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Karel Bouzek - One of the best experts on this subject based on the ideXlab platform.

  • anion selective materials with 1 4 diazabicyclo 2 2 2 octane functional groups for advanced Alkaline Water Electrolysis
    Electrochimica Acta, 2017
    Co-Authors: Jaromír Hnát, Martin Paidar, Michaela Plevova, Jan žitka, Karel Bouzek
    Abstract:

    Abstract In this study a novel Alkaline polymer electrolyte membrane is presented, based on polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (PSEBS) functionalized by the 1,4-diazabicyclo[2.2.2]octane (DABCO) to be used as an electrode compartment separator as well as a catalytic layer binder in the Alkaline Water Electrolysis process with the aim to reduce the concentration of KOH in the liquid electrolyte and to allow the construction of an efficient zero gap-type cell. This material was selected due to the promising properties of both individual components resulting from their molecular structure. The prepared membrane was thoroughly characterized with regard to its stability in an Alkaline environment. The prepared membrane showed an ion-exchange capacity value of 0.76 mmol g −1 dry membrane and ionic conductivity of 7.5 S m −1 at 30 °C. Excellent membrane durability was confirmed for a KOH concentration range up to 10 wt.% and temperature up to 50 °C. Subsequently, the polymer electrolyte was tested in a laboratory Alkaline Water electrolyser using 10 wt.% KOH as a circulating medium showing promising current density of 150 mA cm −2 at 40 °C. In a 150-hour experiment the PSEBS functionalized by DABCO manifested very good stability and high potential for optimization for this process as it showed no signs of chemical degradation.

  • optimization of synthesis of the nickel cobalt oxide based anode electrocatalyst and of the related membrane electrode assembly for Alkaline Water Electrolysis
    Journal of Power Sources, 2017
    Co-Authors: Debabrata Chanda, Jaromír Hnát, Martin Paidar, Tomas Bystron, Karel Bouzek
    Abstract:

    Abstract In this work, the Ni-Co spinel oxides are synthesized via different methods and using different calcination temperatures. Properties of the prepared materials are compared. The best route is selected and used to prepare a Ni1+xCo2−xO4 (−1 ≤ x ≤ 1) series of materials in order to investigate their catalytic activity towards the oxygen evolution reaction (OER). The results show that hydroxide preparation yields NiCo2O4 oxide with the highest activity. 325 °C is identified as the optimum calcination temperature. Subsequently, the catalysts are tested in an Electrolysis cell. To prepare an anode catalyst layer based on NiCo2O4 catalyst on top of a nickel foam substrate for membrane electrode assembly (MEA) construction, following polymer binders are used: anion-selective quaternized polyphenylene oxide (qPPO), inert polytetrafluoroethylene (PTFE®), and cation-selective Nafion®. qPPO ionomer containing MEA exhibited highest OER activity. The current density obtained using a MEA containing qPPO binder attains a value of 135 mA cm−2 at a cell voltage of 1.85 V. After 7 h chronopotentiometric experiment at a constant current density of 225 mA cm−2, the MEA employing PTFE® binder shows higher stability than the other binders in Alkaline Water Electrolysis at 50 °C. Under similar conditions, stability of the PTFE®-binding MEA is examined for 135 h.

  • alkali doped poly 2 5 benzimidazole membrane for Alkaline Water Electrolysis characterization and performance
    Journal of Power Sources, 2016
    Co-Authors: Liliana A Diaz, Jaromír Hnát, Martin Paidar, Karel Bouzek, Nayra Heredia, Mariano M Bruno, Federico A Viva, Horacio R Corti, Graciela C Abuin
    Abstract:

    Abstract The properties and performance of linear and cross-linked KOH doped ABPBI membranes as electrolyte/separator for zero gap Alkaline Water Electrolysis cells are evaluated and compared with a commercial Zirfon® diaphragm. Stability in Alkaline environment, swelling, thermal properties, Water sorption, KOH uptake and conductivity of linear (L-ABPBI) and cross-linked (C-ABPBI) membranes doped with different concentrations of KOH are analyzed. Linear membranes show stability up to 3.0 mol·dm−3 KOH doping, while cross-linked membranes are stable up to 4.2 mol·dm−3 KOH doping. Both kinds of membranes exhibit good thermal stability and reasonable specific ionic conductivity at 22 °C in the range between 7 and 25 mS·cm−1, being slightly higher the conductivity of C-ABPBI membranes than that of L-ABPBI ones. In short-term Electrolysis tests both L-ABPBI and C-ABPBI membranes show better performance than Zirfon diaphragm in the range from 50 to 70 °C. A current density of 335 mA·cm−2 at a cell voltage of 2.0 V is attained with C-ABPBI membranes doped in 3 mol·dm−3 KOH at 70 °C, a performance comparable with that of commercial units operating at temperatures ca. 80 °C and 30 wt% KOH (6.7 mol·dm−3) as electrolyte.

  • the effect of surface modification by reduced graphene oxide on the electrocatalytic activity of nickel towards the hydrogen evolution reaction
    Physical Chemistry Chemical Physics, 2015
    Co-Authors: Debabrata Chanda, Jaromír Hnát, Martin Paidar, Ana S Dobrota, Igor A Pasti, Karel Bouzek
    Abstract:

    To find cheap, efficient and durable hydrogen evolution reaction catalysts is one of the major challenges when developing an Alkaline Water Electrolysis system. In this paper we describe an electrochemically reduced graphene oxide (RGO)-modified Ni electrode, which could be used as a pre-eminent candidate for such a system. The experimentally determined characteristics of this electrode showing superior electrocatalytic activity were complemented by density functional theory calculations. Thermodynamic considerations led to the conclusion that H atoms, formed upon H2O discharge on Ni, spill onto the RGO, which serves as an H adatom acceptor, enabling continuous cleaning of Ni-active sites and an alternative pathway for H2 production. This mode of action is rendered by the unique reactivity of RGO, which arises due to the presence of O surface groups within the graphene structure. The significant electrocatalytic activity and life time (>35 days) of the RGO towards the HER under conditions of Alkaline Water Electrolysis are demonstrated.

  • Synthesis and characterization of NiFe2O4 electrocatalyst for the hydrogen evolution reaction in Alkaline Water Electrolysis using different polymer binders
    Journal of Power Sources, 2015
    Co-Authors: Debabrata Chanda, Jaromír Hnát, Martin Paidar, Jan Schauer, Karel Bouzek
    Abstract:

    Abstract NiFe 2 O 4 electrocatalyst for the hydrogen evolution reaction (HER) has been synthesized using the co-precipitation method of the respective metal ions from Water solution. After calcination of the precipitate, the resulting electrocatalyst was characterized by a broad range of techniques to obtain information on its crystallographic structure, specific surface area, morphology and chemical composition. The electrocatalytic activity towards HER in Alkaline Water Electrolysis was investigated by means of linear sweep voltammetry. The catalyst showed promising electrocatalytic properties. Subsequently three types of binders were used to prepare a cathode catalytic layer based on a catalyst synthesized on top of a nickel foam support, namely an anion-selective quaternized poly(phenylene oxide) (qPPO) ionomer, an electroneutral polymer polytetrafluoroethylene and cation-selective Nafion ® . The resulting membrane-electrode assemblies (MEAs), based on an anion-selective membrane, were tested in an Alkaline Water electrolyzer. In a single-cell test the MEA with a qPPO ionomer exhibited higher HER activity compared to the remaining binders tested. The current density obtained using a MEA containing qPPO binder attained a value of 125 mA cm −2 at a cell voltage of 1.85 V. The stability of the MEA containing qPPO binder was examined by continuous operation for 143 h, followed by 55 h intermittent Electrolysis.

Milica Marceta P Kaninski - One of the best experts on this subject based on the ideXlab platform.

  • characterization of the ni mo catalyst formed in situ during hydrogen generation from Alkaline Water Electrolysis
    International Journal of Hydrogen Energy, 2011
    Co-Authors: Gvozden S Tasic, Aleksandar D Maksic, Sladjana Maslovara, Dragana Zugic, Milica Marceta P Kaninski
    Abstract:

    Abstract Objective of this work was to investigate the electrocatalytic efficiency using quasi-potentiostatic, galvanostatic and impedance spectroscopy techniques of the Ni–Mo catalysts obtained by in situ electrodeposition in an Alkaline, 6 M KOH, electrolyser. In accordance to our previous studies, synergetic effect is observed, with its maximum at industrial conditions (high temperature and current density). The Tafel slopes are around 120 mV and exchange current densities are close to 10−2 mA cm−2 (three orders of magnitude higher compared to the bulk Ni). Moreover, formed deposit possess high stability during prolonged Electrolysis. Results are presented to show the Tafel slopes, the exchange current densities, the apparent energy of activation, the apparent electrochemical surface and the stability of in situ formed Ni–Mo catalyst. Results suggest to significant catalytic performance not only from the increase of the real surface area of electrodes, but also from the true catalytic effect.

  • a study on the co w activated ni electrodes for the hydrogen production from Alkaline Water Electrolysis energy saving
    International Journal of Hydrogen Energy, 2011
    Co-Authors: Milica Marceta P Kaninski, Snezana M Miulovic, Gvozden S Tasic, Aleksandar D Maksic, Vladimir M Nikolic
    Abstract:

    Abstract Hydrogen is considered to be the most promising candidate as a future energy carrier. One of the most used technologies for the electrolytic hydrogen production is Alkaline Water Electrolysis. However, due to high energy requirements of about 4.5–5 kWh/Nm 3 H 2 in most industrial electrolysers, the cost of hydrogen produced in such a way is high. There are various attempts to overcome this problem, like zero-gap cell geometry, development of new diaphragm materials, development of new electrocatalytic materials for electrodes, etc. In continuous search to improve this process using advanced electrocatalytic materials for the hydrogen evolution reaction (HER), based on transition metal series, catalyst based of cobalt and wolfram was investigated as cathode material. On the basis of the results of our experiments, there is a strong indication that the Co–W catalyst reduces energy needs per mass unit of hydrogen produced for more than 20% in some cases. Objective of this work was to investigate the electrocatalytic efficiency using quasi-potentiostatic, galvanostatic and impedance spectroscopy techniques. Results are presented to show the Tafel slopes, the exchange current densities, the apparent energy of activation, the apparent electrochemical surface and the stability of Co–W catalyst. Results suggest to significant catalytic performance not only from the increase of the real surface area of electrodes, but also from the true catalytic effect of the Co–W catalyst.

  • raising efficiency of hydrogen generation from Alkaline Water Electrolysis energy saving
    International Journal of Hydrogen Energy, 2010
    Co-Authors: Vladimir M Nikolic, Snezana M Miulovic, Gvozden S Tasic, Aleksandar D Maksic, Djordje P Saponjic, Milica Marceta P Kaninski
    Abstract:

    Abstract This paper presents an attempt to make the Alkaline electrolytic production of hydrogen more efficient by adding in situ activating compounds in ionic and complex form. Cobalt and tungsten based ionic activators (i.a.), added directly into the electrolyte during the electrolytic process, reduce energy requirements per mass unit of hydrogen produced for about 15%, compared to non-activated system, for a number of current densities in a wide temperature range. Energy saving is higher at higher temperatures and on higher current densities. Structural and morphological characteristic of deposit formed on the cathode during the electrolytic process reveal very interesting and unique pattern with highly developed surface area and uniform distribution of the pores. Obtained deposit also exhibit a long term stability.

Bernd Kieback - One of the best experts on this subject based on the ideXlab platform.

  • ultrashort pulse laser structured titanium surfaces with sputter coated platinum catalyst as hydrogen evolution electrodes for Alkaline Water Electrolysis
    International Journal of Hydrogen Energy, 2018
    Co-Authors: Andreas Gabler, Michael Köhring, Bernd Kieback, Lars Röntzsch, Thomas Gimpel, Thomas Rauscher, Christian Muller, Robert Hahn, Wolfgang Schade
    Abstract:

    Abstract For the first time, we report on micro- and nanostructured Ti surfaces produced by ultrashort-pulse laser processing followed by sputter deposition of Pt aiming at efficient cathode electrodes for Alkaline Water Electrolysis. We studied the laser processing-induced surface morphology, the elemental composition of the surface, the specific surface increase, the wetting behavior as well as the activity of the hydrogen evolution reaction. It is demonstrated that ultrashort-pulse laser structuring in combination with thin layer catalyst deposition can dramatically boost the performance of cathodes for the hydrogen evolution reaction due to the enormous increase in specific surface in combination with superhydrophilic and superwetting properties leading to a rapid gas bubble detachment.

  • Ultrashort pulse laser-structured nickel surfaces as hydrogen evolution electrodes for Alkaline Water Electrolysis
    International Journal of Hydrogen Energy, 2017
    Co-Authors: Andreas Gabler, Christian Immanuel Müller, Michael Köhring, Bernd Kieback, Lars Röntzsch, Thomas Rauscher, Wolfgang Schade
    Abstract:

    Abstract In this study, we report on micro- and nanostructured Ni surfaces produced by an ultrashort pulse laser process as cathode materials for the Alkaline Electrolysis of Water. We studied the influence of the laser-induced microstructure and surface morphology as well as a cyclic voltammetric activation process on the electrochemical activity of the hydrogen evolution reaction. Galvanostatic techniques, steady-state polarization curves to attain Tafel parameters and capacitance calculations via electrochemical impedance spectroscopy were used to analyze the electrodes. The analyses reveal that the ultrashort pulse laser process increases the specific surface on formerly flat Ni surfaces. Further, the cyclic voltammetric activation process gives rise to an increased intrinsic activity. Both effects lead to a strongly reduced overpotential value. This work demonstrates that different processes can be combined to dramatically boost the activity of Ni electrodes for the hydrogen evolution reaction.

  • ni mo b alloys as cathode material for Alkaline Water Electrolysis
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Thomas Rauscher, Bernd Kieback, Andreas U. Schmidt, Christian Muller, Lars Röntzsch
    Abstract:

    Abstract The hydrogen evolution reaction (HER) of nanocrystalline Ni–Mo–B alloys was investigated in Alkaline solution in comparison with the corresponding crystalline materials and polycrystalline nickel. The nanocrystalline alloys, prepared by melt spinning, were investigated towards the HER in 1 M KOH solution at 298 K. An electrochemical activation procedure (cyclic reduction-oxidation pre-treatment) was used to enhance the apparent HER activity. In case of the crystalline Ni–Mo–B master alloys the origin of the activity can mainly be attributed to an increase of the real surface area (roughening) caused by a dissolution of Mo-containing phases. Interestingly, a roughening of nanocrystalline Ni–Mo–B alloys did not occur, probably, because of the very homogenous and fine microstructure of these materials. The higher HER activity of the nanocrystalline Ni–Mo–B alloys is obviously caused by a higher intrinsic activity of the nanocrystalline Ni–Mo–B alloys and a synergistic effect of Mo.

  • electrochemical investigations on amorphous fe base alloys for Alkaline Water Electrolysis
    International Journal of Hydrogen Energy, 2014
    Co-Authors: Christian Muller, Thomas Weisgarber, Bernd Kieback, Andreas U. Schmidt, Thomas Schubert, Thomas Rauscher, Lars Röntzsch
    Abstract:

    Abstract In this work different amorphous melt-spun Fe-alloys (Fe82B18, Fe80Si10B10, Fe60Co20Si10B10) were investigated as cathode materials for the Alkaline Electrolysis of Water. In particular, the influence of cobalt as well as the metalloids boron and silicon on the activity for the hydrogen evolution reaction (HER) was studied in 1 M KOH at 298 K using cyclic voltammetric, galvanostatic and polarization techniques. The electrocatalytic activity was evaluated in the view of the overpotential. It was found that cyclic voltammetric techniques can be used to activate the melt-spun Fe-alloys strongly. Different cyclic voltammetric activation procedures are discussed and the influence of the sweep rate and the potential window on the HER activity was elucidated. The experimental data indicate that the addition of metalloids and, most importantly, of cobalt improves the HER activity of the materials. Thus, the overpotential can be reduced by 200 mV compared to polycrystalline Ni.

Jaromír Hnát - One of the best experts on this subject based on the ideXlab platform.

  • anion selective materials with 1 4 diazabicyclo 2 2 2 octane functional groups for advanced Alkaline Water Electrolysis
    Electrochimica Acta, 2017
    Co-Authors: Jaromír Hnát, Martin Paidar, Michaela Plevova, Jan žitka, Karel Bouzek
    Abstract:

    Abstract In this study a novel Alkaline polymer electrolyte membrane is presented, based on polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (PSEBS) functionalized by the 1,4-diazabicyclo[2.2.2]octane (DABCO) to be used as an electrode compartment separator as well as a catalytic layer binder in the Alkaline Water Electrolysis process with the aim to reduce the concentration of KOH in the liquid electrolyte and to allow the construction of an efficient zero gap-type cell. This material was selected due to the promising properties of both individual components resulting from their molecular structure. The prepared membrane was thoroughly characterized with regard to its stability in an Alkaline environment. The prepared membrane showed an ion-exchange capacity value of 0.76 mmol g −1 dry membrane and ionic conductivity of 7.5 S m −1 at 30 °C. Excellent membrane durability was confirmed for a KOH concentration range up to 10 wt.% and temperature up to 50 °C. Subsequently, the polymer electrolyte was tested in a laboratory Alkaline Water electrolyser using 10 wt.% KOH as a circulating medium showing promising current density of 150 mA cm −2 at 40 °C. In a 150-hour experiment the PSEBS functionalized by DABCO manifested very good stability and high potential for optimization for this process as it showed no signs of chemical degradation.

  • optimization of synthesis of the nickel cobalt oxide based anode electrocatalyst and of the related membrane electrode assembly for Alkaline Water Electrolysis
    Journal of Power Sources, 2017
    Co-Authors: Debabrata Chanda, Jaromír Hnát, Martin Paidar, Tomas Bystron, Karel Bouzek
    Abstract:

    Abstract In this work, the Ni-Co spinel oxides are synthesized via different methods and using different calcination temperatures. Properties of the prepared materials are compared. The best route is selected and used to prepare a Ni1+xCo2−xO4 (−1 ≤ x ≤ 1) series of materials in order to investigate their catalytic activity towards the oxygen evolution reaction (OER). The results show that hydroxide preparation yields NiCo2O4 oxide with the highest activity. 325 °C is identified as the optimum calcination temperature. Subsequently, the catalysts are tested in an Electrolysis cell. To prepare an anode catalyst layer based on NiCo2O4 catalyst on top of a nickel foam substrate for membrane electrode assembly (MEA) construction, following polymer binders are used: anion-selective quaternized polyphenylene oxide (qPPO), inert polytetrafluoroethylene (PTFE®), and cation-selective Nafion®. qPPO ionomer containing MEA exhibited highest OER activity. The current density obtained using a MEA containing qPPO binder attains a value of 135 mA cm−2 at a cell voltage of 1.85 V. After 7 h chronopotentiometric experiment at a constant current density of 225 mA cm−2, the MEA employing PTFE® binder shows higher stability than the other binders in Alkaline Water Electrolysis at 50 °C. Under similar conditions, stability of the PTFE®-binding MEA is examined for 135 h.

  • alkali doped poly 2 5 benzimidazole membrane for Alkaline Water Electrolysis characterization and performance
    Journal of Power Sources, 2016
    Co-Authors: Liliana A Diaz, Jaromír Hnát, Martin Paidar, Karel Bouzek, Nayra Heredia, Mariano M Bruno, Federico A Viva, Horacio R Corti, Graciela C Abuin
    Abstract:

    Abstract The properties and performance of linear and cross-linked KOH doped ABPBI membranes as electrolyte/separator for zero gap Alkaline Water Electrolysis cells are evaluated and compared with a commercial Zirfon® diaphragm. Stability in Alkaline environment, swelling, thermal properties, Water sorption, KOH uptake and conductivity of linear (L-ABPBI) and cross-linked (C-ABPBI) membranes doped with different concentrations of KOH are analyzed. Linear membranes show stability up to 3.0 mol·dm−3 KOH doping, while cross-linked membranes are stable up to 4.2 mol·dm−3 KOH doping. Both kinds of membranes exhibit good thermal stability and reasonable specific ionic conductivity at 22 °C in the range between 7 and 25 mS·cm−1, being slightly higher the conductivity of C-ABPBI membranes than that of L-ABPBI ones. In short-term Electrolysis tests both L-ABPBI and C-ABPBI membranes show better performance than Zirfon diaphragm in the range from 50 to 70 °C. A current density of 335 mA·cm−2 at a cell voltage of 2.0 V is attained with C-ABPBI membranes doped in 3 mol·dm−3 KOH at 70 °C, a performance comparable with that of commercial units operating at temperatures ca. 80 °C and 30 wt% KOH (6.7 mol·dm−3) as electrolyte.

  • the effect of surface modification by reduced graphene oxide on the electrocatalytic activity of nickel towards the hydrogen evolution reaction
    Physical Chemistry Chemical Physics, 2015
    Co-Authors: Debabrata Chanda, Jaromír Hnát, Martin Paidar, Ana S Dobrota, Igor A Pasti, Karel Bouzek
    Abstract:

    To find cheap, efficient and durable hydrogen evolution reaction catalysts is one of the major challenges when developing an Alkaline Water Electrolysis system. In this paper we describe an electrochemically reduced graphene oxide (RGO)-modified Ni electrode, which could be used as a pre-eminent candidate for such a system. The experimentally determined characteristics of this electrode showing superior electrocatalytic activity were complemented by density functional theory calculations. Thermodynamic considerations led to the conclusion that H atoms, formed upon H2O discharge on Ni, spill onto the RGO, which serves as an H adatom acceptor, enabling continuous cleaning of Ni-active sites and an alternative pathway for H2 production. This mode of action is rendered by the unique reactivity of RGO, which arises due to the presence of O surface groups within the graphene structure. The significant electrocatalytic activity and life time (>35 days) of the RGO towards the HER under conditions of Alkaline Water Electrolysis are demonstrated.

  • Synthesis and characterization of NiFe2O4 electrocatalyst for the hydrogen evolution reaction in Alkaline Water Electrolysis using different polymer binders
    Journal of Power Sources, 2015
    Co-Authors: Debabrata Chanda, Jaromír Hnát, Martin Paidar, Jan Schauer, Karel Bouzek
    Abstract:

    Abstract NiFe 2 O 4 electrocatalyst for the hydrogen evolution reaction (HER) has been synthesized using the co-precipitation method of the respective metal ions from Water solution. After calcination of the precipitate, the resulting electrocatalyst was characterized by a broad range of techniques to obtain information on its crystallographic structure, specific surface area, morphology and chemical composition. The electrocatalytic activity towards HER in Alkaline Water Electrolysis was investigated by means of linear sweep voltammetry. The catalyst showed promising electrocatalytic properties. Subsequently three types of binders were used to prepare a cathode catalytic layer based on a catalyst synthesized on top of a nickel foam support, namely an anion-selective quaternized poly(phenylene oxide) (qPPO) ionomer, an electroneutral polymer polytetrafluoroethylene and cation-selective Nafion ® . The resulting membrane-electrode assemblies (MEAs), based on an anion-selective membrane, were tested in an Alkaline Water electrolyzer. In a single-cell test the MEA with a qPPO ionomer exhibited higher HER activity compared to the remaining binders tested. The current density obtained using a MEA containing qPPO binder attained a value of 125 mA cm −2 at a cell voltage of 1.85 V. The stability of the MEA containing qPPO binder was examined by continuous operation for 143 h, followed by 55 h intermittent Electrolysis.

Martin Paidar - One of the best experts on this subject based on the ideXlab platform.

  • anion selective materials with 1 4 diazabicyclo 2 2 2 octane functional groups for advanced Alkaline Water Electrolysis
    Electrochimica Acta, 2017
    Co-Authors: Jaromír Hnát, Martin Paidar, Michaela Plevova, Jan žitka, Karel Bouzek
    Abstract:

    Abstract In this study a novel Alkaline polymer electrolyte membrane is presented, based on polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (PSEBS) functionalized by the 1,4-diazabicyclo[2.2.2]octane (DABCO) to be used as an electrode compartment separator as well as a catalytic layer binder in the Alkaline Water Electrolysis process with the aim to reduce the concentration of KOH in the liquid electrolyte and to allow the construction of an efficient zero gap-type cell. This material was selected due to the promising properties of both individual components resulting from their molecular structure. The prepared membrane was thoroughly characterized with regard to its stability in an Alkaline environment. The prepared membrane showed an ion-exchange capacity value of 0.76 mmol g −1 dry membrane and ionic conductivity of 7.5 S m −1 at 30 °C. Excellent membrane durability was confirmed for a KOH concentration range up to 10 wt.% and temperature up to 50 °C. Subsequently, the polymer electrolyte was tested in a laboratory Alkaline Water electrolyser using 10 wt.% KOH as a circulating medium showing promising current density of 150 mA cm −2 at 40 °C. In a 150-hour experiment the PSEBS functionalized by DABCO manifested very good stability and high potential for optimization for this process as it showed no signs of chemical degradation.

  • optimization of synthesis of the nickel cobalt oxide based anode electrocatalyst and of the related membrane electrode assembly for Alkaline Water Electrolysis
    Journal of Power Sources, 2017
    Co-Authors: Debabrata Chanda, Jaromír Hnát, Martin Paidar, Tomas Bystron, Karel Bouzek
    Abstract:

    Abstract In this work, the Ni-Co spinel oxides are synthesized via different methods and using different calcination temperatures. Properties of the prepared materials are compared. The best route is selected and used to prepare a Ni1+xCo2−xO4 (−1 ≤ x ≤ 1) series of materials in order to investigate their catalytic activity towards the oxygen evolution reaction (OER). The results show that hydroxide preparation yields NiCo2O4 oxide with the highest activity. 325 °C is identified as the optimum calcination temperature. Subsequently, the catalysts are tested in an Electrolysis cell. To prepare an anode catalyst layer based on NiCo2O4 catalyst on top of a nickel foam substrate for membrane electrode assembly (MEA) construction, following polymer binders are used: anion-selective quaternized polyphenylene oxide (qPPO), inert polytetrafluoroethylene (PTFE®), and cation-selective Nafion®. qPPO ionomer containing MEA exhibited highest OER activity. The current density obtained using a MEA containing qPPO binder attains a value of 135 mA cm−2 at a cell voltage of 1.85 V. After 7 h chronopotentiometric experiment at a constant current density of 225 mA cm−2, the MEA employing PTFE® binder shows higher stability than the other binders in Alkaline Water Electrolysis at 50 °C. Under similar conditions, stability of the PTFE®-binding MEA is examined for 135 h.

  • alkali doped poly 2 5 benzimidazole membrane for Alkaline Water Electrolysis characterization and performance
    Journal of Power Sources, 2016
    Co-Authors: Liliana A Diaz, Jaromír Hnát, Martin Paidar, Karel Bouzek, Nayra Heredia, Mariano M Bruno, Federico A Viva, Horacio R Corti, Graciela C Abuin
    Abstract:

    Abstract The properties and performance of linear and cross-linked KOH doped ABPBI membranes as electrolyte/separator for zero gap Alkaline Water Electrolysis cells are evaluated and compared with a commercial Zirfon® diaphragm. Stability in Alkaline environment, swelling, thermal properties, Water sorption, KOH uptake and conductivity of linear (L-ABPBI) and cross-linked (C-ABPBI) membranes doped with different concentrations of KOH are analyzed. Linear membranes show stability up to 3.0 mol·dm−3 KOH doping, while cross-linked membranes are stable up to 4.2 mol·dm−3 KOH doping. Both kinds of membranes exhibit good thermal stability and reasonable specific ionic conductivity at 22 °C in the range between 7 and 25 mS·cm−1, being slightly higher the conductivity of C-ABPBI membranes than that of L-ABPBI ones. In short-term Electrolysis tests both L-ABPBI and C-ABPBI membranes show better performance than Zirfon diaphragm in the range from 50 to 70 °C. A current density of 335 mA·cm−2 at a cell voltage of 2.0 V is attained with C-ABPBI membranes doped in 3 mol·dm−3 KOH at 70 °C, a performance comparable with that of commercial units operating at temperatures ca. 80 °C and 30 wt% KOH (6.7 mol·dm−3) as electrolyte.

  • the effect of surface modification by reduced graphene oxide on the electrocatalytic activity of nickel towards the hydrogen evolution reaction
    Physical Chemistry Chemical Physics, 2015
    Co-Authors: Debabrata Chanda, Jaromír Hnát, Martin Paidar, Ana S Dobrota, Igor A Pasti, Karel Bouzek
    Abstract:

    To find cheap, efficient and durable hydrogen evolution reaction catalysts is one of the major challenges when developing an Alkaline Water Electrolysis system. In this paper we describe an electrochemically reduced graphene oxide (RGO)-modified Ni electrode, which could be used as a pre-eminent candidate for such a system. The experimentally determined characteristics of this electrode showing superior electrocatalytic activity were complemented by density functional theory calculations. Thermodynamic considerations led to the conclusion that H atoms, formed upon H2O discharge on Ni, spill onto the RGO, which serves as an H adatom acceptor, enabling continuous cleaning of Ni-active sites and an alternative pathway for H2 production. This mode of action is rendered by the unique reactivity of RGO, which arises due to the presence of O surface groups within the graphene structure. The significant electrocatalytic activity and life time (>35 days) of the RGO towards the HER under conditions of Alkaline Water Electrolysis are demonstrated.

  • Synthesis and characterization of NiFe2O4 electrocatalyst for the hydrogen evolution reaction in Alkaline Water Electrolysis using different polymer binders
    Journal of Power Sources, 2015
    Co-Authors: Debabrata Chanda, Jaromír Hnát, Martin Paidar, Jan Schauer, Karel Bouzek
    Abstract:

    Abstract NiFe 2 O 4 electrocatalyst for the hydrogen evolution reaction (HER) has been synthesized using the co-precipitation method of the respective metal ions from Water solution. After calcination of the precipitate, the resulting electrocatalyst was characterized by a broad range of techniques to obtain information on its crystallographic structure, specific surface area, morphology and chemical composition. The electrocatalytic activity towards HER in Alkaline Water Electrolysis was investigated by means of linear sweep voltammetry. The catalyst showed promising electrocatalytic properties. Subsequently three types of binders were used to prepare a cathode catalytic layer based on a catalyst synthesized on top of a nickel foam support, namely an anion-selective quaternized poly(phenylene oxide) (qPPO) ionomer, an electroneutral polymer polytetrafluoroethylene and cation-selective Nafion ® . The resulting membrane-electrode assemblies (MEAs), based on an anion-selective membrane, were tested in an Alkaline Water electrolyzer. In a single-cell test the MEA with a qPPO ionomer exhibited higher HER activity compared to the remaining binders tested. The current density obtained using a MEA containing qPPO binder attained a value of 125 mA cm −2 at a cell voltage of 1.85 V. The stability of the MEA containing qPPO binder was examined by continuous operation for 143 h, followed by 55 h intermittent Electrolysis.