Manganese oxide base electrocatalysts for proton-conducting ceramic cells

There has been a strong interest in clean and renewable energy sources due to finite fossil fuel sources, increasing oil prices and environmental concerns. Hydrogen is regarded as the leading candidate fuel, because it releases only H2O during combustion and it is compatible to use in high efficiency fuel system. Steam reforming of hydrocarbon gas is currently the main way to produce hydrogen but still relies on fossil fuel consumption. On the contrary, water electrolysis using electric power generated by renewable energy is attracted as sustainable hydrogen production method. Especially, steam electrolysis using solid electrolyte cells is promising for efficient hydrogen production because high-temperature heat partly offers the energy for water electrolysis, leading favorable kinetics and thermodynamics. Hence, it is motivated to investigate on solid oxide electrolysis cell (SOEC) using proton-conducting ceramics to achieve highly efficient conversion from electrical power into chemical fuel gas directly. However, sufficient performance has not be achieved yet in the current system because large overpotential is needed for oxygen evolution reaction at anode owing to the relatively slow kinetics and the limited active zone in the anode/electrolyte interfaces due to the mismatch of ionic carries, Accordingly, it is a great challenge to develop high performance oxygen electrode with efficient electrocatalytic ability for 4 electron transfer oxygen evolution reaction. Recently, it is reported that high valence state metal oxide reveal superior electrocatalytic activity for water oxidation s because the energy levels between the occupied metal orbital and the O 2p orbital are very close, causing a strong hybridization and facilitating o-o bond formation. Herein, we examined electrocatalytic performance of high valence state Mn(V) oxide Ba3(MnO4)2 as an anode for SOEC This oxide has been reported to be very stable at elevated temperatures in oxidative conditions. Proton-conducting BaZr0.4Ce0.4Y0.2O3-δ (BZCY) was used as proton conducting electrolyte. Bulk electrolyte cell were constructed with a BZCY disc which were prepared by solid state reactive sintering (SSRS) method. The electrolyte precursor powder was prepared by mixing proper amount of BaCO3, CeO2, ZrO2, and Y2O3 according to the desired stoichiometry with the addition of 1.0wt.% NiO as a sintering aid. This mixture was ball-milled for 48 h and uniaxially pressed under 20 MPa for 1 min and then cold-isostatic-pressed under 100 MPa for 1 min. Finally, green pellets were calcined at 1500°C for 10 h so as to obtain dense electrolyte disc (2 mmd, 9 mmf)Pt paste was applied at one side of the surface as a cathode. LSCF or LSCF/Ba3(MnO4)2 mixed ink were screen-printed at the other side of the surface as anode materials. Samples are evaluated by XRD and XAS. The electrochemical impedance spectroscopy and I-V measurements were carried out to evaluate the SOEC properties. Two kinds of anode materials were examined in this research, namely, the cell-1: Pt | BZCY | LSCF and cell-2: Ba3(MnO4)2/LSCF mixed anode cell. The cell-2 showed superior steam electrolytic performance compared to cell-1. The current density of steam electrolysis of cell-2 was 145 mA cm-2 meanwhile cell-1 was 145 mA cm-2 in bias voltage of 1.5 V at 600°C. Impedance spectroscopy was conducted to evaluate the anodic polarization resistance. LSCF anode gives 6 Ω cm2, however, the Ba3(MnO4)2/LSCF composite anode gives 3 Ω cm2. Furthermore, the spectral features were completely different between both. The spectrum of LSCF anode had three semi-circles: high frequency arc (10x-10y Hz), middle frequency arc (10zz-10zy Hz) and low frequency arc (10zz-10zy Hz). On the other hand, Ba3(MnO4)2/LSCF involves only two semi-circles: high frequency arc (10x-10y Hz) and low frequency arc (10zz-10zy Hz). These results indicate Ba3(MnO4)2 changes the reaction pathway of water oxidation electrode/solid electrolyte interface. .The oxygen evolution rate was measured by gas chromatography when electrolysis was performed at a constant current density of 100 mA, 200 mA, and 300 mA. The flax of oxygen from anode side is corresponded to that of calculated from the current density, indicating that the faradaic efficiency was almost 100%. XRD pattern of the sample after electrolysis showed that there were no secondary phases, indicating stability of Ba3(MnO4)2 is enough to use in SOEC anodic condition. The above results suggest the Ba3(MnO4)2 is promising for OER electrocatalysts for SOEC

Design of Antioxidant Nanoparticle, which Selectively Locates and Scavenges Reactive Oxygen Species in the Gastrointestinal Tract, Increasing The Running Time of Mice

Abstract Excess reactive oxygen species (ROS) produced during strong or unfamiliar exercise cause exercise‐induced gastrointestinal syndrome (EIGS), leading to poor health and decreased exercise performance. The application of conventional antioxidants can neither ameliorate EIGS nor improve exercise performance because of their rapid elimination and severe side effects on the mitochondria. Hence, a self‐assembling nanoparticle‐type antioxidant (RNPO) that is selectively located in the gastrointestinal (GI) tract for an extended time after oral administration is developed. Interestingly, orally administered RNPO significantly enhances the running time until exhaustion in mice with increasing dosage, whereas conventional antioxidants (TEMPOL) tends to reduce the running time with increasing dosage. The running (control) and TEMPOL groups show severe damage in the GI tract and increased plasma lipopolysaccharide (LPS) levels after 80 min of running, resulting in fewer red blood cells (RBCs) and severe damage to the skeletal muscles and liver. However, the RNPO group is protected against GI tract damage and elevation of plasma LPS levels, similar to the nonrunning (sedentary) group, which prevents damage to the whole body, unlike in the control and TEMPOL groups. Based on these results, it is concluded that continuous scavenging of excessive intestinal ROS protects against gut damage and further improves exercise performance

Enhanced Performance of Protonic Solid Oxide Steam Electrolysis Cell of Zr-Rich Side BaZr0.6Ce0.2Y0.2O3-delta Electrolyte with an Anode Functional Layer

Proton-conducting solid oxide electrolysis cells (H-SOEC) containing a 15-mu m-thick BaZr0.6Ce0.2Y0.2O3-delta (BZCY622) electrolyte thin film, porous cathode cermet support, and La0.6Sr0.4Co0.2Fe0.8O3-delta anodes were fabricated using a reactive cofiring process at approximately 1400 degrees C. Steam electrolysis was conducted by supplying wet air to the anode at a water partial pressure of 20 kPa. The performance was evaluated using electrochemical measurements and gas chromatography. At 600 degrees C, the cells generated an electrolysis current of 0.47 A cm(-2) at a 1.3 V bias while the Faradaic efficiency reached 56% using 400 mA cm(-2). The electrolysis performance was efficiently improved by introducing a 40-nm-thick La0.5Sr0.5CoO3-delta (LSC) nanolayer as an anode functional layer (AFL). The cells with LSC AFL produced an electrolysis current of 0.87 A cm(-2) at a 1.3 V bias at 600 degrees C, and the Faradaic efficiency reached 65% under 400 mA cm(-2). Impedance analysis showed that the introduction of the AFL decreased the ohmic resistances and improved interfacial proton transfer across the anode/electrolyte interface and polarization resistances related to the anode reaction. These results demonstrate opportunities for future research on AFL to improve the performance of H-SOECs with Zr-rich BaZrxCe1-x-yYyO3-delta electrolytes

Effect of an Air Cleaner Based on Age of Air Distribution Measurement Using the Dynamic Steady-State Concentration

This study aims to determine the range of the effect of an air cleaner in indoor environments. The age of air is often used to evaluate the ventilation performance in indoor air environments, and step-down tracer gas methods are widely used in open-air systems in ventilation rooms. However, conventional experimental methods cannot be used to measure the age of air in air recirculation systems such as an air cleaner that do not have a ventilation system. Previous studies have shown that the dynamic steady-state concentration correlates with the equivalent steady-state concentration in the ventilation room of an open-air system. In this study, we investigated the possibility of determining the age of air by measuring the dynamic steady-state concentration generated in a real space. First, we used the tracer gas experimental technique based on the dynamic steady-state concentration to measure the age of air in a real space when an air cleaner was used. We then performed simulations to confirm the age of air distribution obtained from the tracer gas experiment using computational fluid dynamics (CFD) analysis. A comparison of the experimental and CFD analysis results showed that the effect of an air cleaner covered the entire room