Towards high-performance tubular-type protonic ceramic electrolysis cells with all-Ni-based functional electrodes

Protonic ceramic electrolysis cells (PCECs), which permit high-temperature electrolysis of water, exhibit various advantages over conventional solid oxide electrolysis cells (SOECs), including cost-effectiveness and the potential to operate at low-/intermediate-temperature ranges with high performance and efficiency. Although many efforts have been made in recent years to improve the electrochemical characteristics of PCECs, certain challenges involved in scaling them up remain unresolved. In the present work, we present a twin approach of combining the tape-calendering method with all-Ni-based functional electrodes with the aim of fabricating a tubular-designed PCEC having an enlarged electrode area (4.6 cm2). This cell, based on a 25 µm-thick BaCe0.5Zr0.3Dy0.2O3–δ proton-conducting electrolyte, a nickel-based cermet and a Pr1.95Ba0.05NiO4+δ oxygen electrode, demonstrates a high hydrogen production rate (19 mL min–1 at 600 °C), which surpasses the majority of results reported for traditional button- or planar-type PCECs. These findings increase the scope for scaling up solid oxide electrochemical cells and maintaining their operability at reducing temperatures. © 2019 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of SciencesRussian Foundation for Basic Research, RFBR: 18-38-20063Council on grants of the President of the Russian FederationThis work was supported by the Russian Foundation for Basic Research (grant no. 18-38-20063 ). Dr. D. Medvedev is grateful to the Council of the President of the Russian Federation (scholarship no. СП−161.2018.1) for supporting the studies devoted to new MIEC materials. Other sections are performed within the framework of the budgetary plans of the Institute of High Temperature Electrochemistry

On transition to bursting via deterministic chaos

We study statistical properties of the irregular bursting arising in a class of neuronal models close to the transition from spiking to bursting. Prior to the transition to bursting, the systems in this class develop chaotic attractors, which generate irregular spiking. The chaotic spiking gives rise to irregular bursting. The duration of bursts near the transition can be very long. We describe the statistics of the number of spikes and the interspike interval distributions within one burst as functions of the distance from criticality.Comment: 8 pages, 6 figure

Surface Electronic Structures and Field Emission Currents at Sodium Overlayers on Low-Index Tungsten Surfaces

The total energy distributions (TEDs) of the emission currents in field emission and surface photofield emission and the overlayer-induced modifications in the surface electronic structures from the technologically important W surfaces with the commensurate W(100)/Na c(2x2), W(110)/Na (2x2) and W(111)/Na (1x1) overlayers are calculated. The TEDs obtained by our recent numerical method that extends the full-potential linear augmented plane wave method for the electronic structures to the study of field and photofield emission are used to interpret the shifts of the peaks in the experimental TEDs in field emission and photofield emission from the W(100) and W(110) surfaces at sub-monolayer and monolayer Na coverage. Hybridization of the 3s Na states with the pairs of dz2-like surface states of the strong Swanson hump in clean W(100) and surface resonances in clean W(111) below the Fermi energy shifts these W states by about -1.2 eV and -1.0 eV, thus stabilizing these states, to yield new strong peaks in the TEDs in field emission and photofield emission from W(100)/Na c(2x2) and W(111)/Na (1x1) respectively. The effect of Na intralayer interactions are discussed and are shown to shift the strong s- and p-like peaks in the surface density of states of W(110) below and above the Fermi energy respectively to lower energy with increased Na coverage, in agreement with experiments.Comment: 12 page

Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure

The temperature and pressure dependence of the partial density of phonon states of iron atoms in superconducting Fe1.01Se was studied by 57Fe nuclear inelastic scattering (NIS). The high energy resolution allows for a detailed observation of spectral properties. A sharpening of the optical phonon modes and shift of all spectral features towards higher energies by ~4% with decreasing temperature from 296 K to 10 K was found. However, no detectable change at the tetragonal - orthorhombic phase transition around 100 K was observed. Application of a pressure of 6.7 GPa, connected with an increase of the superconducting temperature from 8 K to 34 K, results in an increase of the optical phonon mode energies at 296 K by ~12%, and an even more pronounced increase for the lowest-lying transversal acoustic mode. Despite these strong pressure-induced modifications of the phonon-DOS we conclude that the pronounced increase of Tc in Fe1.01Se with pressure cannot be described in the framework of classical electron-phonon coupling. This result suggests the importance of spin fluctuations to the observed superconductivity

Структура и транспортные свойства композитных материалов на основе Ce0,8Nd0,2O2-δ и BaCe0,8Nd0,2O3-δ

In the present work the synthesis of materials was carried out by one-step citrate-nitrate method. The optimal synthesis temperature of the powders was chosen on the base of TG-DSC data. Phase nature of the synthesized materials was investigated by XRD and Rietveld refinement data analyzes. The influence of the perovskite phase content in the system of (1-x)Ce0.8Nd0.2O2-δ-xBaCe0.8Nd0.2O3-δ (x = 0 , 0.25, 0.5 , 0.75 and 1) on the crystallite and particle size of powders and structure properties of ceramics (relative density, porosity, grain size) were investigated. Measurements of the electrical conductivity of materials in a wide ranges of temperatures (550-900 °C) and oxygen partial pressure (10-23 ≤ pO2/atm ≤ 0,21) revealed features of transport in the composite system.В настоящей работе проведен синтез материалов путем одностадийного цитрат-нитратного метода. С привлечением данных ТГ-ДСК анализа установлены оптимальные температуры синтеза порошков. Фазовые особенности синтезированных материалов изучены РФА с привлечением метода Ритвелда. Установлено влияние содержания перовскитной фазы в системе (1-x)Ce0,8Nd0,2O2-δ-xBaCe0.8Nd0,2O3-δ (х = 0; 0,25; 0,5; 0,75 и 1) на размеры кристаллитов и частиц порошка. Исследованы керамические свойства (относительная плотность, пористость, размеры зерен) образцов, спеченных при 1500 °С. Исследование электропроводности материалов в широких интервалах температур (550-900 °С) и парциальных давлений кислорода (10-23 ≤ РО2/атм ≤ 0,21) позволило выявить особенности электропереноса в системе (1-x)Ce0,8Nd0,2O2-δ-xBaCe0,8Nd0,2O3-δ.This work was done underfinancial support RFBR grant 13-03-00065, 12-03-33002) and Council for Grants of the President of the Russian Federation (NSP-44.2012.1).Работа выполнена при поддержке РФФИ (№ 13-03-00065, 12-03-33002), а также Совета по грантам Президента РФ (№ СП-44.2012.1)

Shaping bursting by electrical coupling and noise

Gap-junctional coupling is an important way of communication between neurons and other excitable cells. Strong electrical coupling synchronizes activity across cell ensembles. Surprisingly, in the presence of noise synchronous oscillations generated by an electrically coupled network may differ qualitatively from the oscillations produced by uncoupled individual cells forming the network. A prominent example of such behavior is the synchronized bursting in islets of Langerhans formed by pancreatic \beta-cells, which in isolation are known to exhibit irregular spiking. At the heart of this intriguing phenomenon lies denoising, a remarkable ability of electrical coupling to diminish the effects of noise acting on individual cells. In this paper, we derive quantitative estimates characterizing denoising in electrically coupled networks of conductance-based models of square wave bursting cells. Our analysis reveals the interplay of the intrinsic properties of the individual cells and network topology and their respective contributions to this important effect. In particular, we show that networks on graphs with large algebraic connectivity or small total effective resistance are better equipped for implementing denoising. As a by-product of the analysis of denoising, we analytically estimate the rate with which trajectories converge to the synchronization subspace and the stability of the latter to random perturbations. These estimates reveal the role of the network topology in synchronization. The analysis is complemented by numerical simulations of electrically coupled conductance-based networks. Taken together, these results explain the mechanisms underlying synchronization and denoising in an important class of biological models

Safe and complete contig assembly via omnitigs

Contig assembly is the first stage that most assemblers solve when reconstructing a genome from a set of reads. Its output consists of contigs -- a set of strings that are promised to appear in any genome that could have generated the reads. From the introduction of contigs 20 years ago, assemblers have tried to obtain longer and longer contigs, but the following question was never solved: given a genome graph $G$ (e.g. a de Bruijn, or a string graph), what are all the strings that can be safely reported from $G$ as contigs? In this paper we finally answer this question, and also give a polynomial time algorithm to find them. Our experiments show that these strings, which we call omnitigs, are 66% to 82% longer on average than the popular unitigs, and 29% of dbSNP locations have more neighbors in omnitigs than in unitigs.Comment: Full version of the paper in the proceedings of RECOMB 201

A reversible protonic ceramic cell with symmetrically designed Pr2NiO4+δ-based electrodes: Fabrication and electrochemical features

Reversible protonic ceramic cells (rPCCs) combine two different operation regimes, fuel cell and electrolysis cell modes, which allow reversible chemical-to-electrical energy conversion at reduced temperatures with high efficiency and performance. Here we present novel technological and materials science approaches, enabling a rPCC with symmetrical functional electrodes to be prepared using a single sintering step. The response of the cell fabricated on the basis of P-N- BCZD|BCZD|PBN-BCZD (where BCZD = BaCe0.5Zr0.3Dy0.2O3-δ, PBN = Pr1.9Ba0.1NiO4+δ, P = Pr2O3, N = Ni) is studied at different temperatures and water vapor partial pressures (pH2O) by means of volt-ampere measurements, electrochemical impedance spectroscopy and distribution of relaxation times analyses. The obtained results demonstrate that symmetrical electrodes exhibit classical mixed-ionic/electronic conducting behavior with no hydration capability at 750 °C; therefore, increasing the pH2O values in both reducing and oxidizing atmospheres leads to some deterioration of their electrochemical activity. At the same time, the electrolytic properties of the BCZD membrane are improved, positively affecting the rPCC's efficiency. The electrolysis cell mode of the rPCC is found to be more appropriate than the fuel cell mode under highly humidified atmospheres, since its improved performance is determined by the ohmic resistance, which decreases with pH2O increasing. © 2018 by the authors.Российский Фонд Фундаментальных Исследований (РФФИ): 18-38-20063Funding: The majority of this work was carried out under the budgetary plans of Institute of High Temperature Electrochemistry. The design of new electrode materials and their characterization was also funded by the Russian Foundation for Basic Research, grant number 18-38-20063. Dr. Dmitry Medvedev is also grateful to the Council of the President of the Russian Federation (scholarship СП-161.2018.1) for supporting the studies devoted to search of new Co-free electrode materials