bluuebunny/crossref_metadata_2025 huggingface dataset:
Addition of an Eco-Friendly Corrosion Inhibitor in Self-Assembled Monolayers Coatings to Improve Pitting Corrosion Resistance of Stainless Steel
Authors: Rougier Agathe , Melot Jean Marie , Doche Marie-Laure , Touyeras Francis , Roizard Xavier , Lallemand Fabrice , Hihn Jean-Yves
Published: May 2020

In automotive industry and equipment manufacturers, treatment by phosphatation [1] is used both as an adhesion primer before painting and as a lubricant coating [2].This treatment also offers a good protection against corrosion. However, phosphatation is quite harmfull for the environment, producing a lot of waste to be treated. With regards to toxicity, it is composed of concentrated acids, nitrates and nitrites. Eventually, OEM are working to reduce the thickness of this coating which is typically in the range 2-30 µm. The objective of our research is to propose an alternative to steel/phosphate systems by thin organic coating on 304 stainless steel, a low carbon content substrate free of Molybdene available at affordable costs

To fit with the requiered specification while being as attractive as possible, this alternative coating must present a thickness reduced to a few nanometres, be environmentally friendly, non-toxic and easy to use. It must keep the main properties of phosphatation which consist in adhesion or anti-wear. Self-assembled Monolayers (SAMs) [3] coatings were chosen with addition of Aloe Vera as an ecological corrosion inhibitor [4][5]. SAMs are tunable by adjusting either their terminal group or the length of the carbon chain to obtain the desired surface properties and corrosion resistance. Three different terminal groups combined with four carbon chain lengths have been tested to find the molecule providing the best protection against corrosion.

An electrochemical study is carried out to quantify protection against pitting corrosion in a chloride-containing medium. The substrate used being a 304 stainless steel. As pitting corrosion mechanism involves both stable and unstable pits, two types of electrochemical methods are used. Pulsed potentials technic will highlighted unstable pits, while stable pits are analysed by cyclic voltammetry. These measurements are supported by surface analysis (SEM, EDS).

[1] T. W. COSLETT, Treatment of iron or steel for preventing oxidation or rusting, British patent 8667 and US patent 870937, 1906 et 1907

[2] J. BOGI, Phosphate conversion coatings on steel, J Mater Sci (1977) 12, 2235-2240

[3] A. ULMAN, Formation and structure of self-assembled monolayers, Chem. Rev. 1996, 96, 1533-1554

[4] Devarayan, Kesavan, Green Inhibitors for Corrosion of Metals: A Review, Chem Sci Rev Letts, (2012)

[5] M. MEHDIPOUR, Electrochemical noise investigation of Aloe plant extract as green inhibitor on the corrosion of stainless steel in 1M H2SO4, J. Ind. Eng. Chem, (2015), 21, 318-327

Figure 1
(Invited) Magneto-Ionic Control of Heterostructures and Interfaces
Authors: Liu Kai
Published: May 2020

Magneto-ionic approaches for modifying ion distributions in metal/oxide heterostructures offer exciting potentials to control material properties. Our recent studies show that such magneto-ionic effect, even though initiated at metal/oxide interfaces, can extend deep into the rest of the oxide films and drastically tailor their physical properties [1-4].

In antiferromagnetic systems, we have previously demonstrated a controllable positive exchange bias in GdFe/NiCoO [1], and that the oxygen migration can be reversibly driven by an electric field [2]. Recently, we have observed a strong exchange bias in Gd/NiCoO due to the magneto-ionic effect, above the Gd Tc. After electric biasing, up to 35% enhancement of the exchange bias is observed, which can be reset by field-cooling.

In studies of cuprates, we show a simple, scalable approach to tune superconductivity [4]. A thin Gd layer (up to 20 nm) deposited onto epitaxial YBCO films (100nm), is found to leach oxygen from deep within the YBCO and suppress the superconductivity. These effects arise from the combined impact of redox-driven electron doping and modification of the YBCO microstructure.

In ferromagnets chemisorbed with submonolayer oxygen, we have observed strong DMI induced by chemisorption at room temperature. The sign of this DMI and its surprisingly large magnitude are derived by examining the oxygen coverage dependent evolution of domain wall chirality. The large induced DMI has enabled direct writing of magnetic skyrmions.

Our findings demonstrate an effective solid-state ionic approach to control a wide variety of magnetic functionalities, opening up possibilities for electric gating.

This work has been supported by the NSF (DMR-1610060, ECCS-1611424, DMR-1905468, ECCS-1933527) and the nCORE SMART center through SRC/NIST.

[1]. Gilbert, et al, Nat. Commun.,
7, 11050 (2016).

[2]. Gilbert, et al, Nat. Commun.,
7, 12264 (2016).

[3]. Gilbert, et al, Phys. Rev. Mater.
2, 104402 (2018).

[4]. Murray, et al, arXiv: 1911.07275.
Aliovalent Doping Engineered Ti1-XTaxO2 Layer for Ultra-Low Power Resistive Memory Devices
Authors: Barman Arabinda , Kanjilal Aloke
Published: May 2020

Resistive switching (RS) behavior in metal oxides (MO) is governed by the electric field dependent back and forth migration of oxygen vacancies (Vo). Therefore, it is important to regulate the Vos in MO matrix in a systematic manner. Foreign element doping in MO is considered to be beneficial to generate controlled Vo at the vicinity of dopant elements. Based on this, an approach was made to study the RS behavior in Ta-doped TiO2 films on Pt substrates. Prior to thin film deposition, Ti1-xTaxO2 powder was synthesized chemically using Ta and Ti precursor solutions. The Ta-doped TiO2 targets were prepared for pulsed laser deposition of the films on Pt substrates using an laser wavelength of 248 nm. Enhanced RS was observed in 1.11 at. % Ta doped sample with Ron/Roff ratio of ~104 at a voltage as low as 0.25 V. The retention and endurance of the device recorded at 104 s and 105 pulses respectively are exceptionally well. The X-ray diffraction, Secondary Ion Mass Spectroscopy, X-ray absorption spectroscopy and X-ray photoelectron spectroscopy were employed, to investigate the physical and chemical properties of the film and correlated with the improved RS at particular dopant concentration. Further, the dopant concentration dependent stoichiometry was predicted using Energy Dispersive Spectroscopy during Transmission Electron Microscopy study. These observations will be discussed in detail in the light of defect induced RS phenomenon.
Defect Chemistry and Oxygen Ionic Conducting Properties of Gd2O3 at Elevated Temperatures
Authors: Kim Sunho , Tuller Harry L.
Published: May 2020

Gadolinium sesquioxide (Gd2O3), an oxide exhibiting outstanding thermal stability, wide bandgap (>5eV) and relatively high dielectric constant (>14), is attractive as a high-k dielectric for CMOS, particularly when high temperature processing is required. However, in contrast to its conventional application as an electrical insulator, recent research on magneto-ionic devices suggests that Gd2O3 can serve as a solid electrolyte for field driven devices operating near room temperature. [1][2] According to previous research, proton transport in Gd2O3 is relatively swift among the binary oxides. [3] However, the defect chemistry and the oxygen ion conductivity of Gd2O3 have only been researched to a limited extent. In this work, we investigate the defect chemistry and electrical properties of doped and phase controlled Gd2O3 by impedance spectroscopy, as a function of oxygen partial pressure and temperature.

Nominally undoped, as well as intentionally donor and acceptor doped cubic and monoclinic phase polycrystalline specimens of Gd2O3 were prepared. Studies on the two different phases were possible since the monoclinic phase can stabilize below ~1420 K as a metastable phase. Ca2+& Sr2+and Ce4+& Zr4+ were used as acceptor and donor dopants respectively. 2-point impedance measurements were conducted on samples over a wide range of pO2 (10-12
atm – 1 atm) and for 5 isotherms ranging from 695 – 895 ˚C.

By analyzing the measured conductivity in terms of the developed defect model, relevant thermodynamic and kinetic parameters were extracted. In bixbyite (defective fluorite) phase Gd2O3, the formation enthalpy of anion Frenkel pairs was found to be 1.8 eV, lower than those of related fluorite oxides. The monoclinic phase Gd2O3 showed a somewhat higher, but still a rather low anion Frenkel pair formation enthalpy (2.1eV). Surprisingly, the more close-packed monoclinic structured Gd2O3 exhibited higher oxygen ion conductivity than more open cubic structured Gd2O3. The most highly ionic conducting samples of each phase were Ce doped cubic and Sr doped monoclinic Gd2O3, although the donor doped cubic had a significantly lower ionic conductivity and larger migration energy (1.7 eV and 0.8 eV respectively). All the Gd2O3 specimens showed mixed ionic and p-type conduction in synthetic air within the measured temperature range, implying excess oxygen nonstoichiometry.
Fabrication of Fiber Bragg Grating Stretchable Optical Filter By UV Nanorimprint Lithography
Authors: Kim Wonjoong , Lee Heon , Ju Sucheol
Published: May 2020

In this study, we propose a color filter using the characteristics of fiber Bragg grating as a substitute for organic color filter. To make fiber Bragg grating structure, periodic TiO2 grating structure is formed by ultraviolet nanoimprint lithography with a TiO2 nanoparticle dispersion resin. The TiO2 embedded PDMS color filter is completed using transfer printing by sacrificial layer. The reflectance peak is confirmed by a UV-vis-NIR spectrophotometer under strain conditions. When strain is applied, a reflectance peak red shift of color filter occurs. And, the red shift in the FDTD simulation data and actual measured values occur at similar levels, which suggests that the stretchable color filter is feasible.
(Invited) Nanopatterning Functional Metal Oxide Nanostructures By Vapor-Phase Infiltration in Polymer Templates
Authors: Nam Chang-Yong
Published: May 2020

Infiltration synthesis is a process technique derived from atomic layer deposition (ALD), where polymeric templates, such as those lithographically patterned and self-assembled, are infiltrated by vapor-phase inorganic precursors to form novel organic-inorganic hybrids with enhanced materials properties. These hybrids can be further transformed by selectively removing the organic matrix to finally form metal oxide nanostructures with morphology and positional registry as dictated and designed by the starting polymer templates. In this talk, I will highlight a few examples of our recent efforts to generate functional inorganic nanostructures by using infiltration synthesis including, patterning arbitrary metal oxide nanostructures with sub-40 nm linewidth and over 15 aspect ratio, structural characteristics extremely difficult to achieve by conventional microfabrication techniques; fully CMOS compatible, wafer-scale synthesis and integration of in-plane aligned ZnO nanowire array phototransistors; and three-dimensional (3D) ZnO nanomesh structures derived from self-assembled block copolymer (BCP) templates with layer-number-dependent percolative electrical conductance.
Study of Si(100)-SiO2 Interface Trap Time Constant Distributions in Large Area Conventional MOSFETs-Comparison with Submicron Devices
Authors: Bauza Daniel , Guenifi Naima
Published: May 2020

It seems well accepted now that Pb0 centers are the main defects at the Si(100)/SiO2 interface in conventional MOS transistors, even after forming annealing.

Besides, the charge pumping (CP) technique in which a MOSFET is repeatedly switched between inversion and accumulation has been widely used for studying single capture/emission events in deep submicron transistors [1]. In CP, the minority carriers stored into the interface traps in inversion recombine in accumulation with majority carriers from the substrate (n-channel case), providing a CP current which can be studied.

When it was accepted that in submicron MOSFETs the CP current, Icp, was given by Icp = f.q.N, f being the gate signal frequency, q, the electron charge, and N, the number of traps entering Icp, recently, Tsuchiya and co-workers [2,3] studying devices having SiO2 obtained by Rapid Thermal Oxidation, pointed out step heights equal to 2.q among a number of steps from 0 to 2.q. Pb0 centers with their donor-like and acceptor-like states in the lower and upper halves of the silicon bandgap, respectively, were thus measured for the first time in such devices.

As the energy at the interface that can be probed by CP is close to that between these two states, » 0.6 eV, the authors discussed the capability of CP to account for the two components with regard to the gate pulse characteristics.

In the present paper, the traps remaining electrically active at the Si(100)-SiO2 interface in large area conventional MOSFETs after the full technological process including forming gas annealing are studied. This is achieved using techniques developed in recent years that use the variation of the gate signal frequency for different gate voltage swings [4]. Trap time constant distributions are pointed out and studied as function of gate voltage and gate signal frequency. The results are discussed with regard to those reported in [2,3], to the CP models previously proposed and to CP curves simulation [5].

[1] G. Groeseneken et al. , IEEE Trans. Electron Devices 43, 940 (1996).

[2] T. Tsuchiya and Y. Ono, Jap. J. Appl. Phys. 54, 04DC01 (2015).

[3] T. Tsuchiya and P.M. Lenahan, Jap. J. Appl. Phys. 56, 031301 (2017).

[4] Y. Manéglia, F. Rahmoune, and D. Bauza, J. Appl. Phys. 97, 014502 (2004).

[5] D. Bauza, J. Appl. Phys. 94, 3239 2003).
Mid-Wavelength Infrared Responsivity of Colloidal Quantum Dot/Organic Hybrid Photodetectors
Authors: Hafiz Shihab Bin , Al Mahfuz Mohammad Mostafa , Ko Dong-Kyun
Published: May 2020

Colloidal quantum dots have been a spotlight of nanoscience and technology due to their exquisite physical properties that can be harnessed for next generation nanoelectronics and optoelectronics. Particularly, semiconductor quantum dots that are active in the thermal infrared provide a new path for fabricating infrared devices with significantly reduced cost and enable capabilities beyond that offered by conventional semiconductor technologies. In this presentation, we report on recent advances in materials design and device structure for silver selenide mid-infrared quantum dots, building on our recent demonstration of uncooled photoconductive devices. We highlight two key approaches to reduce the high dark current associated with self-doped, intraband quantum dots used in these devices with detailed analyses of the device characteristics.
(Invited) Semiconductor Nanocrystal Optoelectronics of Colloidal Quantum Wells
Authors: Demir Hilmi Volkan
Published: May 2020

Solution-processed semiconductor nanocrystals have been attracting increasingly greater interest in photonics including spectrally pure color conversion and enrichment in quality lighting and display backlighting [1,2]. These nanocrystals span different types and structures of semiconductors in the form of colloidal quantum dots and rods to a more recently developing class of colloidal quantum wells. In this talk, we will introduce the emergent field of nanocrystal optoelectronics using solution-processed quantum dots and wells. In particular, we will present a new concept of all-colloidal lasers developed by incorporating nanocrystal emitters as the optical gain media, intimately integrated into fully colloidal cavities [3]. In the talk, we will then focus on our recent work on the latest rising star of tightly-confined atomically flat nanocrystals, the quasi-2D colloidal quantum wells (CQWs), also popularly nick-named ‘nanoplatelets’. Among various extraordinary features of these CQWs, we will present our most recent discovery that the CQWs uniquely enable record high optical gain coefficients among all colloids [4]. In addition, we will show the controlled stacking and assemblies of these nanoplatelets, which provides us with the ability to tune and master their excitonic properties [5], and present the first accounts of doping them for high-flux solar concentration [6] and precise wavefunction-engineered magnetic properties [7]. Given their current accelerating progress, these solution-processed quantum materials hold great promise to challenge their epitaxial thin-film counterparts in semiconductor optoelectronics in the near future.

[1] H. V. Demir et al., Nano Today 6, 632 (2011).

[2] E. Mutlugün et al., Nano Letters 12, 3986 (2012); T. Özel et al., Nano Letters 13, 3065 (2013); X. Yang et al., ACS Nano 8, 8224 (2014).

[3] B. Güzeltürk et al., Advanced Materials 27, 2741 (2015); and ACS Nano 8, 6599 (2014).

[4] B. Güzeltürk et al., Nano Letters 19, 277 (2019).

[5] O. Erdem et al., Nano Letters 19, 4297 (2019); N. Taghipour et al., ACS Nano 12, 8547 (2018).

[6] M. Sharma et al., Advanced Materials 29, 1700821 (2017); M. Sharma et al., Chemistry of Materials 30, 3265 (2018).

[7] F. Muckel et al., Nano Letters 18, 2047 (2018).

Figure 1
(Invited) Luminescent Organic Solids with Unusual Exciton Multiplicity
Authors: Perepichka Dmitrii , Hamzehpoor Ehsan , Liu Cheng-Hao
Published: May 2020

High quantum yield luminescent organic solids are required for a number of optoelectronic applications, including organic light-emitting diodes (OLEDs) and transistors (OLETs), lasers, etc. The absolute majority of organic materials can only emit efficiently from their singlet excited states. Involving high-multiplicity states (such as triplets) in exciton dynamics has several established and potential benefits; it is required to overcome 25% theoretical efficiency in OLEDs and might enable various magneto-optical devices. We will report our recent findings of (i) purely organic (C, H, N, O only) room temperature phosphors[1] and (ii) stable free radical fluorophores with record-breaking efficiency of triplet and singlet emission, respectively. The lecture will discuss the molecular and supramolecular mechanisms in modulating the emission from high-spin excited states in organic solids.

[1] E. Hamzehpoor, D. F. Perepichka, Crystal Engineering of Room Temperature Phosphorescence in Organic Solids, Angew. Chem. Int. Ed. 2019, DOI: 10.1002/anie.201913393
Development of Modified Silicon Nanoparticles for Energy Storage
Authors: Nurpeissova Arailym , Mukanova Aliya , Bakenov Zhumabay
Published: May 2020

Due to the outstanding electrochemical properties, lithium-ion batteries have become a widely used energy storage technology for diverse types of devices. However, rapid progress in portable electronic devices and electric vehicles requires further essential improvement in the power and energy densities of lithium-ion batteries (LIBs) [1]. Conventional LIBs technology has reached the limit of its gravimetric / volumetric energy densities and power capabilities, reducing its ability to power new electronic devices and / or work as large batteries [2].

Among the promising candidates for anode materials, silicon (Si) has several advantages, including high theoretical capacity (3579 mAh g-1 for Li15Si4 at room temperature), low reaction potential against cathode material, environmental compatibility, low toxicity, and low cost. However, for the practical implementation of Si anodes in LIBs, it is necessary to consider one big critical issue: adaptation of large volume changes. Significant change in volume (4300%) during lithiation / delitration, leads to the volume expansion and grinding of Si particles, which leads to a rapid loss of electrode capacity, as shown in Figure 1a

This work presents the development of a new technology for the preparation of a composite anode material based on spinel Li4Ti5O12 (LTO) and Si with the addition of polyacrylonitrile (PAN) by liquid-phase coating, which demonstrates a synergistic positive effect on the performance of Si anodes (Fig. 1b). The idea lies in the coating the surface of silicon particles with LTO and PAN to suppress the volume expansion and improve the conductivity. The unique structure of LTO with zero deformation during lithiation / delitiation will help to withstand the volume change whereas PAN coating will improve the conductivity of the whole system.

Acknowledgements

This work was supported by the research grant AP05133706 “Innovative high-capacity anodes based on lithium titanate for a next generation of batteries” from the Ministry of Education and Science of the Republic of Kazakhstan and Collaborative Research Program for 2020-2022 "Three-Dimensional All Solid State Rechargeable Batteries".

References

[1] J.M. Tarascon, M. Armand, Issues and challenges facing rechargeable lithium batteries, Nature. 414 (2001) 359–67. https://doi.org/10.1038/35104644.

[2] M.T. McDowell, I. Ryu, S.W. Lee, C. Wang, W.D. Nix, Y. Cui, Studying the kinetics of crystalline silicon nanoparticle lithiation with in situ transmission electron microscopy, Adv. Mater. 24 (2012) 6034–6041. https://doi.org/10.1002/adma.201202744.

Figure 1
(Invited) Bio-Inspired High-Performance and Multi-Functional Surfaces Tailored By Atmospheric Pressure Plasmas
Authors: Polonskyi Oleksandr , Hartig Torge , Uzarski Joshua R , Gordon Michael J
Published: May 2020

This talk will highlight our recent work on the development of atmospheric pressure plasma tools and methods to modify the roughness, surface chemistry, and wettability of dielectric, polymer, and textile surfaces. Dielectric barrier discharges (DBD) at both low (60 Hz) and high frequency (10s kHz, pulsed), along with RF (13.56 MHz) microplasma jets, were used to directly create hydrophobic/philic areas and bio-reactive groups (-COOH, -CFx, -NH2) on surfaces for subsequent immobilization of enzymes and bioactive compounds for sensing, environmental threat detection, and chemical agent destruction. The goal of the work is to provide fundamental understanding of how interfacial properties, namely chemical termination and surface area, roughness geometry and length scale, and incorporation of 2D/3D nanostructures, can impart multi-functionality to different material surfaces. The effect of various plasma operating conditions (e.g., streamer density, frequency, gas atmosphere, power) on wettability contrast, roughness, surface chemistry, and enzyme grafting and viability for different model surfaces will be discussed.
(Invited) Materials Selection for Plasma Catalytic Transformations
Authors: Mehta Prateek , Barboun Patrick , Go David B. , Hicks Jason C. , Schneider William F
Published: May 2020

Nonthermal plasmas are an emerging form of energy input to drive catalytic transformations. Non-thermal plasmas are characterized by a nonequilibrium distribution of energy within the plasma phase, and in principle this nonequilibrium distribution can be harnessed to effect chemical transformations at distinct conditions. The design criteria for catalysts to be coupled to plasmas are different from thermal catalysts. Here we discuss a basic theory of plasma catalysis and its implications for catalytic materials design, along with summarizing experimental results that align with this theory.
Plasma Gas-Phase Electrochemistry to Induce Nanoparticles Exsolution from Non-Stoichiometric Perovskite Oxides
Authors: Khalid Hessan , Haq Atta Ul , Savaniu Cristian , Irvine John T. S. , Mariotti Davide
Published: May 2020

Decoration of metal nanoparticles (NPs) on the surface of perovskite oxides present an innovative way of improving their activity in a vast range of catalytic reactions. Conventional methods used to deposit NPs present limitations and for instance they often result in agglomeration during their operation in the catalytic process. Although exsolution (release of active metal on the surface upon exposure to reducing atmosphere) of catalytically active metal results in non-agglomerated NPs with greater stability, still the procedure is very long (10~30 hours) and energy demanding. Herein, we demonstrate a new dimension in the exsolution of NPs from perovskite oxides by exposing them under plasma, accelerating the exsolution to occur within a few minutes rather than hours. A non-stoichiometric (A-site deficient) perovskite oxides having a composition of La0.43Ca0.37Ti0.94Ni0.06O2.955(LCTN) was synthesized and further treated in a low-pressure plasma. Different plasma parameters (time, power and gas composition) were varied in order to understand the mechanisms involved in this plasma-enhanced exsolution. The exsolved samples were characterized by SEM, XRD, XPS and TEM. It is expected that plasma driven exsolution will open new dimensions in design and anchorage of exsolved NPs and provides solutions for catalysis and electro-catalysis.
(Invited) Leveraging Plasmas for Electrochemical Fuel Production: Synthesizing Novel Low-PGM Oer Catalysts and Enhancing the Rate of Electrochemical Ammonia Production
Authors: Spurgeon Joshua
Published: May 2020

Plasmas have a number of unique properties which researchers may be able to leverage to enhance desired electrocatalyst material properties and steer electrochemical reaction performance. Two examples of the recent application of plasmas for advancements in electrochemical fuel production are presented. In the first, the nonequilibrium reaction environment of an air plasma enabled the synthesis of homogeneous phases of metastable compositions of a mixed W1-xIrxO3-δ alloy. For a low-platinum-group-metal (PGM) composition of only 1% Ir, plasma-synthesized W0.99Ir0.01O3-δ was observed to be an acid-stable oxygen evolution reaction (OER) catalyst of competitive overpotential. Moreover, the plasma-synthesized alloy was observed to have an OER overpotential ~ 570 mV less than that of a thermally oxidized alloy of the same composition. In the second example of a plasma enhancement, a nitrogen plasma was coupled into the cathode of a proton exchange membrane electrolyzer to provide energetically activated N2 species to the electrocatalyst surface and demonstrate a proof-of-concept synergistic enhancement in the rate of ammonia production. At an applied bias of ~3.5 V across the electrolyzer, plasma-assisted operation was observed to produce 47% more ammonia than the combination of plasma-without-bias and bias-without-plasma conditions.
Isolating Organic Half-Reaction Products in Aqueous Solutions Exposed to Nonthermal Plasma
Authors: Oldham Trey , Thimsen Elijah
Published: May 2020

Aqueous media that have been activated by nonthermal plasma operating at atmospheric pressure have attracted interest for biomedical, agricultural, and nanomaterial synthesis applications. Atmospheric pressure plasmas generated with noble gases have been shown to inject free electrons from the gas phase into the aqueous phase, wherein they become solvated. These solvated electrons can create a chemically reducing environment capable of promoting electrochemical reactions. In order to maintain charge neutrality within the solution, the observed reduction half-reaction must be balanced by an oxidation half-reaction occurring elsewhere in the solution. In applications where isolation of the reduction and/or oxidation products is important, such as pharmaceutical synthesis, mass transport between the two half-reactions must be controlled. Isolation of products is relatively straightforward for plasma-assisted electrochemistry, where the half-reactions occur in compartments that are separated by a salt bridge, and each compartment contains either a metal electrode or microplasma. Product separation becomes more complex in the case of electrodeless systems, such as those using plasma jets impinging upon aqueous solutions. Not only are the locations of the half-reactions ill-defined, but they are occurring in the same volume. In this work, the spatial reduction potential profile of solutions containing molecular probes in contact with an atmospheric pressure plasma jet is used to identify the boundary of the two half-reactions. The transport of a molecular probe through the boundary separating the electrodeless cathode from the electrodeless anode was controlled, and the concentration of oxidized and reduced forms of the molecule on either side of the boundary were quantified via a colorimetric assay. The efficacy of the product isolation strategy for electrodeless plasma electrochemical systems will be discussed.
(Invited) Catalyst-Free, Plasma-Driven Electrolytic Synthesis of Ammonia from Nitrogen and Water at Ambient Conditions
Authors: Hawtof Ryan , Ghosh Souvik , Toth Joseph , Guarr Evan , Xu Cheyan , Sankaran R. Mohan , Renner Julie N.
Published: May 2020

A plasma-driven electrolytic process has been developed to produce ammonia from nitrogen and water at ambient conditions. The system features a direct-current, atmospheric-pressure microplasma formed in a flow of nitrogen at the surface of an aqueous, acidic solution. By comparing ammonia yield against experimental controls, including argon gas, and measuring ammonia yield as a function of time, discharge current and solution pH, we show the faradaic efficiency reaches as high as 100%. We also uncover insights into the reaction mechanism by utilizing scavengers, which involves solvated electrons and hydrogen radicals preferentially reacting with nitrogenated species. We anticipate this technology will be promising for distributed ammonia production since it can operate at ambient conditions with only electricity, acidified water, and nitrogen gas as feedstocks.
(Invited) A Thermodynamic Approach to the First Steps of Metal Deposition
Authors: Schuster Rolf
Published: May 2020

The current response of an electrochemical system to a potential pertubation often contains contributions from many parallel processes. A prominent example is Cu underpotential deposition on Au surfaces, where the Cu deposition is accompanied by the coadsorption of anions. Conventional electrochemical methods like cyclic voltammetry mostly obtain information on the total charge and can therefore not a priori discriminate between the involved processes. Electrochemical microcalorimetry may provide additional, independent information, which may help to identify such processes. By measuring the reversibly exchanged heat during an electrochemical reaction, one directly obtains the reaction entropy of the electrochemical process, including all side reactions. Knowledge of the reaction entropy, together with information from conventional electrochemical methods may thus help to disentangle the elementary steps of an electrochemical process. In this contribution we will give examples for:

1. Anion adsorption on metal surfaces with and without metal underpotential deposition. The dependence of the entropy of the adsorption process for anion adsorption on Au(111) surfaces shows a characteristic variation with potential for all studied anions, which points to an interplay between the configurational entropy of the anion layer and structuring of water at the electrode surface. The entropy data will be corroborated by surface plasmon resonance experiments, which obtained information on the reaction volume of the processes.

2. Metal deposition and surface layer formation from metal complexes. The deposition of Ag from Ag-cyanide complexes will be discussed for different CN- Entropy data support the formation of a passivating AgCN layer from [Ag(CN)2]- at low CN- concentrations. The deposition of metallic Ag probably proceeds via direct reduction of [Ag(CN)2]- at all cyanide concentrations.

3. The steps of metal deposition from multi valent ions. The elementary steps of Cu deposition from aqueous Cu2+ solutions are studied by time-resolved heat measurements of the deposition process. The data point to a two-step process where the Cu+ - Cu2+ reaction is an electron transfer process in solution, independent of the ion transfer process to metallic Cu at the electrode.
(Invited) Synergy between Halides and Capping Molecules in the Shape-Selective, Solution-Phase Growth of Metal Nanocrystals: A Theoretical Perspective
Authors: Fichthorn Kristen , Chen Zihao
Published: May 2020

Ag nanocrystals have promising applications in many cutting-edge technologies, which are highly dependent on their shapes. These nanomaterials are typically synthesized using the solution-phase polyol method, which involves AgNO3 salt, capping agent polyvinylpyrrolidone (PVP), and ethylene glycol as the solvent and reducing agent. Chloride and bromide are often added to achieve robust shape control. In the interest of achieving shape-selective syntheses, understanding the mechanistic origins of shape selectivity is important.

Previous theoretical/experimental studies indicate that the preferential binding of PVP to Ag(100) can produce kinetic nanocubes of sufficiently large sizes. Small nanocubes can be synthesized experimentally when chloride is present, while theory predicts that truncated nanocubes are thermodynamically preferred in the presence of chloride and truncated octahedra are thermodynamically preferred without chloride. Here, we use dispersion-corrected density-functional theory to investigate the possibility that there is a synergy in the binding of PVP and chlorine to Ag surfaces, through which nanocubes emerge as the preferred thermodynamic shape.

We study the co-adsorption of PVP dimers and Cl to Ag(100) and Ag(111). We find that the adsorption of Cl influences the binding of PVP in a facet-selective way, such that Cl weakens the binding of PVP to Ag(111) at moderate to high Cl surface coverages, while Cl strengthens the binding of PVP to Ag(100) at low to moderate coverages, before weakening it at high coverages. We construct a contour plot of Ag-PVP-Cl surface energies as a function of the solution-phase Cl and PVP chemical potentials and find the associated Wulff shapes of the Ag nanocrystals. We find that truncated octahedra are thermodynamically preferred at low Clconcentrations / chemical potentials under full protection of PVP and Ag nanocubes are obtained at high Cl concentrations. We also identify a regime at which PVP binds to Ag(100) facets with adsorbed Cl, but is absent from Ag(111) facets. In this regime, kinetic {100}-faceted nanoshapes are likely to be preferred. Time permitting, we will also discuss recent results with bromide. This synergy between PVP and halide indicate a rich ground for kinetic control of Ag nanocrystal structures.
Surfactant Removal from Colloidal Nanocatalysts Used for the the Electrochemical Reduction of CO2
Authors: Hou Yuhui , Hu Huifang , Bort Sami , Broekmann Peter
Published: May 2020

Colloidal nanomaterials have attracted significant interest in the field of high-performance catalyst synthesis. Additives (surfactants) are commonly used in colloid chemistry to control nucleation and growth of the nano-objects from a homogeneous solution. The action of these additives often yields colloidal particles of well-defined size, shape and composition thus being a crucial pre-requisite for systematic studies on structure-reactivity correlations.1-2 However, when left behind on the colloid surface the surfactants might affect its activity or change the selectivity towards certain reaction products by sterically altering reaction sites on the colloid surface. Approaches of surfactant removal shape from the nano-objects which do not change their size and shape are therefore highly desired.

Herein, we report on a systematical investigation on various surfactant removal methods.

Among the surfactant methods studied (including but not restricted to thermal annealing, chemical washing, plasma treatment, and exposure to ozone) photonic curing stands out. Photonic curing is an exposure of matter to intense and short (µs) light pulses. This approach of catalyst activation will exemplarily be demonstrated on the basis of Cu nanowire (Cu-NW) catalysts synthesized by an oleylamine route.3 Whereas the 3D-networks of the as-synthesized Cu-NW catalysts predominantly produce hydrogen as CO2RR product, photonically cured Cu-NWs show a high selectivity towards ethylene formation reaching a Faradaic efficiency of FEC2H4 = 42.4% (JC2H4 = -7.8 mA cm-2, E = -1.1V vs RHE) which can be maintained during prolonged electrolysis of 110 h. The almost quantitative surfactant removal by the photonic curing was confirmed by XPS analysis.

A further beneficial effect of the photonic curing treatment is related to the substantially increased mechanical stabilization of the Cu-NW film on the support electrode induced by a ‘mild’ sintering of Cu-NWs which remains locally confined to their points of contact. A loss of catalyst material or delamination of the catalyst film from the support electrode during massive gas evolution can thus be prevented.

Figure 1. SEM image of Cu-NWs and CO2RR product distribution at -1.1V vs RHE (1 h electrolysis) derived from catalysts treated by various procedures for the removal of the surfactant.

References:

1. Li, J.; Chen, G.; Zhu, Y.; Liang, Z.; Pei, A.; Wu, C.-L.; Wang, H.; Lee, H. R.; Liu, K.; Chu, S.; Cui, Y., Nature Catalysis
2018,
1 (8), 592-600.

2. Gawande, M. B.; Goswami, A.; Felpin, F. X.; Asefa, T.; Huang, X.; Silva, R.; Zou, X.; Zboril, R.; Varma, R. S., Chem Rev
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116 (6), 3722-811

3. Hou Y., Bolat S., Bornet A., Romanyuk Y., Guo H. P. Broekmann ACS Catal. 2019, 9(10), 9518-9529

Figure 1
(Invited) High-Active, Long-Term Stability of Low-Platinum Fuel Cell Electrocatalysts: From in Situ Understanding to Rational Design
Authors: WU Jianbo
Published: May 2020

The Pt based atomic layered core-shell catalysts has been proven to be one of the most promising oxygen reduction (ORR) electrocatalysts with high activity and low usage of Pt.1-5 It is important to directly observe the growing dynamic of Pt atomic layers. On the other hand, corrosion is a major and unavoidable challenge for the degradation of multimetallic core-shell electrocatalysts, which restricts the practical application of this electrocatalysts severely.6-7 Therefore, it is urgent to understand the evolution and mechanism of corrosion of Pt-based core-shell catalysts during the reaction with an aim to the effective utilization of the Pt catalysts. 8

In this presentation, we will report a direct obversation of the formation of core-shell nanostructures involving a hybrid competition with island growth and surface diffusion. Based on this in situ insight, we further demonstrate that the desired atomic layered surface structure can be achieved by adjusting the competition between island deposition and surface diffusion.9 Then, we will show the corrosion behavior of Pd@Pt core-shell electrocatalysts in the etching solution, and indicates that the corrosion behaviors depends on the effects of geometry, surface defect and built-in strain.10-11 Finally, we demonstrate the capability of electrochemistry inside of TEM, showing both the oxidative etching and the re-deposition behaviors during the cyclic oxidation and reduction in CV within TEM.

References:

1. Wu, J.; Yang, H., Platinum-based oxygen reduction electrocatalysts. Acc. Chem. Res.
2013, 46, 1848-1857.

2. Bian, J.; Zhang, H.; Jiang, Y. Y.; Jin, C. H.; Wu, J. B.; Yang, H.; Yang, D. R., Nano Lett. 2015, 15, 7808-7815.

3. Yan, Y. C.; Shan, H.; Li, G.; Xiao, F.; Jiang, Y. Y.; Yan, Y. Y.; Jin, C. H.; Zhang, H.; Wu, J. B.; Yang, D. R., Nano Lett. 2016, 16, 7999-8004.

4. Xiong, Y. L.; Shan, H.; Zhou, Z. N.; Yan, Y. C.; Liu, Y. F.; Tian, H.; Wu, J. B.; Zhang, H.; Yang, D. R., Small, 2017, 13, 1603423.

5. Wang, X.; Choi, S.; Roling, L.; Luo, M.; Ma, C.; Zhang, L.; Chi, M.; Liu, J.; Xie, Z.; Herron, J.; Mavrikakis, M.; Xia, Y. Nat. Commun. 2015, 6, 7594.

6. Lim, B.; Jiang, M.; Camargo, P. H.; Cho, E. C.; Tao, J.; Lu, X.; Zhu, Y.; Xia, Y., Science
2009, 324, 1302-1305.

7. Zhang, L.; Roling, L. T.; Wang, X.; Vara, M.; Chi, M.; Liu, J.; Choi, S.-I.; Park, J.; Herron, J. A.; Xie, Y., Science
2015, 349, 412-416.

8. Wu, J.; Shao, H.; Chen, W; Gu, X.; Tao, P.; Song, C.; Shang, W.; Deng, T, Adv. Mater., 2016, 28, 9686-9712.

9. Wu, J.; Gao, W.; Wen, J.; Miller, D. J.; Lu, P.; Zuo, J. M.; Yang, H., Nano Lett., 2015, 15, 2711–2715.

10. Wu, J.; Gao, W.; Yang, H.; Zuo, J. M., ACS Nano, 2017, 11, 1696-1703.

11. Shan, H.; Gao, W.; Xiong, Y.; Shi, F.; Yan, Y.; Ma, Y.; Shang, W.; Tao, P.; Song, C.; Deng, T.; Zhang, H.; Yang, D. R.; Pan, X. P.; Wu, J., Nat. Commun., 2018, 9, 1011
Inverted Rotating Disk Electrode (iRDE) As Novel Test Bed for Studies on Additive-Assisted Metal Deposition Under Gas-Evolution Conditions
Authors: Moreno-García Pavel , Grozovski Vitali , Gálvez-Vázquez María de Jesús , Kiran Kiran , Mysuru Nisarga , Vesztergom Soma , Broekmann Peter
Published: May 2020

Additive-assisted electrochemical deposition of cobalt for state-of-the-art interconnects is a relevant topic widely investigated by rotating disc electrode (RDE) methods. However, the conclusions drawn from most of the investigations are often incomplete as they fail to quantify the hydrogen evolution component (HER) that inevitably plagues the Co deposition process when the experiments are conducted in aqueous electrolyte. This comprehensive quantitative gas analysis is complicated as it requires hermetic coupling across rotating elements, the hosting cell body and gas analysis techniques, e.g., gas chromatography (GC). Moreover, a fraction of the electrochemically generated gas bubbles typically adheres to the surface of both the RDE working electrode and its embedding shaft preventing it from reaching the solution-gas interface. This partial shielding of electrode’s active sites by bubble retention at the RDE tip undermines the accuracy of the electrochemical measurements and hinders quantitative analysis of the gaseous products collected from the headspace of an electrochemical reactor. Therefore, we present here a novel inverted RDE (iRDE) cell design that helps to overcome these technical limitations. The instrument features important assets: i) it is amenable to the same mathematical treatment as standard (downward facing) RDEs; ii) it is operated air-tight and coupled to on-line GC; and iii) due to its upward facing design, the electrode surface is less prone to blockage by any formed gas bubbles. Particularly we investigate, by means of our iRDE-GC approach, the influence of a model redox active suppressor additive on the electrochemical deposition of cobalt by means of cyclic voltammetry, galvanostatic and potentiostatic electrolysis and online detection of gaseous products by gas chromatography. The electroanalytical results were further supported by SEM and EDX studies. We find that addition of minor amounts (< 100 ppm) of the additive to the standard Co-based VMS solution significantly decreases the rate and efficiency of Co deposition and favours the parasitic hydrogen evolution. Additionally, we are able to identify and quantify reductive decomposition of the additive that comes along with the deposition process. Importantly, our approach improves standard screening studies of plating additives because it succeeds to deconvolute the overall process into its individual components, e.g., Co2+ reduction to elemental Co, HER and additive decomposition.

Figure 1
Highly Stable Zn Metal Anode Enabled By Atomic Layer Deposited Coating for Aqueous Zinc-Ion Batteries
Authors: Liu Jian
Published: May 2020

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted increasing attentions as energy storage technology for large-scale applications, because of low cost, inherent high safety and high capacity (820 mAh g-1 and 5854 Ah L-1). However, the poor rechargeability of Zn anodes limits their development, which is attributed to the dendrite growth, passivation and hydrogen evolution issues in the zinc anode. Herein, an untrathin coating enabled by atomic layer deposition was demonstrated for the protection of metallic Zn anode for aqueous ZIBs. By protecting Zn plate with the ultrathin layer, the Zn surface wettability was improved and the Zn corrosion was inhibited. As a result, the Zn dendrite formation has been effectively suppressed and lifetime has been significantly improved in Zn-Zn symmetric cells. More importantly, we have demonstrated the dendrites were mainly Zn(OH)2 species by the combination of characterization of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscope (HRTEM). With the optimized coating thickness, the surface-coated coated Zn symmetric cells have shown a reduced overpotential (36.5 mV) and a prolonged life span (over 500 h) at 1 mA cm-2. In addition, the surface-coated Zn has been verified in Zn-MnO2 batteries using layered δ-MnO2 as the cathodes and consequently superior electrochemical performance with a high capacity retention of 89.4% after over 1000 cycles at a current density of 1 mA cm-2 (3.33C for MnO2) is demonstrated. It is expected that the novel design of atomic layer deposition protected metal Zn anode will pave a new way to the realization of the high-performance aqueous Zn-ion batteries and as well shed light on the development of other metal anode-based battery systems.
Effect of Ligand-Complex Interactions on the Electrodeposition of Mixed Chromium Metal-Carbide-Oxides from Trivalent Chromium Electrolytes
Authors: Ankora Maxine V. E. , Wijenberg Jacques H.O. J. , Terryn Herman , Mol Johannes M. C.
Published: May 2020

Electrolytic chromium coated steel (ECCS) is packaging steel coated with a thin layer of chromium with an outer layer of chromium oxide. This coating system provides corrosion protection in addition to good adhesion properties due the outer oxide layer. The coating for ECCS is deposited via a hexavalent chromium electrolyte which has been found to be an environmental and health hazard and is therefore subject to restrictions under REACH legislation. A new coating process based on trivalent chromium chemistry has therefore been developed.

According to prior studies, coatings comparable in terms of corrosion resistance to those achieved with the traditional Cr(VI)-based process have been produced with this process [1]–[4]. However, at present there is limited understanding of the mechanism and kinetics of electrodeposition from trivalent chromium based electrolytes. This knowledge is key to optimize the process design for industrial plating lines.

In the present study, we investigate the effect of the chemistry of the Cr(III) complex – as determined by the relative concentration of the formate complexing agent and temperature – on the electrodeposition of mixed chromium metal-carbide-oxide coatings on low carbon steel in a rotating cylinder electrode (RCE) setup.

In this study, low carbon steel samples are electroplated in an aqueous Cr(III) based electrolyte bath with a deposition time of 0.8 s with applied current densities ranging from 20 to 90 A dm-2. The pH of the electrolyte is maintained at 2.6. A rotation speed of 776 RPM is used. SEM and XPS analysis is also performed to determine the effect of the above parameters on the microstructure and composition of the deposits. The amount of Cr deposited is determined using XRF measurements. Relative chromium metal, oxide and carbide contents are determined via XPS analysis. UV-Vis spectra of each of the electrolytes are also measured.

Optical surface analysis shows that of the three regimes distinguishable as a function of current density [2], homogeneous, bright coatings are deposited in regime II (Figure 1). The current range over which acceptable coatings are deposited is significantly wider with higher relative ligand concentrations. Lower applied currents are required with lower bath temperatures. Increasing the chromium ion concentration (at a fixed relative ligand concentration) results in increased Cr metal deposition and an associated decrease in the carbide content of the coating. At higher bath temperatures, carbide formation is favoured. Results also indicate a threshold ligand-to-complex ratio at ~2.0 [HCOO-]/[Cr3+] above which a bright, homogeneous coating is deposited. This threshold corresponds with UV/Vis results which indicate the formation of a new complex species in the electrolyte at that ratio (Figure 2).

Figure 1