Facilitating charge transfer via a Semi-Coherent Fe(PO3)2-Co2P2O7 heterointerface for highly efficient Zn-Air batteries.

Developing reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for achieving high-performance rechargeable Zn-air batteries (ZABs). This study introduced an nitrogen-doped carbon confined with a semi-coherent Fe(PO3)2-Co2P2O7 heterojunction for bifunctional oxygen electrocatalysis. This nanocomposite yielded an ORR half-wave potential of 0.908 V and an OER overpotential of 291 mV at 10 mA/cm2. ZABs incorporating this catalyst yielded impressive performance, including a peak power density of 203 mW/cm2, a specific capacity of 737 mAh/gZn, and promoted stability. Both experimental and theoretical simulations demonstrated that the unique electric field between Fe(PO3)2 and Co2P2O7 promoted efficient charge transport across the heterointerface. This interaction likely modulated the d-band center of the heterojunction, expedite the desorption of oxygen intermediates, thus improving oxygen catalysis and, consequently, ZAB performance. This work illustrates a significant design principle for creating efficient bifunctional catalysts in energy conversion technologies.

2D MXene/MBene Superlattice with Narrow Bandgap as Superior Electrocatalyst for High-Performance Lithium-Oxygen Battery.

Lithium-oxygen (Li-O2) battery with large theoretical energy density (≈3500 Wh kg-1) is one of the most promising energy storage and conversion systems. However, the slow kinetics of oxygen electrode reactions inhibit the practical application of Li-O2 battery. Thus, designing efficient electrocatalysts is crucial to improve battery performance. Here, Ti3C2 MXene/Mo4/3B2-x MBene superlattice is fabricated its electrocatalytic activity toward oxygen redox reactions in Li-O2 battery is studied. It is found that the built-in electric field formed by a large work function difference between Ti3C2 and Mo4/3B2-x will power the charge transfer at the interface from titanium (Ti) site in Ti3C2 to molybdenum (Mo) site in Mo4/3B2-x. This charge transfer increases the electron density in 4d orbital of Mo site and decreases the d-band center of Mo site, thus optimizing the adsorption of intermediate product LiO2 at Mo site and accelerating the kinetics of oxygen electrode reactions. Meanwhile, the formed film-like discharge products (Li2O2) improve the contact with electrode and facilitate the decomposition of Li2O2. Based on the above advantages, the Ti3C2 MXene/Mo4/3B2-x MBene superlattice-based Li-O2 battery exhibits large discharge specific capacity (17 167 mAh g-1), low overpotential (1.16 V), and superior cycling performance (475 cycles).

Measurement of Algal Photosynthesis Using a Clark-Type O2 Electrode.

The Clark-type electrode can be used to assess the rates of photosynthesis by detecting changes in O2 concentration in a culture. This chapter describes a method for a liquid phase measurement of light and dissolved inorganic carbon-dependent photosynthesis using the model green alga Chlamydomonas reinhardtii. The technique can be used to evaluate the presence or efficiency of carbon-concentrating mechanisms.

Enhanced Oxygen Evolution Rate and Anti-interfacial Delamination Property of the SrCo0.9Ta0.1O3-δ@La0.6Sr0.4Co0.2Fe0.8O3-δ Oxygen-Electrode for Solid Oxide Electrolysis Cells.

Interfacial delamination between the oxygen-electrode and electrolyte is a significant factor impacting the reliability of solid oxide electrolysis cells (SOECs) when operating at high voltages. The most effective method to mitigate this delamination is to decrease the interfacial oxygen partial pressure, which can be accomplished by amplifying the oxygen exsolution rate and the O2- transport rate of the oxygen-electrode. In this study, a SrCo0.9Ta0.1O3-δ (SCT) film with an outstanding oxygen surface exchange coefficient and an outstanding O2- conductivity was introduced onto the La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) surface by infiltration. This composite oxygen-electrode exhibited a notably high electrochemical catalytic activity primarily due to the significantly improved O2- transport and oxygen surface exchange rate. Single cells with a 15-LSCF oxygen-electrode achieved a peak power density of 1.33 W cm-2 at 700 °C and a current density of 1.25 A cm-2 at 1.3 V (60% H2O-H2) at 750 °C. Additionally, an electrolysis cell with a 15 wt % SCT-infiltrated LSCF oxygen-electrode demonstrated stable operation even at high current densities for over 330 h with no noticeable delamination. The remarkable durability of the 15-LSCF oxygen-electrode can be attributed to the boosted oxygen exsolution reaction (OER) activity and the suppression of Sr segregation due to SCT infiltration. The impressive OER activity and resistance to interfacial delamination make the 15-LSCF a promising candidate for a composite oxygen-electrode in SOECs.

Oxygen Electrode PrBa0.5Sr0.5Co1.5Fe0.5O5+δ-BaZr0.1Ce0.7Y0.1Yb0.1O3-δ with Different Composite Proportions for Proton-Conducting Solid Oxide Electrolysis Cells.

Proton-conducting solid oxide electrolysis cell (H-SOEC), as a hydrogen production device using proton conductor oxides as an electrolyte, has gained attention due to its various advantages of being more suitable for operating conditions at intermediate and low temperatures. However, its commercialization urgently needs to address the issue of insufficient catalytic activity of the oxygen electrode at lower temperatures. In this work, PrBa0.5Sr0.5Co1.5Fe0.5O5+δ-BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (PBSCF-BZCYYb) series composite materials (denoted as PBSCF-BZCYYb46, PBSCF- BZCYYb55, and PBSCF-BZCYYb64 based on the mass ratios of PBSCF and BZCYYb as 4:6, 5:5, and 6:4, respectively) are prepared and applied as oxygen electrodes for H-SOECs. The H-SOECs with the structure of PBSCF-BZCYYb|BZCYYb|NiO-BZCYYb (active layer)|NiO-BZCYYb (support layer) are prepared and recorded as Cell 1, Cell 2, and Cell 3 with PBSCF-BZCYYb46, PBSCF-BZCYYb55, and PBSCF-BZCYYb64 as oxygen electrodes. The H-SOECs exhibit electrolysis current densities of 669.00, 743.80, and 503.30 mA cm-2 under 1.3 V at 650 °C, respectively. The cells also show considerable stability in the constant voltage electrolysis of 179.5, 152.8, and 83.0 h, respectively. Through the comparison of various electrochemical properties, PBSCF-BZCYYb55 is considered the most promising oxygen electrode material in this work.

Microbial Biosensor for Characterization of a Microorganism: A Review focusing on the Biochemical Activity of Microbial Cells.

Express assessment of the biochemical activity of microorganisms is important in both applied and fundamental research. A laboratory model of a microbial electrochemical sensor formed on the basis of the culture of interest is a device that provides rapidly information about the culture and is cost effective, simple to fabricate and easy to use. This paper describes the application of laboratory models of microbial sensors in which the Clark-type oxygen electrode was used as a transducer. The formation of the models of the reactor microbial sensor (RMS) and the membrane microbial sensor (MMS) and the formation of the response of biosensors are compared. RMS and MMS are based on intact or immobilized microbial cells, respectively. For MMS, the response of biosensor is caused both by the process of transport of substrate into microbial cells and by the process of the initial metabolism of substrate; and only initial substrate metabolism triggers the RMS response. The details of the application of biosensors for the study of allosteric enzymes and inhibition by substrate are discussed. For inducible enzymes, special attention is paid to the induction of microbial cells. This article addresses current problems related to implementation of the biosensor approach and discusses the ways how to overcome these problems.

Intelligent Chip-Controlled Smart Oxygen Electrodes for Constructing Rechargeable Zinc-Air Batteries with Excellent Energy Efficiency and Durability.

High-performance rechargeable oxygen electrodes are key devices for realizing high-specific-energy batteries, including zinc-air and lithium-air batteries. However, these batteries have severe problems of premature decay in energy efficiency by serious corrosion, wide charge-discharge gap, and catalyst peeling off. Herein, we propose a "smart dual-oxygen electrode", which is composed of an intelligent switch control module + heterostructured Fe1Ni3-LDH/PNCNF OER catalysis electrode layer + ion conductive | electronic insulating membrane + Pt/C ORR catalysis electrode layer, where OER and ORR layers are automatically switched by the intelligent switch control module as required. This smart dual-oxygen electrode offers an ultralow energy efficiency decay rate of 0.0067% after 300 cycles during cycling, much lower than that of the commercial Pt/C electrode (1.82%). The assembled rechargeable zinc-air battery (RZAB) displays a super narrow voltage gap and achieves a high energy efficiency of 71.7%, far higher than that of the existing RZABs (about 50%). Therefore, this strategy provides a complete solution for designing various high-performance metal-air secondary batteries.

Closed-Pore Formation in Oxygen Electrodes for Solid Oxide Electrolysis Cells Investigated by Impedance Spectroscopy.

Electrochemical impedance spectroscopy was used to investigate the chemical capacitance of La0.6Sr0.4CoO3-δ (LSC) thin-film electrodes under anodic polarization (i.e., in the electrolysis mode). For this purpose, electrodes with different microstructures were prepared via pulsed-laser deposition. Analysis of dense electrodes and electrodes with open porosity revealed decreasing chemical capacitances with increasing anodic overpotentials, as expected from defect chemical considerations. However, extremely high chemical capacitance peaks with values in the range of 104 F/cm3 at overpotentials of >140 mV were obtained after annealing for several hours in synthetic air and/or after applying high anodic bias voltages of >750 mV. From the results of several surface analysis techniques and transmission electron microscopy, it is concluded that closed pores develop upon both of these treatments: (i) During annealing, initially open pores get closed by SrSO4, which forms due to strontium segregation in measurement gases with minute traces of sulfur. (ii) The bias treatment causes mechanical failure and morphological changes including closed pores in the bulk of dense films. Under anodic polarization, high-pressure oxygen accumulates in those closed pores, and this causes the capacitance peak. Model calculations based on a real-gas equation allow us to properly predict the experimentally obtained capacitance increase. We demonstrate that analysis of the chemical capacitance of oxygen electrodes in solid oxide electrolysis cells can thus be used as a nondestructive observation tool to detect and quantify closed porosity with a lower detection limit between 10-4 and 10-3.

Tuning Electrochemical Performance by Microstructural Optimization of the Nanocrystalline Functional Oxygen Electrode Layer for Solid Oxide Cells.

Further development of solid oxide fuel cell (SOFC) oxygen electrodes can be achieved through improvements in oxygen electrode design by microstructure miniaturization alongside nanomaterial implementation. In this work, improved electrochemical performance of an La0.6Sr0.4Co0.2Fe0.8O3-d (LSCF) cathode was achieved by the controlled modification of the La0.6Sr0.4CoO3-d (LSC) nanocrystalline interlayer introduced between a porous oxygen electrode and dense electrolyte. The evaluation was carried out for various LSC layer thicknesses, annealing temperatures, oxygen partial pressures, and temperatures as well as subjected to long-term stability tests and evaluated in typical operating conditions in an intermediate temperature SOFC. Electrochemical impedance spectroscopy and a distribution of relaxation times analysis were performed to reveal the rate-limiting electrochemical processes that limit the overall electrode performance. The main processes with an impact on the electrode performance were the adsorption of gaseous oxygen O2, dissociation of O2, and charge transfer-diffusion (O2-). The introduction of a nanoporous and nanocrystalline interlayer with extended electrochemically active surface area accelerates the oxygen surface exchange kinetics and oxygen ion diffusions, reducing polarization resistances. The polarization resistance of the reference LSCF was lowered by one order of magnitude from 0.77 to 0.076 Ω·cm2 at 600 °C by the deposition of a 400 nm LSC interlayer at the interface. The developed electrode tested in the anode-supported fuel cell configuration showed a higher cell performance by 20% compared to the cell with the reference electrode. The maximum power density at 700 °C reaches 675 and 820 mW·cm-2 for the reference cell and the cell with the LSC interlayer, respectively. Aging tests at 700 °C under a high load of 1 A·cm2 were performed.

Solid Oxide Cells with Phase-Inversion Tape-Casted Hydrogen Electrode and SrSc0.175Nb0.025Co0.8O3-δ Oxygen Electrode for High-Performance Reversible Power Generation and Hydrogen Production.

Solid oxide cells (SOCs) have been considered as a promising energy conversion and storage device. However, state-of-the-art cells' practical application with conventionally fabricated Ni-(Y2O3)0.08(ZrO2)0.92 (YSZ) cermet hydrogen electrode and La0.8Sr0.2MnO3 perovskite oxygen electrode is strongly limited by the unsatisfactory performance. Instead, new advances in cell materials and fabrication techniques that can lead to significant performance enhancements are urgently demanded. Here, we report a high-performance reversible SOC that consisted of a combination of SrSc0.175Nb0.025Co0.8O3-δ (SSNC) and phase-inversion tape-casted Ni-YSZ, which served as the oxygen and hydrogen electrode, respectively. The hydrogen electrode synthesized from phase-inversion tape-casting showed a high porosity of 60.8%, providing sufficient active sites for hydrogen oxidation in the solid oxide fuel cell (SOFC) mode and H2O electrolysis in the solid oxide electrolysis cell (SOEC) mode. Accordingly, it was observed that the maximum power density of 2.3 W cm-2 was attained at 750 °C in SOFC mode and a current density of -1.59 A cm-2 was obtained at 1.3 V in SOEC mode. Hence, these results reveal that the simultaneous optimization of oxygen and hydrogen electrodes is a pragmatic strategy that improves the performance of SOCs, which may significantly accelerate the commercialization of such an attractive technology.

Origin for electrochemically driven phase transformation in the oxygen electrode for a solid oxide cell.

The next generation of fuel cells, electrolyzers, and batteries requires higher power, faster kinetics, and larger energy density, which necessitate the use of compositionally complex oxides to achieve multifunctionalities and activity. These compositionally complex oxides may change their phases and structures during an electrochemical process-a so-called "electrochemically driven phase transformation." The origin for such a phase change has remained obscure. The aim of this paper is to present an experimental study and a theoretical analysis of phase evolution in praseodymium nickelates. Nickelate-based electrodes show up to 60 times greater phase transformation during operation when compared with thermally annealed ones. Theoretical analysis suggests that the presence of a reduced oxygen partial pressure at the interface between the oxygen electrode and the electrolyte is the origin for the phase change in an oxygen electrode. Guided by the theory, the addition of the electronic conduction in the interface layer leads to the significant suppression of phase change while improving cell performance and performance stability.

Synergy of cobalt vacancies and iron doping in cobalt selenide to promote oxygen electrode reactions in lithium-oxygen batteries.

Electronic structural engineering plays a key role in the design of high-efficiency catalysts. Here, to achieve optimal electronic states, introduction of exotic Fe dopant and Co vacancy into CoSe2 nanosheet (denoted as Fe-CoSe2-VCo) is presented. The obtained Fe-CoSe2-VCo demonstrates excellent catalytic activity as compared to CoSe2. Experimental results and density functional theory (DFT) calculations confirm that Fe dopant and Co defects cause significant electron delocalization, which reduces the adsorption energy of LiO2 intermediate on the catalyst surface, thereby obviously improving the electrocatalytic activity of Fe-CoSe2-VCo towards oxygen redox reactions. Moreover, the synergistic effect between Co vacancy and Fe dopant is able to optimize the microscopic electronic structure of Co ion, further reducing the energy barrier of oxygen electrode reactions on Fe-CoSe2-VCo. And the lithium-oxygen batteries (LOBs) based on Fe-CoSe2-VCo electrodes demonstrate a high Coulombic efficiency (CE) of about 72.66%, a large discharge capacity of about 13723 mA h g-1, and an excellent cycling life of about 1338 h. In general, the electronic structure modulation strategy with the reasonable introduction of vacancy and dopant is expected to inspire the design of highly efficient catalysts for various electrochemical systems.

Catalase Activity in Keratinocytes, Stratum Corneum, and Defatted Algae Biomass as a Potential Skin Care Ingredient.

The generation of reactive oxygen species presents a destructive challenge for the skin organ and there is a clear need to advance skin care formulations aiming at alleviating oxidative stress. The aim of this work was to characterize the activity of the antioxidative enzyme catalase in keratinocytes and in the skin barrier (i.e., the stratum corneum). Further, the goal was to compare the activity levels with the corresponding catalase activity found in defatted algae biomass, which may serve as a source of antioxidative enzymes, as well as other beneficial algae-derived molecules, to be employed in skin care products. For this, an oxygen electrode-based method was employed to determine the catalase activity and the apparent kinetic parameters for purified catalase, as well as catalase naturally present in HaCaT keratinocytes, excised stratum corneum samples collected from pig ears with various amounts of melanin, and defatted algae biomass from the diatom Phaeodactylum tricornutum. Taken together, this work illustrates the versatility of the oxygen electrode-based method for characterizing catalase function in samples with a high degree of complexity and enables the assessment of sample treatment protocols and comparisons between different biological systems related to the skin organ or algae-derived materials as a potential source of skin care ingredients for combating oxidative stress.

Solid Oxide Cell Electrode Nanocomposites Fabricated by Inkjet Printing Infiltration of Ceria Scaffolds.

The enhancement of solid oxide cell (SOC) oxygen electrode performance through the generation of nanocomposite electrodes via infiltration using wet-chemistry processes has been widely studied in recent years. An efficient oxygen electrode consists of a porous backbone and an active catalyst, which should provide ionic conductivity, high catalytic activity and electronic conductivity. Inkjet printing is a versatile additive manufacturing technique, which can be used for reliable and homogeneous functionalization of SOC electrodes via infiltration for either small- or large-area devices. In this study, we implemented the utilization of an inkjet printer for the automatic functionalization of different gadolinium-doped ceria scaffolds, via infiltration with ethanol:water-based La1-xSrxCo1-yFeyO3-δ (LSCF) ink. Scaffolds based on commercial and mesoporous Gd-doped ceria (CGO) powders were used to demonstrate the versatility of inkjet printing as an infiltration technique. Using yttrium-stabilized zirconia (YSZ) commercial electrolytes, symmetrical LSCF/LSCF-CGO/YSZ/LSCF-CGO/LSCF cells were fabricated via infiltration and characterized by SEM-EDX, XRD and EIS. Microstructural analysis demonstrated the feasibility and reproducibility of the process. Electrochemical characterization lead to an ASR value of ≈1.2 Ω cm2 at 750 °C, in the case of nanosized rare earth-doped ceria scaffolds, with the electrode contributing ≈0.18 Ω cm2. These results demonstrate the feasibility of inkjet printing as an infiltration technique for SOC fabrication.

Adjusting the Covalency of Metal-Oxygen Bonds in LaCoO3 by Sr and Fe Cation Codoping to Achieve Highly Efficient Electrocatalysts for Aprotic Lithium-Oxygen Batteries.

Developing high-efficiency dual-functional catalysts to promote oxygen electrode reactions is critical for achieving high-performance aprotic lithium-oxygen (Li-O2) batteries. Herein, Sr and Fe cation-codoped LaCoO3 perovskite (La0.8Sr0.2Co0.8Fe0.2O3-σ, LSCFO) porous nanoparticles are fabricated as promising electrocatalysts for Li-O2 cells. The results demonstrate that the LSCFO-based Li-O2 batteries exhibit an extremely low overpotential of 0.32 V, ultrahigh specific capacity of 26 833 mA h g-1, and superior long-term cycling stability (200 cycles at 300 mA g-1). These prominent performances can be partially attributed to the existence of abundant coordination unsaturated sites caused by oxygen vacancies in LSCFO. Most importantly, density functional theory (DFT) calculations reveal that codoping of Sr and Fe cations in LaCoO3 results in the increased covalency of Co 3d-O 2p bonds and the transition of Co3+ from an ordinary low-spin state to an intermediate-spin state, eventually resulting in the transformation from nonconductor LCO to metallic LSCFO. In addition, based on the theoretical calculations, it is found that the inherent adsorption capability of LSCFO toward the LiO2 intermediate is reduced due to the increased covalency of Co 3d-O 2p bonds, leading to the formation of large granule-like Li2O2, which can be effectively decomposed on the LSCFO surface during the charging process. Notably, this work demonstrates a unique insight into the design of advanced perovskite oxide catalysts via adjusting the covalency of transition-metal-oxygen bonds for high-performance metal-air batteries.

Enhanced Electrochemical Performance of the Fe-Based Layered Perovskite Oxygen Electrode for Reversible Solid Oxide Cells.

Reversible solid oxide cells (RSOCs) present a conceivable potential for addressing energy storage and conversion issues through realizing efficient cycles between fuels and electricity based on the reversible operation of the fuel cell (FC) mode and electrolysis cell (EC) mode. Reliable electrode materials with high electrochemical catalytic activity and sufficient durability are imperatively desired to stretch the talents of RSOCs. Herein, oxygen vacancy engineering is successfully implemented on the Fe-based layered perovskite by introducing Zr4+, which is demonstrated to greatly improve the pristine intrinsic performance, and a novel efficient and durable oxygen electrode material is synthesized. The substitution of Zr at the Fe site of PrBaFe2O5+δ (PBF) enables enlarging the lattice free volume and generating more oxygen vacancies. Simultaneously, the target material delivers more rapid oxygen surface exchange coefficients and bulk diffusion coefficients. The performance of both the FC mode and EC mode is greatly enhanced, exhibiting an FC peak power density (PPD) of 1.26 W cm-2 and an electrolysis current density of 2.21 A cm-2 of single button cells at 700 °C, respectively. The reversible operation is carried out for 70 h under representative conditions, that is, in air and 50% H2O + 50% H2 fuel. Eventually, the optimized material (PBFZr), mixed with Gd0.1Ce0.9O2, is applied as the composite oxygen electrode for the reversible tubular cell and presents excellent performance, achieving 4W and 5.8 A at 750 °C and the corresponding PPDs of 140 and 200 mW cm-2 at 700 and 750 °C, respectively. The enhanced performance verifies that PBFZr is a promising oxygen electrode material for the tubular RSOCs.

Surface atomic modulation of CoP bifunctional catalyst for high performance Li-O2 battery enabled by high-index (211) facets.

The rational design of the surface structure and morphology characteristics of the catalyst at atomic level are the key to improve the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in lithium-oxygen (Li-O2) battery. Here a series of cobalt phosphide (CoP) electrocatalysts with a variety of index facets are successfully prepared including concave polyhedrons CoP exposing with (211) crystal planes (CoP CPHs) spherical nanoparticles CoP exposed with (011) crystal planes and polyhedron particles CoP exposing with (011) and (111) crystal planes. The results show that CoP CPHs based Li-O2 battery presents a large discharge capacity of 33743 mA h g-1 at current density of 50 mA g-1 and a remarkable long cycle life of up to 950 h. The experimental results demonstrates that the CoP CPHs electrode exposing with high-index (211) facets based Li-O2 battery exhibits an extremely low overpotential (0.67 V) ultrahigh specific capacity (33743 mAh g-1) and remarkable long-term stability of up to 950 h. Most importantly density functional theory (DFT) calculations demonstrate the excellent electrocatalytic activity of high-index (211) facets as compared to the low-index (011) and (111) planes are because of the existence of large density of atomic steps edge ledge sites and kinks which supply a wide space for breaking chemical bonds and increasing the reaction activity for oxygen electrode.

Sensitive and selective methanol biosensor using two-enzyme cascade reaction and fluorometry for non-invasive assessment of intestinal bacteria activity.

For understanding the status of intestinal flora non-invasively, methanol (MeOH) has been attracting the attention. In this study, we have developed and compared two different liquid-phase methanol biosensors. One, referred to as the AOD electrosensor, utilized alcohol oxidase (AOD) and an oxygen electrode. It electrochemically measured the decrease in oxygen through AOD-catalyzed oxidation of MeOH. The other, referred to as the AOD-FALDH fluorosensor, exploited a cascade reaction of AOD and formaldehyde dehydrogenase (FALDH) in conjunction with a fiber-optic sensor. It measured increase in the fluorescence from reduced form of ß-nicotinamide adenine dinucleotide (NADH) that was a final product of the two-enzyme cascade reaction. Due to the cascade reaction, the AOD-FALDH fluorosensor showed 3 times better sensitivity along with 335 times wider dynamic range (494 nM-100 mM) than those of the AOD electrosensor (1.5-300 µM). The selectivity to MeOH was also improved by the cascade reaction with AOD-FALDH as no sensor output was observed from other aliphatic alcohols than MeOH in contrast to the AOD electrosensor. Although the use of FALDH resulted in the increase in the sensor output from aldehydes, such as acetaldehyde and formaldehyde, considering their concentrations in body fluids, the influence on the sensor output is limited. These results indicate that incorporating the cascade reaction into fluorometry enables enhanced biosensing of MeOH that will be useful for assessment of intestinal flora with little burden.

Enhancing Bifunctional Electrocatalytic Activities of Oxygen Electrodes via Incorporating Highly Conductive Sm3+ and Nd3+ Double-Doped Ceria for Reversible Solid Oxide Cells.

Solid oxide cells (SOCs) are mutually convertible energy devices capable of generating electricity from chemical fuels including hydrogen in the fuel cell mode and producing green hydrogen using electricity from renewable but intermittent solar and wind resources in the electrolysis cell mode. An effective approach to enhance the performance of SOCs at reduced temperatures is by developing highly active oxygen electrodes for both oxygen reduction and oxygen evolution reactions. Herein, highly conductive Sm3+ and Nd3+ double-doped ceria (Sm0.075Nd0.075Ce0.85O2-δ, SNDC) is utilized as an active component for reversible SOC applications. We develop a novel La0.6Sr0.4Co0.2Fe0.8O3 -δ (LSCF)-SNDC composite oxygen electrode. Compared with the conventional LSCF-Gd-doped ceria oxygen electrode, the LSCF-SNDC exhibits ∼35% lower cathode polarization resistance (0.042 Ω cm2 at 750 °C) owing to rapid oxygen incorporation and surface diffusion kinetics. Furthermore, the SOC with the LSCF-SNDC oxygen electrode and the SNDC buffer layer yields a remarkable performance in both the fuel cell (1.54 W cm-2 at 750 °C) and electrolysis cell (1.37 A cm-2 at 750 °C) modes because the incorporation of SNDC promotes the surface diffusion kinetics at the oxygen electrode bulk and the activity of the triple phase boundary at the interface. These findings suggest that the highly conductive SNDC material effectively enhances both oxygen reduction and oxygen evolution reactions, thus serving as a promising material in reversible SOC applications at reduced temperatures.

Tissue-based biosensor for monitoring the antioxidant effect of orally administered drugs in the intestine.

For a better understanding of the effect of drugs and their interaction with cells and tissues, there is a need for in vitro and ex vivo model systems which enables studying these events. There are several in vitro methods available to evaluate the antioxidant activity; however, these methods do not factor in the complex in vivo physiology. Here we present an intestinal tissue modified oxygen electrode, used for the detection of the antioxidant effect of orally administered drugs in the presence of H2O2. Antioxidants are essential in the defense against oxidative stress, more specifically against reactive oxygen species such as H2O2. Due to the presence of native catalase in the intestine, with the tissue-based biosensor we were able to detect H2O2 in the range between 50 and 500 µM. The reproducibility of the sensor based on the calculated relative standard deviations was 15 ± 6%. We found that the O2 production by catalase from H2O2 was reduced in the presence of a well-known antioxidant, quinol. This indirectly detected antioxidant activity was also observed in the case of orally administered drugs with a reported anti-inflammatory effect such as mesalazine and paracetamol, while no antioxidant activity was recorded with aspirin and metformin.