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Surface spectroscopy analysis and electrochemistry were applied to study the effects of surface preparation by vibratory polishing on the passivity of stainless steel 304L surfaces. Compared to grinding by traditional mechanical polishing, vibratory polishing promotes the enrichment of Cr(III) oxide and hydroxide species in the duplex chemical structure of the surface native oxide film by enhancing selective Fe oxidation and dissolution. As a result, spontaneous passivity, tested in aggressive sulphuric acid electrolyte, is enhanced. However, in the absence of enrichment in Mo(IV) and Mo(VI) species in the passive film, the Cr enrichment does not enhance passivity upon anodic polarisation nor increase the resistance to Cl-induced passivity breakdown and initiation of localised corrosion in accelerated testing conditions. The results provide comprehensive insight into the mechanisms underlying the passivity enhancement of stainless steel by surface engineering. [ABSTRACT FROM AUTHOR]

• Formation of bi-layered films with physisorbed outer and chemisorbed inner layers. • 2-MBI bonding by N to metallic and oxidized Cu, S also involved on metallic Cu. • Formation of Cu(I)−2-MBI complex promoted by cathodic conversion of native Cu oxide. • Increased complex formation owing to Cu(I) ions generated by anodic oxidation. • Cu dissolution inhibited depending on pre-treatment used for interface formation. The interfacial bonding and the layered structure of 2-mercaptobenzimidazole (2-MBI) organic films adsorbed on electrochemically controlled copper surfaces and their corrosion inhibition effects in acidic chloride aqueous solution were investigated using an integrated approach of electrochemical methods and advanced surface analyses by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. It is shown that organic films formed on the copper surfaces are bi-layered with a chemisorbed inner layer and a physisorbed outer layer. In the chemisorbed inner layer, 2-MBI is bonded primarily by its nitrogen atoms with metallic and oxidized copper surfaces. Sulphur atoms are also involved in the bonding mechanism when metallic copper is directly accessible to the 2-MBI molecules. The initial presence of native copper oxides at the interface promotes the formation of Cu(I)-2-MBI metal-organic complexes in the chemisorbed inner layer using cathodic reduction to dissociate the oxide. Metal-organic complexes also form upon anodic polarisation due to Cu(I) ions generated by oxidation of the copper metal. 2-MBI effectively inhibits copper anodic dissolution in varying degrees, between 84% and 93%, depending on the pre-treatment used for the formation of the organic bi-layers. An enhanced protection of the substrate is obtained by adsorbing the 2-MBI inhibitor on an initially oxide-free surface, which is achieved by cathodic pre-treatment in absence of the inhibitor followed by 1 hour exposure to the inhibitor. [ABSTRACT FROM AUTHOR]

Advanced surface analytical techniques were used to study 2-mercaptobenzothiazole (2-MBT) adsorption and interfacial oxide effects on copper, and cyclic voltammetry was used to characterize corrosion inhibition in NaCl solution. 2-MBT adsorbs on metallic copper by its sulphur atoms along with a small fraction of nitrogen atoms. The 2-MBT film formed is thicker when the interfacial oxide is less. Upon anodic polarisation, a direct correlation between the thickness of 2-MBT layer and protection against corrosion initiation is observed. The metal-organic complexes, formed by an interaction between 2-MBT and Cu(I) ions, do not offer additional protection to the substrate. • 2-MBT inhibition of copper initial corrosion in NaCl studied by surface analysis. • 2-MBT adsorption mostly by sulphur atoms and partially by nitrogen atoms. • Thickness of 2-MBT layer dependent on quantity of interfacial oxides present. • Superior protection against corrosion offered by thicker 2-MBT barrier layer. • Metal-organic Cu-2-MBT complexes do not aid in corrosion protection of substrate. [ABSTRACT FROM AUTHOR]

The mechanisms of initial oxide growth on the equiatomic CoCrFeMnNi high entropy alloy were studied in situ by X-ray photoelectron spectroscopy on clean, oxide-free surfaces exposed stepwise to low-pressure gaseous oxygen. Cr(III), Mn(III), Fe(III), Co(II) but no Ni(II) oxides were formed at 100 °C, and Mn(II) at 200 °C. Data quantification revealed a transition mechanism from selective initial oxidation to 3D kinetically-controlled growth, leading to stratification of the oxide film. Formation of the Co-rich outer layer above the Cr-rich inner layer first formed implies predominant cationic outward oxide growth supported by the overall stoichiometry of the film. • Initial oxide growth studied in situ starting from clean, oxide free surface. • Valence of oxides formed on CoCrFeMnNi HEA at 100 and 200 °C characterized. • Transition from selective initial oxidation to kinetically-controlled oxide growth revealed. • Stratification mechanism during early build-up of the surface oxide unravelled. • Predominant cationic outward oxide growth supported by overall stoichiometry. [ABSTRACT FROM AUTHOR]

• Surface oxide layers formed on 2304 duplex stainless steel are investigated. • The native surface and the passivated surface are compared. • An innovative coupling of XPS and ToF-SIMS is used. • The oxide layers formed on austenite and ferrite phases are locally characterized. • The effect of passivation on the surface oxide layer is discussed. This work reports an innovative methodology based on the coupling of XPS and ToF-SIMS in order to study the surface oxide layer formed on austenite and ferrite phases of duplex stainless steels. The native oxide film obtained after mechanical polishing and the passive film obtained after electrochemical passivation in 0.05 M H 2 SO 4 were investigated. Chromium and molybdenum contents were found to be higher in the oxide layer formed on ferrite phase. Nickel and nitrogen enrichments were found to be more pronounced under the oxide layer formed on austenite phase. The effect of passivation on the surface oxide layer is discussed. [ABSTRACT FROM AUTHOR]

Highlights • Duplex stainless steel and corresponding single phase alloys are compared. • The native oxide films formed after mechanical polishing are studied. • A coupling of XPS and ToF-SIMS is used. • The thickness, composition and chemical states of the oxide layer are investigated. • The link between the chemical compositions of the bulk and the surface is discussed. Abstract The surface oxide films formed after mechanical polishing on duplex stainless steel and corresponding single phase alloys were characterized by XPS and ToF-SIMS. The native oxide films are mixtures of oxides and hydroxides composed of Fe(III), Mo(IV) and Mo(VI) in the outer region and Cr(III) in the inner region. Nickel, molybdenum and nitrogen are enriched in the underlying metal while chromium and molybdenum are enriched in the oxide layer. The contents of alloying elements in the oxide layer and/or in the underlying metal are found to be directly related to their content in the bulk of the alloys. [ABSTRACT FROM AUTHOR]

The ideal solid oxide fuel cells (SOFCs) can be powered by readily available hydrocarbon fuels containing impurities. While this is commonly recognized as a key advantage of SOFC, it also, together with the elevated operating temperature, becomes the main barrier impeding the in-situ or operando investigations of the anode surface chemistry. Here, using a well-designed quenching experiment, we managed to characterize the near-surface structure of La 0.4 Sr 0.6 TiO 3+δ (LST) anode in SOFCs fuelled by H 2 S-containing methane. This new method enabled us to clearly observe the surface amorphization and sulfidation of LST under simulated SOFC operating conditions. The ∼1 nm-thick two dimensional sulfur-adsorbed layer was on top of the disordered LST, containing –S, –SH and elemental sulfur species. In SOFC test, such “poisoned” anode showed increased performances: a ten-fold enhanced power density enhancement (up to 30 mW cm −2 ) and an improved open circuit voltage (from 0.69 V to 1.17 V). Moreover, its anodic polarization resistance in methane decreased to 21.53 Ω cm 2 , a difference of 95% compared with the sulfur-free anode. Control experiments confirmed that once the adsorbed sulfur species were removed electrochemically, methane conversion slowed down simultaneously till full stop. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ions mass spectrometry (ToF-SIMS) analyses were performed to characterize the interaction of Cu with mercaptobenzothiazole (MBT) in aqueous solution for 1 h and 24 h in absence and presence of NaCl. The fingerprints of the molecules are identified with XPS (S, N and C signals). The analysis of the Cu 2p core level and Auger Cu peaks allow us to show that the Cu metal is covered by a Cu 2 O oxide layer whose thickness increases with exposure time in the absence of MBT. It is found that MBT forms multilayers on Cu oxide and inhibits the oxide layer growth. The XPS data are consistent with MBT adsorbed on oxide in multilayers, with a small fraction adsorbed on metallic Cu. These interactions are then further characterized using ToF-SIMS. The results suggest adsorption of the MBT molecules in a strongly bonded layer through both S atoms of the organic molecule oriented towards the surface, covered by a weakly bonded multilayer. Quantitative treatments of XPS intensities allows us to evaluate a layer thickness of 23 Å and 32 Å after 1 h and 24 h, respectively. Co-adsorbed water is also identified. The presence of water in the organic layer (ratio H 2 O/MBT = 0.28) may explain the orientation of the molecules with S directed towards the surface and N interacting through H bonds with water molecules, as suggested by complementary DFT calculations. The adsorption of MBT is similar in presence of NaCl and in pure water, and also inhibits the oxide growth. In addition, MBT adsorption inhibits the adsorption of Cl on the Cu surface. Inductively Coupled Plasma Optical Emission Spectrophotometry (ICP OES) experiments demonstrate that MBT adsorption inhibits Cu dissolution, even after 20 days immersion in NaCl. Thus, we demonstrated that MBT, by adsorbing and forming a full monolayer at the Cu surface, inhibits further oxide growth, Cl adsorption and copper dissolution in NaCl. [Display omitted] • MBT adsorbs on Cu immersed in water and forms multilayers with thicknesses of 2.3–3.2 nm. • Adsorbed MBT inhibits the copper oxide growth, Cl adsorption and copper dissolution in NaCl. • The first MBT layer close to the substrate is bonded to copper via the two S atoms oriented towards the surface. • Water is present in the organic film in a ratio H 2 O/MBT = 0.28. • Water in the organic film has a determinant role in molecule orientation, as shown by DFT calculations. • A fraction of MBT is adsorbed on metallic copper, healing some depassivated areas. [ABSTRACT FROM AUTHOR]

The adsorption of a model protein, the bovine serum albumin (BSA), on plasma-deposited silver nanocomposite thin films was investigated in situ by quartz crystal microbalance (QCM) and ex situ by X-ray photoelectron spectroscopy (XPS). For comparison, BSA adsorption was also studied on pure silver sample and on the polymeric matrix without silver nanoparticles. Both techniques showed that BSA adsorption systematically occurred, regardless of the chemical composition of the solid surface. BSA adsorption was found to be a fast and irreversible process. For the adsorbed BSA layer characterization, a general island model was considered. The height of the protein islands ( h ) and their surface coverage ( γ ) were estimated from combined QCM and XPS data. On the polymeric matrix, the surface coverage was low whereas on pure silver sample and on the nanocomposite film, it was significantly increased. From QCM measurements, mass loss at a constant rate, ascribed to the release and dissolution of Ag particles from the nanocomposite film into the surrounding solution, was observed before and after BSA adsorption, with two different associated rates. The decrease of the silver release rate after BSA adsorption is explained by silver particles coverage by protein islands. BSA molecules adsorbed on silver nanoparticles have a “blocking” effect, decreased the rate of silver nanoparticle release. However, silver dissolution as Ag + ions may still occur. [ABSTRACT FROM AUTHOR]

• 5-sulfosalicylate as an inhibitor in 0.6 M NaCl electrolyte is used for Mg-air battery. • Upon the inhibitor application the improved discharge voltage and battery lifetime are observed. • Almost a four-fold reduction of the hydrogen evolution and a reduced Mg corrosion are noticed. • A modified structure and composition of the surface layer is observed. This work aims at employing sodium 5-sulfosalicylate (5-S-Sal) corrosion inhibitor into aqueous NaCl electrolyte to improve the discharge performance of Mg-air battery and decrease the side reactions of Mg anode. The corrosion tests at open circuit potential show a four-fold decrease of hydrogen evolution when 5-S-Sal inhibitor is added. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analyses show that due to the presence of 5-S-Sal inhibitor, a corrosion resistant layer has a lower quantity of Mg(OH) 2 (by ∼15%) than that formed in NaCl electrolyte. The surface enrichment in S-like species originating from inhibitor molecule could have an important effect on a decreased corrosion and slow down the H 2 evolution. Within a range of concentrations of 5-S-Sal in NaCl electrolyte (0.05 to 0.15 M), the best discharge performances are achieved with 0.1 M inhibitor. The discharge voltage of full Mg-air battery improves from ∼1.58 to ∼1.82 V at 0.5 mA/cm2 and the discharge lifetime is extended from around 12.5 to around 80 h. Scanning electron microscopy and 3D topography laser microscopy indicate that during the discharge tests much smaller surface degradation occurs and a more uniform surface layer is formed in the presence of inhibitor in the NaCl-based electrolyte. [ABSTRACT FROM AUTHOR]

X‐ray photoelectron spectroscopy analysis was applied to investigate the thermal stability under ultra‐high vacuum environment of the surface oxide film formed by electrochemical passivation of a newly designed Cr15Fe10Co5Ni60Mo10 (at.%) multi‐principal element alloy and providing the alloy superior localized corrosion resistance compared to conventional stainless steels and alloys. A spectral decomposition methodology involving the subtraction of Auger peaks overlapping the Fe 2p and Co 2p core level regions was applied for quantification of the oxide film composition and thickness. The results show that, at 100°C, the passive oxide film is mainly dehydrated and dehydroxylated. Obvious loss of Ni hydroxide and conversion of Mo (VI) to Mo (IV) species are observed at 200°C, with further reduction of Mo species to Mo (III) observed at 300°C. In this temperature range, the total cation quantity in the oxide film remains stable despite the compositional alteration. At 400°C, Cr (III) oxide forms at the expense of Fe and Mo oxides, resulting in an oxide film essentially consisting of chromium oxide. At 500°C, Cr (III) oxide is eliminated, making the passive film unstable at this temperature. Possible Cr oxide removal mechanisms are discussed. [ABSTRACT FROM AUTHOR]

Understanding Extracellular Polymeric Substances (EPS) interaction on a well-defined chromium surface is of importance especially for biocorrosion processes. Adsorption of EPS extracted from Pseudoalteromonas NCIMB 2021 on Cr surfaces was investigated using in situ quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS). We show that EPS adsorption is an irreversible process. The amount of adsorbed EPS increases with increasing EPS concentration in solution. For low EPS concentration, the surface is only partially covered by EPS, whereas a continuous organic film of around 15 nm is formed at the surface for high EPS concentrations. An in-depth structuration of this organic layer is evidenced with a strong enrichment of proteins in the inner part and of polysaccharides in the outer part. Adhesion of Pseudoalteromonas NCIMB 2021 has been tested on Cr surfaces covered or not by EPS extracted from Pseudoalteromonas NCIMB 2021. EPS conditioning with a 15 nm film inhibits bacterial adhesion on Cr, showing that this organic film has efficient anti-adhesive properties. [Display omitted] • Irreversible adsorption of EPS extracted from Pseudoalteromonas on Cr surfaces. • Chemical composition of EPS not maintained after adsorption on the Cr surface. • In-depth structuration of the film: proteins inside and polysaccharides outside. • EPS conditioning with a 15 nm film inhibits bacterial adhesion on Cr. [ABSTRACT FROM AUTHOR]

For several decades, various peptides have been under investigation to prevent ischemia/reperfusion (I/R) injury, including cyclosporin A (CsA) and Elamipretide. Therapeutic peptides are currently gaining momentum as they have many advantages over small molecules, such as better selectivity and lower toxicity. However, their rapid degradation in the bloodstream is a major drawback that limits their clinical use, due to their low concentration at the site of action. To overcome these limitations, we have developed new bioconjugates of Elamipretide by covalent coupling with polyisoprenoid lipids, such as squalenic acid or solanesol, embedding self-assembling ability. The resulting bioconjugates were co-nanoprecipitated with CsA squalene bioconjugate to form Elamipretide decorated nanoparticles (NPs). The subsequent composite NPs were characterized with respect to mean diameter, zeta potential, and surface composition by Dynamic Light Scattering (DLS), Cryogenic Transmission Electron Microscopy (CryoTEM) and X-ray Photoelectron Spectrometry (XPS). Further, these multidrug NPs were found to have less than 20% cytotoxicity on two cardiac cell lines even at high concentrations, while maintaining an antioxidant capacity. These multidrug NPs could be considered for further investigations as an approach to target two important pathways involved in the development of cardiac I/R lesions. [ABSTRACT FROM AUTHOR]

Abstract: An XPS investigation was carried out of the surface films, formed by exposure to ultrapure water, on mechanically ground Mg and the two Mg–Al intermetallic compounds: Al3Mg2 and Mg17Al12. The mechanically ground Mg surface had a film of MgO at the Mg metal surface covered by a Mg(OH)2 layer, formed by the reaction of the MgO with water vapour in the air. Upon immersion in ultrapure water, this film converted to a duplex film with an inner MgO layer next to the Mg metal and an external porous hydroxide layer. For both intermetallics, the XPS data is consistent with (i) preferential dissolution of Mg and (ii) a 10nm thick film on the surface after immersion in ultrapure water; the film composition on Al3Mg2 was whilst on Mg17Al12 the composition was . [Copyright &y& Elsevier]

[Display omitted] • Chemical speciation of buried interface on rough substrates. • Sputtering by GD-OES and ToF-SIMS to access interfaces for XPS analysis. • GD-OES homogenous sputtering of thin conversion coating on rough substrate. • Application of Auger nanoprobe for characterization of local coating distribution. • Homogenous in-depth distribution of Cr in conversion coating. In order to describe the chemical composition and the distribution of a thin trivalent chromium conversion coating on rough electrodeposited Zn-based alloy substrate, a methodology combining surface analytical and sputtering techniques was used. A sputtering by argon in glow discharge optical emission spectrometry (GD-OES) and by oxygen using time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to monitor the in-depth chemical composition evolution of the conversion coating and define the metal-conversion coating interface. Surface topography measurements were performed by high resolution 3D optical microscope. The chemical characterization of the conversion coating on the top surface and near the rough metal-oxide interface inside the craters was performed by X-ray photoelectron spectroscopy. The local depth and composition of the conversion layer inside and outside the craters were performed by Auger electron spectroscopy nanoprobe equipped with coaxial detector to prevent from shadowing effect during measurement. The results indicated inhomogeneous sputtering inside the ToF-SIMS craters, which was attributed to the shadowing effect, caused by the roughness of the substrate and the 45° incidence angle ion gun. GD-OES sputtering appeared homogeneous in different areas inside the crater despite the roughness of the substrate, which was attributed to the perpendicular incidence angle of the sputtering. [ABSTRACT FROM AUTHOR]

Abstract: The interaction of 1,2-diaminoethane (DAE) with ZnO thin films prepared by electrodeposition and magnetron sputtering was investigated by X-ray photoelectron spectroscopy (XPS). The samples were exposed to organic solution of 0.5M DAE–p-xylene in an Ar atmosphere glove box (O2 and H2O <5ppm), directly connected to the XPS analysis chamber by an anaerobic and anhydrous transfer system. A clear interaction of DAE with the ZnO surface is evidenced by the presence of a high intensity N1s peak at BE=399.5±0.2eV and C1s at BE=286.3±0.2eV which are attributed to C–N bonding. The atomic ratio C:N was very close to 1:1 consistent with the molecular, non-dissociative adsorption of DAE on the ZnO layer. No significant difference in adsorption of DAE was observed for three different ZnO surfaces despite slight differences in their acid/base properties as evidenced by the O/OH ratio. The results are interpreted in terms of adsorption on Brönsted acid sites. A uniform layer model was used to approximate the DAE film thickness, which was found to be around 10Å on three studied samples. The N1s and C1sB signals were observed to decrease on sample exposure to vacuum and/or X-ray irradiation and additional N1sB peak appeared at lower binding energy at around 398.5±0.2eV. This is interpreted by the desorption and modification of DAE, indicating low stability of the adsorbed state on ZnO. The exposure to water of the sample with adsorbed DAE causes a significant decrease of the N1sA and C1sB peak intensities attributed to the adsorbed DAE molecule, demonstrating the instability of the DAE–ZnO interface in water. [Copyright &y& Elsevier]

[Display omitted] • Interfacial passivation mechanisms studied on Cr- and Mo-containing alloy surfaces. • D 2 O labelling applied to study the growth of nanometer-thick passive oxide film. • D-labelled species mostly detected in outer hydroxide layer of passive film. • Minor inward hydroxyl diffusion from electrolyte during anodic passivation. • Key role of hydroxyls initially in native oxide in forming Cr hydroxide. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with deuterium labelling (D 2 O), and X-ray photoelectron spectroscopy (XPS) were applied to investigate the interfacial transport mechanisms of hydroxyls between aqueous electrolyte and outer part of the protective oxide film during passivation of Cr 15 Fe 10 Co 5 Ni 60 Mo 10 multi-principal element alloy surfaces. A ToF-SIMS signal treatment methodology was developed to retrieve the in-depth distribution of deuterated hydroxides in the nanometer-thick surface oxide film. After immersion at free potential or anodic passivation in acidified D 2 O, the initial bilayer structure is retained. The use of heavy water electrolyte has no effect on the composition alterations induced by passivation. Deuterated species were detected mostly in the outer layer of the surface oxide film. Pure inward hydroxyl diffusion from electrolyte/oxide to oxide/metal interface is excluded from being primarily responsible for oxide film growth induced by anodic passivation. The hydroxyls from the dissolving hydroxide species are retained in the oxide film and participate in forming Cr hydroxide, thus reducing the hydroxyl surface uptake from the electrolyte. This work provides deeper insight into the mechanisms of oxide growth and corrosion protection induced by anodic passivation. [ABSTRACT FROM AUTHOR]

• XPS and ToF-SIMS techniques were applied to understand biofilm-surface interaction. • The effect of Escherichia coli on the passive film composition has been explored. • Escherichia coli adhesion leads to a Cr enrichment of the passive film. • A mechanism involving bacterial metabolism explains passive film modifications. Modifications of the passive film on stainless steel (316 L) after Escherichia coli adhesion in the early stage of biofilm formation were investigated by XPS (X-ray Photoelectron Spectroscopy) and ToF-SIMS (Time-of-Flight Secondary Ions Mass Spectrometry). This work evidences an enrichment in Cr(III) in the presence of bacteria, which is known to improve corrosion resistance. The iron depletion is assigned to synthesis by bacteria of organic molecules (siderophore) that specifically chelate Fe3+ ions from the passive layer, followed by the reduction of Fe3+ into Fe2+ ions by the bacterium and finally release of these reduced species into the aqueous solution. [ABSTRACT FROM AUTHOR]

The need of carbon sources for the chemical industry, alternative to fossil sources, has pointed to CO2 as a possible feedstock. While CO2 electroreduction (CO2R) allows production of interesting organic compounds, it suffers from large carbon losses, mainly due to carbonate formation. This is why, quite recently, tandem CO2R, a two‐step process, with first CO2R to CO using a solid oxide electrolysis cell followed by CO electroreduction (COR), has been considered, since no carbon is lost as carbonate in either step. Here we report a novel copper‐based catalyst, silver‐doped copper nitride, with record selectivity for formation of propanol (Faradaic efficiency: 45 %), an industrially relevant compound, from CO electroreduction in gas‐fed flow cells. Selective propanol formation occurs at metallic copper atoms derived from copper nitride and is promoted by silver doping as shown experimentally and computationally. In addition, the selectivity for C2+ liquid products (Faradaic efficiency: 80 %) is among the highest reported so far. These findings open new perspectives regarding the design of catalysts for production of C3 compounds from CO2. [ABSTRACT FROM AUTHOR]

The need of carbon sources for the chemical industry, alternative to fossil sources, has pointed to CO2 as a possible feedstock. While CO2 electroreduction (CO2R) allows production of interesting organic compounds, it suffers from large carbon losses, mainly due to carbonate formation. This is why, quite recently, tandem CO2R, a two‐step process, with first CO2R to CO using a solid oxide electrolysis cell followed by CO electroreduction (COR), has been considered, since no carbon is lost as carbonate in either step. Here we report a novel copper‐based catalyst, silver‐doped copper nitride, with record selectivity for formation of propanol (Faradaic efficiency: 45 %), an industrially relevant compound, from CO electroreduction in gas‐fed flow cells. Selective propanol formation occurs at metallic copper atoms derived from copper nitride and is promoted by silver doping as shown experimentally and computationally. In addition, the selectivity for C2+ liquid products (Faradaic efficiency: 80 %) is among the highest reported so far. These findings open new perspectives regarding the design of catalysts for production of C3 compounds from CO2. [ABSTRACT FROM AUTHOR]

• Corrosion inhibition and interfacial bonding of 2-MBT studied on copper. • Electrochemistry combined with advanced surface analysis by XPS and ToF-SIMS. • Inhibition enhanced by cathodic reduction of interface before 2-MBT adsorption. • 2-MBT bonded to metallic copper and copper oxide islands via the S atoms. • Exo- and endocyclic S atoms released by dissociation and bonded to metallic Cu. Electrochemistry along with advanced surface analyzes (X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry) were implemented to investigate copper corrosion inhibition by 2-mercaptobenzothiazole (2-MBT) in hydrochloric aqueous solution and the effects of electrochemical control on the formation of the inhibiting interface. It is shown that reducing the native surface oxide by cathodic reduction prior to exposure to the inhibitor drastically decreases the rate of anodic dissolution. Additionally, increasing the exposure time of the metal surface to the inhibitor results in even better protection against dissolution. 2-MBT adsorbs as multilayers and bonds to both metallic copper and residual copper oxide islands via its sulphur atoms. Partial dissociation of the molecule, releasing the exocyclic sulphur, which then bonds to metallic Cu, is observed. Further dissociation of the molecule, releasing the endocyclic sulphur, is induced by anodic polarization, forming defects in the organic layer and thus compromising the barrier properties of the organic layer. [ABSTRACT FROM AUTHOR]

To use water as the source of electrons for proton or CO2 reduction within electrocatalytic devices, catalysts are required for facilitating the proton-coupled multi-electron oxygen evolution reaction (OER, 2 H2O→O2+4 H++4 e−). These catalysts, ideally based on cheap and earth abundant metals, have to display high activity at low overpotential and good stability and selectivity. While numerous examples of Co, Mn, and Ni catalysts were recently reported for water oxidation, only few examples were reported using copper, despite promising efficiencies. A rationally designed nanostructured copper/copper oxide electrocatalyst for OER is presented. This material derives from conductive copper foam passivated by a copper oxide layer and further nanostructured by electrodeposition of CuO nanoparticles. The generated electrodes are highly efficient for catalyzing selective water oxidation to dioxygen with an overpotential of 290 mV at 10 mA cm−2 in 1 m NaOH solution. [ABSTRACT FROM AUTHOR]

To use water as the source of electrons for proton or CO2 reduction within electrocatalytic devices, catalysts are required for facilitating the proton-coupled multi-electron oxygen evolution reaction (OER, 2 H2O→O2+4 H++4 e−). These catalysts, ideally based on cheap and earth abundant metals, have to display high activity at low overpotential and good stability and selectivity. While numerous examples of Co, Mn, and Ni catalysts were recently reported for water oxidation, only few examples were reported using copper, despite promising efficiencies. A rationally designed nanostructured copper/copper oxide electrocatalyst for OER is presented. This material derives from conductive copper foam passivated by a copper oxide layer and further nanostructured by electrodeposition of CuO nanoparticles. The generated electrodes are highly efficient for catalyzing selective water oxidation to dioxygen with an overpotential of 290 mV at 10 mA cm−2 in 1 m NaOH solution. [ABSTRACT FROM AUTHOR]

Ion transport mechanisms in growing oxide films on Ni-20Cr and Ni-20Cr-10Mo alloys have been investigated by ToF-SIMS with in situ re-oxidation using 18O isotopic tracer. Whereas the growth is controlled by pure anionic diffusion on Ni-20Cr alloy, the behavior is drastically modified by Mo addition. A mixed cationic and anionic growth mechanism and a reduced diffusion rate of moving species are observed on the alloy containing molybdenum. The passivation in sulfuric acid, which increases the inner Cr oxide barrier layer thickness, also reduces the diffusion rate of the moving species for both Ni-20Cr and Ni-20Cr-10Mo alloys. Significantly higher re-oxidation temperatures are needed to observe the ion transport mechanisms in passive oxides formed on Ni-20Cr and Ni-20Cr-10Mo alloys, as compared to native oxides. Mo addition and electrochemical passivation have synergistic effects that reduce the diffusion rate of moving species through the surface oxide films and thus reinforce the corrosion resistance of the oxide films formed on Ni alloys. [ABSTRACT FROM AUTHOR]

Abstract: Anodic oxidation of molybdenum in weakly acidic, nearly neutral and weakly alkaline electrolytes was studied by voltammetric and electrochemical impedance spectroscopic measurements in a wide potential and pH range. Current vs. potential curves were found to exhibit two pseudo-Tafel regions suggesting two parallel pathways of the dissolution process. Electrochemical impedance spectra indicated the presence of at least two reaction intermediates. X-ray photoelectron spectroscopic (XPS) results pointed to the formation of an oxide containing Mo(IV), Mo(V) and Mo(VI), the exact ratio between different valence states depending on potential and pH of the solution. A physico-chemical model of the processes is proposed and a set of kinetic equations for the steady-state current vs. potential curve and the impedance response are derived. The model is found to reproduce quantitatively the current vs. potential curves and impedance spectra at a range of potentials and pH and to agree qualitatively with the XPS results. Subject to further improvement, the model could serve as a starting point for the optimization of the electrochemical fabrication of functional molybdenum oxide coatings. [Copyright &y& Elsevier]

Abstract: A corrosion mechanism is proposed for Al3Mg2, based on electrochemical tests, XPS, and depth profiling using XPS and ToF-SIMS. After short (∼2min) solution exposure, the surface consists of a surface film above dealloying. The dealloying is attributed to selective Mg dissolution and the surface rearrangement of Al into islands, although the metallic Al could alternatively be formed by two reduction reactions. The surface film thickness was ∼10nm. After exposure to ultra-pure water, the composition was AlMg1.3O0.2(OH)5.1 corresponding to Al(OH)3·1.1Mg(OH)2·0.2MgO. After exposure to 0.01M Na2SO4, the composition was AlMg0.2O0.4(OH)2.5 corresponding to Al(OH)3·0.1Al2O3·0.2MgO. Longer exposure produced a thicker surface film, more pronounced metallic Al islands and more MgH2. Three possibilities are identified for MgH2 formation. Al(OH)3 formation is attributed to a precipitation reaction. Bulk nanoporous Al3Mg2 formation is predicted to be possible by Mg dealloying of Mg17Al12. [Copyright &y& Elsevier]

Abstract: Spherical microbeads functionalized with two types of chemical groups (NH2,OH) were chosen as a simplified bacterial model, in order to elucidate the role of macromolecular interactions between specific biopolymers and 316L stainless steel, in the frame of biofilm formation in the marine environment. NH2 microbeads were used in their native form or after covalent binding to BSA or different representative poly-amino acids. OH microbeads were used in their native form. Adhesion force between microbeads and bare or BSA-coated stainless steel was quantified at nanoscale. Shear-flow-induced detachment experiments were combined with a simplified version of a theoretical model, based on the balance of hydrodynamic forces and torque exerted on microbeads. A maximal adhesion force of 27.6±8.5nN was obtained for BSA-coated NH2 microbeads. The high reactivity of OH functional groups was assessed (adhesion force of 15.6±4.8nN for large microbeads). When charge-conducting stainless steel was coated with BSA, adhesion force was significantly lower than the one estimated with the bare surface, probably due to an increase in hydrophilic surface properties or suppression of charge transfer. The mechanism for microbead detachment was established (mainly rolling). The flow chamber and the associated theoretical modelling were demonstrated to be a relevant approach to quantify nanoscale forces between interacting surfaces. [Copyright &y& Elsevier]

[Display omitted] • No significant evolution of the oxide thickness induced by acid pre-treatment. • Important Cu enrichment at the oxide/metal interface after acid pretretment. • The highest Cu enrichment in H 2 SO 4 : Cu0 at interface & Cu oxide in the oxide layer. • IMPs: total dealloying in HNO 3 /H 2 SO 4 & partial removal in HNO 3 bath. • Formation of Cu-rich remnant & possible Cu redeposition after H 2 SO 4 treatment. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to analyse the surface modifications of AA-2024-T3 induced by model pre-treatment baths such as H 2 SO 4 , HNO 3 , and in a mixture of both acids. These acids are commonly used for pickling treatment, applied before conversion coating deposition. ToF-SIMS and XPS measurements showed a significant copper enrichment in metallic and oxidised states, localised at the oxide/metal interface. The sulphuric acid treatment led to the highest Cu enrichment. A lower dissolution rate of AA-2024 was observed by inductively coupled plasma optical emission spectroscopy (ICP-OES). It was concluded that the surface enrichment in Cu is mainly associated with dealloying of intermetallic particles by selective dissolution of the less noble elements. [ABSTRACT FROM AUTHOR]

Abstract: Cyclic voltammetry, XPS, RBS and AFM have been combined to study the ageing mechanism of Li intercalation in V2O5 thin films prepared by thermal oxidation of vanadium metal. Multi-cycling tests were performed in 1M LiClO4-PC in the potential range E ∈[3.8, 2.8V] versus Li/Li+, corresponding to the α-to-δ phase transition. XPS and AFM were performed using direct anaerobic and anhydrous transfer. Capacity fading remains inferior to 20% during ∼2500 cycles. XPS shows slight modifications of the oxide composition with a V4+ concentration increasing from ∼5% prior to cycling to ∼16–27% after cycling, due to Li trapped in the oxide film and to the loss of V2O5 active material. The presence of lithium carbonate and lithium-alkyl carbonate species evidences the formation of the so-called SEI layer. AFM evidences the loss of crystalline material by grain exfoliation from the outer V2O5 layer of the oxide film. By further exfoliation, the inner VO2 layer of the oxide film is reached and pits are formed, occupying ∼9–13% of the surface. This de-cohesion at grain boundaries is attributed to the strain generated by repeated lattice distortions. After 3300 cycles, the disappearance of lithium carbonates, whereas Li-alkyl carbonates and/or Li-alkoxides remain on the surface, indicates the dissolution and/or conversion of the SEI layer. After 4500 cycles, the oxide film became very labile and could be stripped away by rinsing to reveal the vanadium metal substrate. [Copyright &y& Elsevier]

Abstract: The intercalation and deintercalation mechanisms of lithium into V2O5 thin films prepared by thermal oxidation of vanadium metal have been studied by X-ray photoelectron spectroscopy (XPS) using a direct anaerobic and anhydrous transfer from the glove box (O2 and H2O<1ppm), where the samples were electrochemically treated, to the XPS analysis chamber. Vanadium in the as-prepared oxide films is mostly (from 93 to 96% depending on samples) in a pentavalent state (V5+) with a stoichiometric O/V concentration ratio fitting that of V2O5. Four to seven percent of VO2 is also observed. After the 1st and the 2nd intercalation steps at E =3.3 and 2.8V versus Li/Li+, respectively, the V2p core level spectra evidence a partial reduction to V4+ states with a remaining concentration of 73 and 56% of V5+, in agreement with the intercalation of about 1/2mol of Li per V2O5 mol at each intercalation step. Intercalated lithium was observed at a binding energy of 56.1eV for Li1s. Changes of the electronic structure of the V2O5 thin film after intercalation are evidenced by the observation, at a binding energy of 1.3eV, of occupied V3d states (V4+) originally empty in the pristine film (V5+). The V2p and Li1s core level spectra show that the process of Li intercalation is partially irreversible. In the first cycle, 34 and 14% of the vanadium ions remain in the V4+ state after deintercalation at E =3.4 and 3.8V versus Li/Li+, respectively, indicating a partially irreversible process already after the 1st deintercalation. The analyses of C1s and O1s XP spectra show the formation of a solid–electrolyte interface (SEI). The analyzed surface layer includes lithium carbonate and Li-alkoxides. [Copyright &y& Elsevier]

Oxide layers grown on the surface provide an effective way of protecting metallic materials against corrosion for sustainable use in a broad range of applications. However, the growth of cavities at the metal/oxide interface weakens the adherence of the protective layer and can promote its spallation under service conditions, as observed for alumina layers formed by selective oxidation of aluminide intermetallic alloys used in high-temperature applications. Here we show that direct atomic-scale observations of the interface between an ultrathin protective oxide layer (alumina) grown on an intermetallic titanium aluminide substrate (TiAl) can be performed with techniques sensitive to the topmost atomic layers at the surface. Nanocavities resulting from the self-assembling of atomic vacancies injected at the interface by the growth mechanism of the protective oxide are observed for the first time, bringing new insight into the understanding of the fate of injected cavities in oxidation processes. [ABSTRACT FROM AUTHOR]

• Surface oxide layers formed on CoCrFeMnNi High Entropy Alloy are investigated by XPS and ToF-SIMS. • An XPS methodology based on analysis of the 3p core level spectra was developed. • The native oxide and passive films are compared. • The oxide film on HEA is duplex comprising a Cr/Mn inner oxide layer and a Cr/Fe/Co outer oxide/hydroxide layer. • The effect of electrochemical passivation on the surface oxide layer is discussed. XPS and ToF-SIMS analysis have been combined with electrochemical measurements to determine the corrosion behavior of the equiatomic CoCrFeMnNi high entropy alloy. An XPS methodology based on analysis of the 3p core level spectra was developed to determine the composition and thickness of oxide films. Both native oxide (∼1.4 nm) and passive films (∼ 1.6 nm) formed in acidic medium are duplex, comprising Cr and Mn inner layer and Cr/Fe/Co mixture outer layer. No nickel is observed in the oxide layer. The effects of exposure of the native film to sulfuric acid and passivation under anodic polarization have been investigated. [ABSTRACT FROM AUTHOR]

Electrochemical polarization measurements were combined with surface analysis by Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), X-Ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) to study the alterations of the passive film on 316 L austenitic stainless steel induced by the presence of chlorides in sulfuric acid electrolyte. The work was performed at a stage of initiation of localized corrosion preceding metastable pitting at the micrometer scale as verified by current transient analysis and AFM. The results show that Cl− ions enter the bilayer structure of the surface oxide already formed in the native oxide-covered initial surface state at concentrations below the detection limit of XPS (<0.5 at%), mostly in the hydroxide outer layer where Fe(III) and Mo(IV,VI) species are concentrated but barely in the oxide inner layer enriched in Cr(III). Their main effect is to produce a less resistive passive state by poisoning dehydroxylation and further Cr(III) and Mo(IV,VI) enrichments obtained in the absence of chlorides. This detrimental effect can be suppressed by pre-passivation in a Cl−-free electrolyte, which blocks the entry of chlorides in the passive film, including in the outer exchange layer, and enables the beneficial aging-induced variations of the composition to take place despite the presence of chlorides in the environment. [ABSTRACT FROM AUTHOR]

• The air-formed oxide on Hastelloy BC-1 contained Cr- and Mo- rich regions in the inner and outer oxide, respectively. • Empirical evidence shows O atom incorporation at the outer interfaces of both the Cr- and Mo-rich regions of the oxide. • Heating the air-formed oxide to 300 °C did not increase its thickness, but, further heating to 500 °C led to the thickening. • In all cases, temperature increases induced structural modification to the oxides which then reverted during oxidation. This paper presents insight into the structure and transport mechanisms involved in the surface oxidation of Hastelloy BC-1, gained by means of in situ time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The native, air-formed oxide, comprising Cr-rich (inner) and Mo-rich (outer) layers, was found to be on the order of 1–2 nm thick. Oxide thickness did not change when the temperature was increased to 300 °C in oxygen atmosphere but increased to ˜10 nm after exposure at 500 °C. The mechanisms of oxide growth/maintenance as well as observations on the effect of elevated temperatures on oxide structure are discussed. [ABSTRACT FROM AUTHOR]

It is generally believed that CO2 electroreduction to multi‐carbon products such as ethanol or ethylene may be catalyzed with significant yield only on metallic copper surfaces, implying large ensembles of copper atoms. Here, we report on an inexpensive Cu‐N‐C material prepared via a simple pyrolytic route that exclusively feature single copper atoms with a CuN4 coordination environment, atomically dispersed in a nitrogen‐doped conductive carbon matrix. This material achieves aqueous CO2 electroreduction to ethanol at a Faradaic yield of 55 % under optimized conditions (electrolyte: 0.1 m CsHCO3, potential: −1.2 V vs. RHE and gas‐phase recycling set up), as well as CO electroreduction to C2‐products (ethanol and ethylene) with a Faradaic yield of 80 %. During electrolysis the isolated sites transiently convert into metallic copper nanoparticles, as shown by operando XAS analysis, which are likely to be the catalytically active species. Remarkably, this process is reversible and the initial material is recovered intact after electrolysis. [ABSTRACT FROM AUTHOR]

It is generally believed that CO2 electroreduction to multi‐carbon products such as ethanol or ethylene may be catalyzed with significant yield only on metallic copper surfaces, implying large ensembles of copper atoms. Here, we report on an inexpensive Cu‐N‐C material prepared via a simple pyrolytic route that exclusively feature single copper atoms with a CuN4 coordination environment, atomically dispersed in a nitrogen‐doped conductive carbon matrix. This material achieves aqueous CO2 electroreduction to ethanol at a Faradaic yield of 55 % under optimized conditions (electrolyte: 0.1 m CsHCO3, potential: −1.2 V vs. RHE and gas‐phase recycling set up), as well as CO electroreduction to C2‐products (ethanol and ethylene) with a Faradaic yield of 80 %. During electrolysis the isolated sites transiently convert into metallic copper nanoparticles, as shown by operando XAS analysis, which are likely to be the catalytically active species. Remarkably, this process is reversible and the initial material is recovered intact after electrolysis. [ABSTRACT FROM AUTHOR]

Low corrosion protection performances of Trivalent Chromium Process (TCP) coatings with reference to Chromium Conversion Coatings (CCC) deposited on aluminium alloys can be overcome by application of post-treatment processes. This work shows the effect of post-treatment bath (containing hydrogen peroxide and lanthanum salt) on the chemical composition, structure and the corrosion performances of TCP coating deposited on AA 2024-T3 aluminium alloy. Different times of post-treatment bath were applied on the TCP coating and the samples were analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS) and Glow Discharge-Optical Emission Spectrometry (GD-OES). The ToF-SIMS and GD-OES depth profiles show that the post-treatment time has no influence on the thickness of the TCP coating and on its bi-layered structure. It is composed of an outer layer, rich in zirconium and chromium oxides and an inner layer rich in aluminium oxides and oxy-fluorides. 3D ToF-SIMS images reveal an enrichment of Cr and Zr-like species over the surface of intermetallic particles with reference to alloy matrix, whereas a homogenous distribution of La is observed. The analysis of in-depth distribution shows that La is present principally in the outer part of the TCP coating. The La concentration increases with increasing post-treatment time. The effect of post-treatment time on protection was evaluated by Electrochemical Impedance Spectroscopy (EIS) and Linear Sweep Voltammetry (LSV) in a 0.001 M NaCl + 0.1 M Na 2 SO 4 electrolyte. The increased post-treatment time enhances the cathodic inhibition against oxygen reduction. The post-treatment provides improved coating homogeneity and sealing properties. • No thickness and structure modification of TCP coating induced by post-treatment • Significant inhibition of the cathodic oxygen reduction induced by post-treatment • Increase of La and decrease of Cr in TCP with higher post-treatment time • Homogenous surface distribution of La responsible for sealing coating defects [ABSTRACT FROM AUTHOR]

Abstract Bio-induced precipitation of lead-bearing minerals is investigated in bacterial biofilms grown by Shewanella oneidensis MR-1 under aerobic conditions. Under the different conditions investigated, thermodynamic calculations establish that the stable mineral phases expected to precipitate are either wulfenite PbMoO 4 or cerussite PbCO 3. However, observations by electron microscopy show that the first solids precipitated within hours at the experimental solution/biofilm interface are crystals of about 20 nm in diameter of pyromorphite Pb 5 (PO 4) 3 (OH,Cl). In Mo-bearing systems, the precipitation of the thermodynamically-predicted wulfenite phase is delayed compared to the abiotic experiment and is observed only after seven days of lead exposure. The initial lead phosphate crystals observed on the extracellular polymeric substances are assumed to result from concurrent local abundances of adsorbed Pb2+ ions and phosphate groups released by metabolically active cells. Scanning electron microscopy observations of samples milled by focused ion beam reveal effective diffusion-limited precipitation of pyromorphite within the well-preserved biofilm porosity. Graphical abstract Unlabelled Image Highlights • Biofilm activity drives pyromorphite (Pb 5 (PO 4) 3 Cl) precipitation. • The thermodynamically-stable wulfenite formation is delayed in biofilm. • Focused ion beam milled sections of the biofilm reveal gradients in lead biomineralization. [ABSTRACT FROM AUTHOR]

• Investigation of native and passive surface films formed on Ni-20 at.% Cr alloy surfaces. • Surface analysis by in situ electrochemical measurements combined with advanced ex situ surface analysis. • Mechanistic understanding of the effects of high-temperature hydrogen annealing pretreatment. • Enhanced corrosion resistance of electrochemically passivated surface by high-temperature hydrogen annealing pretreatment. • Increase in Cr enrichment of initially weakly protected sites of the inner barrier layer. The effect of high-temperature annealing under hydrogen gas (H 2) surface preparation on a binary polycrystalline Ni-20 at.% Cr alloy was investigated in comparison with conventional mechanical grinding surface preparation. Duplex surface films with inner Cr(III) oxide and outer Ni(II) and Cr(III) hydroxide layers natively formed before and after H 2 annealing were characterized by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. A thinner and less homogeneous inner barrier layer formed after H 2 annealing caused an oxidation peak at the active/passive transition in the linear sweep voltammetry measurement in a 0.5 M H 2 SO 4 solution. Despite this high oxidation peak, passivation of the H 2 annealed surface resulted in the formation of a more corrosion resistant inner layer than on the mechanically ground surface, as demonstrated by electrochemical impedance spectroscopy. The corrosion resistant passive film formation of the H 2 annealed surface is attributed to the increased Cr enrichment of the inner layer caused by the selective Ni dissolution providing corrosion resistance to the initially weakly protected sites of the natively formed surface film. [ABSTRACT FROM AUTHOR]

The role of the SiC substrate surface on the resistance to the local initiation of tarnishing of thin-layered silver stacks for demanding space mirror applications was studied by combined surface and interface analysis on model stack samples deposited by cathodic magnetron sputtering and submitted to accelerated aging in gaseous H 2 S. It is shown that suppressing the surface pores resulting from the bulk SiC material production process by surface pretreatment eliminates the high aspect ratio surface sites that are imperfectly protected by the SiO 2 overcoat after the deposition of silver. The formation of channels connecting the silver layer to its environment through the failing protection layer at the surface pores and locally enabling H 2 S entry and Ag 2 S growth as columns until emergence at the stack surface is suppressed, which markedly delays tarnishing initiation and thereby preserves the optical performance. The results revealed that residual tarnishing initiation proceeds by a mechanism essentially identical in nature but involving different pathways short circuiting the protection layer and enabling H 2 S ingress until the silver layer. These permeation pathways are suggested to be of microstructural origin and could correspond to the incompletely coalesced intergranular boundaries of the SiO 2 layer. [ABSTRACT FROM AUTHOR]

In this work, we addressed the local degradation mechanisms limiting the prelaunch environmental durability of thin-layered silver stacks for demanding space mirror applications. Local initiation and propagation of tarnishing were studied by combined surface and interface analysis on model stack samples consisting of thin silver layers supported on lightweight SiC substrates and protected by thin SiO2 overcoats, deposited by cathodic magnetron sputtering and submitted to accelerated aging in gaseous H2S. The results show that tarnishing is locally initiated by the formation of Ag2S columns erupting above the stack surface. Ag2S growth is promoted at high aspect ratio defects (surface pores) of the SiC substrate as a result of an imperfect protection by the SiO2 overcoat. Channels most likely connect the silver layer to its environment through the protection layer, which enables local H2S entry and Ag2S growth. The silver sulfide columns grow in number and size eventually leading to coalescence with increasing H2S exposure. In more advanced stages, tarnishing slows down owing to saturation of all pre-existing imperfectly protected sites of preferential sulfidation. However, it progresses radially at the basis of the Ag2S columns underneath the protection layer, consuming the metallic silver layer and deteriorating the protecting overcoat. [ABSTRACT FROM AUTHOR]

Fe-based air alkaline batteries are promising candidates for large scale energy storage due to their low cost, eco-friendliness and high energy density. In this work, pure iron was studied as negative electrode of Fe-air batteries with and without Na 2 S added to the KOH alkaline electrolyte in order to bring new insight on the mechanisms of inhibition of the hydrogen evolution reaction (HER) and improvement of the electrochemical performances of the Fe electrode. Electrochemical (CV, galvanostatic discharge), spectroscopic (XPS, ToF-SIMS) and microscopic (SEM) analysis were applied to characterize the effect of the sulfide additive (Na 2 S) on the electrochemical behavior of Fe electrodes and their chemical and morphological modifications. Surface analysis performed by XPS and ToF-SIMS revealed the formation of a markedly thicker oxide/hydroxide layer. The mechanism of formation of this thick oxide/hydroxide layer is initiated by the adsorption of sulfur (S ads ) at the oxide/metal interface that inhibits the HER during the first stages of electrochemical process and promotes subsequent anodic oxidation. With the Na 2 S electrolyte additive, Fe(0)/Fe(II) conversion/deconversion is suppressed and charge/discharge proceeds mostly by Fe(II)/Fe(III) conversion/deconversion with improved capacity owing to the porous morphology of the oxide/hydroxide layer. [ABSTRACT FROM AUTHOR]

The effects of surface pretreatments (degreasing and pickling) on the characteristics of the Trivalent Chromium Process (TCP) coating on pure aluminum and on AA2024-T351 aluminum alloy were investigated here by means of surface sensitive techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The XPS and ToF-SIMS results evidence that the TCP coating homogeneity is strongly dependent on the pretreatment process used. The TCP coverage factor, calculated from XPS results, is significantly lower, on both pure aluminum and AA2024-T351 alloy surface, when a pickling step is applied. One of the main effects of pickling pretreatment is strong metallic copper enrichment at the surface of the 2024 alloy, associated with chemical dissolution of Al-Cu intermetallic particles. However, it is evidenced here, that the copper enrichment is not detrimental for the quality of the TCP coating. The coating failure, observed when the pickling step is applied, can be assigned to a faster kinetics of the coating growth leading to formation of thicker conversion coating more susceptible to cracking or to the localized presence of aluminum fluoride species leading to the appearance of coating defects or detachment. [ABSTRACT FROM AUTHOR]

Room temperature ionic liquids (RTILs) attract much attention as a new type of environmentally benign electrolytes for Li-ion batteries due to their numerous interesting physicochemical properties. Here, in this paper, Li intercalation/deintercalation in presence of the N -butyl- N -methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR 14 TFSI) and N -methyl- N -propylpyrrolidinium bis(fluorosulfonyl)imide (PYR 13 FSI) containing 0.3 M LiTFSI, was evaluated in a thin 100 nm layer of V 2 O 5 deposited on Al substrate by atomic layer deposition. Potentiodynamic tests performed in LiTFSI/Pyr 14 TFSI show a quasi-reversible Li intercalation during 10 cycles (between 2.4 and 5 V) with an average coulombic efficiency of 99%. The capacity, calculated from the 1st cycle, is found to be 182 mAh g −1 , about 19% (±2%) higher than the theoretical capacity reported for V 2 O 5 (147 mAh g −1 ). X-ray photoelectron spectroscopy analysis confirms that the intercalation of more than 1 mol of Li + per V 2 O 5 is achieved as also the possible presence of a solid permeable interface (SPI) layer on the V 2 O 5 surface. Likewise, the Li + in-depth distribution on the V 2 O 5 layer after intercalation in RTILs measured by time-of-flight secondary ion mass spectrometry ion depth profiles, show small irreversible electrode modifications with the presence of lithium through the entire V 2 O 5 layer with significant lithium trapping at the V 2 O 5 layer/Al substrate interface. [ABSTRACT FROM AUTHOR]

ToF-SIMS and XPS are combined to study the adsorption of tetradecyl-benzyldimethyl-ammonium (BDA-C14) bromide corrosion inhibitor on carbon steel surface. BDA-C14 forms a protective layer with N-containing polar head group interacting with carbon steel surface. The adsorbed inhibitor surface coverage strongly depends on immersion time and inhibitor concentration. A maximum and uniform coverage is found for sufficiently long exposure times at a critical inhibitor concentration of about 25 ppm w. The uniform adsorbed inhibitor layer formed on the surface mitigates the formation of iron chloride/hydroxide intermediates and thus enhances the corrosion protection of carbon steel in aggressive environment. • The adsorption of BDA-C14 corrosion inhibitor on carbon steel surface was studied by ToF-SIMS and XPS. • The inhibitor forms a protective layer with N-containing polar head group interacting with carbon steel surface. • The adsorbed inhibitor surface coverage strongly depends on immersion time and inhibitor concentration. • The critical concentration for a maximum and uniformed inhibitor coverage on carbon steel is determined. • The uniform adsorbed inhibitor layer on carbon steel can mitigate the formation of iron chloride/hydroxide intermediates. [ABSTRACT FROM AUTHOR]

The high self-corrosion rate of Mg in aqueous electrolyte generates H 2 , which is the main impediment to restrict the utilization of Mg-air batteries. However, organic/inorganic hybrid electrolyte is prone to reduce the Mg degradation. Herein, the effect of different ethanol fractions in water with 0.6 M NaCl on corrosion behavior of Mg and battery discharge performances is demonstrated. The significant corrosion inhibition in a high content of ethanol (≥20 vol%) in electrolyte is attributed to the formation of a thinner, more corrosion protective layer enriched in magnesium oxide as demonstrated by scanning electron microscopy, X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Contrarily, in water-based electrolyte a thick, porous and rough layer principally composed of magnesium hydroxide is formed. By varying the ethanol to water fraction in the electrolyte in full battery cell, it is shown that even a small ethanol content (≤ 5 vol%), can greatly enhance the electrochemical performances of Mg anode. Within several ethanol content, 0.5 vol% demonstrates the best performances with a limited corrosion rate and greatly improves the discharge performance and the battery lifetime. It is demonstrated here that application of inorganic/organic dual electrolyte is a promising and easy way towards a well-controlled Mg anode reactivity and improved performances of Mg-air battery. [Display omitted] • Significant corrosion inhibition in high content of ethanol (≥ 20 vol%). • Formation of a thinner, more corrosion protective layer enriched in MgO in presence of ethanol. • Growth of a thick, porous and rough layer composed of Mg(OH) 2 in water-based electrolyte. • The best discharge performance and battery lifetime in 0.5 vol% ethanol content. [ABSTRACT FROM AUTHOR]

n -Si/SiO x /Ni photoanodes are investigated for upconversion photoinduced electrochemiluminescence (PECL) employing the 3-aminophthalhydrazide (luminol)-hydrogen peroxide (H 2 O 2) model electrochemiluminescent (ECL) system at pH 13. We show that IR excitation of the photoanode at 850 nm produces PECL emission at 440 nm resulting in an anti-Stokes shift of -410 nm at biases higher than 0 V vs Ag/AgCl. Due to the alkaline pH value of the electrolyte that prevents Ni dissolution, this upconverting system is active for a longer period (several hours) than reported durations for similar photoanodes operating at neutral pH. The PECL intensity can be controlled by the applied potential and the power density of the incident IR light. This new PECL system opens up promising perspectives for light-addressable electrodes, microscopy, and imaging. [ABSTRACT FROM AUTHOR]

Electrochemical and surface analyses were applied to study the corrosion mechanisms of aluminium protected by ultra-thin (≤50 nm) alumina coatings grown by atomic layer deposition. Corrosion takes place via residual channel defects connecting the substrate to the electrolyte through the insulating coating. The data evidence the growth of a spurious aluminium oxide film at the substrate/coating interface in the reactor, that is beneficial to the sealing performance of the thinner films (10 nm). The resistance to the initiation of localized corrosion by pitting is increased with thicker films (20 and 50 nm) owing to improved sealing and barrier properties. [ABSTRACT FROM AUTHOR]

A plasma-deposited coating, containing silver nanoparticles embedded in an organosilicon matrix, was synthesized, using AISI 316L stainless steel as the underlying substrate. The coating antibacterial property was evaluated on the Gram-negative Escherichia coli K12 MG1655 and the Gram-positive Staphylococcus aureus MW2 strains, by combining indirect (plate counting) and in situ (fluorescent bacteria labelling) methods. Both approaches were shown to be highly complementary and converged on a maximal antibacterial efficacy against E. coli , as plate counts showed a decrease of 6 and 1 Log and dead bacteria represented 25% and 2% of the total adhering bacteria for E. coli and S. aureus , respectively. The coating antibacterial potential was then determined over time on E. coli biofilm. Whatever the biofilm age, growth inhibition was observed due to silver-mediated bacteriostatic effect. The coating bactericidal activity was initially strong. However, differences between coated and bare stainless steel surfaces tended to collapse above a 2-day contact time. A thorough characterization of the film properties after ageing in biological suspension or saline solution (short and longer-term exposures) revealed an oxidation of both the organosilicon matrix and the silver nanoparticles, accompanied by silver release at the extreme surface. However, a silver reservoir was still present and potentially active in the deep layers of the coating. [ABSTRACT FROM AUTHOR]

(Fe,Cr)-binary oxide thin film electrodes were prepared as negative electrode material for lithium-ion micro-batteries by thermal growth on a stainless steel (AISI 410, FeCr 12.5 ) current collector. The mechanisms of lithiation/delithiation were investigated by means of electrochemical (CV, galvanostatic cycling), spectroscopic (XPS, ToF-SIMS) and microscopic (SEM, AFM) analytical techniques. The as-prepared (Fe, Cr)-binary oxide electrodes exhibit a good cycling performance except the first discharge/charge cycle where a high irreversible capacity is observed due to formation of a solid electrolyte interphase (SEI) layer. The influence of substituting an oxidized iron by an oxidized chromium (Cr x Fe 2− x O 3 phase) was evaluated. The data show that the inferior electrochemical conversion activity of substituted oxidized chromium results in hindering lithium transport in the bulk thin film electrode. It was observed that the irreversible morphology modifications together with SEI evolution are critical to capacity degradation while retaining good coulombic efficiency. [ABSTRACT FROM AUTHOR]