Wei Yuan,Lichun Cheng,Tianrui Xia,Yucheng Chen,Qianxing Long,Qingrong Yao,Shunkang Pan,Chaohao Hu
Perovskite LaCoO 3 has unique mixed ionic electronic and structural defects, which has high research value in microwave absorption field. LaCoO 3 precursor was prepared by sol-gel method, and LaCo 1− x Fe x O 3 (Fe-LCO, x = 0, 0.05, 0.1 and 0.15) with rhombic symmetric structure was successfully synthesized at 600 °C. By refinement of X-ray diffraction (XRD) (Rietveld analysis), it was found that Fe doping makes LaCoO 3 lattice constant and cell volume increase. As a dielectric loss microwave absorbing material, the electromagnetic attenuation of LaCoO 3 is mainly due to the conduction loss, while the interface and dipole polarization are secondary reasons. It finds that Fe doping can improve the wave absorption performance of LaCoO 3 . The best absorbing performance was obtained when Fe content is x = 0.1, with the maximum reflection loss of − 38.99 dB at 10.8 GHz and the effective absorption bandwidth (RL<−10 dB) is 4.48 GHz, while the corresponding thickness was only 3 mm. In summary, LaCoO 3 has broad application prospects in X and Ku bands.
Bian Bao,Yana Liu,Mingzi Sun,Bolong Huang,Yang Hu,Pengfei Da,Deguang Ji,Pinxian Xi,Chun-Hua Yan
Realizing the rational design of perovskite oxides with controllable compositions and nanostructures remains a tremendous challenge for the development of efficient electrocatalysts. Herein, a ligand-assisted synthetic strategy to fabricate perovskite oxides LaCo 1− x Fe x O 3 with yolk-shell nanostructures is developed. Benefiting from the unique structural and compositional merits, LaCo 0.75 Fe 0.25 O 3 exhibits an overpotential of 310 mV at a current density of 10 mA cm −2 and long-term stability of 100 h for the oxygen evolution reaction. In situ Raman spectroscopy demonstrates that Fe substitution facilitates the pre-oxidation of Co sites and induces the surface reconstruction into active Co oxyhydroxides at a relatively lower applied potential, guaranteeing excellent catalytic performances. Density functional theory calculations unravel that the appropriate introduction of Fe into perovskite LaCoO 3 leads to the improved electroactivity and durability of the catalyst for the oxygen evolution reaction (OER). Fe-3d orbitals show a pinning effect on Co-3d orbitals to maintain the stable valence state of Co sites at the low overpotential of the OER. Furthermore, Zn–air batteries (ZABs) assembled with LaCo 0.75 Fe 0.25 O 3 display a high open circuit potential of 1.47 V, superior energy density of 905 Wh kg −1 Zn , and excellent stability in a large temperature range. This work supplies novel insights into the future developments of perovskite-based electrocatalysts.
Bang Xiao,Anqi Jiao,Yiran Zhang,Lin Yang,Xuteng Zhao,Chunping Wu,Dongdong Guo,Reggie Zhan,He Lin
NH 3 detection is of great significance for precise control of the SCR system. In this paper, mixed potential type ammonia sensor using LaCo 1-x Fe x O 3 sensing electrode, YSZ electrolyte, and Pt reference electrode was developed. LaCo 1-x Fe x O 3 sensing materials were made by flame spray pyrolysis technique, and Fe B-site substitution was implemented to enhance the sensing performance. It was observed that in the concentration range of 20–70 ppm at 475 °C, the sensor using LaCo 0.9 Fe 0.1 O 3 as sensing electrode exhibited the highest sensing signal and sensitivity to ammonia among the LaCo 1-x Fe x O 3 -SE sensors (x = 0, 0.05, 0.1, 0.2, 0.3). A sectional linear relationship between the response value change( Δ V ) of that sensor and the logarithm of ammonia concentration within the range of 2–15 ppm and 15–70 ppm was noticed, and the sensitivities were 17.52 and 87.22 mV/decade, respectively. Its lower detection limit reached 2 ppm at 475 °C. Its excellent sensing properties are ascribed to enriched oxygen vacancies and high electrocatalytic performance of the perovskite electrode. Moreover, the sensor exhibited good selectivity against CH 4 , CO, NO, NO 2 , and good stability against oxygen and water vapor concentration fluctuation. Besides, the sensing response to 50 ppm ammonia has been tested for 22 days and only a slight fluctuation within 7 % was observed. Furthermore, the mixed potential sensing mechanism of the sensor was discussed.
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