Bismuth Doped Lanthanum Ferrite Perovskites as Novel Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells

Bismuth is doped to lanthanum strontium ferrite to produce ferrite-based perovskites with a composition of La_0.8‑xBi_<i>x</i>Sr_0.2FeO_3‑δ (0 ≤ <i>x</i> ≤ 0.8) as novel cathode material for intermediate-temperature solid oxide fuel cells. The perovskite properties including oxygen nonstoichiometry coefficient (δ), average valence of Fe, sinterability, thermal expansion coefficient, electrical conductivity (σ), oxygen chemical surface exchange coefficient (<i>K</i>_chem), and chemical diffusion coefficient (<i>D</i>_chem) are explored as a function of bismuth content. While σ decreases with <i>x</i> due to the reduced Fe⁴⁺ content, <i>D</i>_chem and <i>K</i>_chem increase since the oxygen vacancy concentration is increased by Bi doping. Consequently, the electrochemical performance is substantially improved and the interfacial polarization resistance is reduced from 1.0 to 0.10 Ω cm² at 700 °C with Bi doping. The perovskite with <i>x</i> = 0.4 is suggested as the most promising composition as solid oxide fuel cell cathode material since it has demonstrated high electrical conductivity and low interfacial polarization resistance

Forearm length and actual size corresponding to 2L (1/12 of the forearm length) for each of the 8 participants.

<p>Forearm length and actual size corresponding to 2L (1/12 of the forearm length) for each of the 8 participants.</p

Electrode placement on the forearm for selective stimulation of finger extension/flexion

<div><p>It is still challenging to achieve a complex grasp or fine finger control by using surface functional electrical stimulation (FES), which usually requires a precise electrode configuration under laboratory or clinical settings. The goals of this study are as follows: 1) to study the possibility of selectively activating individual fingers; 2) to investigate whether the current activation threshold and selective range of individual fingers are affected by two factors: changes in the electrode position and forearm rotation (pronation, neutral and supination); and 3) to explore a theoretical model for guidance of the electrode placement used for selective activation of individual fingers. A coordinate system with more than 400 grid points was established over the forearm skin surface. A searching procedure was used to traverse all grid points to identify the stimulation points for finger extension/flexion by applying monophasic stimulation pulses. Some of the stimulation points for finger extension and flexion were selected and tested in their respective two different forearm postures according to the number and the type of the activated fingers and the strength of finger action response to the electrical stimulation at the stimulation point. The activation thresholds and current ranges of the selectively activated finger at each stimulation point were determined by visual analysis. The stimulation points were divided into three groups (“Low”, “Medium” and “High”) according to the thresholds of the 1^st activated fingers. The angles produced by the selectively activated finger within selective current ranges were measured and analyzed. Selective stimulation of extension/flexion is possible for most fingers. Small changes in electrode position and forearm rotation have no significant effect on the threshold amplitude and the current range for the selective activation of most fingers (<i>p</i> > 0.05). The current range is the largest (more than 2 mA) for selective activation of the thumb, followed by those for the index, ring, middle and little fingers. The stimulation points in the “Low” group for all five fingers lead to noticeable finger angles at low current intensity, especially for the index, middle, and ring fingers. The slopes of the finger angle variation in the “Low” group for digits 2~4 are inversely proportional to the current intensity, whereas the slopes of the finger angle variation in other groups and in all groups for the thumb and little finger are proportional to the current intensity. It is possible to selectively activate the extension/flexion of most fingers by stimulating the forearm muscles. The physiological characteristics of each finger should be considered when placing the negative electrode for selective stimulation of individual fingers. The electrode placement used for the selective activation of individual fingers should not be confined to the location with the lowest activation threshold.</p></div

Isomeric organic ligand dominating polyoxometalate-based hybrid compounds: synthesis and as electrocatalysts and pH-sensitive probes

<p>By introducing isomeric organic ligands into polyoxometalate (POM) systems, two new POM-based hybrid compounds, [Cu₆(<i>m</i>-pyttz)₂(H₂O)][HPMo₁₂O₄₀] (<b>1</b>) and [Ag₃(<i>p</i>-H₂pyttz)(<i>p</i>-Hpyttz)Cl][H₂PMo₁₂O₄₀]·6H₂O (<b>2</b>) (<i>m</i>-/<i>p</i>-H₂pyttz = 3-(pyrid-3/4-yl)-5(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), have been hydrothermally synthesized and characterized. Single-crystal structural analysis shows the <i>m</i>-pyttz ligands link Cu^I ions to generate a two-dimensional layer with hanger-like rhombus, which is pillared by the PMo₁₂ anions in <b>1</b>. Compound <b>2</b> exhibits a three-dimensional supramolecular framework, in which PMo₁₂ anions are building blocks facilitating the extension of the whole structure. The influence of the coordination modes of <i>m</i>-/<i>p</i>-H₂pyttz on the structures is discussed in detail. Furthermore, electrochemical properties of <b>1</b> and <b>2</b> have been studied and they display excellent electrocatalytic activities toward the reduction of nitrite and hydrogen peroxide and pH-dependent electrochemical behaviors.</p

Activation thresholds of several adjacent stimulus points under different forearm positions (Participant D).

<p>Activation thresholds of several adjacent stimulus points under different forearm positions (Participant D).</p

Stimulation points were affected by two factors and its corresponding finger angles.

<p>(A) The effect of stimulation point displacement relative to the skin on the finger activation threshold and the selective range of each individual finger were investigated. (B) The negative electrode was placed at distances of 0L, 1L, 1.414L, and 2L away from the center of the original electrode to study whether different electrode positions caused the changes in the activation threshold and selective activation range of individual fingers. (C) The IMU sensor module was used to record the 3D finger movement angle data.</p

Coordinate system established for the determination of stimulation points of the finger extension and flexion.

<p>Coordinate system established for the determination of stimulation points of the finger extension and flexion.</p

Forearm length and actual size corresponding to 2L (1/12 of the forearm length) for each of the 8 participants.

<p>Forearm length and actual size corresponding to 2L (1/12 of the forearm length) for each of the 8 participants.</p

Activation thresholds (left) and selective ranges (right) of individual fingers.

<p>(*) represents a difference in the activation thresholds at different electrode positions. (†) indicates a significant difference in the selective activation thresholds of fingers at the same grid point in different forearm positions. The results are shown as the means ± SD (<i>n</i> = 8). *^, † <i>p</i> < 0.05 as determined by two-way analysis of variance.</p

Trends of angle variations of the thumb MCP and IP joints.

<p>The angles were tested in supine and neutral forearm postures.</p