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42 results on '"Ma, Pengjun"'

15. Trace‑H2O2 Boosting the Reaction Kinetics of H2SO4 Intercalation into Graphite for the High-Oxidation Efficiency Preparation of Graphene Oxide for Na Ion Storage.

Author

Yang, Juan, Chen, Lu, Liu, Bao, Yang, Bingjun, Xie, Hai, Hu, Yue, Ma, Pengjun, and Tai, Zhixin

Abstract

Graphite sulfate (H2SO4-GICs), as a key precursor for graphene oxide (GO) synthesis, is difficult to synthesize by spontaneously forming H2SO4-GICs due to its huge diffusion resistance. Therefore, it is still a crucial challenge for improving the reaction kinetics of graphite flakes to form H2SO4-GICs. In this work, we discover that the amount of H2O2 plays an important role in determining the formation of H2SO4-GICs in the intercalation process. The trace H2O2 can trigger more O* during the reaction process, leading to the lattice distortion and reducing the interlayer diffusion resistance of graphite, and it was found that reducing the volume ratio of H2O2 would promote the intercalation of H2SO4 into graphite and form the stage-I H2SO4-GICs. Exfoliation efficiency and oxidation degree were improved after oxidation reaction. We also confirm that this method works for the exfoliation of large graphite, demonstrating the high-efficiency energy supply by adding minimal stoichiometric H2O2. The pretreated GO by trace-H2O2 (PGO-100:1) exhibits a large interlayer spacing due to the complete exfoliation; after reduction as Na+ ion storage anode material, RPGO-100:1 displays a high rate performance as well as outstanding kinetic behavior, indicating that the increased interlayer space of graphite resulting from the deep oxidation benefits fast migration of Na+ ions toward a high capacity contribution and improved rate capability. [ABSTRACT FROM AUTHOR]

Published
2023
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28. Photothermal Conversion Applications of the Transition Metal (Cu, Mn, Co, Cr, and Fe) Oxides with Spinel Structure

Author

Ma, Pengjun

Subjects
Science / Physics / Electromagnetism
Abstract

The transition metal (Cu, Mn, Co, Cr, and Fe) oxides with spinel structure can be used as solar absorber materials due to their unique properties. Copper-based spinel ceramic pigments have been successfully prepared by sol-gel combustion method at low temperatures. Subsequently, spinel ceramic pigments have been employed to fabricate selective absorber paint coating by spraying-coating. The paint coating showed good spectral selectivity and thermal stability at low-to-mid temperature region. Spinel ceramic films have also been deposited on metal substrates by one dipping/annealing cycle. Spinel phase for single-layer ceramic film could be achieved at low annealing temperatures, and the single-layer ceramic film showed good spectral selectivity and benign thermal stability. Results presented here show that spinel compounds based on transition metal (Cu, Mn, Co, Cr, and Fe) oxides are promising materials for photothermal conversion applications.

Published
2017

29. A surface engineering strategy for the stabilization of zinc metal anodes with montmorillonite layers toward long-life rechargeable aqueous zinc ion batteries

Author

Wang, Wenbo, Xu, Ruifeng, Zhang, Xu, Wang, Peiyu, Yang, Bao, Yang, Bingjun, Yang, Juan, Su, Kailimai, Ma, Pengjun, Deng, Yanan, Fan, Xianfeng, and Chen, Wanjun

Abstract

Surface engineering strategy for constructing the MMT protection layer on the surface of Zn anode suppresses dendrite formation and harmful parasitic reactions for long-living rechargeable aqueous zinc-ion batteries (AZIBs).

Published
2024
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38. Highly efficient visible-light-driven photocatalytic degradation of rhodamine B by a novel Z-scheme Ag3PO4/MIL-101/NiFe2O4compositeElectronic supplementary information (ESI) available. See DOI: 10.1039/c8cy00182k

Author

Zhou, Tianhong, Zhang, Guozhen, Zhang, Hongwei, Yang, Hao, Ma, Pengjun, Li, Xiaoting, Qiu, Xiaoli, and Liu, Gang

Abstract

The effectiveness of metal–organic frameworks (MOFs) as solid-state electron mediators for rhodamine B (RhB) degradation in a Z-scheme photocatalysis system is demonstrated. Novel Z-scheme Ag3PO4/MIL-101/NiFe2O4(APO/MOF/NFO) composites were synthesized by an in situprecipitation method and employed to degrade RhB dye under visible-light irradiation. The photocatalytic activity results demonstrated that the Z-scheme APO/MOF/NFO(20%) photocatalyst showed relatively improved photocatalytic activity and stability in the degradation of RhB over the individual APO, NFO and APO/NFO materials. By the electrochemical and fluorescence measurements, the APO/MOF/NFO(20%) material also showed a larger transient photocurrent, lower impedance, and longer fluorescence lifetime (7.68 ns). Comparing the activity results with the characterization results, it was indicated that the photocatalytic activity depends on the rapid transfer of electrons from APO to NFO through the three-dimensional structure of the MOF. Furthermore, the possible mechanism for the photodegradation process of APO/MOF/NFO(20%) was proposed to illustrate excellent photocatalytic activity. The present study has paved a new way for using the attractive MOF in the design of a new and efficient system for organic dye degradation in wastewater.

Published
2018
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42. The Charge Storage Mechanisms of 2D Cation‐Intercalated Manganese Oxide in Different Electrolytes.

Author

Zhang, Qingnuan, Levi, Mikhael D., Dou, Qingyun, Lu, Yulan, Chai, Yinguang, Lei, Shulai, Ji, Hengxing, Liu, Bao, Bu, Xudong, Ma, Pengjun, and Yan, Xingbin

Subjects
CHARGE storage diodes, CLATHRATE compounds, MANGANESE oxides, RAMAN spectroscopy, ENERGY dissipation
Abstract

2D ion‐intercalated metal oxides are emerging promising new electrodes for supercapacitors because of their unique layered structure as well as distinctive electronic properties. To facilitate their application, fundamental study of the charge storage mechanism is required. Herein, it is demonstrated that the application of in situ Raman spectroscopy and electrochemical quartz crystal microbalance with dissipation monitoring (EQCM‐D), provides a sufficient basis to elucidate the charge storage mechanism in a typical 2D cation‐intercalated manganese oxide (Na0.55Mn2O4·1.5H2O, abbreviated as NMO) in neutral and alkaline aqueous electrolytes. The results reveal that in neutral Na2SO4 electrolytes, NMO mainly displays a surface‐controlled pseudocapacitive behavior in the low potential region (0–0.8 V), but when the potential is higher than 0.8 V, an intercalation pseudocapacitive behavior becomes dominant. By contrast, NMO shows a battery‐like behavior associated with OH− ions in alkaline NaOH electrolyte. This study verifies that the charge storage mechanism of NMO strongly depends on the type of electrolyte, and even in the same electrolyte, different charging behaviors are revealed in different potential ranges which should be carefully taken into account when optimizing the use of the electrode materials in practical energy‐storage devices. A molecular‐level understanding of the charging mechanisms for 2D cation‐intercalated manganese oxide, by using operando Raman spectroscopy and an electrochemical quartz crystal microbalance with dissipation monitoring. The results show the charge storage mechanism of Na0.55Mn2O4·1.5H2O strongly depends on the type of electrolyte, and even in the same electrolyte, different charging behaviors are revealed in different potential ranges. [ABSTRACT FROM AUTHOR]

Published
2019
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