A green method for synthesizing 1,4-dihydropyridines (1a-j) by a one-pot reaction of various aldehydes, ethyl acetoacetate, and ammonium carbonate, catalyzed by a seashell and kaolin powders, mixed and calcined at 500 and 800 °C, under solvent-free conditions, has been developed. The catalyst was characterized by physicochemical techniques, namely, X-ray diffraction (XRD), electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The mixture composed of 20

Polystyrene (PS)/Gold (Au) is used for a wide range of applications, including composite nanofibers, catalysis, organic memory devices, and biosensing. In this work, PS films were deposited on silicon substrates via a spin coating technique followed by treatment with argon (Ar) plasma admixed with ammonia (NH3), oxygen (O2), or tetrafluoroethane (C2H2F4). X-Ray photoelectron spectroscopy (XPS) analysis revealed modified surface chemistry for Ar/O2, Ar/NH3, or Ar/C2H2F4 plasma treatment through the incorporation of oxygen, nitrogen, or fluorine groups, respectively. Size-controlled magnetron sputter deposition of Au nanoparticles (NP) onto these plasma-treated PS films was investigated via XPS and AFM techniques. The interaction of the Au NPs, as probed from the XPS and AFM measurements, is discussed by referring to changes in surface chemistry and morphology of the PS after plasma treatment. The results demonstrate the effect of surface chemistry on the interaction of Au NPs with polymer support having different surface functionalities. The XPS results show that significant oxygen surface incorporation resulted from oxygen-containing species in the plasma itself. The surface concentration of O increased from 0.4% for the pristine PS to 4.5 at%, 35.4 at%, and 45.6 at% for the Ar/C2H4F4, Ar/NH3, and Ar/O2, respectively. The water contact angle (WCA) values were noticed to decrease from 98° for the untreated PS to 95°, 37°, and 15° for Ar/C2H2F4, Ar/NH3, and Ar/O2 plasma-modified PS samples, respectively. AFM results demonstrate that surface treatment was also accompanied by surface morphology change. Small Au islands are well dispersed and cover the surface, thus forming a homogeneous, isotropic structure. The reported results are important for exploiting Au NPs use in catalysis and sensing applications.

The development of environment-friendly, low-cost and efficient catalyst preparation processes has always been a major issue in the field of catalysis. Wet chemistry methods are often used but these techniques are not sustainable, as post waste solution treatment remains an important drawback. Here an innovative dry low-pressure plasma process for metal nanoparticles supported nanocatalysts preparation is reported. The solid metal and oxide support precursors are physically mixed and then exposed to a radiofrequency Ar/N-2 plasma discharge, leading to the precursor degradation and the subsequent nanoparticles generation, without pre- or post- preparation steps. The metal nanoparticle loading and the particle size of metal and oxide support can be easily tuned by changing the ratio of the precursor materials, making the process simple, versatile, highly efficient, and scalable. As a proof of concept, gold nanoparticles (Au NPs) supported on titanium dioxide (TiO2) were prepared and tested as nanocatalysts for toluene (C7H8) degradation at temperatures ranging from 25 to 450 degrees C. Up to 100% of C7H8 conversion into CO2 was achieved over the Au-TiO2 nanocatalysts, demonstrating that this dry method is a very efficient way to prepare highly active nanocatalysts.

The impact of a titania (TiO2) support film surface on the catalytic activity of gold nanoparticles (Au NP) was investigated. Using the reactive dc-magnetron sputtering technique, TiO2 films with an amorphous, anatase, and nitrogen-doped anatase crystal structure were produced for a subsequent role as a support material for Au NP. Raman spectra of these TiO2 films revealed that both vacuum and NH3 annealing treatments promoted amorphous to anatase phase transformation through the presence of a peak in the 513–519 cm−1 spectral regime. Furthermore, annealing under NH3 flux had an associated blue shift and broadening of the Raman active mode at 1430 cm−1, characteristic of an increase in the oxygen vacancies (VO). For a 3 to 15 s sputter deposition time, the Au NP over TiO2 support films were in the 6.7–17.1 nm size range. From X-ray photoelectron spectroscope (XPS) analysis, the absence of any shift in the Au 4f core level peak implied that there was no change in the electronic properties of Au NP. On the other hand, spontaneous hydroxyl (–OH) group adsorption to anatase TiO2 support was instantly detected, the magnitude of which was found to be enhanced upon increasing the Au NP loading. Nitrogen-doped anatase TiO2 supporting Au NP with ~21.8 nm exhibited a greater extent of molecular oxygen adsorption. The adsorption of both –OH and O2 species is believed to take place at the perimeter sites of the Au NP interfacing with the TiO2 film. XPS analyses and discussions about the tentative roles of O2 and –OH adsorbent species toward Au/TiO2 systems corroborate very well with interpretations of density functional theory simulations.

Five perovskite materials of the general formula La1–xSrxMn1-yZnyO3 (x = 0, 1, 2, 3, and y = 0, 2) were successfully synthesized by the citric acid sol-gel route and characterized by scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunner-Emmet-Teller (BET) technique and X-ray photoelectron spectroscopy (XPS). The materials were employed as heterogeneous catalysts in the Hantzsch reaction, producing 1,4-dihydropyridine derivatives. Incorporating Zn into the parent perovskite LaMnO3 improved the catalytic activity, which was greatly enhanced by the simultaneous introduction of Sr. In addition to the positive effect of Zn and Sr incorporation, the results also showed that the catalytic activity was related to the surface Mn4+ content and acidic character. The La0.9Sr0.1Mn0.8Zn0.2O3 catalyst was recycled and reused four times after demonstrating significant catalytic activity in a polar protic solvent (ethanol). After four cycles of use, the catalyst did not exhibit a significant reduction in catalytic activity, despite the formation of some secondary phases revealed by XRD and XPS analyses. Zn and Sr doubly partial substitution in lanthanum manganite perovskite resulted in a high catalytic activity of the Hantzsch reaction. The results showed that the catalytic activity is related to the creation of oxygen vacancies and the defect associations, in addition to surface acidity and Mn4+ content

In this study, the tuning of the KOH electrolyte composition is proposed as a strategy to drastically limit the capacitance fade of vanadium nitride (VN) electrode. We demonstrate that the use of a V5+ (as VO4 (3-) vanadates anions) containing KOH electrolyte enhances the cycling stability of VN thin film electrode: a loss of 59% of the capacitance is observed for the electrode tested in KOH over 3000 consecutive cycles. After V5+ addition in the electrolyte, the capacitance fade is decreased to 23%. Furthermore, the presence of V5+ species in the solution leads to VN capacitance enhancement from 379 mF cm(-2) for V5+ ions free electrolyte up to 577 mF cm(-2) at 5 mV s(-1) for V5+-containing KOH solution. The enhanced cycling stability is attributed to the stabilization of an oxide/oxynitride layer at the VN surface, instead of its dissolution, thanks to the chemical equilibrium shift of the VN dissolution reaction. This simple and innovative strategy consisting in tuning the electrolyte composition opens new pathways for other systems that suffer from electrode dissolution in the electrolyte while being electrochemically cycled.

In this paper, we report on the electrochemical behavior of zinc (Zn) anode in Zn–MnO2 battery tested in aqueous NH4Cl electrolyte with a concentration ranging from 0.01 to 1 M without any additives. The Zn electrode shows the lowest corrosion behavior for the 0.1 M concentration. Such corrosion decrease was attributed to a shielding effect due to the formation of a corrosion layer expressed by a higher charge transfer resistance (Rct) of 270 Ω. The X-ray diffraction (XRD) analysis shows that it constitutes by ZnO, Zn(OH)2 and Zn(NH3)2Cl2. The Zn was successfully assembled with MnO2 to form a Zn/MnO2 cell using 0.1 M NH4Cl electrolyte. Two types of MnO2 powders were experimented as cathode namely nanostructured MnO2 (NMD) and commercial MnO2 (EMD). It was found that NMD gives the best performance in terms of output voltage and specific energy. Indeed, the Zn/NMD cell has a voltage of 1.743 V which is higher than that of Zn/EMD (1.674 V) at a current of 1 mA. It was found that the cells voltage decreased after 4 h of continuous discharge to 1.712 V and 1.660 V, respectively. Moreover, the Zn/NMD cell can reach a highest specific energy of 228.30 mWh/g. Therefore, our Zn/NMD cell can be used for a high-performance primary battery and take over Zn/MnO2 battery market.

ZnO thin films were synthesized on silicon and glass substrates using the plasma-enhanced chemical vapor deposition (PECVD) technique. Three samples were prepared at substrates temperatures of 200, 300, and 400 °C. The surface chemical composition was analyzed by the use of X-Ray Photoelectron spectroscopy (XPS). Structural and morphological properties were studied by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Optical properties were carried out by UV-visible spectroscopy. XPS spectra showed typical peaks of Zn(2p3/2), Zn(2p1/2), and O(1s) of ZnO with a slight shift attributed to the substrate temperature. XRD analysis revealed hexagonal wurtzite phases with a preferred (002) growth orientation that improved with temperature. Calculation of grain size and dislocation density revealed the crystallization improvement of ZnO when the substrate temperature varied from 200 to 400 °C. SEM images of ZnO films showed textured surfaces composed of grains of spherical shape uniformly distributed. The transmittance yields are reaching 80%, and the values of the band-gap energy indicate that the ZnO films prepared by PECVD present transparent and semiconducting properties.

Pure and Mg-doped manganese oxide thin films were synthesized on heated glass substrates using the spray pyrolysis technique. The surface chemical composition was investigated by the use of X-ray photoelectron spectroscopy (XPS). Structural and morphological properties were studied by using X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscopy (AFM). Optical properties were characterized by UV-visible spectroscopy. XPS spectra showed typical Mn (2p3/2), (2p1/2) and O (1s) peaks of Mn3O4 with a slight shift attributed to the formation of different chemical states of manganese. XRD analysis revealed the tetragonal phase of Mn3O4 with a preferred (211) growth orientation that improved with Mg-doping; likewise, grain size is observed to increase with the Mg doping. SEM images of Mn3O4 films showed rough surfaces composed of uniformly distributed nanograins whose size decreases with the Mg-doping. The manganese oxide films surface observed in AFM show a textured, rough and porous surface. The combination of transmittance and absorption data in the UV-visible range allowed determining the energy values of the Eg band gap (1.5–2.5 eV). The decrease of the band gap with the Mg-doping increase is attributed to the influence of the greater size of the Mg2+ ion in the manganese oxide lattice.

Manganese oxide (MnOx) is a low cost and environment-friendly electrode material for supercapacitors. Although most efforts have been devoted to increase the surface area of this material, the role of surface defects in different MnOx polymorphs towards improvement of its capacitance remains to be thoroughly investigated. In this paper, the results from electrodeposition of mesoporous MnOx thin film electrodes and the effect of rapid thermal annealing (RTA) on their electrochemical storage behavior are presented and discussed. X-ray photoelectron spectroscopy (XPS) analyses showed an increase of the Mn2+/Mn3+ ratio as well as hydroxyl group defects on the surface of the annealed electrodes. The as-deposited MnOx did not manifest any capacitance behavior in 1.0 M Na2SO4 electrolyte solution. However, after RTA treatment, the specific capacitance was tremendously enhanced. An areal capacitance as high as 110 mF cm(-2) at 5 mV s(-1) was recorded in 1.0 M Na2SO4 electrolyte with a capacitance retention of 74% after 5000 charge-discharge cycles. Furthermore, the RTA treatment of electrodes significantly decreased the charge transfer resistance value from 0.678 x 10(6) Omega for the pristine MnOx electrode to 39.13 Omega for the treated one. Based on structural and surface chemistry evolution of the MnO2 films after annealing, the electrochemical storage behavior of annealed MnOx is discussed.

Matthew R. Linford1, Vincent S. Smentkowski2*, John T. Grant3, C. Richard Brundle4, Peter M.A. Sherwood5, Mark C. Biesinger6, Jeff Terry7, Kateryna Artyushkova8, Alberto Herrera-Gómez9, Sven Tougaard10, William Skinner11, Jean-Jacques Pireaux12, Christopher F. McConville13, Christopher D. Easton14, Thomas R. Gengenbach14, George H. Major1, Paul Dietrich15, Andreas Thissen15, Mark Engelhard16, Cedric J. Powell17, Karen J. Gaskell18 and Donald R. Baer16 Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA; General Electric Research, Niskayuna, NY 12309, USA; Surface Analysis Consultant, Clearwater, FL 33767, USA; C.R. Brundle & Associates, Soquel, CA 95073, USA; University of Washington, Box 351700, Seattle, WA 98195, USA; Surface Science Western, University of Western Ontario, London, Ontario N6G 0J3, Canada; Department of Physics, Illinois Institute of Technology, Chicago, IL 60616, USA; Physical Electronics, Chanhassen, MN 55317, USA; CINVESTAV – Unidad Queretaro, Real de Juriquilla 76230, Mexico; Department of Physics, University of Southern Denmark, Odense 5230, Denmark; Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia; University of Namur, Namur Institute of Structured Matter, B-5000 Namur, Belgium; College of Science, RMIT University, Melbourne, VIC 3001, Australia; CSIRO Manufacturing, Ian Wark Laboratories, Clayton, VIC 3168, Australia; SPECS Surface Nano Analysis GmbH, 13355 Berlin, Germany; Pacific Northwest National Laboratory, Richland, WA 99354, USA; National Institute of Standards and Technology, Gaithersburg, MD 20899, USA and University of Maryland, College Park, MD 20742, USA

ZnO is known to be photocatalytic, but with limited performances due to the strong electron-hole recombination after irradiation. The integration of ZnO nanomaterials on a conductive and high surface area carbon substrate is thus a potential alternative to obtain a significant improvement of the photocatalytic performance. Moreover, the carbon functionalization is expected to have a significant role in the adsorption/degradation mechanisms of dye, due to the difference in wettability or surface charge. In this view, ZnO photocatalytic nanoparticles have been deposited on high surface area carbon xerogel substrate (CXG), using a new and original plasma process, consisting in the degradation of a solid organometallic directly on the carbon substrate (no gaseous precursor). In addition to the ZnO nanoparticle formation, the plasma treatment allows the carbon functionalization. The ZnO/CXG composite has been tested for the degradation of Rhodamine B (RhB) in aqueous media and compared with and O-2 or NH3 plasma-treated xerogels (without nanoparticles) to identify the significant role of the substrate and its modification in the RhB adsorption and degradation mechanism. The high photocatalytic activity of ZnO/CXG composite is attributed to (i) the formation of small (810 nm) and well-crystallized ZnO nanoparticles anchored to the carbon substrate and (ii) to the modification of the xerogel surface chemistry. Indeed, O-2 plasma treatment of the CXG promotes the generation of hydroxyl, carbonyl and carboxyl surface functional groups, which are polar and acidic, while the NH3 plasma treatment mainly leads to the formation of polar and basic amino groups. While both plasma treatments promote the formation of polar functional groups, which enhance the CXG wettability, the formation of acidic groups is identified as beneficial for the adsorption of the RhB dye, while basic groups are detrimental. (C) 2020 Elsevier Inc. All rights reserved.

The use of efficient, durable and low-impact processes for the environment is highly desirable to synthesize nanomaterials for various applications. A new approach is presented to synthesize nanoparticles on different powder substrates. The process is based on the plasma degradation of solid organometallic precursors mixed with the powder substrate in order to generate e.g. new catalytic systems. Compared to conventional wet chemistry, plasma processing offers the advantage of reducing the environmental impact of the synthesis by reducing the energy consumption and relying on a solvent-free and waste-free scalable process. The novelty and high versatility of the process is demonstrated in this work. Choosing the right discharge parameters (pressure, reactive gas , plasma power,…), amorphous or crystalline monometallic, bimetallic, oxide or nitride nanoparticles can be produced, onto inorganic (such as TiO2) or carbon-based substrates like graphene, carbon xerogel or carbon nanotubes. Results have been obtained for various nanoparticles, including transition (Mn, Fe, Ni), post transition (Zn, Al), and noble metals (Cu, Pt, Pd, Rh). Moreover, the organometallic precursor(s) decomposition and the subsequent nanoparticles synthesis can be monitored in situ using optical emission spectroscopy of the plasma discharge. Applications in photocatalysis, magnetic materials, or catalysts for fuel cells are demonstrated.

Among the different coatings developed for proton exchange membrane fuel cell steel bipolar plate, nitride-based coatings present several advantages compared to gold or polymeric coating: high chemical stability, low interfacial contact resistance and reasonable cost. In this work, 50 nm thick chromium nitride coatings are deposited by reactive magnetron sputtering on 316L stainless steel foil. They are optimized to fulfill the Department of Energy targets in terms of interfacial contact resistance (ICR) and corrosion resistance, with values of 8.4 m Omega cm(-2) (at 100 N cm(-2)) and 0.10 mu A cm(-2) (in 0.6 M H2SO4 solution at 0.48 V-vs (SCE) potential) respectively. Moreover, they retain their excellent properties after high deformation (biaxial deformation of 20% in x-axis and 5% in y-axis), giving the possibility to achieve, in line, the stamping of a bipolar plate from a coated foil. The etching of the substrate, prior to the coating deposition, appears to be determinant to obtain low and stable corrosion current and ICR. The removing of interfacial oxyde leads to better coating adhesion and improves the corrosion resistance and electrical conductivity. The enhancement of the properties (low ICR and high corrosion resistance) is durable, with no signicant change of the ICR value up to 200 days after deposition. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Multifunctional nanohybrid materials such as gold (Au) nanoparticles attached to the carbon nanostructures can be incorporated into devices for in vivo/in vitro detection of various analytes, catalysis and imaging purposes. In this work, vertically aligned carbon nanosheets (CNS) were grown over silicon substrate, followed by direct current plasma-sputtered deposition of Au for different times. The Au-CNS hybrid nanostructures so produced were characterized for surface and cross-sectional morphologies, phase composition and surface chemistry by means of scanning electron microscope, x-ray diffraction and x-ray photoelectron spectroscope techniques. The Au-CNS exhibit vertically aligned, dendritic wall morphology with different degrees of dispersion on the substrate. The electrochemical (EC) behavior of the different Au-CNS samples was investigated for application as electrochemical transductors. The EC activity was investigated by both cyclic voltammetry and electrochemical impedance spectroscopy in the presence of [Fe(CN)6]3−/4−. The variations in active surface area and roughness of different electrodes were evaluated in order to explore application of such Au-NS in the EC biosensors operating via the direct electron transfer process. The EC results show remarkable properties such as high diffusion coefficient (Do), low peak-to-peak separation value (ΔE) for the oxidation and reduction processes of the [Fe(CN)6]3−/4− redox system and low surface resistivity. Such Au-CNS nanohybrid structures are promising for use in photoelectrochemical cells, sensing devices, catalysis, surface-enhanced Raman spectroscopy and biotechnology applications.

Silicon nanowire (SiNW) arrays were coated with chromium nitride (CrN) for use as supercapacitor electrodes. The CrN layer of different thicknesses was deposited onto SiNWs using bipolar magnetron sputtering method. The areal capacitance of the SiNWs-CrN, as measured in 0.5 M H2SO4 electrolyte, was as high as 180 mFcm(-2) at a scan rate of 5 mVs(-1) (equivalent to 31.8 mF cm(-2) at 1.6 mA cm(-2)) with an excellent electrochemical retention of 92% over 15 000 cycles. This work paves the way toward using CrN modified 3D SiNWs arrays for micro-supercapacitor application.

The enhancement of the surface area and ordering of mesopores is a key parameter to increase the specific capacitance of electrochemical capacitors (ECs). These parameters can improve the electrolyte accessibility to the active material in order to improve its charge storage. In this work, magnetron sputtering at glancing angle (GLAD) is used in order to enhance the porosity of CrN for use as electrode material in ECs. The GLAD technique consists on tilting the substrate according to the deposition flux allowing the formation of well-separated columns due to a ballistic shadowing effect. Four different tilts of 0 degrees, 45 degrees, 60 degrees and 75 degrees were explored. While the CrN films deposited at 0 degrees or 75 degrees do not show any capacitive behaviour, a high areal capacitance is obtained at 45 degrees or 60 degrees (35.4 mF cm(-2) at a current density of 1.2 mA cm(-2) in 0.5 M H2SO4 electrolyte) with a good cycling stability over 10,000 cycles. On chip interdigitated micro-supercapacitors (MSCs) were assembled with a maximum energy density of 2 mu Wh.cm(-2) (15.3 mWh.cm(-3)) at a power density of 20 mu W cm(-2) (0.15 W cm(-3)). The GLAD strategy can be generalised to other materials deposited by physical vapour deposition techniques, for highly porous electrodes, with improved electrochemical energy storage properties. (C) 2019 Elsevier Ltd. All rights reserved.

A strategy to reduce critical raw metals in nanocatalysts is to synthesizenanocomposites based on defective or bimetallic nanoparticles deposition on carbon nanomaterials. Conventional solution-based methods suffer from the extensive use of solvents and difficult scalability. In this study, defective Pt-Ni nanoparticles are formed on graphene nanoplatelets thanks to an original approach based on simultaneous or sequential low-temperature oxygen plasma treatments of nickel and platinum acetylacetonates. The two processing conditions produce aggregated Pt-Ni nanoparticles with variable morphologies, size crystallinities, and oxidation states. The materials analytical characterizations show that the sequential treatment promotes small Pt-Ni particle aggregates nucleation, while the simultaneous treatment leads to complex interconnected Pt-Ni-based phases. Such defective nanoparticles are promising for multiple applications in catalysis and energy. [GRAPHICS] .

The kinetics and mechanism of oxygen reduction reaction (ORR) in alkaline medium are studied on lanthanum nickelate materials La2−x−yNdxPryNiO4±δ (x = 0, 0.3 and 0.5; y = 0 and 0.2) using the electrochemical technique of the rotating disk electrode in a 0.5-M solution of NaOH. The oxide powders are synthesized by the citrate–nitrate method. Structural and surface characterizations are performed by X-ray diffraction (XRD) and X-ray photoelectron spectrometry (XPS), while the morphology is studied by scanning electron microscopy (SEM). Electrochemical studies are carried out by linear voltamperometry, cyclic voltamperometry, and impedance spectroscopy. The doped and undoped electrocatalyst composites (La2−x−yNdxPryNiO4±δ/C), made of the rare earth nickel oxides mixed with carbon black (Vulcan XC-72(C)), are deposited as a thin layer on a glassy carbon substrate. At room temperature, the undoped electrocatalyst La2NiO4±δ material shows single-step kinetics unlike the doped materials. The doping by the rare earths Nd or/and Pr significantly enhances the electrical conductivity of the electrode under air and the diffusion of oxygen. On the other hand, the steric hindrance between the atomic oxygen orbital (π-orbital (O2)–π-orbital (O2)) and the dz2–orbital (Ni)–π-orbital (O2) influences the training model of the liaison (dz2(Ni)–π (O2)). The structure, oxygen adsorption, and oxidation states of the catalyst elements have a large influence on the mechanism and kinetics of the ORR. The LNNO3/C and LNPNO5/C electrocatalysts have better electrocatalytic performances, which allow them to be used as a bifunctional electrocatalyst for the reduction of oxygen in alkaline media.