhibited exceptionally high enrichment of Pb, Zn, Cd and As. High levels of bioavailable HMs were also observed in some samples, which may enter the human food chain through agricultural activities. Further analyses by Scanning Transmission Electron Microscopy - Energy Dispersive Spectroscopy (STEM-EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) showed the presence of Zn smelting by-products such as Fe oxides, ZnO and PbSO4 even in nanoscale particles retained by the soils. Elemental mapping by EDS confirmed a close association of the studied HMs with the smelting waste particles. All these results signify that high levels of HM-contamination from historical artisanal zinc smelting activities still persist and threaten the health of local residents, despite the fact that the major industrial-derived-contamination period ended >15 years ago. Our findings highlight pivotal concerns in similar artisanal-smelting-affected farmland soils of suspected contamination, due to less-expected toxic elements such as Tl, which may cause high ecological health risks.

The formation kinetics of Cr2O3dispersed Cu synthesized by Cryo-milling

AbstractNano-crystalline (nc) Cu with Cr2O3dispersoid (~4 vol.%) was successfully made by reactive-milling at 210 K with a mixture of pure Cu, Cu2O, and Cr powder. The vacuum hot pressing (HP) was performed at 1123 K and 50 MPa for 2h to consolidate the milled powder for further analysis. TEM (Transmission Electron Microscopy) work revealed that the HPed materials were comprised with a mixture of the nc-Cu and a homogeneous distribution of Cr2O3dispersoids. The microstructure and Vickers hardness of the as-milled powder and the HPed materials were characterized by standard metallographic techniques. The grain size of the Cu was measured using Scherrer’s formula (XRD) and TEM observation; the Cr2O3dispersoid size was estimated from the HADDF (High Angle Annular Dark Field) images and element mapping by STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy) works. The formation kinetics and coarsening of the Cr2O3dispersoids in Cu matrix were discussed based on the calculations with thermodynamic parameters in comparison with those of Al2O3.

Microwave-Assisted synthesis of Anisotropic copper–silver nanoparticles

This paper focuses on the synthesis of shaped copper-silver nanoparticles (CuAg NPs) via microwave irradiation (MW). CuAg NPs were formed by reacting aqueous copper(II) nitrate hemi(pentahydrate) (Cu(NO3)2.2.5H2O), silver nitrate (AgNO3) and sodium acrylate (C3H3NaO2) at room temperature (RT) and hydrothermal temperature (HT). Shape formation was influenced by the HT and the sequence of reducing the precursors. By reducing Cu(NO3)2.2.5H2O and AgNO3 with C3H3NaO2 at different temperatures and manipulating the reduction sequence, variable sizes and shapes of CuAg core-shell NPs were formed. When Ag+ ions were reduced on preformed Cu NPs at RT, spherical NPs that featured (111) faucets were produced. The MW synthesis produced octahedra and rods NPs depending on whether Cu2+ and Ag+ ions were co-reduced or Ag+ ions were reduced on preformed Cu NPs. The morphology was examined by high transmission electron microscopy (HRTEM). The NP compositions were examined via scanning transmission electron microscopy - energy dispersive spectroscopy (STEM-EDS) and X-ray photoelectron spectroscopy (XPS).

Decarboxylation of stearic acid over Ni/MOR catalysts

AbstractBACKGROUNDOils derived from plants, animal fats, and algae contain both saturated and unsaturated fatty acids. These fatty acids can be converted into liquid fuels and chemicals in the presence of active solid catalysts.RESULTSNickel‐based catalysts were supported on mordenite via ion exchange synthesis and evaluated for the deoxygenation of stearic acid to diesel fuels. By tuning the synthesis pH, loadings of over 20 wt% Ni were obtained. Catalysts synthesized at pH 8.5 displayed the highest Ni loading and the highest activity for the decarboxylation/decarbonylation of stearic acid under inert nitrogen gas atmospheres, yielding 47% heptadecane. Characterization included scanning transmission electron microscopy‐energy‐dispersive spectroscopy (STEM‐EDS), X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), inductively coupled plasma atomic emission spectroscopy (ICP‐AES), N2 physisorption and thermogravimetric analysis (TGA), providing new insights into the recyclability of the catalyst. The observed loss of catalytic activity upon recycling was attributed to the agglomeration of Ni nanoparticles and the accumulation of carbonaceous coke.CONCLUSIONThis work demonstrates that Ni‐based catalysts supported on mordenite zeolite can effectively convert stearic acid into heptadecane. Yields to heptadecane were as high as 47%. Mechanistically, the reaction proceeds by decarboxylation and decarbonylation pathways. © 2019 Society of Chemical Industry

Kinetics of interfacial microstructural variation across insulator-thermoelectric semiconductor interface and its effects on thermoelectric properties of magnesium silicide thin films

Thermoelectric semiconductor magnesium silicide epitaxial films were fabricated on insulating (001) alumina (Al2O3) and (111) magnesium oxide (MgO) substrates using low temperature (220 °C) RF magnetic sputtering followed by high temperature (500 °C) annealing. Cross sectional studies of interfaces by bright field transmission electron microscopy reveals the formation of an interfacial region over a length scale of ∼30 to 120 nm for films deposited on MgO substrate and magnesia buffered Al2O3 substrates. A more detailed analysis using scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) studies clearly showed that Mg2Si film grown on magnesia buffer and MgO substrate indicate the formation of O and Si rich interfacial layer over a range of length scales (30–120 nm), while there is no such formation for the film deposited on Al2O3 substrate. The electrical conductivity of the film deposited on alumina substrate shows ∼60% higher value than the film on magnesia substrate. Further, the Seebeck coefficient measurement showed almost similar magnitude, at the same time of opposite polarity between film on alumina substrate (positive) and the film on magnesia substrate (negative). Changes in the carrier concentration arising due to the formation of an interfacial layer can be primary influence for the observed anomaly between two films. The theoretical modeling based on standard space charge kinetics across the multi-layer structures comprising alumina substrate-magnesia buffer-Mg2Si thin film, clearly indicates the possibility of oxygen migration from magnesia buffer layer when annealing temperature is increased above ∼750 °C.

Modulating Ferroelectric Response in Colloidal Semiconductor Nanocrystals through Cation Exchange

We report the appearance of ferroelectric behavior in CdSSe nanocrystals arising from a room-temperature cation exchange of semiconductor nanoparticles. Cation exchange reactions were performed on colloidal CdSSe nanocrystals using antimony, tin, and gold salts. The degree of exchange was determined using scanning transmission electron microscopy–energy-dispersive spectroscopy and the ferroelectric response was measured using a Sawyer-Tower circuit. As the percent exchange of tin(IV) was varied, the ferroelectric properties were optimized at ∼30 and 70% as a result of intracrystal atomic displacements. The amount of disorder can be minimized by selecting the exchange cation that exhibits the largest change in saturation polarization with the least amount of exchange. The ability to tune the structure and ferroelectric response of nanostructures could offer new routes toward the development of ferroelectric random-access memory devices as well as lower the cost of energy-harvesting applications.

A Characterization Study of Reactive Sites in ALD-Synthesized WOx/ZrO2 Catalysts

A series of ZrO2-supported WOx catalysts were prepared using atomic layer deposition (ALD) with W(CO)6, and were then compared to a WOx/ZrO2 catalyst prepared via conventional impregnation. The types of sites present in these samples were characterized using temperature-programmed desorption/thermogravimetric analysis (TPD-TGA) measurements with 2-propanol and 2-propanamine. Weight changes showed that the WOx catalysts grew at a rate of 8.8 × 1017 W atoms/m2 per cycle. Scanning transmission electron microscopy/energy-dispersive spectroscopy (STEM-EDS) indicated that WOx was deposited uniformly, as did the 2-propanol TPD-TGA results, which showed that ZrO2 was completely covered after five ALD cycles. Furthermore, 2-propanamine TPD-TGA demonstrated the presence of three types of catalytic sites, the concentrations of which changed with the number of ALD cycles: dehydrogenation sites associated with ZrO2, Brønsted-acid sites associated with monolayer WOx clusters, and oxidation sites associated with higher WOx coverages. The Brønsted sites were not formed via ALD of WOx on SiO2. The reaction rates for 2-propanol dehydration were correlated with the concentration of Brønsted sites. While TPD-TGA of 2-propanamine did not differentiate the strength of Brønsted-acid sites, H–D exchange between D2O and either toluene or chlorobenzene indicated that the Brønsted sites in tungstated zirconia were much weaker than those in H-ZSM-5 zeolites.

Engineering Ru@Pt Core-Shell Catalysts for Enhanced Electrochemical Oxygen Reduction Mass Activity and Stability

Improving the performance of oxygen reduction reaction (ORR) electrocatalysts is essential for the commercial efficacy of many renewable energy technologies, including low temperature polymer electrolyte fuel cells (PEFCs). Herein, we report highly active and stable carbon-supported Ru@Pt core-shell nanoparticles (Ru@Pt/C) prepared by a wet chemical synthesis technique. Through rotating disc electrode testing, the Ru@Pt/C achieves an ORR Pt mass-based activity of 0.50 A mgPt−1 at 0.9 V versus the reversible hydrogen electrode (RHE), which exceeds the activity of the state-of-the-art commercial Pt/C catalyst as well as the Department of Energy 2020 PEFC electrocatalyst activity targets for transportation applications. The impact of various synthetic parameters, including Pt to Ru ratios and catalyst pretreatments (i.e., annealing) are thoroughly explored. Pt-based mass activity of all prepared Ru@Pt/C catalysts was found to exceed 0.4 mgPt−1 across the range of compositions investigated, with the maximum activity catalyst having a Ru:Pt ratio of 1:1. This optimized composition of Ru@Pt/C catalyst demonstrated remarkable stability after 30,000 accelerated durability cycles (0.6 to 1.0 V vs. RHE at 125 mV s−1), maintaining 85% of its initial mass activity. Scanning transmission electron microscopy energy dispersive spectroscopy (STEM-EDS) analysis at various stages of electrochemical testing demonstrated that the Pt shell can provide sufficient protection against the dissolution of the otherwise unstable Ru core.

Ag+-assisted heterogeneous growth of concave Pd@Au nanocubes for surface enhanced Raman scattering (SERS)

AgNO3 is often used in the preparation of Au nanostructures since Ag-based substances (AgBS) can selectively be adsorbed on Au(100) and significantly modulate the growth of Au nanocrystals. High-index-faceted Au nanostructures have demonstrated excellent performance in catalysis and surface enhanced Raman scattering (SERS), thus attracting the interest of many researchers in the past several decades. Herein, high-index-faceted Pd@Au concave nanocubes (CNCs) were prepared using AgBS as growth-directing agents in the heterogeneous growth of Au on Pd nanocubes (NCs). During the growth of Pd@Au CNCs, Au atoms are initially deposited on the Pd{100} facets leading to the formation of thin Au shells, and then AgBS are quickly adsorbed on the formed Au(100), favoring the growth along and the formation of Pd@Au CNCs. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS), high angle annular dark field (HAADF), and scanning transmission electron microscopy EDS (STEM-EDS) were used to systematically investigate the growth of Pd@Au CNCs. We also demonstrated that the high-index-faceted Pd@Au CNCs exhibited excellent SERS performances.

Investigation regarding the role of chloride in organic-inorganic halide perovskites obtained from chloride containing precursors.

As the photovoltaic performance of a device is strongly influenced by the morphology of perovskite, achieving precise control over the crystal formation of organic-inorganic halide perovskites synthesized in the ambience of chloride ions has garnered much attention. Although the resulting morphology dictates the performance of the device considerably, the understanding of the role of chloride ions has been scant. To unravel this mystery, we investigated three different organic-inorganic halide perovskite materials grown from the chloride-containing precursors under different but optimized conditions. Despite the presence of chloride ions in the reaction mixture, scanning transmission electron microscopy- energy dispersive spectroscopy (STEM-EDS) reveals that the CH3NH3PbI3 perovskites formed are chloride-free. Moreover bright field transmission electron microscopy indicates that chloride ions effect the growth of the CH3NH3PbI3.

Effects of ZrO2 doping on HfO2 resistive switching memory characteristics

A resistive switching (RS) random access memory device with ZrO2-doped HfO2 exhibits better RS performance than that with pure HfO2. In particular, Ires, Vres, and Vset are reduced by approximately 58%, 38%, and 39%, respectively, when HfO2 is doped with ZrO2 (9 at. %). In addition, the ZrO2 doping in HfO2 makes the distribution of most parameters steeper. Transmission electron microscopy (TEM) analysis reveals that the deposited zirconium-doped hafnium oxide (HZO) (9 at. %) is polycrystalline. Elemental mapping results by scanning TEM–energy dispersive spectroscopy also prove that ZrO2 is uniformly distributed in the HZO (9 at. %) film. The possible mechanism for the improvement in the RS characteristics is also suggested on the basis of the X-ray photoelectron spectroscopy results and filamentary RS mechanism. These results suggest that the ZrO2 doping into HfO2 likely not only will reduce power consumption but also will improve cyclic endurance by controlling the nonstoichiometric phase.

Temperature dependent relocation of the cesium primary ion beam during SIMS analysis

The ability to control and accurately measure the cesium concentration, [Cs], is a critical step toward understanding the role of Cs in the SIMS MCs+ technique. We have developed a method to alter the instantaneous [Cs] by using electron gun heating (in situ) during Cs bombardment and found that heating (ex situ) during the X‐ray photoelectron spectroscopy (XPS) analysis provides a qualitative depth distribution of the implanted Cs. The effectiveness of in situ and ex situ heating is explored on (100) silicon and (100) indium arsenide. Cs build‐up curves are studied to determine if in situ heating produces secondary ion yields that are favorable for the MCs+ technique. In addition to XPS, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and scanning transmission electron microscopy/energy dispersive spectroscopy (STEM/EDS) are utilized to measure [Cs]. The goal of this work is to improve the quantification of the MCs+ technique used in SIMS by understanding the material dependent behavior (incorporation and retention) of Cs and how it affects the MCs+ analysis. Copyright © 2014 John Wiley & Sons, Ltd.

Synthesis of New Earth-abundant Kesterite Cu2MgSnS4 Nanoparticles by Hot-injection Method

Abstract A new earth-abundant element material Cu2MgSnS4 was synthesized by hot-injection methods. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy elucidated that as-prepared nanoparticles are Kesterite Cu2MgSnS4 without binary compounds coexisting. Scanning transmission electron microscopy–energy-dispersive spectroscopy element mapping shows the copper, magnesium, tin, and sulfur elements distributed uniformly in the nanoparticles. The result of the UV–vis absorption spectra revealed that the Cu2MgSnS4 nanoparticles have an optical band gap of 1.63 eV, which is suitable for application in the field of photovoltaic cells.

Nature of Surface Film on Matrix Phase of Mg Alloy AZ80 Formed in Water

The nature of the surface film formed on the α-Mg matrix phase of AZ80 in pure H2O was investigated using scanning transmission electron microscopy–energy-dispersive spectroscopy (STEM-EDS). Thin foil cross sections of the film/substrate interface were prepared using focused ion beam (FIB) milling. The film formed consists of a diffuse bilayer structure. A relatively thick, more-hydrated outer layer is found to form on a thinner, less-hydrated inner layer. Al is found to be enriched in both layers relative to the substrate, but is enriched to a higher level within the outer layer. No evidence of an inner aluminum oxide (Al2O3)-rich skeletal layer is observed. The EDS analyses suggest that the more-hydrated outer layer is comprised of double Mg-Al hydroxide-type compound, which is formed as a corrosion product.

Direct observation of the passive layer on high nitrogen stainless steel used as bipolar plates for proton exchange membrane fuel cells

The purpose of this report is to directly observe the passive layer and concentration behavior of nitrogen interstitially incorporated in Ni-saving high nitrogen stainless steel (HNS) using an aberration corrected scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) or – electron energy loss spectroscopy (EELS). The thickness of the passive layer barely changed after 1000h single cell operation, compared with the as-polished state. The observed passive layer was thin (3nm) and mainly composed of chromium oxide, as confirmed by STEM-EDS. It was confirmed that nitrogen was not present in the passive layer, but was concentrated at the interface between the passive layer and the metal bulk. The concentrated area ranged approximately 2nm to steel bulk from the interface. With help of the STEM-EDS and EELS, we were able to understand the nature of the passive layer for Ni-saving HNS, which caused remarkable improvement of the cell performance due to superior corrosion resistance.