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102. SF₆ degradation in γ-Al₂O₃ packed DBD system : effects of hydration, reactive gases and plasma-induced surface charges

Author

Cui, Zhaolun, Zhou, Chang, Jafarzadeh, Amin, Zhang, Xiaoxing, Hao, Yanpeng, Li, Licheng, and Bogaerts, Annemie

Subjects
Chemistry, Physics
Abstract

Packed-bed DBD (PB-DBD) plasmas hold promise for effective degradation of greenhouse gases like SF6. In this work, we conducted a combined experimental and theoretical study to investigate the effect of the packing surface structure and the plasma surface discharge on the SF6 degradation in a gamma-Al2O3 packing DBD system. Experimental results show that both the hydration effect of the surface (upon moisture) and the presence of excessive reactive gases in the plasma can significantly reduce the SF6 degradation, but they hardly change the discharge behavior. DFT results show that the pre-adsorption of species such as H, OH, H2O and O-2 can occupy the active sites (Al-III site) which negatively impacts the SF6 adsorption. H2O molecules pre-adsorbed at neighboring sites can promote the activation of SF6 molecules and lower the reaction barrier for the S-F bond-breaking process. Surface-induced charges and local external electric fields caused by the plasma can both improve the SF6 adsorption and enhance the elongation of the S-F bonds. Our results indicate that both the surface structure of the packing material and the plasma surface discharge are crucial for SF6 degradation performance, and the packing beads should be kept dry during the degradation. This work helps to understand the underlying mechanisms of SF6 degradation in a PB-DBD system.

Published
2023

118. Study of Electrostatic Motion Behavior and Inhibition of Metallic Particles in GIS/GIL

Author

Lu, Xinsheng, Tian, Yi, Niu, Haotian, Shi, Haonan, Chen, Menghan, Li, Ying, Bai, Fan, Ma, Feiyue, Huang, Xinbo, Li, Shengtao, Li, Licheng, and Li, Husheng

Abstract

The most frequent insulation defect appears to be the presence of small amounts of spherical, linear, and other shapes of micro metallic particles in Gas Insulated Switchgear (GIS) and Gas Insulated Transmission Line (GIL). It poses a major risk for partial discharge if the metallic particles travel to the location with a high field strength. The study to inhibit the movement of metal particles and thus solve the issue of metallic particle contamination is the key technical challenge to effectively improve the insulation strength. In this article, we present a mathematical-physical model applicable to the real structure with complex electric field and various types of particles using the finite element method (FEM) and the differential element method (DEM). This study shows that the asymmetry of the electrostatic force caused by the asymmetry of the particle shape is the main cause of the complex motion behavior. The model can predict several unique occurrences, including the one-sided lifting of longer linear particles, and our experiments have confirmed these predictions. The method of dielectric coating for particle motion inhibition is investigated, and a significant inhibition effect is observed as the lift-off voltage of the particles is dramatically increased.

Published
2024
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119. Progress of photocatalytic CO2reduction toward multi-carbon products

Author

Fang, Jiaojiao, Zhu, Chengyang, Hu, Huiling, Li, Jiaqi, Li, Licheng, Zhu, Haiyan, and Mao, Junjie

Abstract

The photocatalytic CO2reduction reaction (CO2RR) represents a promising solution to alleviate environmental and energy issues stemming from CO2emissions while simultaneously enabling the production of high-value multi-carbon fuels. However, the efficient generation of multi-carbon products remains challenging due to high kinetic barriers, sluggish C–C coupling processes, and intricate reaction pathways. This review provides a comprehensive overview of the latest advancements in synthesizing C2+products through CO2photoreduction, highlighting the crucial role of active site design and the C–C coupling mechanism. Specifically, we emphasize the correlation between the structure of active sites and the key intermediates of C–C coupling, which is fundamental for achieving deep photoconversion of CO2. Finally, we offer a glimpse into future challenges and prospects, outlining potential directions for the development of CO2-to-multicarbon photoconversion, aiming to contribute novel insights to this exciting field.

Published
2024
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120. Breakpoint and Moisture Detection Method Based on Distributed Brillouin Optical Fiber Built in Buffer Layer of High-Voltage XLPE Cable

Author

Cheng, Yanting, Hao, Yanpeng, Li, Qishun, Hui, Baojun, Tian, Wanxing, Tan, Haotian, Chen, Linhao, and Li, Licheng

Abstract

In recent years, the water-blocking tape in high-voltage (HV) crosslinked polyethylene (XLPE) cable has suffered from penetrating moisture frequently, which affects its safe and stable operation, while there are no effective detection methods yet. In this article, a 110 kV cable sample was prepared, with a single-mode fiber of 30 m built in it. Meanwhile, a distributed detection system for built-in optical fiber of 110 kV cable was established and the criterion for Brillouin optical time domain reflectometry (BOTDR) breakpoint detection method was proposed. The comparison test of breakpoint detection methods for built-in optical fiber was carried out using BOTDR and optical time domain reflectometry (OTDR). Besides, detection tests of moisture water blocking tape including its drying process were launched using BOTDR. The relationship of Brillouin frequency shift (BFS) with moisture length, position, and drying process of the tape was studied. The results have demonstrated that BOTDR plays a better role in detecting breakpoint with poor-quality end face than OTDR. By using BOTDR to detect moisture tape in cable, the BFS decreases sharply when moisture length over some thresholds and linearly falls with increasing moisture length. As time passes, the BFS gradually increases, which can characterize drying process.

Published
2024
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135. Discharge Randomness and Attraction Process of Epoxy Surface on Discharge Channel in SF6 Gas Under Uniform Electric Field

Author

Liu, Lin, Hao, Yanpeng, Zhang, Qiaogen, Liang, Chengjun, and Li, Licheng

Abstract

It is generally believed that due to the electric field distortion effect and the photoemission process of the solid surface, the discharge channel near the solid surface tends to develop along the surface than that in bulk gas. One way to improve insulation performance is to avoid the solid surface from participating in the gas discharge process. However, the mechanism of the solid surface’s effect on the gas discharge process is still unclear. In this article, we recorded high-speed framing pictures of the discharge process in SF6 gas near the epoxy surface under lightning impulse voltage in the uniform electric field. The arc pictures show that the attraction effect of the solid surface to the discharge channel is related to the surface shape, gas gap height, and distance from the discharge channel to the solid surface. Besides, discharge randomness also plays a role, which is more obvious in the cylinder insulator than in the conical insulator, for the surface with conical shape could easily attract and arrest the discharge channel to its surface. According to the pictures of discharge process near the cylinder surface, we found that the photoemission process occurs in the streamer stage but has little effect on the attraction effect. The leader initiates after the streamer bridges the gas gap, and its random stepped walk could induce the attraction effect from the solid surface: only when the random stepped leader deflects close to the solid surface, the discharge channel could be further attracted to the solid surface by the electrostatic force, especially its normal component. The result indicates that there are three points to prevent the solid surface from participating in the gas discharge process and further improve insulation performance: choose a cylinder shape (avoid a conical shape), keep the surface away from the high electric field area where discharge may start, and reduce the normal component of the surface electric field.

Published
2023
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139. SF₆ catalytic degradation in a γ-Al₂O₃ packed bed plasma system : a combined experimental and theoretical study

Author

Cui, Zhaolun, Zhou, Chang, Jafarzadeh, Amin, Meng, Shengyan, Yi, Yanhui, Wang, Yufei, Zhang, Xiaoxing, Hao, Yanpeng, Li, Licheng, and Bogaerts, Annemie

Subjects
Chemistry
Abstract

Effective abatement of the greenhouse gas sulphur hexafluoride (SF6) waste is of great importance for the environment protection. This work investigates the size effect and the surface properties of gamma-Al2O3 pellets on SF6 degradation in a packed bed dielectric barrier discharge (PB-DBD) system. Experimental results show that decreasing the packing size improves the filamentary discharges and promotes the ignition and the maintenance of plasma, enhancing the degradation performance at low input powers. However, too small packing pellets decrease the gas residence time and reduce the degradation efficiency, especially for the input power beyond 80 W. Besides, lowering the packing size promotes the generation of SO2, while reduces the yields of S-O-F products, corresponding to a better degradation. After the discharge, the pellet surface becomes smoother with the appearance of S and F elements. Density functional theory calculations show that SF6 is likely to be adsorbed at the Al-III site over the gamma-Al2O3(110) surface, and it is much more easily to decompose than in the gas phase. The fluorine gaseous products can decompose and stably adsorb on the pellet surface to change the surface element composition. This work provides a better understanding of SF6 degradation in a PB-DBD system.

Published
2022

140. Plasma-catalytic methanol synthesis from CO₂ hydrogenation over a supported Cu cluster catalyst : insights into the reaction mechanism

Author

Cui, Zhaolun, Meng, Shengyan, Yi, Yanhui, Jafarzadeh, Amin, Li, Shangkun, Neyts, Erik, Hao, Yanpeng, Li, Licheng, Zhang, Xiaoxing, Wang, Xinkui, and Bogaerts, Annemie

Subjects
Chemistry
Abstract

Plasma-catalytic CO, hydrogenation for methanol production is gaining increasing interest, but our understanding of its reaction mechanism remains primitive. We present a combined experimental/computational study on plasma-catalytic CO, hydrogenation to CH3OH over a size-selected Cu/gamma-Al2O3 catalyst. Our experiments demonstrate a synergistic effect between the Cu/gamma-Al2O3 catalyst and the CO2/H-2 plasma, achieving a CO2 conversion of 10% at 4 wt % Cu loading and a CH3OH selectivity near 50% further rising to 65% with H2O addition (for a H2O/CO2 ratio of 1). Furthermore, the energy consumption for CH3OH production was more than 20 times lower than with plasma only. We carried out density functional theory calculations over a Cu-13/gamma-Al2O3 model, which reveal that the interfacial sites of the Cu-13 cluster and gamma-Al2O3 support show a bifunctional effect: they not only activate the CO2 molecules but also strongly adsorb key intermediates to promote their hydrogenation further. Reactive plasma species can regulate the catalyst surface reactions via the Eley-Rideal (E-R) mechanism, which accelerates the hydrogenation process and promotes the generation of the key intermediates. H2O can promote the CH3OH desorption by competitive adsorption over the Cu-13/gamma-Al2O3 surface. This study provides new insights into CO2 hydrogenation through plasma catalysis, and it provides inspiration for the conversion of some other small molecules (CH4, N-2, CO, etc.) by plasma catalysis using supported-metal clusters.

Published
2022

142. SF6 Degradation in a γ-Al2O3 Packed DBD System: Effects of Hydration, Reactive Gases and Plasma-Induced Surface Charges.

Author

Cui, Zhaolun, Zhou, Chang, Jafarzadeh, Amin, Zhang, Xiaoxing, Hao, Yanpeng, Li, Licheng, and Bogaerts, Annemie

Subjects
SURFACE charges, PLASMA flow, PLASMA gases, HYDRATION, SURFACE structure, SURFACES (Technology)
Abstract

Packed-bed DBD (PB-DBD) plasmas hold promise for effective degradation of greenhouse gases like SF6. In this work, we conducted a combined experimental and theoretical study to investigate the effect of the packing surface structure and the plasma surface discharge on the SF6 degradation in a γ-Al2O3 packing DBD system. Experimental results show that both the hydration effect of the surface (upon moisture) and the presence of excessive reactive gases in the plasma can significantly reduce the SF6 degradation, but they hardly change the discharge behavior. DFT results show that the pre-adsorption of species such as H, OH, H2O and O2 can occupy the active sites (AlIII site) which negatively impacts the SF6 adsorption. H2O molecules pre-adsorbed at neighboring sites can promote the activation of SF6 molecules and lower the reaction barrier for the S-F bond-breaking process. Surface-induced charges and local external electric fields caused by the plasma can both improve the SF6 adsorption and enhance the elongation of the S-F bonds. Our results indicate that both the surface structure of the packing material and the plasma surface discharge are crucial for SF6 degradation performance, and the packing beads should be kept dry during the degradation. This work helps to understand the underlying mechanisms of SF6 degradation in a PB-DBD system. [ABSTRACT FROM AUTHOR]

Published
2023
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143. Surface-Modified CeO2‑Octahedron-Supported Pt Nanoparticles as Ethylene Scavengers for Fruit Preservation.

Author

Wei, Haiying, Li, Licheng, Zhang, Tingwei, Seidi, Farzad, Chen, Qiang, and Xiao, Huining

Abstract

Catalytic oxidation of ethylene associated with the preservation of fruits and vegetables (F&V) at low temperatures remains challenging. To address this issue, CeO2-octahedron-supported Pt catalysts were synthesized and modified by capacitively coupled plasma for efficient catalytic oxidation of C2H4. After the plasma treatment, CeO2 with rich oxygen vacancies was created, which acted as a support to facilitate the regulation of the size and dispersion of Pt nanoparticles. Compared with Pt/pristine CeO2, the Pt/plasma-modified CeO2 catalyst (Pt/CeO2-P) showed significantly higher reactivity. More than 99.9% of ethylene conversion induced by Pt/CeO2-P could be sustained longer than 50 h at 25 °C, and 30 min even at 0 °C. Thus, Pt/CeO2 interface engineering by plasma modification technology is particularly promising for low-temperature catalytic oxidation of ethylene. Moreover, a comprehensive characterization was conducted to elucidate the reaction pathway and oxidation mechanism. From the preservation test using bananas as fruit samples, it was found that Pt/CeO2-P delayed postharvest deterioration and ripening of bananas due to the excellent ethylene scavenging effect created by the catalyst, thus demonstrating the great potential applications in F&V preservation. [ABSTRACT FROM AUTHOR]

Published
2023
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148. A Contactless Current Sensor Based on TMR Chips

Author

Li, Peng, primary, Tian, Bing, additional, Li, Licheng, additional, Wang, Zhiming, additional, Lv, Qiancheng, additional, Zhou, Ke, additional, Xu, Changbao, additional, Liu, Zhong, additional, Yin, Xu, additional, and Zhang, Jiaming, additional

Published
2022
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