Reactivity Of Metal Surfaces Research Articles

Facile Characterization of the Lithium Metal/Electrolyte Interface through Nonlinear Electrochemical Impedance Spectroscopy

Next-generation lithium metal batteries have demonstrated the high energy densities necessary for electric vehicles and thus have the potential to enable the widespread electrification of transportation.1 However, mass adaptation of lithium metal batteries is challenged by the unsatisfactory cycle life resulting from the lack of electrolytes compatible with the highly reactive lithium metal surface. The uncontrolled interactions between the lithium anode and the electrolyte results in the continuous depletion of both participants and/or the formation of electrically isolated lithium, which ultimately reduces the cycle life. While progress in electrolyte engineering offers hints on the role of the electrolyte in essential battery processes (eg., the formation of a stable solid-electrolyte interphase layer and favorable deposited lithium morphologies), further improvements in lithium metal batteries necessitates a deeper understanding of the lithium metal/electrolyte interface.The performance of lithium metal battery electrolytes is often gauged by the ratio between the discharge and charge capacities, or the Coulombic efficiency (CE). An electrolyte with a high CE indicates that the discharge and charge capacities were nearly equal, or that very little lithium was lost to undesirable side processes during cycling. A typical CE experiment, such as the popular Aurbach method, involves several cycles of plating and stripping a lithium reservoir from a copper substrate at one current density.2 With hundreds of cycles, a single CE test can be time-consuming, presenting a bottleneck in electrolyte research.Here, we integrate nonlinear electrochemical impedance spectroscopy (NLEIS) into a modified Aurbach method to evaluate the evolution of the lithium metal/electrolyte interface with cycling and detect earlier signs of lower CE electrolytes. With the same instrumentation as its linear counterpart, NLEIS utilizes a moderate AC current amplitude to elicit a weakly nonlinear voltage response that is sensitive to kinetic, transport, and thermodynamic processes. Notably, the second harmonic voltage response is formed by the differences between the battery electrodes, making NLEIS a powerful diagnostic tool for detecting subtle changes.3,4 This work introduces a methodology that could enable faster characterization of lithium metal electrolytes, yet opens the path for more in-depth kinetic studies. G. M. Hobold et al., Nat. Energy, 6, 951–960 (2021).B. D. Adams, J. Zheng, X. Ren, W. Xu, and J. G. Zhang, Adv. Energy Mater., 8, 1–11 (2018).Y. Ji and D. T. Schwartz, J. Electrochem. Soc., 170, 123511 (2023).4. Y. Ji and D. T. Schwartz, J. Electrochem. Soc., 171, 023504 (2024). Figure 1

Unsupervised machine learning reveals eigen reactivity of metal surfaces

The reactivity of metal surfaces is a cornerstone concept in chemistry, as metals have long been used as catalysts to accelerate chemical reactions. Although fundamentally important, the reactivity of metal surfaces has hitherto not been explicitly defined. For example, in order to compare the activity of two metal surfaces, a particular probe adsorbate, such as O, H, or CO, has to be specified, as comparisons may vary from probe to probe. Here we report that the metal surfaces actually have their own intrinsic/eigen reactivity, independent of any probe adsorbate. By employing unsupervised machine learning algorithms, specifically, principal component analysis (PCA), two dominant eigenvectors emerged from the binding strength dataset formed by 10 commonly used probes on 48 typical metal surfaces. According to their chemical characteristics revealed by vector decomposition, these two eigenvectors can be defined as the covalent reactivity and the ionic reactivity, respectively. Whereas the ionic reactivity turns out to be related to the work function of the metal surface, the covalent reactivity cannot be indexed by simple physical properties, but appears to be roughly connected with the valence-electron number normalized density of states at the Fermi level. Our findings expose that the metal surface reactivity is essentially a two-dimensional vector rather than a scalar, opening new horizons for understanding interactions at the metal surface.

Novel dynamic method based on CV-SECM and SWV-SECM for the in situ chemical imaging of reactive metal surfaces undergoing corrosion and corrosion inhibition illustrated with the case of copper corrosion inhibition by benzotriazole

A novel dynamic method for the chemical imaging of actively corroding metal surfaces using scanning electrochemical microscopy (SECM) is proposed by using CV-SECM and SWV-SECM. This consists of an adequate coupling of a repetitive voltammetric operation at the SECM tip while conducting the rastering routine for scanning a reactive copper surface, as well as its inhibition by benzotriazole. In this method, gold microelectrodes are employed as SECM tips, and therefore their electrochemical behaviour towards collection and redissolution of Cu2+ ions from synthetic solutions containing Cu2+ ions. Next, the dynamic application of voltammetric methods for the collection and stripping of copper on the Au probes while mapping copper surfaces was investigated. The proof of concept first involved continuous cyclic voltammetry (CV-SECM) in an acidified NaCl solution, in terms of Cu2+ dissolution and surface redox activity (with SECM in the feedback mode). Then, square wave voltammetry (SWV-SECM) was used to detect small copper dissolution from corroding and inhibitor-protected metal surfaces. The results are consistent with a heterogeneous nature of copper degradation and the development of protective films and passive layers.

Planar BN-Doped Nanographenes on Reactive Metal Surfaces: A Promising Pathway for the Preparation of BN-Doped Graphene Layers

Planar BN-Doped Nanographenes on Reactive Metal Surfaces: A Promising Pathway for the Preparation of BN-Doped Graphene Layers

Corrosion Performance of Ti6Al7Nb Alloy in Simulated Body Fluid for Implant Application Characterized Using Macro- and Microelectrochemical Techniques

In this paper, the applicability of Ti6Al7Nb as a more biocompatible alternative for bone and dental implants than Ti6Al4V and pure titanium in terms of corrosion resistance and electrochemical inertness is investigated. The chemical inertness and corrosion resistance of the Ti6Al7Nb biomaterial were characterized by a multi-scale electrochemical approach during immersion in simulated physiological environments at 37 °C comparing its behavior to that of c.p. Ti, Ti6Al4V, and stainless steel. The establishment of a passive regime for Ti6Al7Nb results from the formation of a thin layer of metal oxide on the surface of the material which prevents the action of aggressive species in the physiological medium from direct reaction with the bulk of the alloy. Conventional electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) provide quantified information on the surface film resistance and its stability domain that encompasses the potential range experienced in the human body; unfortunately, these methods only provide an average estimate of the exposed surface because they lack spatial resolution. Although local physiological environments of the human body are usually simulated using different artificial physiological solutions, and changes in the electrochemical response of a metallic material are observed in each case, similar corrosion resistances have been obtained for Ti6Al7Nb in Hank’s and Ringer’s solutions after one week of immersion (with a corrosion resistance of the order of MΩ cm2). Additionally, scanning electrochemical microscopy (SECM) provides in situ chemical images of reactive metal and passive dielectric surfaces to assess localized corrosion phenomena. In this way, it was observed that Ti6Al7Nb exhibits a high corrosion resistance consistent with a fairly stable passive regime that prevents the electron transfer reactions necessary to sustain the metal dissolution of the bulk biomaterial. Our results support the proposition of this alloy as an efficient alternative to Ti6Al4V for biomaterial applications.

Regulating lithium metal interface using seed-coating layer for high-power batteries

• Li metal interface is engineered using seed-coating of N-rich graphene quantum dots. • A regulated SEI on Li metal assures ultra-stable cyclability even at 30 mA cm −2 . • Li is uniformly guided beneath seed-coating layer with dendrite-free plating. • Robust and stable composite SEI mitigates continuous consumption of electrolyte. Li metal has received heightened attention as an anode material for next-generation batteries due to its extremely large theoretical specific capacity. Employing Li metal anodes, however, involves considerable challenges, such as the formation of Li dendrites, depletion of electrolyte, and breakage of the solid electrolyte interphase layer. These issues potentially limit cell cycle life and pose safety risks. While recent studies demonstrated promising results, facile and scalable methods for achieving high power Li metal batteries are still elusive. Herein, the interface of lithium metal is regulated by seed-coating of nitrogen-rich graphene quantum dots (N-GQDs), which facilitates the formation of a robust and stable solid electrolyte interface layer. The highly lithiophilic nature of N-GQDs enables uniform lithium ionic flux even at high current densities and promotes dendrite-free lithium plating morphology with a low nucleation overpotential of 3 mV (45 mV for bare copper). Such a robust layer enables highly reversible Li plating/stripping in symmetric cell configuration for over 8,000 h at a current density of 30 mA cm −2 . Furthermore, the lithium iron phosphate-coupled full cell performs stable cycling for over 500 cycles. The introduction of seed layers represents a viable strategy for achieving high-power Li metal batteries by regulating the highly reactive lithium metal surface.

Accurate Simulations of the Reaction of H2 on a Curved Pt Crystal through Machine Learning.

Theoretical studies on molecule–metal surface reactions have so far been limited to small surface unit cells due to computational costs. Here, for the first time molecular dynamics simulations on very large surface unit cells at the level of density functional theory are performed, allowing a direct comparison to experiments performed on a curved crystal. Specifically, the reaction of D2 on a curved Pt crystal is investigated with a neural network potential (NNP). The developed NNP is also accurate for surface unit cells considerably larger than those that have been included in the training data, allowing dynamical simulations on very large surface unit cells that otherwise would have been intractable. Important and complex aspects of the reaction mechanism are discovered such as diffusion and a shadow effect of the step. Furthermore, conclusions from simulations on smaller surface unit cells cannot always be transfered to larger surface unit cells, limiting the applicability of theoretical studies of smaller surface unit cells to heterogeneous catalysts with small defect densities.

Segmentation of Workpiece Rust Based on Cross Maximum

Rust is an oxide produced by the reaction of metal and alloy surface with oxygen. It is a defect that greatly affects the quality of the workpiece. In order to solve the problem of rust segmentation more conveniently, a threshold segmentation algorithm based on cross extremum method is proposed, which determines the threshold of rust segmentation adaptively combining the global and local features of the image. Firstly, as the threshold is hard to determine in the small and medium area rust segmentation of a workpiece, the super red method and saturation method are combined to pre-process the image. Secondly, because the gray value of the rust spot area is the maximum value of the image neighborhood, the cross-extremum method is used to extract the characteristic points of the rust spot. Finally, the threshold of rust segmentation is determined according to the proposed feature points. Experiments show that the horizontal and vertical extremum method can complement each other to extract the feature points of rust as fully as possible. And the algorithm can extract some feature points of rust better for different workpieces in varying backgrounds. The detection accuracy of the algorithm reaches 96.3%, which has important signification of application.

First-principles study of nickel reactivity under two-dimensional cover: Ni2C formation at rotated graphene/Ni(111) interface

Recent experiments indicate that the reactivity of metal surfaces changes profoundly when they are covered with two-dimensional (2D) materials. Nickel, the widespread catalyst choice for graphene (G) growth, exhibits complex surface restructuring even after the G sheet is fully grown. In particular, due to excess carbon segregation from bulk nickel to surface upon cooling, a nickel carbide (${\mathrm{Ni}}_{2}\mathrm{C}$) phase is detected under rotated graphene (RG) but not under epitaxial graphene (EG). Motivated by this experimental evidence, we construct different G/Ni(111) interface models accounting for the two types of G domains. Then, by applying density functional theory, we illuminate the microscopic mechanisms governing the structural changes of nickel surface induced by carbon segregation. A high concentration of subsurface carbon reduces the structural stability of Ni(111) surface and gives rise to the formation of thermodynamically advantageous ${\mathrm{Ni}}_{2}\mathrm{C}$ monolayer. We show the restructuring of the nickel surface under RG cover and reveal the essential role of G rotation in enabling high density of favorable C binding sites in the Ni(111) subsurface. As opposed to RG, the EG cover locks the majority of favorable C binding sites preventing the build-up of subsurface carbon density to a phase transition threshold. Therefore we confirm that the conversion of C-rich Ni surface to ${\mathrm{Ni}}_{2}\mathrm{C}$ takes place exclusively under RG cover, in line with the strong experimental evidence.

Density Functional Theory for Molecule-Metal Surface Reactions: When Does the Generalized Gradient Approximation Get It Right, and What to Do If It Does Not.

While density functional theory (DFT) is perhaps the most used electronic structure theory in chemistry, many of its practical aspects remain poorly understood. For instance, DFT at the generalized gradient approximation (GGA) tends to fail miserably at describing gas-phase reaction barriers, while it performs surprisingly well for many molecule–metal surface reactions. GGA-DFT also fails for many systems in the latter category, and up to now it has not been clear when one may expect it to work. We show that GGA-DFT tends to work if the difference between the work function of the metal and the molecule’s electron affinity is greater than ∼7 eV and to fail if this difference is smaller, with sticking of O2 on Al(111) being a spectacular example. Using dynamics calculations we show that, for this system, the DFT problem may be solved as done for gas-phase reactions, i.e., by resorting to hybrid functionals, but using screening at long-range to obtain a correct description of the metal. Our results suggest the GGA error in the O2 + Al(111) barrier height to be functional driven. Our results also suggest the possibility to compute potential energy surfaces for the difficult-to-treat systems with computationally cheap nonself-consistent calculations in which a hybrid functional is applied to a GGA density.

Surface-controlled reversal of the selectivity of halogen bonds

Intermolecular halogen bonds are ideally suited for designing new molecular assemblies because of their strong directionality and the possibility of tuning the interactions by using different types of halogens or molecular moieties. Due to these unique properties of the halogen bonds, numerous areas of application have recently been identified and are still emerging. Here, we present an approach for controlling the 2D self-assembly process of organic molecules by adsorption to reactive vs. inert metal surfaces. Therewith, the order of halogen bond strengths that is known from gas phase or liquids can be reversed. Our approach relies on adjusting the molecular charge distribution, i.e., the σ-hole, by molecule-substrate interactions. The polarizability of the halogen and the reactiveness of the metal substrate are serving as control parameters. Our results establish the surface as a control knob for tuning molecular assemblies by reversing the selectivity of bonding sites, which is interesting for future applications.

Methane dry reforming on supported cobalt nanoparticles promoted by boron

Stable operations for catalytic dry reforming of methane (DRM) are essential for industrial applications. High stability for syngas production can be achieved via a kinetic balance between formation of carbon species and their removal by oxygen species on the metal surface, which clears the surface for further reaction steps. This study reports highly stable performance by a boron-doped cobalt catalyst as a non-noble-metal coking-free catalyst. Although the precise location of doped boron could not be identified experimentally because of its low concentration, density functional theory calculations suggested that interstitial boron (B) is most likely present in the subsurface region of cobalt (Co) surfaces. B-doping was shown both experimentally and computationally to increase the reactivity of Co catalysts toward both methane (CH4) and carbon dioxide (CO2). Moreover, B-doping was found to balance the amounts of surface C and O and maintain the reduced state of Co surfaces while in a steady-state. Nevertheless, a negative kinetic order with respect to CO2 partial pressure indicates that steady-state surface coverage of oxygen species originating from CO2 dissociation was prevalent on B-doped Co, consistent with the coking-free nature of the catalyst. This study introduces a promising Co–B catalyst design for controlling metal surface reactivity toward DRM and relevant catalytic reactions.

Directing Chemistry at Electrodes Using Precisely-Defined Electrochemical Interfaces

Molecular-level understanding of chemistry occurring at electrode-electrolyte interfaces (EEIs) during charge transfer processes as a function of electric field strength and concentration gradient is necessary to enable the rational design of more efficient electrochemical technologies for energy storage. The scientific challenge is to unravel convoluted interfacial interactions (i.e., adsorption, coordination, transport) and control the reaction pathways that lead to formation of desired products over unwanted byproducts. Ultimately the objective is to modulate the evolution of the solid-electrolyte interphase (SEI) in batteries for enhanced performance and durability. Soft landing of mass-selected ions, a versatile approach to surface modification, is ideally suited to preparation of well-defined interfaces with predetermined electrochemically active ions. The “atom-by-atom” precision of ion soft landing enables experiments that unravel the complexity associated with the multitude of interfacial processes occurring simultaneously at electrified interfaces. We present evidence for a substantial advancement in understanding such complex interfacial reactions on Mg battery electrodes employing user-defined layer-by-layer assembly of electrochemically active cations and solvated counter-ions with precisely-selected stoichiometry and concentration. As an example, ion soft landing combined with operando infrared reflection-absorption spectroscopy (IRRAS) and in-situ x-ray photoelectron spectroscopy (XPS) was used to characterize the decomposition of counter electrolyte anions and solvent molecules on Mg electrodes. Furthermore, we explored using an aliovalent doped metal (e.g., Al) on the Mg surface to control the decomposition and stabilize the SEI layer formation as a function of both concentration and potential. Our in-situ multimodal analysis enabled the capture of spectroscopic signatures from key chemical transformations of electrolyte anions and solvent molecules on reactive metal surfaces. These experimental results were correlated with the evolution of the SEI layer as predicted by theory to provide molecular-level insight into the reaction mechanism. In summary, our unique approach allowed us to acquire more delineated understanding of electrochemical transformations across length scales in operating EEIs and aids in the rational design of improved sustainable electrochemical energy technologies.

Manos Mavrikakis

ChemCatChemVolume 11, Issue 13 p. 2941-2941 InterviewFree Access Manos Mavrikakis First published: 05 June 2019 https://doi.org/10.1002/cctc.201900802AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Abstract Professor Mavrikakis was interviewed in celebration of his ACS Gabor Somorjai Award 2019. Manos Mavrikakis Professor Mavrikakis was interviewed in celebration of his ACS Gabor Somorjai Award 2019. Position: Paul A. Elfers Professor of Chemical Engineering, University of Wisconsin-Madison (USA) E-mail: emavrikakis@wisc.edu Homepage: http://directory.engr.wisc.edu/che/Faculty/Mavrikakis_Manos/ ORCID: 0000-0002-5293-5356 Education: Diploma, Chemical Engineering; National Technical University of Athens (1988) MS Chemical Engineering; University of Michigan – Ann Arbor (1989) MS Applied Mathematics; University of Michigan – Ann Arbor (1993) PhD Chemical Engineering & Scientific Computing; University of Michigan – Ann Arbor (1994). Advisors: John L. Gland and Johannes W. Schwank. Postdoc – University of Delaware (1996-97). Advisor: Mark A. Barteau. Marie Curie Postdoctoral Fellow – Technical University of Denmark (1997-1999). Advisor: Jens K. Nørskov. Awards: 2019 ACS Gabor A. Somorjai Award for Creative Research in Catalysis; 2014 AIChE R. H. Wilhelm Award in Chemical Reaction Engineering; 2009 Paul H. Emmett Award in Fundamental Catalysis. Hobbies: Science fiction/biographies; hiking Figure 1Open in figure viewerPowerPoint Manos Mavrikakis The thing I like most about my work is the frequency at which new scientific questions pop up in research. Chemistry/science is fun because you can satisfy your personal curiosity about how nature works. Young people should study chemistry because it has a very wide range of applications affecting quality of life. The secrets of being a successful scientist are to be dedicated and committed to your goals. The most important lesson I have learnt is that hard work is essential to success. What is the secret of running a successful group? Lead by example – scientific integrity and hard work ethics are some of the core values a group leader should instill in their group members. Do you have any tips for fruitful collaborations? Define expectations from the very beginning in terms of deliverables and timeline. Respect the needs of all parties when gathering data and take time to think on how to rationalize them. Always engage in healthy scientific discussions, which should be approached with an open mind. It is okay to play devil's advocate with a constructive attitude. What do you consider the most exciting developments in your field? The development of new powerful materials characterization techniques that allow scientists to discover unexpected atomic-scale information about catalysts, under reaction conditions that are closer than ever to real operating conditions. This information enables the construction of more accurate models which, combined with powerful theoretical methods, allows a deeper understanding of how catalysts work. My 3 top papers: 1“Effect of Strain on the Reactivity of Metal Surfaces”: M. Mavrikakis, B. Hammer, J. K. Nørskov, Phys. Rev. Lett. 1998, 81, 2819. (Strain can be found everywhere and can be used to manipulate the reactivity of catalysts). CrossrefWeb of Science®Google Scholar 2“Alloy Catalysts Designed from First Principles”: J. Greeley, M. Mavrikakis, Nat. Mater. 2004, 3, 810. (Importance of adsorbate-induced segregation in bimetallic catalysts). CrossrefCASPubMedWeb of Science®Google Scholar 3“Mechanism of Methanol Synthesis on Copper through CO and CO2 hydrogenation”: L. C. Grabow, M. Mavrikakis, ACS Catal. 2011, 1, 365. (Methanol synthesis over copper catalysts is one of the most important large-scale industrial processes). CrossrefCASWeb of Science®Google Scholar Volume11, Issue13July 4, 2019Pages 2941-2941 This article also appears in:Catalysis Awards FiguresReferencesRelatedInformation

Evaluation of diazonium gold(III) salts in forensic chemistry: Latent fingerprint development on metal surfaces

Evaluation of diazonium salts in forensic chemistry will vastly benefit in the design of novel developers for latent fingerprints on metal surfaces used as crime tools. We used the easily reducible aryldiazonium salt stabilized with tetrachloroaurate anion of the formula [NO2-4-C6H4N≡N]AuCl4. Localized elemental analysis, after 2 h of contact with the aryldiazonium salt, using X-ray fluorescence (XRF) and energy dispersive spectroscopy (EDS) showed the deposition of gold on the fingerprints collected on copper, lead and aluminum. Poor development obtained from the non-gold aryldiazonium salt [NO2-4-C6H4N≡N]BF4, in addition the temporal evolution of the deposition over 24 h showed images of poor contrast and scattered minor deposits. It can be noticed from the images collected using scanning electron microscopy (SEM) and stereomicroscope that the grafted film was not filling the grooves but selectively adhered to the eccrine prints on copper and lead however showed indiscriminate deposition on aluminum surface at high concentrations. Obliteration of developed fingerprints was not observed on all surfaces. The degraded contrast on aluminum after the visible overflow of the trenches is a limitation of diazonium on highly reactive metal surfaces according to the electrochemical series. It can be concluded that copper surface is the most successful among the three metals. The gold film aided to visualize the three levels of primary, secondary and tertiary fingermarks at high level of details. Reduced gold on fingerprints can be beneficial in archiving and future analysis.

Use of a blast coating process to promote adhesion between aluminium surfaces for the automotive industry

ABSTRACTThe influence of surface roughness on adhesive bond strength for aluminium to aluminium bonding is investigated. firstly, the effect of varying surface roughness is investigated using grit-blast surface preparation. this is then compared to a novel ambient temperature blast coating technique known as coblast which, using a co-incident blast stream of abrasive and coating media, simultaneously removes a surface’s native passivation layer while depositing an active epoxy primer coating on the newly-exposed reactive metal surface. a range of al2o3 abrasive media with particle sizes from < 13 m to < 1200 m were used to prepare the varying surface roughness profiles. characterisation techniques such as surface profilometry, sem, edx, x-ray diffraction and light microscopy were used to investigate the level of coating coverage along with the degree of plastic deformation induced in the substrate as a result of the coating procedure. in addition, a modified lap shear test was conducted along with salt fog corrosion testing. results indicate that replacement of the grit-blast treatment with the epoxy coblast coating gives cohesive failure and an increase in lap shear strength of up to 15% before corrosion testing and up to 36% after 240 hours in a salt fog chamber.

In Situ Apparatus to Study Gas–Metal Reactions and Wettability at High Temperatures for Hot-Dip Galvanizing Applications

The understanding of gas–metal reactions and related surface wettability at high temperatures is often limited due to the lack of in situ surface characterization. Ex situ transfers at low temperature between annealing furnace, wettability device, and analytical tools induce noticeable changes of surface composition distinct from the reality of the phenomena.Therefore, a high temperature wettability device was designed in order to allow in situ sample surface characterization by x-rays photoelectron spectroscopy after gas/metal and liquid metal/solid metal surface reactions. Such airless characterization rules out any contamination and oxidation of surfaces and reveals their real composition after heat treatment and chemical reaction. The device consists of two connected reactors, respectively, dedicated to annealing treatments and wettability measurements. Heat treatments are performed in an infrared lamp furnace in a well-controlled atmosphere conditions designed to reproduce gas–metal reactions occurring during the industrial recrystallization annealing of steels. Wetting experiments are carried out in dispensed drop configuration with the precise control of the deposited droplets kinetic energies. The spreading of drops is followed by a high-speed CCD video camera at 500-2000 frames/s in order to reach information at very low contact time. First trials have started to simulate phenomena occurring during recrystallization annealing and hot-dip galvanizing on polished pure Fe and FeAl8 wt.% samples. The results demonstrate real surface chemistry of steel samples after annealing when they are put in contact with liquid zinc alloy bath during hot-dip galvanizing. The wetting results are compared to literature data and coupled with the characterization of interfacial layers by FEG-Auger. It is fair to conclude that the results show the real interest of such in situ experimental setup for interfacial chemistry studies.

Dissociative Adsorption, Dissolution, and Diffusion of Hydrogen in Liquid Metal Membranes. A Phenomenological Model

There is only limited experimental data and theoretical treatment available in the literature on hydrogen sorption and diffusion in liquid metals, in stark contrast with that in solid metals. This paper utilizes our predictive phenomenological model requiring minimal input, the Pauling Bond Valence-Modified Morse Potential (PBV-MMP) model, for estimating the thermodynamic and kinetic parameters of hydrogen solution and diffusion in liquid metals treated as quasi-crystalline. The PBV-MMP model is a refinement of the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) model for estimating the energetics of solid metal surface reactions. The sequential kinetic steps of hydrogen dissociative surface adsorption on the feed side, subsurface penetration, and atomic interstitial diffusion in the bulk, followed by these steps in reverse on the permeate side, are thus treated via the PBV-MMP model within Eyring’s transition-state theory framework, while the entropic changes are evaluated via Eyring’s free vo...

The influence of flow velocity on electrochemical reaction of metal surface

In order to find out the effect of fluid flow velocity on electrochemical reaction, the electrochemical parameters of super 13Cr stainless steel in 3.5% NaCl aqueous solution were measured by a jet flow system at different flow velocities. The electrochemical characters such as open-circuit potential and polarization curve were monitored online using a three-electrode electrochemical system. The results show that the increase of wall shear stress caused by the high flow velocity leads to the rupture of passive films and the exposure of fresh metal in the corrosive media, which causes the increase of corrosion rate. Meanwhile, the corrosion rate shows a significant growth when the flow velocity is less than 0∼10.0 m/s. But it gradually decreases after reaching a maximum value.

Two-step photochemical inorganic approach to the synthesis of Ag-CeO2 nanoheterostructures and their photocatalytic activity on tributyltin degradation

Abstract Herein, we report a simple, sustainable and low-cost approach to design Ag-CeO 2 nanoheterostructures in pure aqueous and ethanol containing aqueous solutions via photochemical UV-light driven process with no capping agents nor stabilizers required. To this end, photochemically synthesized CeO 2 nanoparticles were applied as photoactive compounds in order to generate formation of metallic silver nanoparticles. Irradiation of deaerated CeO 2 suspensions in the presence of Ag + resulted in the rise of a strong surface plasmon resonance band with a maximum at 393–422 nm in the absorption spectra of the solutions, indicating formation of small metallic silver particles. Faster formation of Ag nanoparticles with the lower amount of silver precursor being required was observed when ethanol was introduced to the reaction solution before the irradiation. This implies that oxidative reactions can be strongly suppressed in deaerated ethanol containing solutions with respect to the pure aqueous media. Not only was the overall efficiency of the process remarkably increased by the use of alcohol, but also smaller and more uniform silver nanoparticles with a size comparable to that of ceria nanoparticles (around 15 nm) were formed when compared to those synthesized without radical scavengers as revealed by TEM analysis. The proposed photochemical approach enables the production of silver-semiconductor system without employing organic stabilizers, thus resulting in formation of nanoparticles with “clean”, highly reactive metal surface. The as-synthesized silver-ceria nanoheterostructures demonstrated enhanced visible light driven photocatalytic activity on tributyltin (TBT) degradation if compared to pure ceria nanoparticles.