Papers

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pccp 2015 Emanuele Moioli, Robin Mutschler, Andreas Züttel
Renewable energy storage by CO2⁠ and H2⁠ conversion to methane and methanol: Assessment for small scale applications
Renewable and Sustainable Energy Reviews (2019), https://doi.org/10.1016/j.rser.2019.03.022
This study analyses the power to methane and the power to methanol processes in the view of their efficiency in energy storage. A systematic investigation of the differences on the two production systems is performed. The energy storage potential of CO2⁠ to methanol and methane is assessed in a progressive way, from the ideal case to the real process. In ideal conditions, where no additional energy is required for the reaction and CO2⁠ is fully converted into products, energy storage is 8% more efficient in methanol than methane. However, the Sabatier reaction can be performed with a lower degree of complexity than the CO2⁠ to methanol reaction. For this rea- son, the methanol production process is analysed in detail. The influence of the process configuration and the energy requirements for the various necessary unit operations is investigated, and a ranking among various the alternatives is obtained. Single stage, recycle and cascade reactors are compared and assessed in terms of en- ergy requirements for the operation and energy storage in the product. For small scale applications, the cascade reactor is the most suitable process technology, because it does not require additional energy and allows high yield to methanol. With the current technology, we demonstrate that a hybrid process, including both the CO2⁠ hydrogenation to methanol and methane, is the most effective method to achieve a high conversion of renewable energy to carbon-based fuels with a significant fraction of liquid product.
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pccp 2015 Jose Bellosta von Colbe, Jose-Ramon Ares, Jussara Barale, Marcello Baricco, Craig Buckley, Giovanni Capurso, Noris Gallandat, David M. Grant, Matylda N. Guzik, Isaac Jacob, Emil H. Jensen, Torben Jensen, Julian Jepsen, Thomas Klassen, Mykhaylol V. Lototskyy, Kandavel Manickam, Amelia Montone, Julian Puszkiel, Sabrina Sartori, Drew A. Sheppard, Alastair Stuart, Gavin Walker, Colin J. Webb, Heena Yang, Volodymyr Yartys, Andreas Züttel, Martin Dornheim
“Application of hydrides in hydrogen storage and compression: Achievements, outlook and perspectives”
International Journal of Hydrogen Energy (2019)

https://doi.org/10.1016/j.ijhydene.2019.01.104
Metal hydrides are known as a potential efficient, low-risk option for high-density hydrogen storage since the late 1970s. In this paper, the present status and the future perspectives of the use of metal hydrides for hydrogen storage are discussed. Since the early 1990s, interstitial metal hydrides are known as base materials for Ni – metal hydride rechargeable batteries. For hydrogen storage, metal hydride systems have been developed in the 2010s [1] for use in emergency or backup power units, i. e. for stationary applications.
With the development and completion of the first submarines of the U212 A series by HDW (now Thyssen Krupp Marine Systems) in 2003 and its export class U214 in 2004, the use of metal hydrides for hydrogen storage in mobile applications has been established, with new application fields coming into focus.
In the last decades, a huge number of new intermetallic and partially covalent hydrogen absorbing compounds has been identified and partly more, partly less extensively characterized.
In addition, based on the thermodynamic properties of metal hydrides, this class of materials gives the opportunity to develop a new hydrogen compression technology. They allow the direct conversion from thermal energy into the compression of hydrogen gas without the need of any moving parts. Such compressors have been developed and are nowadays commercially available for pressures up to 200 bar. Metal hydride based compressors for higher pressures are under development. Moreover, storage systems consisting of the combination of metal hydrides and high-pressure vessels have been proposed as a realistic solution for on-board hydrogen storage on fuel cell vehicles.
In the frame of the “Hydrogen Storage Systems for Mobile and Stationary Applications” Group in the International Energy Agency (IEA) Hydrogen Task 32 “Hydrogen-based energy storage”, different compounds have been and will be scaled-up in the near future and tested in the range of 500 g to several hundred kg for use in hydrogen storage applications.
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pccp 2015 C. Milanese, T.R. Jensen, B.C. Hauback, C. Pistidda, M. Dornheim, H. Yang, L. Lombardo, A. Zuettel, Y. Filinchuk, P. Ngene, P.E. de Jongh, C.E. Buckley, E.M. Dematteis, M. Baricco
Complex hydrides for energy storage
International Journal of Hydrogen Energy (2019)
https://doi.org/10.1016/j.ijhydene.2018.11.208
In the past decades, complex hydrides and complex hydrides-based materials have been thoroughly investigated as materials for energy storage, owing to their very high gravimetric and volumetric hydrogen capacities and interesting cation and hydrogen diffusion properties. Concerning hydrogen storage, the main limitations of this class of materials are the high working temperatures and pressures, the low hydrogen absorption and desorption rates and the poor cyclability. In the past years, research in this field has been focused on understanding the hydrogen release and uptake mechanism of the pristine and catalyzed materials and on the characterization of the thermodynamic aspects, in order to rationally choose the composition and the stoichiometry of the systems in terms of hydrogen active phases and catalysts/destabilizing agents. Moreover, new materials have been discovered and characterized in an attempt to find systems with properties suitable for practical on-board and stationary applications. A significant part of this rich and productive activity has been performed by the research groups led by the Experts of the International Energy Agreement Task 32, often in collaborative research projects. The most recent findings of these joint activities and other noteworthy recent results in the field are reported in this paper.
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pccp 2015 Andrzej Gladysiak, Tu N. Nguyen, Mariana Spodaryk, Jung‐Hoon Lee, Jeffrey B. Neaton, Andreas Züttel, Kyriakos C. Stylianou
Incarceration of Iodine in a Pyrene‐Based Metal–Organic Framework
Chem. Eur. J.  25 (2019), pp. 501 –506
A pyrene‐based metal‐organic framework (MOF) SION‐8 captured iodine (I2) vapor with a capacity of 460 and 250 mg g−1MOF at room temperature and 75 °C, respectively. Single‐crystal X‐ray diffraction analysis and van‐der‐Waals‐corrected density functional theory calculations confirmed the presence of I2 molecules within the pores of SION‐8 and their interaction with the pyrene‐based ligands. The I2–pyrene interactions in the I2‐loaded SION‐8 led to a 104‐fold increase of its electrical conductivity compared to the bare SION‐8. Upon adsorption, ≥95 % of I2 molecules were incarcerated and could not be washed out, signifying the potential of SION‐8 towards the permanent capture of radioactive I2 at room temperature.
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pccp 2015 Emanuele Moioli, Noris Gallandat, Andreas Züttel
Parametric sensitivity in the Sabatier reaction over Ru/Al2O3 – theoretical determination of the minimal requirements for reactor activation
REACTION CHEMISTRY & ENGINEERING 4:1 (2019), pp.100-111
The methanation of carbon dioxide is an option for chemical storage of renewable energy together with greenhouse gas reutilization because it offers a product with a high energy density. The reaction CO2 + 4H(2) CH4 + 2H(2)O is performed on a Ru/Al2O3 catalyst and is strongly exothermal. For this reason, the reactor design must take into account an efficient thermal management system to limit the maximal temperature and guarantee high CO2 conversion. Additionally, the methanation reactor is subject to parameter sensitivity. This phenomenon can generate instability in the operation of a power to gas plant, due to the variability in the hydrogen production rate. Here we present a parametric study of the thermal properties of the reaction and determine the minimal feed temperature for the normal operation of a reactor. The minimal temperature required is determined by several parameters, such as pressure, space velocity and properties of the cooling system. For adiabatic reactors, the required feed temperature is 210 degrees C for a space velocity of 3000 h(-1) and a pressure of 10 bar. The space velocity strongly affects the positioning of the ignition point, causing a large variability of the feed temperature required. At the same time, the optimal working point of the reactor is at the minimal activation temperature. The properties of cooled reactors are elucidated, showing how the interrelationship between cooling and feed temperature makes the management of this class of reactors more challenging. On the base of the modelling results, we propose a reactor configuration that adjusts the thermodynamic limitations and respects the minimal requirements for reaction ignition, allowing a more stable operation and avoiding the functioning at excessive temperature.
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pccp 2015 Mariana Spodaryk, KunZhao, Jie Zhang, Emad Oveisi, Andreas Züttel,
The role of malachite nanorods for the electrochemical reduction of CO2 to C-2 hydrocarbons
ELECTROCHIMICA ACTA 297 (2019), pp.: 55-60
The electrochemical reduction of CO2 to higher hydrocarbons is a very challenging process that has high potential for the storage of large amounts of renewable energy with a high gravimetric and volumetric energy density. The distribution of hydrocarbons from the electrocatalytic reduction of CO2 is primarily determined by the interaction of the cathode material with the CO2 in the electrolyte. While the research on the electrochemical CO2 reduction focuses on the cathode metal and surface structure of the metals, recently evidence was found that the metal itself may not be the active species but rather the product formed from the metal and CO2. In this paper, we report about the synthesis, catalytic activity and selectivity of nanostructured metal carbonate, i.e. malachite, as a highly active catalyst for the electrochemical synthesis of C2 hydrocarbons. These first results obtained on Cu2(OH)2CO3 nanorod-structured “trees” show that carbonate, not the pure metal, is the active catalytic species. This new catalyst favors the production of ethylene (C2H4) and ethane (C2H6) with significantly higher Faradaic efficiency than that of the pure Cu surface.
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pccp 2015 Spodaryk, Mariana; Gasilova, Natalia; Zuttel, Andreas
Hydrogen storage and electrochemical properties of LaNi5-xCux hydride-forming alloys
JOURNAL OF ALLOYS AND COMPOUNDS 775 (2019), pp.175-180
LaNi5-type alloys are commercial materials for the negative electrode in Ni-MH rechargeable batteries. Partial substitution of La by mischmetal (Mm) and of Ni by elements like Co, Al, and Mn significantly improve the cycle stability and high-rate discharge capacity of the electrodes. The partial substitution of Ni by Cu was studied previously for several selected ternary alloys with a special focus on crystal structure change upon substitution and gas phase hydrogen absorption. We present in this paper the results of the study of the electrochemical activation, discharge kinetics, equilibrium charge/discharge, and cycle life of electrodes made from four different LaNi5-xCux (x = 0.1, 0.5, 0.9, 1) alloys in order to provide full insights into utilization of these alloys.
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pccp 2015 Loris Lombardo, Heena Yang, Andreas Züttel
Destabilizing sodium borohydride with an ionic liquid
Materials Today Energy 9 (2018), pp. 391-396
Sodium borohydride (NaBH4) is a complex hydride containing 10.5% of its mass as hydrogen; however, itis too stable to desorb hydrogen at room temperature. An ionic liquid (IL), vinylbenzyl trimethy-lammonium chloride, was applied to modify the charge distribution in BH4and promote the dehydro-genation of NaBH4. The effect of IL concentration as well as particle size on the amount of desorbedhydrogen was investigated. The dehydrogenation reaction of the ILeNaBH4complex was exothermic(negative enthalpy), which is in contrast to the endothermic hydrogen desorption reaction for pureNaBH4(positive enthalpy). The enthalpy of the ILeNaBH4complex for dehydrogenation was lower thanNaBH4due to the interactions of the cation, the IL, and the borohydride. Dehydrogenation of the mixture(mass ratio of NaBH4:IL¼1:2) started below 160C, with a maximum hydrogen desorption capacity of2.1 wt%. The strong amine cation in the IL led to destabilization of the borohydride by polarization, thusresulting in improved dehydrogenation of the complex hydride. The enthalpy of the dehydrogenationreaction was4.8 kJ mol1of hydrogen. The exothermic nature of the reaction was caused by defor-mation of the lattice and destabilization from the IL.
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pccp 2015 Tu N. Nguyen, Stavroula Kampouri, Bardiya Valizadeh, Wen Luo, Daniele Ongari, Ophélie Marie Planes, Andreas Züttel, Berend Smit, and Kyriakos C. Stylianou
Photocatalytic Hydrogen Generation from a Visible-Light-Responsive Metal-Organic Framework System: Stability versus Activity of Molybdenum Sulfide Cocatalysts
ACS Appl. Mater. Interfaces, 2018, 10 (36), pp 30035–30039
We report the use of two earth abundant molybdenum sulfide-based cocatalysts, Mo3S132– clusters and 1T-MoS2 nanoparticles (NPs), in combination with the visible-light active metal–organic framework (MOF) MIL-125-NH2 for the photocatalytic generation of hydrogen (H2) from water splitting. Upon irradiation (λ ≥ 420 nm), the best-performing mixtures of Mo3S132–/MIL-125-NH2 and 1T-MoS2/MIL-125-NH2 exhibit high catalytic activity, producing H2 with evolution rates of 2094 and 1454 μmol h–1 gMOF–1 and apparent quantum yields of 11.0 and 5.8% at 450 nm, respectively, which are among the highest values reported to date for visible-light-driven photocatalysis with MOFs. The high performance of Mo3S132– can be attributed to the good contact between these clusters and the MOF and the large number of catalytically active sites, while the high activity of 1T-MoS2 NPs is due to their high electrical conductivity leading to fast electron transfer processes. Recycling experiments revealed that although the Mo3S132–/MIL-125-NH2 slowly loses its activity, the 1T-MoS2/MIL-125-NH2 retains its activity for at least 72 h. This work indicates that earth-abundant compounds can be stable and highly catalytically active for photocatalytic water splitting, and should be considered as promising cocatalysts with new MOFs besides the traditional noble metal NPs.
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pccp 2015 Stavroula Kampouri, Tu N. Nguyen, Mariana Spodaryk, Robert G. Palgrave, Andreas Züttel, Berend Smit, and Kyriakos C. Stylianou
Concurrent Photocatalytic Hydrogen Generation and Dye Degradation Using MIL-125-NH2 under Visible Light Irradiation
Adv. Funct. Mater.28 (2018), 1806368
The impact of different transition metal-based co-catalysts toward photocatalytic water reduction when they are physically mixed with visible-light active MIL-125-NH2 is first systematically studied. All co-catalyst/MIL-125-NH2 photocatalytic systems are found to be highly stable after photocatalysis, with the NiO/MIL-125-NH2 and Ni2P/MIL-125-NH2 systems exhibiting high hydrogen (H2) evolution rates of 1084 and 1230 μmol h−1 g−1, respectively. Second, how different electron donors affect the stability and H2 generation rate of the best Ni2P/MIL-125-NH2 system is investigated and it is found that triethylamine fulfils both requirements. Then, the electron donor is replaced with rhodamine B (RhB), a dye that is commonly used as a simulant organic pollutant, with the aim of integrating the photocatalytic H2 generation with the degradation of RhB in a single process. This is of supreme importance as replacing the costly (and toxic) electron donors with hazardous molecules present in wastewater makes it possible to oxidize organic pollutants and produce H2 simultaneously. This is the first study where a metal–organic framework (MOF) system is used for this dual-photocatalytic activity under visible light illumination and the proof-of-concept approach envisions a sustainable waste-water remediation process driven by the abundant solar energy, while H2 is produced, captured, and further utilized.
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pccp 2015 Shiqi Huang, Mostapha Dakhchoune, Wen Luo, Emad Oveisi, Guangwei He, Mojtaba Rezaei, Jing Zhao, Duncan T.L. Alexander, Andreas Züttel, Michael S. Strano & Kumar Varoon Agrawal
Single-layer graphene membranes by crack-free transfer for gas mixture separation
NATURE Communications 9 (2018), pp. 2632
The single-layer graphene film, when incorporated with molecular-sized pores, is predicted to be the ultimate membrane. However, the major bottlenecks have been the crack-free transfer of large-area graphene on a porous support, and the incorporation of molecular-sized nanopores. Herein, we report a nanoporous-carbon-assisted transfer technique, yielding a relatively large area (1mm2), crack-free, suspended graphene film. Gas-sieving (H2/CH4 selectivity up to 25) is observed from the intrinsic defects generated during the chemical- vapor deposition of graphene. Despite the ultralow porosity of 0.025%, an attractive H2 permeance (up to 4.1×10−7molm−2s−1Pa−1) is observed. Finally, we report ozone functionalization-based etching and pore-modification chemistry to etch hydrogen-selective pores, and to shrink the pore-size, improving H2 permeance (up to 300%) and H2/CH4 selectivity (up to 150%). Overall, the scalable transfer, etching, and functionalization meth- ods developed herein are expected to bring nanoporous graphene membranes a step closer to reality.
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pccp 2015 Yang, Heena; Lombardo, Loris; Luo, Wen; Kim, Whajung; Zuttel, Andreas
Hydrogen storage properties of various carbon supported NaBH4 prepared via metathesis
Int. J. of Hydrogen Energy 43:14 (2018), pp. 7108 – 7116
Sodium borohydride nanoparticles prepared via the metathesis reaction between LiBH4 and NaCl were successfully deposited on various carbon supporting materials such as graphite, graphene oxide and carbon nanotubes. The X-ray diffraction analyses were conducted to identify the phase of NaBH4 deposited on various carbon supporting materials. The transmittance electron micrograph analyses were also conducted to investigate the particle size and dispersion of NaBH4 within carbon supporting materials. The particle size and size distribution of NaBH4 on graphite were observed to be larger and broader than of other two supporting materials, graphene oxide and CNT due to the lower surface energy as compared to GO and CNT. The bonding state of NaBH4 was confirmed by the Fourier-transformed infrared spectroscopy analysis. The TG and PCT results show that the hydrogen desorption of the NaBH4 deposited on carbon supports takes place at temperature (130 °C∼) significantly lower than that of pure NaBH4 (above 500 °C) and the amount of desorption was in the order of graphene oxide (12.3 mass %) > CNT (9.8 mass %) > graphite (5.7 mass %). The reversibility of hydrogen adsorption after five cycles of adsorption-desorption showed that NaBH4/GO and NaBH4/CNT were much better than that of pure NaBH4 due to excellent structural stability.
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pccp 2015 Mutschler, Robin; Moioli, Emanuele; Luo, Wen; Gallandat, Noris; Zuettel, Andreas
CO2 hydrogenation reaction over pristine Fe, Co, Ni, Cu and Al2O3 supported Ru-comparison and activation energy determination
JOURNAL OF CATALYSIS 366 (2018), pp.139 – 149
Fe, Co, Ni and Cu are the main non-noble industrially significant catalysts in the CO2 and CO gas phase hydrogenation reaction towards hydrocarbons and alcohols. These catalysts are typically supported on metal oxides such as SiO2, TiO2, Al2O3 and ZnO, in order to maximize the activity towards the desired reaction. The role of the supporting material is to stabilize the catalytic nanoparticles and to prevent sintering at the elevated reaction temperatures and pressures. The supporting phase can improve the reaction activity or even have a crucial role in the reaction, as is the case, e.g. for the Methanol synthesis over Cu based catalysts supported on ZnO. Studying the metals without a supporting oxide phase is of great importance for the fundamental understanding of the catalytic activity of the metal phase. Therefore, we investigated the pristine transition metals Fe, Co, Ni and Cu (diluted with silica glass beads to avoid sintering) towards their activity in the CO2 hydrogenation reaction and determined the activation energy. An Al2O3 supported Ruthenium catalyst with 0.5 mass percent of Ru loading was taken as reference system. It was found that Co, Ni and Ru/Al2O3 are mostly active in the Sabatier reaction, while Fe is active in the reverse water gas shift reaction. Cu as pristine metal shows no catalytic activity. C2+ hydrocarbons were formed on Co in low concentrations. For the calculation of the activation energy, the kinetically determined temperature range of the reaction is identified with a high resolution in time by means of a quantitative gas analysis method with an online mass spectrometer. The observation activation energy of the CO2 hydrogenation reaction was determined to be 50 kJ/mol over Fe, 77 kJ/mol over Co, 74 kJ/mol over Ni and 73 kJ/mol over the Ru/Al2O3 catalyst. This indicates similar reaction pathways over Co, Ni and Ru/Al2O3 and a different reaction mechanism on Fe.
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pccp 2015 Mutschler, Robin; Luo, Wen; Moioli, Emanuele; Zuttel, Andreas
Fast real time and quantitative gas analysis method for the investigation of the CO2 reduction reaction mechanism
REVIEW OF SCIENTIFIC INSTRUMENTS 89 (2018), 114102
We present a new fast real time and quantitative gas analysis method by means of mass spectrometry (MS), which has approximately an order of magnitude faster sampling rate in comparison with a traditional gas chromatography. The method is presented and discussed on the example of the CO2 reduction reaction. The advantages of the method are the possibility to analyze the reaction kinetics, where the kinetically determined reaction range is often only tens of degrees wide. Furthermore, due to the fast sampling rate, the experiments are much shorter and effects due to possible aging of the catalyst are significantly reduced. The quantification of the gas partial pressures is achieved by calibrating the Faraday detector in the quadrupole MS for the expected reactants and products. One major challenge to achieve a quantitative measurement with the MS is to correct for the pressure fluctuations over the probing capillary over the course of the experiment. This fluctuation is compensated in the analysis by normalizing the sum of all calculated partial pressures to the measured reaction pressure for every measured spectrum. With that, a precise, fast, and quantitative gas analysis is achieved. This is the fundament for, e.g., the kinetic reaction analysis where a high data point density is required. The method is discussed on the example of the CO2 hydrogenation reaction to CH4 on a commercial Ru/Al2O3 catalyst. Additionally, the key features of the gas controlling and analysis setup built for the CO2 hydrogenation reaction are described.
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pccp 2015 Luo, Wen; XIE, Wei; Mutschler, Robin; Oveisi, Emad; De Gregorio, Gian Luca; Buonsanti, Raffaella; Züttel, Andreas
Selective and stable electroreduction of CO2 to CO at the copper/indium interface
ACS Catal. 8:7 (2018), pp 6571–6581
Electrochemical reduction of CO2 using renewable energy is a promising strategy to mitigate the CO2 emissions and to produce valuable chemicals. However, the lack of highly selective, highly durable, and nonprecious-metal catalysts impedes the applications of this reaction. In this work, copper-nanowire-supported indium catalysts are proposed as advanced electrocatalysts for the aqueous electroreduction of CO2. The catalysts are synthesized by a facile method, which combines In3+ deposition on Cu(OH)2 nanowires, mild oxidation, and in situ electroreduction procedures. With a thin layer of metallic In deposited on the surface of the Cu nanowires, the catalyst exhibits a CO Faradaic efficiency of ∼93% at −0.6 to −0.8 V vs RHE; additionally, an unprecedented stability of 60 h is achieved. The characterization results combined with density functional theory (DFT) calculations reveal that the interface of Cu and In plays an essential role in determining the reaction pathway. The calculation results suggest that the Cu–In interface enhances the adsorption strength of *COOH, a key reaction intermediate for CO production, while destabilizes the adsorption of *H, an intermediate for H2 evolution. We believe that these findings will provide guidance on the rational design of high-performance bimetallic catalysts for CO2 electroreduction by creating the metal–metal interface structure.
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pccp 2015 Kun Zhao, Ligang Wang, Marco Calizzi, Emanuel Moioli, Andreas Züttel
In situ Control of the Adsorption Species in CO2Hydrogenation: Determination of Intermediates and Byproducts
J. Phys. Chem. C, 122:36 (2018), pp 20888–20893
CO2 hydrogenation over catalysts is a potentially exciting method to produce fuels while closing the CO2 cycle and mitigating global warming. The mechanism of this process has been controversial due to the difficulty in clearly identifying the species present and distinguishing which are reaction intermediates and which are byproducts. We in situ manipulated the independent formation and hydrogenation of each adsorption species produced in CO2 hydrogenation reaction over Ru/Al2O3 using operando diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS) and executed a novel iterative Gaussian fitting procedure. The adsorption species and their role in the CO2 hydrogenation reaction have been clearly identified. The adsorbed carbon monoxide (CO*) of four reactive structures was the key intermediate of methane (CH4) production. Bicarbonate (HCO3–*), formed on the metal–support interface, appeared to be not only the primary product of CO2 chemisorption but also a reservoir of CO* and consisted of the dominate reaction steps of CO2 methanation from the interface to the metal surface. Bidentate formate (Bi-HCOO–*) formed on Ru under a certain condition, consecutively converting to CO* to merge into the subsequent methanation process. Nonreactive byproducts of the reaction were also identified. The evolution of the surface species revealed the essential steps of the CO2 activation and hydrogenation reactions which were inevitably initiated from HCO3–* to CO* and finally from CO* to CH4.
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pccp 2015 Noris Gallandat, Robin Mutschler, Vincent Vernay, Heena Yang, Andreas Züttel
Experimental Performance Investigation of a 2kW Methanation Reactor
Sustainable Energy Fuels, 2 (2018),pp. 1101-1110
A 2 kW methanation reactor was designed, built and tested for the gas phase hydrogenation of CO2 to CH4. The reactor is a single-stage, fixed-bed reactor. A commercial catalyst with 0.5% wt Ru on an alumina support was applied and characterized using TEM imaging. A thermal model of the process was developed in order to effectively design the cooling system and estimate the temperature gradients within the reactor. The conversion efficiency was investigated experimentally using transmission infrared spectroscopy. The reactor temperature set point was varied from 140 °C to 400 °C, the space velocity ranged from 0.14 s−1 to 0.55 s−1 (corresponding to 0.40–1.55 ml g−1 s−1) and the pressure was set to 5 bar. A maximal conversion of 99% was measured at a temperature of 260 °C and a space velocity of 0.14 s−1. A CO2 conversion of 97% was reached at a target flow rate of 50 g h−1 H2 and a temperature set point of 280 °C. Such conversions are very high for a single-stage reactor and are partly due to the inhomogeneous temperature distribution within the catalyst bed, which allowed the balancing of the kinetic and thermodynamic effects. The reactor presented in this paper is installed as a part of the small-scale demonstrator of renewable energy to synthetic hydrocarbon conversion of EPFL Valais/Wallis.
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pccp 2015 Noris Gallandat, Jérémie Bérard, François Abbet and Andreas Züttel
Small-scale demonstration of the conversion of renewable energy to synthetic hydrocarbons
Sustainable Energy Fuels, 1 (2017), pp. 1748-1758
The design and build of a pilot plant for the conversion of solar energy to synthetic hydrocarbons is presented. In addition to technical realization, valuable economic parameters and information about suppliers are presented. The average power of the installation is set to 2 kW, which corresponds to the world average energy consumption of a single person. The main components of the system are photovoltaic cells, batteries, an electrolyser, a metal hydride storage and compression system, a CO2 capture unit and chemical reactors. The installation allows studying the energy flows and reservoirs and the interaction between different components, comparing the performance of competing technologies and establishing an energetic and economic database from the real world. Further, the operating parameters such as pressure, temperatures and energy flows are recorded at different locations to enable for system modeling and advanced optimization techniques to be applied on real data. Last, the degradation of the various components will be investigated under actual working conditions.
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pccp 2015 J.-P. Brog, A. Crochet, J. Seydoux, Martin J. D. Clift, B. Baichette, S. Maharajan, H. Barosova, P. Brodard, M. Spodaryk, A. Züttel, B. Rothen-Rutishauser, N. Hee Kwon and K. M. Fromm
Characteristics and properties of nano-LiCoO2 synthesized by pre-organized single source precursors: Li-ion difusivity, electrochemistry and biological assessment
Journal of J. Nanobiotechnol (2017), DOI 10.1186/s12951-017-0292-3
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pccp 2015 N. Gallandat, K.Romanowicz and A. Züttel
An Analytical Model for the Electrolyser Performance Derived from Materials Parameters
Journal of Power and Energy Engineering 5 (2017), pp. 34-49
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pccp 2015 P. A. Szilagyi, D. M. Rogers, I. Zaiser, E. Callini, S. Turner, A. Borgschulte, A. Züttel, H. Geerlings, M. Hirscher and B. Dam
Functionalised metal–organic frame-works: a novel approach to stabilising single metal atoms
J. Mater. Chem. A 5 (2017), 15559, DOI: 10.1039/c7ta03134c
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pccp 2015 Heena YANG, Andreas ZÜTTEL, Shindong KIM, Youngdon KO, and Whajung KIM
Effect of boron doping on graphene oxide for ammonia adsorption
ChemNanoMat 3 (2017), pp. 794 –797
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pccp 2015 Y.D. KO, H.N. YANG, A. ZÜTTEL, S.D. KIM, Wha Jung KIM
Membrane electrode assembly fabricated with the combination of Pt/C and hollow shell structured-Pt-SiO2/ZrO2 sphere for self-humidifying proton exchange membrane fuel cell
J. Power Sources 367 (2017), pp. 8-16
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pccp 2015 Samir Barman, Arndt Remhof, Ralph Koitz, Marcella Iannuzzi, Olivier Blacque, Yigang Yan, Thomas Fox, Jürg Hutter, Andreas Züttel, Heinz Berke
Post-Synthesis Amine Borane Functionalization of a Metal-Organic Framework and Its Unusual Chemical Hydrogen Release Phenomenon
Chemistry-A European Journal 23:37 (2017), pp. 8823 – 8828
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pccp 2015 Wen LUO, and Spyridon ZAFEIRATOS
A Brief Review of the Synthesis and Catalytic Applications of Graphene-Coated Oxides
ChemCatChem 9 (2017), pp. 2432 – 2442
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pccp 2015 S.I. Orimo, A. Züttel, M. Hirscher, M. Spodaryk
Preface to the special issue on “The 15th International Symposium on Metal-Hydrogen systems (MH2016), Interlaken, Switzerland, 7. – 12. August 2016
Int. J. Hydrogen Energy (2017), http://dx.doi.org/10.1016/j.ijhydene.2017.07.131
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pccp 2015 Callini, E., Atakli, Z.Ö.K., Hauback, B.C. et al.
Complex and Liquid Hydrides for Energy Storage
Appl. Phys. A (2016) 122: 353. doi:10.1007/s00339-016-9881-5
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pccp 2015 S. Kato, S. K. Matam, P. Kerger, L. Bernard, C. Battaglia, D. Vogel, M. Rohwerder, A. Züttel
The Origin of the Catalytic Activity of a Metal Hydride in CO2 Reduction
Angew Chem Int Ed. Engl. 2016 May 10; 55 (20):6028-32. doi: 10.1002/anie.201601402
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pccp 2015 E. Callini, P. Á. Szilágyi, M. Paskevicius, N. P. Stadie, J. Réhault, C. E. Buckley, A. Borgschulte and A. Züttel
Stabilization of volatile Ti(BH4)3 by nano-confinement in a metal–organic framework
Chemical Science 7 (2016), pp. 666 – 672.
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pccp 2015 Nikola Biliskov, Danijela Vojta, Laszlo Kotai, Imre Miklos Szilagyi, David Hunyadi, Tibor Pasinszki, Sandra Flincec Grgac, Andreas Borgschulte, Andreas Züttel
High Influence of Potassium Bromide on Thermal Decomposition of Ammonia Borane
J. Physical Chemistry C 120:44 (2016), pp. 25276 – 25288
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pccp 2015 E. Callini, K.-F. Aguey-Zinso, R Ahuja, J. R. Ares, S. Bals, N. Biliškov, S. Chakraborty, G. Charalambo-poulou, A.-L. Chaudhary, F. Cuevas, B. Dam, P. de Jongh, M. Dornheim, Y. Filinchuk, J. Grbović Novaković, M. Hirscher, T. R. Jensen, P. B. Jensen, N. Novaković, Q. Lai, F. Leardini, D. M. Gattia, L. Pasquini, T. Steriotis, S. Turner, T. Vegge, A. Züttel, A. Montone
Nanostructured materials for solid-state hydrogen storage: A review of the achievement of COST Action MP1103
International Journal of Hydrogen Energy Volume 41, Issue 32, 24 August 2016, Pages 14404–14428.
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pccp 2015 Jianmei Huang, Yigang Yan, Arndt Remhof, Yucheng Zhang, Daniel Rentsch, Yuen S. Au, Petra E. de Jongh, Fermin Cuevas, Liuzhang Ouyang, Min Zhua and Andreas Züttel
A novel method for the synthesis of solvent-free Mg(B3H8)2
Dalton Trans., 45, (2016), pp. 3687.
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  E. Callini, S. Kato, P. Mauron, A. Züttel
“Surface Reactions are Crucial for Energy Storage”

CHIMIA International Journal for Chemistry, Volume 69, Number 5, May 2015, pp. 269-273(5)
Reactions between gas molecules, e.g. H2 and CO2 and solids take place at the surface. The electronic states and the local geometry of the atomic arrangement determine the energy of the adsorbate, i.e. the initial molecule and the transition state. Here we review our research to identify the surface species, their chemical state and orientation, the interaction with the neighbouring molecules and the mobility of the adsorbed species and complement the experimental results with thermodynamic modelling. The role of the Ti was found to be a bridge between the charged species preventing the individual movement of the ions including charge separation. The Ti has no catalytic effect on the hydrogen sorption reaction in borohydrides. The physisorption of molecular hydrogen is too weak at ambient temperature to reach a significant hydrogen storage density. The addition of a hydrogen dissociation catalyst to a nanoporous material with a large specific surface area may potentially enable the spillover of hydrogen atoms from the metal catalyst to the surface of the porous material and chemisorb on specific sites with a much higher binding energy compared to physisorption. The intercalation of alkali metals in C60 fullerenes increases the interaction energy of hydrogen with the so-called metal fullerides significantly. Sterical diffusion barriers by partial oxidation of the surface of borohydrides turned out to redirect the reaction path towards pure hydrogen desorption and suppress the formation of diborane, a by-product of the hydrogen evolution reaction from borohydrides previously undetected. The combination of a newly developed gas controlling system with microreactors allows us to investigate complex reactions with small quantities of nano designed new catalytic materials. Furthermore, tip-enhanced Raman spectroscopy (TERS) will allow the investigation of the reactions locally on the surface of the catalyst and the near ambient pressure photoelectron spectroscopy enables analysis of the surfaces in ultra-high vacuum and in situ interaction with the adsorbates i.e. while the reaction takes place. This brings us in a unique position for the investigation of the heterogeneous reactive systems. The mechanism of the Ti catalysed hydrogen sorption reactions in alanates was recently established based on spectroscopic investigations combined with thermodynamic analysis of the transition states.
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  Züttel Andreas; Mauron Philippe; Kato Shunsuke; Callini Elsa; Holzer Marco; Huang Jianmei
“Storage of Renewable Energy by Reduction of CO2 with Hydrogen”
CHIMIA International Journal for Chemistry, Volume 69, Number 5, May 2015, pp. 264-268(5)
The main difference between the past energy economy during the industrialization period which was mainly based on mining of fossil fuels, e.g. coal, oil and methane and the future energy economy based on renewable energy is the requirement for storage of the energy fluxes. Renewable energy, except biomass, appears in time- and location-dependent energy fluxes as heat or electricity upon conversion. Storage and transport of energy requires a high energy density and has to be realized in a closed materials cycle. The hydrogen cycle, i.e. production of hydrogen from water by renewable energy, storage and use of hydrogen in fuel cells, combustion engines or turbines, is a closed cycle. However, the hydrogen density in a storage system is limited to 20 mass% and 150 kg/m3 which limits the energy density to about half of the energy density in fossil fuels. Introducing CO2 into the cycle and storing hydrogen by the reduction of CO2 to hydrocarbons allows renewable energy to be converted into synthetic fuels with the same energy density as fossil fuels. The resulting cycle is a closed cycle (CO2 neutral) if CO2 is extracted from the atmosphere. Today’s technology allows CO2 to be reduced either by the Sabatier reaction to methane, by the reversed water gas shift reaction to CO and further reduction of CO by the Fischer–Tropsch synthesis (FTS) to hydrocarbons or over methanol to gasoline. The overall process can only be realized on a very large scale, because the large number of by-products of FTS requires the use of a refinery. Therefore, a well-controlled reaction to a specific product is required for the efficient conversion of renewable energy (electricity) into an easy to store liquid hydrocarbon (fuel). In order to realize a closed hydrocarbon cycle the two major challenges are to extract CO2 from the atmosphere close to the thermodynamic limit and to reduce CO2 with hydrogen in a controlled reaction to a specific hydrocarbon. Nanomaterials with nanopores and the unique surface structures of metallic clusters offer new opportunities for the production of synthetic fuels.
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  Remhof, Arndt; Yan, Yigang; Rentsch, Daniel, Andreas Borgschulte, Craig M. Jensen and Andreas Züttel
“Solvent-free synthesis and stability of MgB12H12
JOURNAL OF MATERIALS CHEMISTRY A Volume: 2 Issue: 20 Pages: 7244-7249 Published: 2014
MgB12H12 has been widely discussed as an intermediate in the hydrogen sorption cycles of Mg(BH4)(2), but its properties such as stability and reactivity are still unknown. We achieved the synthesis of MgB12H12 via the reaction between Mg(BH4)(2) and B2H6 at 100 to 150 degrees C. When bulk Mg(BH4)(2) was used as the starting material, a yield of 10.2 to 22.3 mol% was obtained, which was improved to 92.5 mol% by using Mg(BH4)(2) nanoparticles. The as-synthesized MgB12H12 decomposed into boron between 400 and 600 degrees C, preceded by a possible polymerization process. The formation mechanism of MgB12H12 and its role in the decomposition process of Mg(BH4)(2) are discussed.
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  Chong, M.; Callini, E.; Borgschulte, A., Züttel A., and Jensen C. M.
Dehydrogenation studies of the bimetallic borohydrides”
RSC ADVANCES Volume: 4 Issue: 109 Pages: 63933-63940 Published: 2014
One of the major issues associated with the use of borohydride complexes for hydrogen storage is the thermodynamic stability of these materials, with the Group I and II complexes also requiring the most demanding temperatures to facilitate dehydrogenation. In recent years, the idea of modulating thermodynamic properties by combining metals with different stabilities (as monocation borohydrides) has come to light. By incorporating a cation with ionic bonding characteristics, it has been proposed that the volatile Sc borohydrides can be stabilized to an extent that diborane release is prevented. We show, using in situ IR and TG analysis, that these complexes do indeed release significant quantities of diborane, which is an irrevocable barrier to reversibility. Our findings suggest that the Group I/Sc bimetallic borohydrides are not suitable for hydrogen storage.
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  Elsa Callini, Andreas Borgschulte, Cedric L. Hugelshofer, Anibal J. Ramirez-Cuesta, Andreas Züttel
The Role of Ti in Alanates and Borohydrides: Catalysis and Metathesis”
JOURNAL OF PHYSICAL CHEMISTRY C Volume: 118 Issue: 1 Pages: 77-84 Published: JAN 9 2014
Ti catalyzes the hydrogen sorption reaction in alanates and allows the measurement of pressure composition isotherms, that is, the reaction equilibrates at each point of the isotherm. Although some effects of Ti compounds addition to borohydrides have been shown, our measurements show that the hydrogen desorption reaction from borohydrides is not catalyzed by Ti, when the system is exposed to a gas flow. The reabsorption of hydrogen by the products of the desorption reaction requires high temperatures and high pressures. Furthermore, the reaction pathway for the hydrogen desorption is different from the absorption one and as a consequence the borohydrides do not equilibrate with the gas phase during the hydrogen sorption reactions. Ti in borohydrides leads to the formation of stable and volatile Ti-containing species, for example, (Ti(BH4)(3)). This is a metathesis reaction, that is, a bimolecular process involving the exchange of bonds between the two reacting chemical species. In this paper, we have investigated via spectroscopy measurements the hydrogen sorption reactions of NaAlH4 and LiBH4 with Ti catalyst in view of the changes in the solid phase as well as in the gas phase.
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  Mattia Gaboardi, Andreas Bliersbach, Giovanni Bertoni, Matteo Aramini, Gina Vlahopoulou, Daniele Pontiroli, Philippe Mauron, Giacomo Magnani, Giancarlo Salviati, Andreas Züttel and Mauro Riccò
Decoration of graphene with nickel nanoparticles: study of the interaction with hydrogen”
JOURNAL OF MATERIALS CHEMISTRY A Volume: 2 Issue: 4 Pages: 1039-1046 Published: 2014
Graphene obtained from thermal exfoliation of graphite oxide was chemically functionalized with nickel nanoparticles (NPs) without exposing the system to oxidizing agents. Its structural, physical and chemical properties have been studied by means of TEM, X-ray photoelectron and Raman spectroscopies, and SQuID magnetometry. The formation of 17 nm super-paramagnetic (SPM) monodispersed Ni NPs was observed. Nitrogen sorption experiments at 77 K yield a Brunauer-Emmet-Teller specific surface area (BET-SSA) of 505 m(2) g(-1) and helium adsorption at room temperature gives a skeletal density of 2.1 g cm(-3). The interaction with atomic hydrogen was investigated by means of Muon Spin Relaxation (mu SR) showing a considerable fraction of captured muonium (similar to 38%), indicative of strong hydrogen-graphene interactions. Hydrogen adsorption has been measured via pressure concentration isotherms demonstrating a maximum of 1.1 mass% of adsorbed hydrogen at 77 K and thus a 51% increased hydrogen adsorption compared to other common carbon based materials.
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  P. Á. Szilágyi, E. Callini, A. Anastasopol, C. Kwakernaak, S. Sachdeva, R. van de Krol, H. Geerlings, A. Borgschulte, A. Züttel and B. Dam
Probing hydrogen spillover in [email protected](Cr) with a focus on hydrogen chemisorption”
PHYSICAL CHEMISTRY CHEMICAL PHYSICS Volume: 16 Issue: 12 Pages: 5803-5809 Published: 2014
Palladium nanoparticles can split the dihydrogen bond and produce atomic hydrogen. When the metal nanoparticles are in intimate contact with a hydrogen-atom host, chemisorption of H-atoms by the host has been suggested to occur via the hydrogen spillover mechanism. Metal-organic frameworks were predicted to be able to act as effective chemisorption sites, and increased ambient-temperature hydrogen adsorption was reported on several occasions. The intimate contact was supposedly ensured by the use of a carbon bridge. In this work, we show that it is possible to introduce catalyst palladium particles into MOF’s pores and simultaneously ensuring good contact, making the employment of the carbon bridge redundant. The addition of Pd nanoparticles indeed increases the ambient-temperature hydrogen uptake of the framework, but this is found to be solely due to palladium hydride formation. In addition, we show that the hydrogen atoms do not chemisorb on the host framework, which excludes the possibility of hydrogen spillover.
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  Stadie, Nicholas P.; Callini, Elsa; Richter, Bo, Jensen Torben R, Borgschulte Andreas, Züttel Andreas
Processing as a Route to the Clean Dehydrogenation of Porous Mg(BH4)2
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Volume: 136 Issue: 23 Pages: 8181-8184 Published: JUN 11 2014
Compounds of interest for chemical hydrogen storage at near ambient conditions are specifically tailored to be relatively unstable and thereby desorb H-2 upon heating. Their decomposition must be performed in the absence of impurities to achieve clean dehydrogenation products, which is particularly challenging for an emerging class of microporous complex hydride materials, such as gamma-phase Mg(BH4)(2), which exhibits high surface area and readily adsorbs (sometimes undesired) molecular species. We present a novel strategy toward the purification of yMg(BH4)(2) using supercritical nitrogen drying techniques, (1) showing that clean hydrogen can be released from Mg(BH4)(2) under mild conditions and (2) clarifying the origin of diborane among the decomposition products of stable borohydrides, a topic of critical importance for the reversibility and practical applicability of this class of hydrogen storage compounds. This technique is also widely applicable in the pursuit of the high-purity synthesis of other porous, reactive compounds, an exciting future class of advanced functional materials.
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  Mariana Spodaryk, Larisa Shcherbakova, Anatoly Sameljuk, Valentina Zakaznova-Herzog, Beat Braem, Marco Holzer, Philippe Mauron, Arndt Remhof, Yurii Solonin, Andreas Züttel
Effect of composition and particle morphology on the electrochemical properties of LaNi5-based alloy electrodes”
JOURNAL OF ALLOYS AND COMPOUNDS Volume: 607 Pages: 32-38 Published: SEP 15 2014
Al and Co substituted LaNi5-based intermetallic compounds were investigated as negative electrode materials in alkaline KOH-electrolyte. The structure, morphology and electrochemical properties of gas-atomised and cast LaNi4.5Al0.5 and LaNi2.5Co2.4Al0.1 alloys were investigated and the effect of the substitutions and the production method on the surface and bulk composition is compared to cast LaNi5 as a reference.
While the rapid solidification of the gas-atomised alloys affects the site energy distribution for hydrogen on the interstitial sites, the activation and degradation mechanism of the electrodes cycle life is dominated by the elemental composition of the alloy and especially the surface. Therefore, the alloys with the larger Al content activate within a few cycles and also degrade faster as compared to the alloys with a high Co content. Furthermore, the dissolution of Al leads to a highly active surface with a lower reaction resistance, which leads to an order of magnitude increased high rate dischargeability.
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  Yan, Yigang; Remhof, Arndt; Rentsch, Daniel; Züttel Andreas
The role of MgB12H12 in the hydrogen desorption process of Mg(BH4)2
CHEMICAL COMMUNICATIONS Volume: 51 Issue: 4 Pages: 700-702 Published: 2015
The presence of MgB12H12 has often been considered as the major obstacle for the reversible hydrogen storage in Mg(BH4)2. This communication provides evidence that the MgB12H12 phase (or [B12H12](2-) monomer) does not exist in the decomposition products of Mg(BH4)(2) at temperatures ranging from 265 to 400°C, and thereby it will not act as a dead end.
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  Mariana Spodaryk, Larisa Shcherbakova, Anatoly Sameljuk, Adrian Wichser, Valentina Zakaznova-Herzog, Marco Holzer, Beat Braem, Oleg Khyzhun, Philippe Mauron, Arndt Remhof, Yurii Solonin, Andreas Züttel
Description of the capacity degradation mechanism in LaNi5-based alloy electrodes”
JOURNAL OF ALLOYS AND COMPOUNDS Volume: 621 Pages: 225-231 Published: FEB 5 2015
The mechanism of the capacity degradation of LaNi5-based alloy electrodes was investigated with a special focus on the influence of the alloy and surface composition, as well as the unique structure obtained by gas atomisation. The electrochemical properties, especially the cycle life curve (i.e. the capacity as a function of the cycle number of LaNi4.5Al0.5, LaNi2.5Co2.4Al0.1, (La + Mm) Ni3.5Co0.7Al0.35Mn0.4Zr0.05, and MmNi(4.3)Al(0.2)Mn(0.5) alloy electrodes), was analysed and modelled. The capacity degradation upon cycling is determined by the chemical state of the alloy elements and the solubility of their oxides. The cycle life curves for the alloy electrodes without Co exhibited a rapid activation (3-4 cycles to reach maximum capacity), as well as rapid degradation (130-180 cycles for 50% maximum discharge capacity). LaNi2.5Co2.4Al0.1 and (La + Mm) Ni3.5Co0.7Al0.35Mn0.4Zr0.05 alloy electrodes activated after 7-10 cycles and showed very stable discharge behaviour (more than 400 cycles). The Co-containing alloy electrodes primarily lose the cycle stability because of mechanical decrepitation, whereas the alloys without Co suffer from selective dissolution of the unstable elements in the potential window, which was shown by our model of alloy degradation and confirmed by means of SEM, WDX, and ICP-OES data.were obtained.