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MoS2-x films were electrodeposited cathodically onto copper rod substrates from a solution, containing MoS42- as the common Mo and S ion precursor. The catalyst loading was varied by adjusting electrodeposition conditions – applied potential and deposition time. A typical set of HER electrocatalyst experiments (polarization, Tafel slope analysis) carried out in 0.5 M H2SO4 was applied on the deposited MoS2-x films. Analysis of surface morphology (SEM) and chemical composition (EDS) were also performed. Electrochemical impedance spectroscopy in the same acidic media was used to evaluate the catalyst-solution interface and the interfacial kinetics (by calculating double layer capacitance and charge transfer resistance), as well as characterize the hydrogen adsorption process (adsorption capacitance and resistance). A linear correlation between electrodeposition time and double layer capacitance was observed. However, the charge transfer resistance was found to decrease until it plateaued at longer deposition times. The MoS2-x film, deposited for 7200 s at -1.0 V (vs. Ag/AgCl), reached 10 mA cm-2 HER current at -0.18 V (vs. RHE), and represented the best result of this study. Electrochemical impedance spectroscopy (EIS) was further applied to evaluate the subtle changes in the MoS2-x films' semiconductor properties after HER stability tests (at -40 mA cm-2), and to estimate the number of active sites on the material. EIS, in comparison to cyclic voltammetry or roughness factor calculations, is a completely non-destructive method that can be applied to accurately assess the system under investigation. ; This is a post-peer-review, pre-copyedit version of an article published in Electrochimica Acta. The final authenticated version is available online at: https://doi.org/10.1016/j.electacta.2019.06.002. This study has partially received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 778357 and from European Social Fund, project No ...

In this study, galvanostatic electrodeposition techniques were employed for the achieved of new composite polymer: polypyrrole - sodium dioctyl sulfosuccinate/poly N-ethylaniline (PPY-AOT/PNEA) coatings on the Co67Cr29W4 alloy electrode surface. The PPYAOT/PNEA coating has been synthesized on the Co67Cr29W4 alloy electrode by galvanostatic deposition from aqueous solutions 0.1 M NEA, 0.1M PY, 0.01 M AOT and 0.5 M H2SO4 solution at various current densities (1mA/cm2 , 2mA/cm2 and 8mA/cm2 ) in different molar ratio. The sodium dioctyl sulfosuccinate (AOT) as a dopant ion used in electropolymerization process be able to a significant influence on the electrochemical activity of the composite polymer. The polymeric composite coatings were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) techniques. The results denoted that the electroactive behaviors of the composite polymer mainly depend on the molar ratio of monomers, the applied density current and times of electrodeposition. It has been established that the cobalt based alloy substrate had a meaningful influence on the electrochemical activity of the polypyrrole and poly(N-ethylaniline) composite films and that as in the existence of polymeric film, anodization of these modified electrodes obtained in constitution of an oxides complex film and polymeric layers together. All of the composite films were a very promising electrode material for application in supercapacitor, corrosion protection coatings or sensor employments.

Funding Information: This research received funding from the European Union Framework Program for Research and Innovation Horizon 2020 under Grant Agreement No. 721385 (EU MSCA-ETN SOCRATES; project website: https://www.etn-socrates.eu ). The GoldTail (Grant No. 319691, ML) and NoWASTE (Grant No. 297962, KY) projects funded by the Academy of Finland are greatly acknowledged. The authors thank the laboratory personnel at VTT and Metso Outotec for their skillful technical assistance with the experimental work. Publisher Copyright: © 2021, The Author(s). ; Recently, an emerging electrodeposition-redox replacement (EDRR) method was demonstrated to provide exceptionally efficient gold recovery from cyanide-free hydrometallurgical solutions. However, the effect of electrode material and its corrosion resistance in this process was overlooked, even though the EDRR process is carried out in extremely corrosive, acidic chloride solution that also contains significant amounts of strong oxidants, i.e., cupric ions. In the current study, nickel alloy C-2000, stainless steels 316L and 654SMO, and grade 2 titanium were for the first time critically evaluated as potential cathode materials for EDRR. The particular emphasis was placed on better understanding of the effect of cathode substrate on the overall efficiency of the gold recovery process. The use of a multiple attribute decision-making method of material selection allowed reaching of a well-founded compromise between the corrosion properties of the electrodes and process efficiency of gold extraction. The 654SMO steel demonstrated outstanding performance among the examined materials, as it enabled gold recovery of 28.1 pct after 3000 EDRR cycles, while its corrosion rate (CR) was only 0.02 mm/year. ; Peer reviewed

We describe a fast, simple and low temperature electrochemical technique for the preparation of zinc oxide layers on rigid and flexible substrates. The layers, prepared from a zinc nitrate precursor, are of high structural and optical quality. They have been optimized to be applied as efficient electron transport layers in CH3NH3PbI3-sensitized perovskite solar cells (PSCs). We show that an electrodeposition time of only two minutes and a low processing temperature are sufficient to fabricate solar cells with a power conversion efficiency close to 11%, with a high short circuit current and a small J–V curve hysteresis. The key parameters of the cell functioning have been analyzed over a large applied voltage range by the impedance spectroscopy technique. The solar cell characteristic changes with the ZnO layer deposition time are explained by the variation of the recombination and charge transfer resistances. ; J.Z. acknowledges the Guangzhou Government for scholarship (Oversea Study Program of the Guangzhou Elite Project). We thank Dr Odile Majerus for the help in Raman spectroscopy measurements.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) ; Portuguese FCT Funding Agency ; EU ERDF (FEDER) ; Spanish Government ; CAPES: 88881.132671/2016-01 ; CNPq: 141257/2014-8 ; Portuguese FCT Funding Agency: PEst-OE/QUI/UI0100/2013 ; Spanish Government: TEC2014-51940-C2-R ; The electrodeposition of metals generally employs several additives to avoid the formation of undesirable byproducts such as oxides and hydroxides. Although the deposition of metals is still the main goal in the most metals electroplating, the applicability of these byproducts might be an interesting field which is not explored in detail so far. In this work, the significance of water splitting reaction in clean energy production, employing NiFe hydroxides formed during the metals electrodeposition, is demonstrated for oxygen evolution reaction. The synthetized materials are composites of three components easily prepared in one-step by means of electrodeposition. Specifically, a granular NiFe alloy is obtained over which local pH variation and chloride presence induce the formation of a layered double hydroxide structure. The study of the influence of solution composition, deposition time, and deposition potential on the catalytic properties of the composites with respect to the oxygen evolution reaction are analyzed. Deposition times of few seconds, deposition potentials in the range -1.4 to -1.6 V vs. Ag/AgCl/KCl3M, and solutions containing Fe(II), Ni(II) and high chloride concentrations, lead to the best catalysts, showing an eta(10 mA cm 2) about 0.280 V. (C) 2018 Elsevier B.V. All rights reserved.

[EN] An effective n-type doping of ZnO thin films electrochemically synthetized was achieved by varying the chloride ion concentration in the starting electrolyte. The ratio between chloride and zinc cations was varied between 0 and 2 while the zinc concentration in the solution was kept constant. When the concentration of chloride in the bath increases an effective n-type doping of ZnO films takes place. n-type doping is evidenced by the rise of donors concentration, obtained from Mott-Schottky measurements, as well as from the blueshift observed in the optical gap owing to the Burstein-Moss effect. ; This work was supported by Spanish Government through MCINN grant MAT2009-14625-C03-03 and European Commission through NanoCIS project FP7-PEOPLE-2010-IRSES (ref. 269279). ; Cembrero Coca, P.; Mollar García, MA.; Singh, K.; Marí Soucase, B. (2013). Effective electrochemical n-type doping of ZnO thin films for optoelectronic window applications. Journal of Solid State Electrochemistry. 2(7):Q108-Q112. https://doi.org/10.1149/2.023307jss ; S ; Q108 ; Q112 ; 2 ; 7 ; Guill�n-Santiago, A., de la L. Olvera, M., Maldonado, A., Asomoza, R., & Acosta, D. R. (2004). Electrical, structural and morphological properties of chemically sprayed F-doped ZnO films: effect of the ageing-time of the starting solution, solvent and substrate temperature. physica status solidi (a), 201(5), 952-959. doi:10.1002/pssa.200306727 ; Oba, F., Choi, M., Togo, A., & Tanaka, I. (2011). Point defects in ZnO: an approach from first principles. Science and Technology of Advanced Materials, 12(3), 034302. doi:10.1088/1468-6996/12/3/034302 ; Oh, B.-Y., Jeong, M.-C., Lee, W., & Myoung, J.-M. (2005). Properties of transparent conductive ZnO:Al films prepared by co-sputtering. Journal of Crystal Growth, 274(3-4), 453-457. doi:10.1016/j.jcrysgro.2004.10.026 ; Manouni, A. E., Manjón, F. J., Mollar, M., Marí, B., Gómez, R., López, M. C., & Ramos-Barrado, J. R. (2006). Effect of aluminium doping on zinc oxide thin films grown by spray ...

142 153 198 ; S ; Despite the development and synthesis of new electrode materials for hydrogen generation in alkaline water electrolyzers has been a research topic widely exploited in the last years, stability tests on the obtained cathodes have been restricted to long-term potentiostatic/galvanostatic experiments which do not fulfil the real operating conditions that take place in those devices. In this work, two different Service Life Tests have been designed and implemented, aiming at including particular conditions (i.e. inverse polarity and short-circuit) in the durability and catalytic activity of cathode characterization. For this purpose, Ni/Cu bilayered porous electrodes were prepared using different Ni electrodeposition times (15, 30 and 45 min) following a double template electrochemical method. It has been confirmed that the electrode with the lowest Ni content can be considered as a promising electrocatalyst for hydrogen production under industrial conditions because of its optimal activity and stability after the two sets of testing conditions. In particular, electrochemical studies demonstrated that an inversion in polarity can positively affect the electrode performance, as a consequence of the synergetic interaction between CuO/Cu(OH)(2) and beta-Ni(OH)(2) species formed at potentials below the oxygen evolution domain. The authors gratefully acknowledge financial support given by the Generalitat Valenciana (PROMETEO/2010/023) and Spanish Government (Ministerio de Ciencia e Innovation) for the postgraduate grants AP2007-01243 (Carlos Valero-Vidal) and AP2007-03737 (Isaac Herraiz-Cardona). Valero Vidal, C.; Herraiz Cardona, I.; Pérez-Herranz, V.; Igual Muñoz, AN. (2016). Stability of 3D-porous Ni/Cu cathodes under real alkaline electrolyzer operating conditions and its effect on catalytic activity. Applied Catalysis B: Environmental. 198:142-153. doi:10.1016/j.apcatb.2016.05.030

Despite the development and synthesis of new electrode materials for hydrogen generation in alkaline water electrolyzers has been a research topic widely exploited in the last years, stability tests on the obtained cathodes have been restricted to long-term potentiostatic/galvanostatic experiments which do not fulfil the real operating conditions that take place in those devices. In this work, two different Service Life Tests have been designed and implemented, aiming at including particular conditions (i.e. inverse polarity and short-circuit) in the durability and catalytic activity of cathode characterization. For this purpose, Ni/Cu bilayered porous electrodes were prepared using different Ni electrodeposition times (15, 30 and 45 min) following a double template electrochemical method. It has been confirmed that the electrode with the lowest Ni content can be considered as a promising electrocatalyst for hydrogen production under industrial conditions because of its optimal activity and stability after the two sets of testing conditions. In particular, electrochemical studies demonstrated that an inversion in polarity can positively affect the electrode performance, as a consequence of the synergetic interaction between CuO/Cu(OH)(2) and beta-Ni(OH)(2) species formed at potentials below the oxygen evolution domain. ; The authors gratefully acknowledge financial support given by the Generalitat Valenciana (PROMETEO/2010/023) and Spanish Government (Ministerio de Ciencia e Innovation) for the postgraduate grants AP2007-01243 (Carlos Valero-Vidal) and AP2007-03737 (Isaac Herraiz-Cardona). ; Valero Vidal, C.; Herraiz Cardona, I.; Pérez-Herranz, V.; Igual Muñoz, AN. (2016). Stability of 3D-porous Ni/Cu cathodes under real alkaline electrolyzer operating conditions and its effect on catalytic activity. Applied Catalysis B: Environmental. 198:142-153. https://doi.org/10.1016/j.apcatb.2016.05.030 ; S ; 142 ; 153 ; 198

Abstract: A characteristic of obtaining metal powders by direct current electrolysis is changes in the morphology of particles over the loose deposit layer thickness up to the formation of large spherulites. Deposits should be periodically removed from the cathode in order to obtain a powder with homogeneous composition. This paper justifies the choice of the parameter describing the change in loose deposit properties and proposes a method for determining the periodicity of its removal from the cathode. Loose zinc deposits were obtained at 25°C from zincate electrolyte containing 0.3 mol L–1 of ZnO and 4 mol L–1 of NaOH at a current setpoint exceeding six times the limiting diffusion current calculated using the smooth electrode. Electrode potential, deposit thickness and evolved hydrogen volume were measured directly in the process of electrolysis. Current redistribution between the metal reduction and hydrogen evolution leads to a change in the structure of loose deposit particles. It is shown that the differential current efficiency of zinc is the parameter describing the change in the loose zinc deposit density. Its value should not exceed 0.96, in order to ensure deposition of loose deposit with homogeneous properties. A further increase in current efficiency will lead to the formation of aggregates at the deposit growth front. It is proposed to determine the periodicity of loose deposit removal from the cathode using the empirical equation for the time dependency of differential current efficiency of zinc. The mathematical and statistical analysis of the data obtained in six replicates was carried out. The interval approach made it possible to significantly narrow the range of permissible differential current efficiency values and, as a consequence, to determine empirical equation coefficients with acceptable accuracy and calculate the growth time period of a deposit with homogeneous structure. The obtained approach can be used to estimate the time period of loose metal deposition accompanied by hydrogen evolution. © 2020, Allerton Press, Inc. ; This study was supported by the Government of the Russian Federation, regulation no. 211, state assignment no. 0836-2020-003.

This study was conducted in an attempt to understand the effect of a stirred liquid cadmium cathode (LCC) on the electrodeposition of U and U/RE on Cd. For this purpose, a series of electrowinning tests were performed using an LCC equipped with a Cd stirrer. Initially, three runs of the U electrodeposition tests were conducted using LiCl-KCl-UCl3 at 500°C under a constant current. From the results obtained from the initial three runs, it was found that the maximum deposited amount of U was 7.4 wt% U/Cd. U dendrite formation on the LCC crucible was not observed across each of the three runs. Three additional runs were conducted using LiCl-KCl-UCl3-RECl3 to determine the extent of U/RE electrodeposition. The maximum number of moles of U + RE metals deposited was 0.07, a value estimated to be 2.14 times higher than the solubility limits exhibited by these metals in Cd. The results of this study show that the use of a Cd stirrer significantly improves the extent of U deposition.

The chromate conversion treatment is widely used, but it requires highly toxic chromic acid solutions with the consequent effluent disposal and ecological problems. The removal of these toxic chemicals is considered a priority within European Union. The corrosion resistance of three alternative treatments applied on electrogalvanised steel, and immersed in aerated 0.3 M Na2 SO4 solution, pH 10, at 25 °C, was investigated using electrochemical techniques. Their performance was compared with the obtained using the traditional Cr6+-based treatment in the same conditions. The achieved results show that the alternative coatings exhibited discrete protective properties in the sulphate solution. The nitro-cobalt chemical conversion treatment showed similar protective properties than the traditional Cr6+-based treatment, while with the Cr3+-based treatment those were very poor. The phosphate treatment initially performed acceptably but as the time elapsed, its protective properties decreased. ; Facultad de Ingeniería

For corrosion protection of high strength steels electroplated cadmium coatings are still applied in safety relevant applications like in the military and aviation sector because of their excellent characteristics. But cadmium should be replaced due to its toxicity. The most promising alternative are zinc-nickel alloy coatings with 10 - 14% nickel. However, like cadmium deposition also ZnNi plating implicates the risk of hydrogen embrittlement of high strength steel base material. While for cadmium electroplating this problem has been solved since decades, a non-embrittling process for ZnNi electrodeposition has not yet been developed. This was the aim of the present work performed within a publicly funded joint industry project. By in-situ hydrogen permeation measurements the parameters of a commercial ZnNi deposition process were modified to minimize the hydrogen uptake of the high strength steel 300M. By total hydrogen balancing it was determined for the first time, which percentage of the total amount of hydrogen produced was absorbed by the material and how this percentage influences the embrittlement behaviour of the steel. For successful prevention of hydrogen embrittlement it was proved to be fundamental to choose process parameters that yield an appropriate morphology of the ZnNi coating which facilitates the effusion of the absorbed hydrogen during thermal treatment. By measurements of hydrogen effusion the critical hydrogen concentration range was determined. Thus, it was found that ZnNi, Ni and Zn coatings can store significant amounts of diffusible hydrogen which can diffuse into the steel base material at a later time and cause hydrogen embrittlement. In case of bright-Cd coatings a differing behaviour was found indicating a separate failure mechanism. The investigations performed resulted in a non-embrittling galvanic ZnNi deposition process for high strength steels which currently is in the industrialization phase.

Nanostructured NiFe film was obtained on silicon with a thin gold sublayer via pulsed electrodeposition and annealed at a temperature from 100 to 400◦C in order to study the effect of heat treatment on the surface microstructure and mechanical properties. High-resolution atomic force microscopy made it possible to trace stepwise evolving microstructure under the influence of heat treatment. It was found that NiFe film grains undergo coalescence twice—at ~100 and ~300°C—in the process of a gradual increase in grain size. The mechanical properties of the Au/NiFe nanostructured system have been investigated by nanoindentation at two various indentation depths, 10 and 50 nm. The results showed the opposite effect of heat treatment on the mechanical properties in the near-surface layer and in the material volume. Surface homogenization in combination with oxidation activation leads to abnormal strengthening and hardening-up of the near-surface layer. At the same time, a nonlinear decrease in hardness and Young's modulus with increasing temperature of heat treatment characterizes the internal volume of nanostructured NiFe. An explanation of this phenomenon was found in the complex effect of changing the ratio of grain volume/grain boundaries and increasing the concentration of thermally activated diffuse gold atoms from the sublayer to the NiFe film. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. ; Funding: The work was supported by Act 211 Government of the Russian Federation, contract № 02.A03.21.0011.

The chromate conversion treatment is widely used, but it requires highly toxic chromic acid solutions with the consequent effluent disposal and ecological problems. The removal of these toxic chemicals is considered a priority within European Union. The corrosion resistance of three alternative treatments applied on electrogalvanised steel, and immersed in aerated 0.3 M Na2 SO4 solution, pH 10, at 25 °C, was investigated using electrochemical techniques. Their performance was compared with the obtained using the traditional Cr6+-based treatment in the same conditions. The achieved results show that the alternative coatings exhibited discrete protective properties in the sulphate solution. The nitro-cobalt chemical conversion treatment showed similar protective properties than the traditional Cr6+-based treatment, while with the Cr3+-based treatment those were very poor. The phosphate treatment initially performed acceptably but as the time elapsed, its protective properties decreased. ; Fil: Tomachuk, C. R. . National Nuclear Energy Commission; Brasil ; Fil: Elsner, Cecilia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Tecnología de Pinturas (i); Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina ; Fil: Di Sarli, A. R. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Tecnología de Pinturas (i); Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina