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632 results on '"Liu, Jingjun"'

41. Guinier–Preston Zones Featuring PtCu Nanocrystals: Coherency Strain Fields Reshaping the Band Structure for Oxygen Reduction Electrocatalysis

Author

Chen, Zhiguo, Chen, Jingkun, Fu, Jingbo, Wang, Qiheng, Chen, Yonghong, and Liu, Jingjun

Abstract

Microstructurally distorted Pt-based nanoalloys with unusual structural defects like Guinier–Preston (GP) zones with in situ coherency strain fields may be suitable for substantially improving their electrocatalytic performance for the oxygen reduction reaction (ORR) in acidic conditions. Herein, GP zones contributing PtCu nanoalloys were first fabricated by additive manufacturing, starting with the formation of metallic Cu clusters as orderly crystal nuclei on ZIF-8-derived carbon, followed by the additive manufacturing of chemically reduced Pt and Cu on the formed clusters in ethylene glycol at 190 °C. The atomic-scale GP zones give rise to high-level coherent strain fields across the nanocrystals, boosting the ORR kinetics. This catalyst exhibits an ultrahigh oxygen reduction half-wave potential of 0.934 V (vs RHE) and a mass activity (MA) of 0.68 A mgPt–1. After the accelerated degradation test of 50,000 cycles, the achieved MA improved instead of decreasing, rising from 0.68 to 0.89 A mgPt–1, surpassing that of commercial Pt/C significantly. The significantly improved activity is attributed to the coherency strain fields reshaping the band structure and reconstructing a favorable charge density for active Pt sites. Importantly, the interface-anchored GP zones, maintaining a completely coherent relationship with the matrix, can effectively impede metal atom migration, segregation, or leaching, thus enhancing long-term stability. Therefore, the novel GP-type alloys may pave another way for designing advanced catalysts in the realm of current energy storage and conversion fields like fuel cells.

Published
2024
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44. Applied Voltage‐Activated Fe─N─C Catalysts for Pem Fuel Cells.

Author

Wang, Qiheng, Zhang, Jin, Wang, Xingdong, Liu, Qingtao, Liu, Jingjun, Zhuang, Zhongbin, and Shui, Jianglan

Subjects
PROTON exchange membrane fuel cells, CATALYSTS
Abstract

The practical application of non‐precious Fe─N─C catalysts in proton exchange membrane fuel cells (PEMFCs) continues to remain one of the major challenges due to their relatively poor oxygen reduction reaction (ORR) performance in acid. In this work, a fast and facilely performance enhancement strategy is first proposed for various Fe─N─C catalysts by supplying different direct‐current voltages to achieve a rapid solid‐state activation at room temperature. The voltage‐activated state‐of‐the‐art Fe─N─C catalyst has demonstrated a peak power density of 1.1 W cm−2 for PEMFC and remarkably increased long‐term durability for ORR. The substantially improved performance can be attributed to the formation of highly active ketone‐decorated (edge‐hosted) FeN4 sites and substantially boosts coupled proton−electron transfer (CPET) by improving the conductivity of the as‐synthesized Fe─N─C with an interpenetrating network structure. The interconnected micro‐nodes within the interpenetrating network are the main active regions for the ORR, evidenced by an optimized structural model based on the above typical morphology. Therefore, this finding provides an innovative and facile idea for solving the activity and stability deficiency for promising Fe─N─C for commercial PEMFC. [ABSTRACT FROM AUTHOR]

Published
2024
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47. Protective effect of citrus flavone against acute hypoxia in cultured human intestinal smooth muscle cells and the mechanism

Author

LIU Jingjun, WANG Xiaoming, SHEN Chengfeng, DENG Bingnan, and CHEN Demei

Subjects
citrus flavonoids, hypoxia, intestinal smooth muscle cells, mitochondria, apoptosis, Medicine (General), R5-920
Abstract

Objective To investigate the protective effect of citrus flavone on cultured human intestinal smooth muscle cells (HISMCs) against acute hypoxia and explore the mitochondrial mechanism. Methods Cultured HISMCs were exposed to acute hypoxia with 1%, 3%, or 5% O2 (5% CO2, 94% N2) for 6 h or with 1% O2 for 3, 6, and 9 h. The cells cultured in 1% O2 (5% CO2, 94% N2) were treated with citrus flavonoids (300 or 600 μg/mL) for 6 h. Mitochondrial membrane potential and the cell apoptotic rate were determined with flow cytometry, and the activities of caspase-3 and caspase-8 were detected using Ac-DEVD-pNA and AC-IETD-pNA colorimetry, respectively. The total content of TR3 nuclear orphan receptor (TR3) in the hypoxic cells and its content in the mitochondria were determined with Western blotting. We also tested the effect of TR3 overexpression on the protective effect of 600 μg/mL citrus flavonoids in the HISMCs exposed to 1% O2. Results Acute hypoxia resulted in significantly decreased mitochondrial membrane potential, enhanced caspase-3 and caspase-8 activities, and increased apoptosis in cultured HISMCs (P < 0.05). Citrus flavonoids effectively enhanced mitochondrial membrane potential level, suppressed the mitochondrial apoptotic pathway (P < 0.05), and inhibited the translocation of TR3 to the mitochondria in the hypoxic cells. Overexpression of TR3 significantly attenuated the protective effect of citrus flavonoids on the hypoxic cells (P < 0.05). Conclusion Citrus flavonoids protect intestinal smooth muscle cells against hypoxic injury by regulating mitochondrial translocation of TR3.

Published
2020
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