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Magnetic field-assisted method has been proved as an effective method to improve oxygen evolution reaction performance (OER) of water splitting, however, the essential reason for the improvement of OER performance still remains unclear. Herein, Ni 1- x Zn x Fe 2 O 4 ferrites were prepared by the combination of hydrothermal and calcination method, the magnetic properties, oxygen evolution reaction performance and the effect of applied magnetic field on OER performance were studied and discussed according to the magnetic properties and ion site situation. The magnetic field effect depended on the applied magnetic field strength and the magnetic magnetization density of catalysts, it was attributed to changes of electron state and redistribution of ions in the spinel structure. The overpotential decreased by approximately 50 mV and its double layer capacitance increased about 60 % at 125 mT applied magnetic field. The results provided a newness research view for the domain of electrochemistry. [ABSTRACT FROM AUTHOR]

In this work, Ni-doped LiMn 2 O 4 spinel oxides were studied as the cathode materials of low temperature proton ceramic fuel cell. Increasing the content of doping Ni to 0.5, the calculated active energy of the polarization process of the cell decreased from 0.62 to 0.49 eV. The cell performance increased with the Ni doping of LiMn 2 O 4 cathode, and the optimal power density reached to 547 mW cm−2 at 550 °C with a low polar resistance of 0.42 Ω cm2 for LiNi 0.5 Mn 1.5 O 4. Ni partially replacing Mn at the B site could increase the content of Mn4+, resulting in the increase of oxygen vacancy content to maintain the charge balance, which is beneficial to the oxygen reduction reaction. These results demonstrate that spinel oxide could be a promising cathode material with highly oxygen reduction activity for advanced low temperature solid ceramic fuel cells. [ABSTRACT FROM AUTHOR]

In this work, Ni-doped LiMn 2 O 4 spinel oxides were studied as the cathode materials of low temperature proton ceramic fuel cell. Increasing the content of doping Ni to 0.5, the calculated active energy of the polarization process of the cell decreased from 0.62 to 0.49 eV. The cell performance increased with the Ni doping of LiMn 2 O 4 cathode, and the optimal power density reached to 547 mW cm−2 at 550 °C with a low polar resistance of 0.42 Ω cm2 for LiNi 0.5 Mn 1.5 O 4. Ni partially replacing Mn at the B site could increase the content of Mn4+, resulting in the increase of oxygen vacancy content to maintain the charge balance, which is beneficial to the oxygen reduction reaction. These results demonstrate that spinel oxide could be a promising cathode material with highly oxygen reduction activity for advanced low temperature solid ceramic fuel cells. [ABSTRACT FROM AUTHOR]

Chromium-based spinels with multiple mixed valence states have been considered as promising electrocatalysts. However, they are rarely reported as electrochemical sensors. Herein, spinel CoCr 2 O 4 nanocrystals with mixed redox couplings were controllably synthesized through a simple sol-gel method followed by air calcination at 500 °C and 600 °C. The X-ray photoelectron spectrum analyses reveal that CoCr 2 O 4 -500 and CoCr 2 O 4 -600 products possess different surface ratios of Co3+/Co2+ and Cr3+/Cr2+. Meanwhile, non-enzymatic H 2 O 2 electrochemical sensors were successfully fabricated by drop-coating the aforementioned nanomaterials onto the surface of bare glassy carbon electrode (GCE). Amongst, CoCr 2 O 4 -500/GCE shows high sensitivity (1016 μA mM-1 cm-2), low detection limit (150 nM) and wide detection range to H 2 O 2 in 0.1 M NaOH solution. These important indicators are better than those of CoCr 2 O 4 -600/GCE. It is also the first time to achieve highly sensitive detection of H 2 O 2 by pure chromite spinels so far. Such excellent electrochemical sensing performance stems from the synergistic effect of its large apparent electrode area, high electrical conductivity and proper surface ratio of mixed redox couplings for Co3+/2+/Cr3+/2+. Moreover, it also exhibits good selectivity, stability and recovery rate to trace H 2 O 2 in milk whey, mouthwash and contact lens cleaning solution. [Display omitted] [ABSTRACT FROM AUTHOR]

A new spinel oxide CoFe 1.9 Li 0.1 O 4 (CFLO) has been synthesized as a cathode material for proton-conducting solid oxide fuel cells. CFLO has good structure stability up to 900 °C. In addition, the material can survive in both CO 2 and steam-containing atmospheres. Compared with the Li-free sample, the Li-doping strategy significantly regulates the material's electronic structure. The low valence of Li leads to the increased amount of Fe and Co cations with higher valences. Furthermore, doping Li creates more oxygen vacancies at the material surface, which benefits the oxygen reduction reaction (ORR). The improved cathode performance for CFLO has been demonstrated that a cell using CFLO cathode reaches a peak power density of 1052 mW cm−2 at 700 °C. The cell performance is 60% larger than the Li-free cell, and similar results can be detected at other testing temperatures. In addition, the CFLO cell shows good long-term stability in the working condition. This study proposes the Li-doping strategy to modify spinel oxides and also provides a new spinel oxide as a high-performing cathode for H–SOFCs. [ABSTRACT FROM AUTHOR]

We mainly focused on synthesis of boron doped cobalt gallium oxide (B doped CoGa 2 O 4) nanoparticles. In the study, varied amount of B doped CoGa 2 O 4 nanopowders were produced employing Sol-Gel technique. The structural characterizations of the particles were performed using x-ray powder diffractometer (XRD) and x-ray photoelectron spectroscopy (XPS) measurements. Rietveld refinements were utilized to investigate B atom replacement and thus, the changes in lattice parameters. Furthermore, the reflectance and absorbance performances were measured by UV–visible spectrophotometer in order to determine electronic energy level configurations through the band gap. The relationship between crystal structural and formation of electronic energy levels was also investigated according to the locations of substituted B atoms. [ABSTRACT FROM AUTHOR]

Phase relations within the "FeO–V 2 O 3 " oxide system at 1473 K in the oxygen partial pressure range from 5.98 × 10−15 to 2.39 × 10−8 atm were determined using the chemical equilibrium and quench method followed by XRD and EPMA measurements. There exist four univariant equilibria and two invariant equilibria in the "FeO–V 2 O 3 " oxide system. According to the determined phase relations, a phase diagram of this system was constructed by plotting log ( p O 2 / a t m ) versus the molar ratio of V/(Fe + V). Furthermore, the magnetic properties of a series of spinel Fe 3- x V x O 4 compounds prepared under different oxygen partial pressures were measured at room temperature. It was revealed that Fe 3- x V x O 4 compounds with Fe/V larger than 1.2 are magnetic, and their magnetizations increase remarkably with the increasing of the molar ratio of Fe/V. In addition, for the Fe 3- x V x O 4 compound with fixed molar ratio of Fe/V, its saturation magnetization increases slightly with the increasing of the oxygen partial pressure in which the compound was prepared. [ABSTRACT FROM AUTHOR]

A solid oxide fuel cell (SOFC) stack requires metallic interconnects to electrically connect unit cells, while preventing fuel from mixing with oxidant. During SOFC operations, chromia scales continue to grow on the interconnect surfaces, resulting in a considerable increase of interfacial resistance, and at the same time, gaseous Cr species released from the chromia scales degrades the cathode performance. To address these problems, in this study, protective Mn 2 CuO 4 coatings are fabricated on metallic interconnects (Crofer 22 APU) via a plasma spray (PS) process. The PS technique involves direct spray deposition of molten Mn 2 CuO 4 onto the interconnect substrate and leads to the formation of high-density Mn 2 CuO 4 coatings without the need for post-heat-treatment. The thickness, morphology, and porosity of the PS-Mn 2 CuO 4 coating are found to depend on the processing parameters, including plasma arc power, gas flow rate, and substrate temperature. The PS-Mn 2 CuO 4 coating fabricated with optimized parameters is completely impermeable to gases and has high adhesion strength on the interconnect substrate. Furthermore, no resistive chromia scales are formed at the coating/substrate interface during the PS process. As a result, the PS-Mn 2 CuO 4 -coated interconnects show a very low area-specific resistance below 10 mΩ cm 2 at 800 °C in air and excellent stability during both continuous operation and repeated thermal cycling. This work suggests that an appropriate combination of the material and coating process provides a highly effective protective layer for SOFC interconnects. [ABSTRACT FROM AUTHOR]