Oxygen surface exchange kinetics of erbia-stabilized bismuth oxide

The surface oxygen exchange kinetics of bismuth\ud oxide stabilized with 25 mol% erbia (BE25) has been studied\ud in the temperature and pO2 ranges 773–1,023 K and 0.1–\ud 0.95 atm, respectively, using pulse-response 18O–16O isotope\ud exchange measurements. The results indicate that BE25\ud exhibits a comparatively high exchange rate, which is rate\ud determined by the dissociative adsorption of oxygen. Defect\ud chemical considerations and the observed pO2\ud 1=2 dependence\ud of the rate of dissociative oxygen adsorption suggest\ud electron transfer to intermediate superoxide ions as the rate\ud determining step in surface oxygen exchange on BE2

Comparative Study of Epoxy-CsH2PO4 Composite Electrolytes and Porous Metal Based Electrocatalysts for Solid Acid Electrochemical Cells

[EN] Electrochemical cells based on acid salts (CsH2PO4) have attracted great interest for intermediate temperature, due to the outstanding proton conductivity of acid salts. In this work, electrodes and electrolyte were optimized following different strategies. An epoxy resin was added to the CsH2PO4 material to enhance the mechanical properties of the electrolyte, achieving good conductivity, enhanced stability, and cyclability. The electrodes configuration was modified, and Ni sponge was selected as active support. The infiltration of different oxide nanoparticles was carried out to tailor the electrodes resistance by promoting the electrocatalyst activity of electrodes. The selection of a cell supported on the electrode and the addition of an epoxy resin enables the reduction of the electrolyte thickness without damaging the mechanical stability of the thinner electrolyte.Funding from Spanish Government (MINECO ENE2014-57651 grant) is kindly acknowledged. We greatly appreciated using the Convergence Research Laboratory (established by the MNU Innovation Support Project in 2020) to conduct this research. This work was financially supported by the Spanish Government (Grants SEV-2016-0683 and RTI2018-102161) and the Generalitat Valenciana (PROMETEO/2018/006). The authors want also to acknowledge the Electron Microscopy Service from the Universitat Politècnica de València for their support in the SEM analysis performed in this work.Navarrete Algaba, L.; Yoo, C.; Serra Alfaro, JM. (2021). Comparative Study of Epoxy-CsH2PO4 Composite Electrolytes and Porous Metal Based Electrocatalysts for Solid Acid Electrochemical Cells. Membranes. 11(3):1-14. https://doi.org/10.3390/membranes11030196S11411

Synchrotron study of the garnet-type oxide Li6CaSm2Ta2O12

Hexalithium calcium disamarium(III) ditantalum(V) dodeca­oxide, Li6CaSm2Ta2O12, crystallizes in a cubic garnet-type structure. In the crystal structure, disordered Li atoms occupy two crystallographic sites. One Li has a tetra­hedral coordination environment in the oxide lattice, whereas the other Li atom occupies a significantly distorted octa­hedral site, with site occupancies for the two Li atoms of 0.26 (7) and 0.44 (2), respectively. Ca and Sm atoms are statistically distributed over the same crystallographic position with a occupancy of 2/3 for Sm and of 1/3 for Ca, and are eightfold coordinated by O atoms. The TaO6 octa­hedron is joined to six others via corner-sharing LiO4 tetra­hedra. One Li and the O atoms lie on general positions, while the other atoms are situated on special positions. The Sm/Ca position has 222, Ta has , and the tetra­hedrally coordinated Li atom has site symmetry

Determination of the thermoelectric properties of a skutterudite-based device at practical operating temperatures by impedance spectroscopy

Skutterudite-based thermoelectric materials are promising candidates for waste heat recovery applications at intermediate temperatures (300–500 °C) owing to their high dimensionless figure of merit and power factor. Recently, several researchers have reported the high performance of skutterudite-based thermoelectric devices obtained by optimizing the crystal structure and microstructure of skutterudite materials and developing metallization layers for device fabrication. Despite extensive research efforts toward maximizing the power density and thermoelectric conversion efficiency of skutterudite-based devices, the thermoelectric properties of such devices after fabrication remain largely unknown. Here, we systematically investigated the factors that affect the thermoelectric properties of skutterudite-based devices within the range of practical operating temperatures (23–450 °C). We successfully prepared a two-couple skutterudite-based device with titanium metallization layers on both sides of the thermoelectric legs and characterized it using scanning and transmission electron microscopy and specific contact resistance measurements. Impedance spectroscopy measurements of the two-couple skutterudite-based device revealed the figure of merit of the device and enabled the extraction of three key thermoelectric parameters (Seebeck coefficient, thermal conductivity, and electrical conductivity). The impedance spectra and extracted parameters depended strongly on the measurement temperature and were mainly attributable to the thermoelectric properties of skutterudite materials. These observations demonstrate the interplay between the properties of thermoelectric materials and devices and can aid in directing future research on thermoelectric device fabrication

Ag/Ni Metallization Bilayer: A Functional Layer for Highly Efficient Polycrystalline SnSe Thermoelectric Modules

The structural and electrical characteristics of Ag/Ni bilayer metallization on polycrystalline thermoelectric SnSe were investigated. Two difficulties with thermoelectric SnSe metallization were identified for Ag and Ni single layers: Sn diffusion into the Ag metallization layer and unexpected cracks in the Ni metallization layer. The proposed Ag/Ni bilayer was prepared by hot-pressing, demonstrating successful metallization on the SnSe surface without interfacial cracks or elemental penetration into the metallization layer. Structural analysis revealed that the Ni layer reacts with SnSe, forming several crystalline phases during metallization that are beneficial for reducing contact resistance. Detailed investigation of the Ni/SnSe interface layer confirms columnar Ni-Sn intermetallic phases [(Ni3Sn and Ni3Sn2) and Ni5.63SnSe2] that suppress Sn diffusion into the Ag layer. Electrical specific-contact resistivity (5.32 9 104 X cm2) of the Ag/Ni bilayer requires further modification for development of high-efficiency polycrystalline SnSe thermoelectric modules. (c) 2016 The Minerals, Metals & Materials Society4

Electrochemical synthesis of ammonia from water and nitrogen catalyzed by nano-Fe2O3 and CoFe2O4 suspended in a molten LiCl-KCl-CsCl electrolyte

Nano-Fe2O3 and CoFe2O4 were suspended in molten salt of alkali-metal chloride (LiCl-KCl-CsCl) and their catalytic activity in electrochemical ammonia synthesis was evaluated from potentiostatic electrolysis at 600 K. The presence of nanoparticle suspension in the molten chloride resulted in improved production of NH3, recording NH3 synthesis rate of 1.78x10(-10) mol s(-)1 cm(-2) and 3.00x10(-10) mol s(-1) cm(-2) with CoFe2O4 and Fe2O3, which are 102% and 240% higher than that without the use of a nanocatalyst, respectively. We speculated that the nanoparticles triggered both the electrochemical reduction of nitrogen and also chemical reaction between nitrogen and hydrogen that was produced from water electro-reduction on cathode. The use of nanocatalysts in the form of suspension offers an effective way to overcome the sluggish nature of nitrogen reduction in the molten chloride electrolyte

Electrochemical Synthesis of Ammonia from Water and Nitrogen in Ethylenediamine under Ambient Temperature and Pressure

In this study, a novel electrolysis cell based on ethylenediamine (EDA) as a cathodic solvent was developed for NH3 electro-synthesis. The NH3-generating cathode chamber was filled with 0.1 M LiCl/EDA and separated by a cation exchange membrane from the anodic compartment, which was filled with 0.05 M H2SO4 aqueous solution. It appeared that EDA was cathodically stable, and thus electron-stealing medium destruction was substantially avoided. The faradaic efficiency for NH3 synthesis was 17.2%, producing 7.73 x 10(-7) mol NH3 for 1 h electrolysis at a cell voltage of 1.8 V with the charge consumption of 1.3 C. (C) 2016 The Electrochemical Society. All rights reserved