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In this work, dual-phase dense composites based on BaCe0.65Zr0.20Y0.15O3-? (BCZ20Y15)-Ce0.85M0.15O2-? (MDC15, M = Y and Gd) were explored as hydrogen transport membranes. Indeed, the combination of a proton conducting phase (BCZ20Y15) and an electronic conductor (MDC15) in an all-ceramic dense membrane allows a selective H2 separation thanks to the incorporation of H2 in the structure as charge protonic defects and electrons or holes. The working temperatures and durability exhibited by these oxides make them appealing for applications under harsh conditions, allowing the intensification of industrial processes, that enhances the overall efficiency by coupling reaction and separation in a single unit (membrane reactors) [1, 2]. The preparation and the functional assessment performed on these membranes will be presented, highlighting the most important prerequisites for practical applications, namely their transport properties, hydrogen permeation fluxes and stability behaviour under operation conditions, especially in the presence of H2, CO2 and H2S. ____ [1] C. Mortalò, S. Barison, E. Rebollo, M. Fabrizio, Mixed Ionic-Electronic Conducting Membranes for Hydrogen Separation in Membrane engineering for the treatment of gases, Volume 2, 2nd Edition, Ed. E. Drioli, G. Barbieri and A. Brunetti, RSC, in press. [2] E. Rebollo, C. Mortalò, S. Escolástico, S.Boldrini, S. Barison, J. M. Serra, and M. Fabrizio, Energy and Environmental science 8, 3675-3686, (2015).

Among different technologies, dense ceramic membranes are prospective candidates for separation and purification of H2 in non-galvanic mode. By using integrated systems such as membrane reactors, in which both the reaction and separation are carried out in the same device, the system efficiency increases and makes scale-down economically efficient. Materials investigated for high-temperature hydrogen separation are divided into two classes: (i) single-phase materials and (ii) dual-phase materials, including cer-met and cer-cer composites. Moreover, mixed ionic-electronic conducting membranes are divided by their architecture into symmetric (self-supported) and asymmetric systems consisting of a dense ceramic supported on a porous substrate. Better understanding of the complex phenomena involved during H2 separation is necessary in order to tailor the materials composition. In fact, ceramic architectures based on dense mixed ion-electron conductors (MIECs) are extremely selective at medium-high temperatures (up to 900 °C) but do not reach yet the minimum-targeted flux of 30 mL min-1 cm-2 required to apply them in industrial processes. Nowadays, the best fluxes are of a few mL min-1 cm-2 and are obtained on dual-phase perovskites. Tubular membranes are technologically preferred respect to planar ones. With this aim, this chapter provides an overview of recent research on the most promising ceramics and ceramic composites and a reminder of the hydrogen-selective permeation mechanism in ceramic-based membranes.

Ceramic-ceramic (cer-cer) composites constituted by perovskite proton conductor BaCe0.65Zr0.20Y0.15O3-? (BCZ20Y15) and doped ceria (Ce0.85M0.15O2-? M = Y or Gd, YDC15 or GDC15) as electronic conductor had demonstrated notable performance as dense H2-separation membranes, with H2 flux values among the highest reported in literature for this kind of systems [1]. Long-term stability and degradation mechanisms are critical issues for these dual-phase membranes. The working conditions are really challenging: H2 purification is carried out at high temperatures in harsh reducing environments containing H2O, CO, CO2, and sulphides. In such conditions, many undesired phenomena such as structural changes, cation diffusion, mechanical alterations or chemical reactions could occur damaging the membranes properties. The purpose of the present study is to evaluate the chemical and mechanical behaviour of BCZ20Y15-GDC15 and BCZ20Y15-YDC15 composite membranes in conditions of practical interest. Materials and methods Experiments were performed on high density samples of BCZ20Y15-GDC15 and BCZ20Y15-YDC15 (50:50 or 60:40 volume ratio) prepared as described elsewhere [1]. BCZ20Y15, GDC15 and YDC15 single-phase specimens were prepared following a corresponding procedure for comparison purposes. All samples were exposed to syngas, H2 and H2S at different temperatures. The crystal structure before and after the treatments was studied by means of X-ray diffraction (XRD) while the evolution on the microstructure of the cross-sections and the surfaces of the samples was evaluated by scanning electron microscopy- Energy-dispersive X-ray spectroscopy (SEM-EDS). The characterization of the mechanical properties was performed through nano-indentation and the surface roughness was evaluated by a contact stylus profiler. Results and discussion The nano-indentation measurements allow to determine the variations occurred on the Young's modulus (E) and hardness (H) of the composite membranes and of the single-phase precursors induced by the different treatments. With the aim to detect the evolution and/or the stability of the mechanical properties, caused by harsh environments at high temperatures for a long period, nano-mechanical analyses were carried out also on samples in the "as prepared" state, having the same compositions of those thermally treated. A statistical approach was used to process the collected nanoindentation data, to achieve high reliability of the measurements. Moreover, the presence of alteration products such as carbonates in the samples treated in CO2 or of any defect induced by the reduction of ceria-based materials was evaluated by XRD and SEM-EDS investigations. The collected data indicate that the composite membranes show better overall performance in terms of both chemical and mechanical properties, compared to the single-phase precursors. Conclusions The possible degradation mechanisms together with thermally and mechanically induced stresses could compromise the long-term stability during operation of BCZ20Y15-GDC15 and BCZ20Y15-YDC15 dense membranes for H2 separation. For this purpose, these cer-cer composites were exposed to conditions of practical interest and characterized in terms of mechanical properties (Young's modulus (E) and hardness (H)), chemical composition and crystal structure (SEM-EDS and XRD) in order to obtain a better understanding of their behaviour under harsh conditions and validate their potential practical applications. Acknowledgments The authors are grateful to Dr. Rosalba Gerbasi, Dr. Naida El Habra and Dr. Simona Barison for their help in XRD and SEM analyses. This work has been funded by the Italian National Research Council - Italian Ministry of Economic Development Agreement "Ricerca di sistema elettrico nazionale". References 1. E. Rebollo, C. Mortalò, S. Escolástico, S.Boldrini, S. Barison, J. M. Serra, and M. Fabrizio, Energy Environ. Sci., 8, pp.3675-3686, 2015.

The efficient separation of pure H2 from a gas mixture is a critical stage for large scale production of this energy carrier. H2-selective membranes represent an appealing option to recover hydrogen from low-quality gas e.g. from biomass. Protonic-ceramic have received considerable attention due to their potential application as mixed ionic-electronic conductor (MIEC) separation membranes for H2 production. In MIEC membranes, the separation and transport of H2 occurs electrochemically in the form of protons and electrons. In a non-galvanic mode, the membrane must have both high electronic and high proton conductivities [1]. Still, a stable single phase material with those properties is rather challenging. Indeed, an enhancement of proton conductivity through doping is generally related to a decrease on the electronic conductivity and on the stability of this kind of ceramics. Another strategy is to obtain the desired functional properties through composite membranes formed by two compatible ceramic phases. In this work, BaCe0.85-xZrxY0.15O3-? perovskites and doped CeO2 fluorites have been combined in different volume ratios to fabricate "ceramic-ceramic" composite membranes for H2 separation. It has been demonstrated that barium cerate-zirconate solid solutions BaCe0.85-xZrxY0.15O3-? (x: 0.20, 0.30) stabilize the perovskite structure without sacrificing protonic conductivity [2]. On the other hand, doped ceria oxides shows remarkable n-type electronic conductivity under H2 separation conditions. Furthermore, they enhance the stability against CO2 and H2O of the cerate material in the composite membranes. The optimal preparation and sintering conditions of the dense membranes have been determined through XRD and SEM techniques. OCV and a.c. impedance spectroscopy (EIS) have been carried out to study the electrochemical behaviour of the composites. In addition, the stability against CO2 and syn-gas (mandatory under operational H2 separation conditions) was evaluated by different methods. Finally, the H2-permeation of these dense membranes was measured, reaching hydrogen fluxes among the highest achieved for bulk mixed protonic-electronic membranes reported so far. References [1] T. Norby, R. Hausgrud, Nonporous Inorganic Membranes, 2006, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. [2] S. Barison Et al., J. Mater. Chem., 2010, 18, 5120- 5128.

The production of pure hydrogen usually requires its extraction from a gas mixture. In fact, one of the critical stages related to the use of hydrogen as an energy carrier is the development of efficient and competitive techniques that separate hydrogen from other by-products such as steam, hydrocarbons, carbon dioxide and other gases. Membranes for hydrogen purification represent an appealing alternative to the current commercially available pressure swing adsorption (PSA) technology. In this context, mixed proton and electron conductors (MPEC) oxides are attractive candidates to be used as dense ceramic membranes for H2 separation due to their particular properties. These materials incorporate hydrogen into their lattice as charge protonic defects which means that, theoretically, they are 100% selective towards hydrogen separation. Furthermore, the properties of these oxides (i.e. working temperatures, durability) endow membranes that could be directly integrated into industrial processes or used in the so-called catalytic membrane reactors. Recently, BaCe0.65Zr0.20Y0.15O3-? (BCZ20Y15) and Ce0.85M0.15O2-? (M = Y and Gd) dual-phase membranes were explored by our group [1] reaching hydrogen permeability values among the highest ever reported for bulk MPEC membranes. The highest permeation flux was attained for the 50:50 volume ratio BaCe0.65Zr0.20Y0.15O3-? and Ce0.85Gd0.15O2-? membrane, reaching values of 1.27 mL·min-1·cm-2 at 755°C and 2.40 mL·min-1·cm-2 at 1040°C. The long term stability and degradation mechanisms are critical issues for these systems. Working conditions are really challenging: hydrogen purification is carried out at high temperatures in harsh environments containing H2O vapour, CO, CO2, and sulphides. Structural changes, chemical reactions, cation diffusion and other undesired phenomena could occur damaging the performance of membranes, even if TGA analysis and permeation tests indicate that the composites were stable in CO2. In this work, BCZ20Y15-GDC15 composites were exposed to different environments at high temperatures and then characterized by means of XRD and SEM techniques. The objective of this study is to systematically examine the chemical stability of the membranes in order to obtain a better understanding of their capability for practical applications.

Hydrogen separation from syngas at high temperatures (>=600°C) is one of the most important H2-producing technologies and it has attracted wide interest in the last decades. Mixed ionic-electronic conductor (MIEC) ceramic materials have received considerable attention due to their potential application as separation membranes in these processes [1]. In MIEC membranes, the separation and transport of H2 occurs electrochemically in the form of protons and electrons. In a non-galvanic mode, the membrane must have both electronic and proton conductivities [2]. Y-doped BaCe1-xZrxO3-? (BCZY) perovskite oxides are promising candidates for the development of such membranes because they combine the high proton conductivity of barium cerates with the chemical stability of barium zirconates in CO2-containing atmospheres, such as syn gas conditions [3]. However, the electronic conductivity exhibited by these materials may be not sufficient to work as H2 separation membranes. The performances of BCZY in this field can be improved by adding a second electronic conductor phase [2]. In the present work, symmetric dense cer-cer membranes for hydrogen separation based on BaCe0.65Zr0.20Y0.15O3-? (BCZ20Y15) and Ce0.85M0.15O2-? (M = Y and Gd, hereafter YDC15 and GDC15) were prepared. After checking the chemical compatibility between precursors, the optimal sintering conditions were individuated, obtaining dense and crack free samples with homogeneous grain distribution. The influence of different composites on electrical properties and H2 permeability performances was thoroughly studied. In particular, BCZ20Y15-YDC15 and BCZ20Y15-GDC15 membranes exhibited an improved hydrogen flow when the sweep side of the membrane was hydrated. In these conditions, the hydrogen flux of BCZ20Y15-GDC15 in the 50:50 volume ratio reached values of 0.27 mL·min-1·cm-2 at 755°C, currently one of the highest H2 flows obtained for bulk mixed protonic-electronic membranes. The stability of these materials under CO2-containing atmosphere was evaluated by thermogravimetry analyses. These composite systems showed a very good chemical stability under CO2-rich atmosphere, supporting their use for hydrogen separation membranes in practical applications. The influence of the different phenomena associated to the permeability mechanism, namely protonic transport, electronic conduction and water splitting, are still to be clarified and should be the beginning for a valuable discussion. [1] T. Norby and R. Haugsrud Dense ceramic mebranes for hydrogen separation in: A. F. Sammels and M.V. Mundschau Nonporous inorganic membranes for chemical processing Wiley-VCH Verlag GmbH & Co. KGaA (2006) 1-48. [2] J.W. Phair, S.P.S. Badwal Ionics 12 (2006) 103-115. [3] S. Barison, M. Battagliarin, T. Cavallin, L. Doubova, M. Fabrizio, C. Mortalò, S. Boldrini, L. Malavasi, R. Gerbasi Journal of Materials Chemistry 18 (2008) 5120-5128.

Genomic imprinting is the modification of the genome so that genes from only one (rather than two) of the parental alleles are expressed. The mechanism underlying imprinting is epigenetic, occurring via changes in DNA methylation and histone modifications rather than through alterations in the DNA sequence. To date, nine different imprinting disorders have been clinically and genetically identified and a considerable research effort has been focused on determining the cause of the corresponding methylation defects.

Several endocrine diseases that share resistance to PTH are grouped under the term pseudohypoparathyroidism (PHP). Patients with PHP type Ia show additional hormone resistance, defective erythrocyte G(s)alpha activity, and dysmorphic features termed Albright's hereditary osteodystrophy (AHO). Patients with PHP-Ib show less diverse hormone resistance and normal G(s)alpha activity; AHO features are typically absent in PHP-Ib. Mutations affecting G(s)alpha coding exons of GNAS and epigenetic alterations in the same gene are associated with PHP-Ia and -Ib, respectively. The epigenetic GNAS changes in familial PHP-Ib are caused by microdeletions near or within GNAS but without involving G(s)alpha coding exons.