Stabilité chimique et structurale de pérovskites céramiques de conductrice protoniques pour piles à combustible et électrolyseurs

The chemical and structural stability of well-densified ceramics potentially used as H2/air fuelcell/electrolyzer (and perhaps in CO2/Hydrocabons Converter) electrolyte or electrodes vs. CO2-free/saturated pressurized water has been studied. The pressurization maximizes the efficiency of theenergy conversion systems. Four types of pervoskite-related oxide ceramics were concerned:BaCe0.4Zr0.5Y0.1Zn0.04O3-d (BCZYZ), SrZr0.9Er0.1O3-d (SZE), Ln2NiO4+d (LNO, Ln = La, Pr, Nd), andLa0.6Sr0.4Co0.2Fe0.8O3-d (LSCF6428). Dense ceramic samples were exposed at 550°C to water vaporpressure in an autoclave for days to weeks. The protonation treatments were performed in twodifferent conditions: operating condition (£20 bar of CO2-free water pressure, 550°C) and acceleratedaging conditions (³40 bar of CO2-free/CO2-saturated water pressure, 550°C). The pristine and‘protonated’ samples were characterized using various analysis techniques: Optical Microscopy,Thermogravimetry, Thermal Expansion, (micro/macro) ATR FTIR, Raman micro-spectroscopy, X-rayand Neutron Scattering. The study reveals that under the operating condition (£20 bar), the stability ofLNO/LSCF6428 electrode materials and of SZE electrolyte appears good, while the BCZYZelectrolyte exhibit significant corrosion. The superior stability of LSFC6428 exposed in extreme CO2-water vapor atmosphere was demonstrated about 5 to 30 times better than LNO and SZE homologues.The surface secondary phases form at the grain boundary. The protonation modifies more or less thestructure symmetry, the unit-cell volume/parameter and the phase transition sequence in relation withthe modification of the oxygen vacancy distribution. The proton doping level for different samples isalso discussed.La stabilité structurale et chimique de céramiques bien densifiées candidates pour leur utilisation comme électrolyte ou matériau d'électrode de piles à combustible, électrolyseur H2/air ou même de convertisseur CO2/Hydrocarbures a été étudiée vis-à-vis de l'eau sous pression (autoclave, eau pauvre ou saturée en CO2). La pressurisation maximise l'efficacité des dispositifs. Quatre familles de pérovskites ont été considérées: BaCe0.4Zr0.5Y0.1Zn0.04O3- (BCZYZ), SrZr0.9Er0.1O3- (SZE), Ln2NiO4+ (LNO, Ln = La, Pr, Nd), and La0.6Sr0.4Co0.2Fe0.8O3- (LSCF6428). Les céramiques denses sont traitées à 550°C en autoclave plusieurs jours à plusieurs semaines, soit dans des conditions de fonctionnement ( 20 bar, eau sans CO2, 550°C), soit en vieillissement accéléré ( 40 bar eau sans ou saturée de CO2, 550°C). Les céramiques ont été analysées avant et après 'protonation' par Microscopie Optique, Thermogravimétrie, Expansion Thermique, (micro/macro) ATR FTIR, Raman micro-Spectroscopie, diffraction des rayons X et des neutrons. En condition de fonctionnement ( 20 bar), la stabilité des matériaux d'électrodes LNO/LSCF6428 et de l'électrolyte SZE est bonne, alors que la céramique BCZYZ se corrode. La céramique LSFC6428 soumis à des conditions sévères (eau saturée en CO2, 40 bar) est 5 à 30 fois moins corrodée que les composés LNO and SZE. La corrosion s'initie en surface, aux joints de grains. La protonation modifie plus ou moins la symétrie, le volume et les paramètres de la maille unitaire ainsi que les transitions de phase en relation avec la modification de la distribution/organisation des lacunes d'oxygène. Le niveau de dopage en proton des différents matériaux est aussi discuté

Identification of metals and metalloids as hazardous elements in PM2.5 and PM10 collected in a coastal environment affected by diffuse contamination

The nature of the PM2.5 and PM10 varies enormously depending on the anthropogenic activities developed in the surrounding environment. These particles can include Hazardous Elements (HEs), such as heavy metals, which can be considered dangerous for the human health. For this reason, determining the nature of those HEs that are present in the surrounding atmosphere can help to comprehend possible emission sources and to establish new strategies to reduce air pollution. In this work, a cost-effective self-made passive sampler (SMPS) was tested as a tool to collect different size of PM containing metals as HEs. The SMPS was installed in a 20th century historic building (Punta Begona Galleries, Getxo, ~ Basque Country, Spain), located just in front of the sea and thus, immersed in a coastal environment. This location is affected by the activities developed in a marina and in a port, and by the diffuse influence of several industries and a power station. The annual average for PM10 and PM2.5 were approximately 22 mg/ m3 and 10 mg/m3 , respectively. For develop this study, non-invasive elemental (Scanning Electron Microscope coupled to Energy Dispersive X-ray Spectrometry) and molecular (Raman microscopy) microspectroscopic techniques were used. Thanks to this methodology it was possible to determine in PM10 and PM2.5, the presence of heavy metals such as Fe, Cr, Ti, Pb, Zn, Ce, etc., most of them as oxides but also embedded in different aggregations with aluminosilicates, phosphates, halides, sulfates, etc

PM10 spatial distribution and metals speciation study in the Bilbao metropolitan area during the 2017–2018 period

Speciation of respirable particles is becoming increasingly important from an epidemiological and analytical point of view to determine the potential effects of air pollution on human health. For this reason, current laws and analytical sampling methods focus on particle size, as it turns out to be the main factor for the greater or lesser penetration into the airways. In this sense, particles of less than 10 μm in diameter (<10 μm), referred to as PM10, are the particles that have a higher capacity for access to the respiratory tract and, therefore, more significant effect on them. In this sense, one of the most important factors that have a key role in the PM10 atmospheric pollution effect is the dispersion effect with the direct influence of natural effects such as wind, rain, topography apart from others. In this work, PM10 data extracted from the Basque Government environmental stations (19 sampling points) in the Biscay province (Basque Country, north of Spain) were combined with the results obtained from the use of self-made passive samplers (SMPS) in the same sampling points areas and subsequently, the sample analysis with a non-invasive elemental technique (Scanning Electron Microscope coupled to Energy Dispersive X-ray Spectrometry) was carried out. Thanks to this methodology, it was possible to determine a wide variety of metals in PM10 such as Al, Fe, Cr, Ni, Pb, Zn, Ti, etc. Most of them present as oxides and others as part of natural aggregations such as quartz, aluminosilicates, phosphates etc

Kinetics of Catalytic Oxidation of Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid over LaMn1-xNixO3-d Perovskite Oxide

This present research aims at studying the kinetic reaction of HMF oxidation which is influenced by temperature gradient and Mn/Ni cation ratio in a lanthanum-based perovskite oxide catalyst. The result can be a fruitful database for the further development of the semi-industrial FDCA derivatives production process. Three Mn/Ni cation ratios of LaMnO3-d, LaMn0.5Ni0.5O3-d, and LaNiO3-d catalysts were selected and prepared by the Sol-Gel method. The bulk chemical species and oxidation states of secondary metal elements (Mn and Ni) for all synthesized perovskite-oxide catalysts were characterized by X-ray absorption near edge structure (XANES). The result of the distinct ratio of Mn3+/Mn4+ ions significantly affected the oxidation reaction of HMF. The LaMn0.5Ni0.5O3-d and LaMnO3-d catalysts achieved high catalytic performance for the HMF oxidation reaction at 120 °C for 4 hrs. The kinetic parameters and activation energy were successfully estimated and reported

Evaluating sulfates and nitrates as enemies of the recent constructions: Spectroscopic and thermodynamical study

Salt crystallization is one of the major problems currently faced by the field of architecture and construction. Its effects are devastating to the extent that they may even lead to loss of material. Although many innovative and resistant materials have been developed in the last years, in most of the constructions, salt crystallization is a persistent problem. Salts crystallizations are formed by the dissolution and subsequent precipitation of the soluble salts present in the material itself or due to the formation of new ones because of the reaction between original components of the building materials with salts coming from infiltration waters or with acid aerosols present in the atmosphere. Among others, some of the most common salts that can crystallize in the building materials are nitrates and sulfates. Both of them are soluble compounds, which can mobilize throughout the material easily, reprecipitate, and generate volume changes responsible for fissures, fractures, and even the loss of building material. In this work, a specific study of salts crystallizations in a recent construction erected in 2013 in Amorebieta (Basque Country, North of Spain) using a different kind of materials has been studied. The materials affected by salts are joint mortars, which in a first step were characterized by X‐ray diffraction and Raman microscopy to determine the mineralogical composition. In a second step, a soluble salts tests by ion chromatography was applied to approach quantitatively the impact of the salts. Finally, in a third step, the reactions that give rise to the decay products (thenardite, nitrocalcite, and/or epsomite mainly) were proposed and confirmed through a thermodynamic modellin

Chemical and structural stability of proton conducting perovskite ceramic for fuel cells and electrolyzers

La stabilité structurale et chimique de céramiques bien densifiées candidates pour leur utilisation comme électrolyte ou matériau d'électrode de piles à combustible, électrolyseur H2/air ou même de convertisseur CO2/Hydrocarbures a été étudiée vis-à-vis de l'eau sous pression (autoclave, eau pauvre ou saturée en CO2). La pressurisation maximise l'efficacité des dispositifs. Quatre familles de pérovskites ont été considérées: BaCe0.4Zr0.5Y0.1Zn0.04O3- (BCZYZ), SrZr0.9Er0.1O3- (SZE), Ln2NiO4+ (LNO, Ln = La, Pr, Nd), and La0.6Sr0.4Co0.2Fe0.8O3- (LSCF6428). Les céramiques denses sont traitées à 550°C en autoclave plusieurs jours à plusieurs semaines, soit dans des conditions de fonctionnement ( 20 bar, eau sans CO2, 550°C), soit en vieillissement accéléré ( 40 bar eau sans ou saturée de CO2, 550°C). Les céramiques ont été analysées avant et après 'protonation' par Microscopie Optique, Thermogravimétrie, Expansion Thermique, (micro/macro) ATR FTIR, Raman micro-Spectroscopie, diffraction des rayons X et des neutrons. En condition de fonctionnement ( 20 bar), la stabilité des matériaux d'électrodes LNO/LSCF6428 et de l'électrolyte SZE est bonne, alors que la céramique BCZYZ se corrode. La céramique LSFC6428 soumis à des conditions sévères (eau saturée en CO2, 40 bar) est 5 à 30 fois moins corrodée que les composés LNO and SZE. La corrosion s'initie en surface, aux joints de grains. La protonation modifie plus ou moins la symétrie, le volume et les paramètres de la maille unitaire ainsi que les transitions de phase en relation avec la modification de la distribution/organisation des lacunes d'oxygène. Le niveau de dopage en proton des différents matériaux est aussi discuté.The chemical and structural stability of well-densified ceramics potentially used as H2/air fuelcell/electrolyzer (and perhaps in CO2/Hydrocabons Converter) electrolyte or electrodes vs. CO2-free/saturated pressurized water has been studied. The pressurization maximizes the efficiency of theenergy conversion systems. Four types of pervoskite-related oxide ceramics were concerned:BaCe0.4Zr0.5Y0.1Zn0.04O3-d (BCZYZ), SrZr0.9Er0.1O3-d (SZE), Ln2NiO4+d (LNO, Ln = La, Pr, Nd), andLa0.6Sr0.4Co0.2Fe0.8O3-d (LSCF6428). Dense ceramic samples were exposed at 550°C to water vaporpressure in an autoclave for days to weeks. The protonation treatments were performed in twodifferent conditions: operating condition (£20 bar of CO2-free water pressure, 550°C) and acceleratedaging conditions (³40 bar of CO2-free/CO2-saturated water pressure, 550°C). The pristine and‘protonated’ samples were characterized using various analysis techniques: Optical Microscopy,Thermogravimetry, Thermal Expansion, (micro/macro) ATR FTIR, Raman micro-spectroscopy, X-rayand Neutron Scattering. The study reveals that under the operating condition (£20 bar), the stability ofLNO/LSCF6428 electrode materials and of SZE electrolyte appears good, while the BCZYZelectrolyte exhibit significant corrosion. The superior stability of LSFC6428 exposed in extreme CO2-water vapor atmosphere was demonstrated about 5 to 30 times better than LNO and SZE homologues.The surface secondary phases form at the grain boundary. The protonation modifies more or less thestructure symmetry, the unit-cell volume/parameter and the phase transition sequence in relation withthe modification of the oxygen vacancy distribution. The proton doping level for different samples isalso discussed

Packaging to prolong shelf life of preservative-free white bread

This research studied various types of packaging to prolong the shelf life of non-preservative white bread. Three types of blown film packages were used, i.e. a single LDPE layer incorporated with an oxygen scavenger, a single LDPE layer containing an oxygen absorber sachet, and three layers of LDPE laminated with O-nylon. The effects of modified packaging atmosphere, i.e. 5, 10, and 21 vol. % of oxygen in nitrogen balance, on the shelf life was also included. Characterization of the packaging films was carried out using several techniques, such as Oxygen Transmission Rate (OTR) and an optical microscopy. Headspace gases, microbial count, as well as physical appearance were used to evaluate the shelf life. The optical microscopic images showed that incorporating the oxygen scavenger into the plastic film produced small pores, contributing to a passive function of the films as their OTRs were significantly enhanced. However, the microbial growth on bread stored in those packages was suppressed, implying that the intermediate generated from scavenging reaction might act as a fungistatic. Even though the scavenging capability of the oxygen absorber sachet lasted only for 4 days, the fungi and mould development thereafter was still lower compared to the package without the sachet. The prolonging white bread shelf life was found to be primarily dependent on two factors. The package with a high oxygen barrier such three-layer films defeated microorganisms. With a low initial oxygen level of around 5% by volume, the bread shelf life could be prolonged up to 5–7 days

Study on Chlorinated Gas Adsorption Using Activated Carbon via Polyvinyl Chloride (PVC) Stepwise Pyrolysis Process

In this research, we studied the chlorinated gas adsorption process using activated carbon. Two types of granular activated carbon were employed: GAC800 and GAC1200; with specific surface areas of 800 m2/g and 1200 m2/g, respectively. In order to optimize the polyvinyl chloride (PVC) dehydrochlorination conditions, three parameters were studied: (i) the type of precursor—PVC and PVC mixed with charcoal (1:1 by weight)—(ii) the temperature—300 and 400 °C—and (iii) the retention time—30, 120, and 240 min. Mohr’s method and acid-base titration were used to estimate the captured amount of chlorinated gas. The results indicated that the PVC dehydrochlorination occurred completely about 69–73 wt.% at 400 °C for 240 min. The amount of chloride ion was detected around 1–2 mmol/LNaOH. The estimated HCl adsorption capacity for the GAC800 and GAC1200 samples potentially absorbed 0.27 mgHCl/gGAC and 0.21 mgHCl/gGAC, respectively. In addition, the efficiency for GAC800 and GAC1200 was reported to 37.95% and 28.92%, respectively

Protonation and structural/chemical stability of Ln2NiO4+δ ceramics vs. H2O/CO2: high temperature / water pressure ageing tests

Mixed ionic-electronic conductors (MIEC) such as rare-earth nickelates with a general formula Ln 2 NiO 4+δ (Ln=La, Pr, Nd) appear as potential cathodes for energy production and storage systems: fuel cells, electrolysers and CO 2 converters. Since a good electrode material should exhibit important stability in operating conditions, the structural and chemical stability of different nickelate-based, well-densified ceramics have been studied using various techniques: TGA, dilatometry, XRD, Raman scattering and IR spectroscopy. Consequently, La 2 NiO 4+δ (LNO), Pr 2 NiO 4+δ (PNO) and Nd 2 NiO 4+ δ (NNO) have been exposed during 5 days to high water vapour pressure (40 bar) at intermediate temperature (550°C) in an autoclave device, the used water being almost free or saturated with CO 2 . Such protonation process offers an accelerating stability test and allows the choice of the most pertinent composition for industrial applications requiring a selected material with important life-time. In order to understand any eventual change of crystal structure, the ceramics were investigated in as-prepared, pristine state as well as after protonation and deprotonation (due to thermal treatment till 1000°C under dry atmosphere). The results show the presence of traces or second phases originating from undesirable hydroxylation and carbonation, detected in the near-surface layers. The proton/water insertion modifies the structure symmetry and the unit-cell volume whatever the low amount (<0.5 wt% equivalent H 2 O). This result is consistent with long range interaction and in contradiction with the formation of hydroxyl species hypothesis. The reaction mechanisms evidenced after autoclave treatment may be useful to understand the reaction occurring at the electrode surface in SOFC/HTSE systems

Structural stability of anhydrous proton conducting SrZr0.9Er0.1O3-δ perovskite ceramic vs. protonation/deprotonation cycling: Neutron diffraction and Raman studies☆

International audienceLong-term chemical and structural stability of an ion conducting ceramic is one of the main criteria for its selection as an electrolytic membrane in energy plant devices. Consequently, medium density SrZr0.9Er0.1O3-δ (SZE) anhydrous proton conducting ceramic – a potential electrolyte of SOFC/PCFC, was analysed by neutron diffraction between room temperature and 900 °C. After the first heating/cooling cycle, the ceramic pieces were exposed to water vapour pressure in an autoclave (500 °C, 40 bar, 7 days) in order to incorporate protonic species; the protonated compound was then again analysed by neutron diffraction. This procedure was repeated two times. At each step, the sample was also controlled by TGA and Raman spectroscopy. These studies allow the first comprehensive comparison of structural and chemical stability during the protonation/deprotonation cycling. The results reveal good structural stability, although an irreversible small contraction of the unit-cell volume and local structure modifications near Zr/ErO5[] octahedra are detected after the first protonation. After the second protonation easy ceramic crumbling under a stress is observed because of the presence of secondary phases (SrCO3, Sr(OH)2) well detected by Raman scattering and TGA. The role of crystallographic purity, substituting element and residual porosity in the proton conducting perovskite electrolyte stability is discussed