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Steam activation of Fe-N-C catalyst for advanced power performance of alkaline hydrazine fuel cells

Journal of Energy Chemistry 2022年第1期31卷 276-285,I0008页

作者： Sooan Bae Jihyeon Park Yuna Hwang Jin-Soo Park Jaeyoung Lee Beomgyun Jeong Research Center for Materials Analysis Korea Basic Science Institute169-14&Gwahak-roDaejeon 34133Republic of Korea School of Earth Sciences and Environmental Engineering Gwangju Institute of Science and Technology123 Cheomdangwagi-ro.Buk-guGwangju 61005Republic of Korea Department of Green Chemical Engineering Sangmyung University31 Sangmyungdae-gilDongnam-gu.CheonanChungnam Province 31066Republic of Korea Ertl Center for Electrochemistry and Catalysis Gwangju Institute of Science and Technology123 Cheomdangwagi-roBuk-giiGwangju 61005Republic of Korea

Alkaline hydrazine liquid fuel cells(AHFC) have been highlighted in terms of high power performance with non-precious metal catalysts.Although Fe-N-C is a promising non-Pt electrocatalyst for oxygen reduction reaction(ORR),the surface density of the active site is very low and the catalyst layer should be thick to acquire the necessary number of catalytic active sites.With this thick catalyst layer,it is important to have an optimum pore structure for effective reactant conveyance to active sites and an interface structure for faster charge transfer.Herein,we prepare a Fe-N-C catalyst with magnetite particles and hierarchical pore structure by steam activation.The steam activation process significantly improves the power performance of the AHFC as indicated by the lower IR and activation voltage losses.Based on a systematic characterization,we found that hierarchical pore structures improve the catalyst utilization efficiency of the AHFCs,and magnetite nanoparticles act as surface modifiers to reduce the interracial resistance between the electrode and the ion-exchange membrane.

关键词： Alkaline hydrazine fuel cell Oxygen reduction reaction Electrocatalyst Steam activation ohmic loss Interfacial resistance Surface modifier

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Forward-wave enhanced radiation in the terahertz electron cyclotron maser

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Chinese Physics B 2022年第12期31卷 643-649页

作者：高子超杜朝海李繁弘张子文李思琦刘濮鲲 School of Electronics Peking UniversityBeijing 100871China

Based on the principle of electron cyclotron maser(ECM),gyrotrons are among the most promising devices to generate powerful coherent terahertz(THz)radiation and play a vital role in numerous advanced THz applications.Unfortunately,THz ECM systems using a conventional high-Q cavity were theoretically and experimentally demonstrated to suffer from strong ohmic losses,and,accordingly,the wave output efficiency was significantly reduced.A scheme to alleviate such a challenging problem is systematically investigated in this paper.The traveling-wave operation concept is employed in a 1-THz third harmonic gyrotron oscillator,which strengthens electron-wave interaction efficiency and reduces the ohmic dissipation,simultaneously.A lossy belt is added in the interaction circuit to stably constitute the traveling-wave interaction,and a down-tapered magnetic field is employed to further amplify the forward-wave(FW)component.The results demonstrate that the proportion of ohmic losses is nearly halved,and output efficiency is nearly doubled,which is promising for further advancement of high-power continuous-wave operation of the ECM-based devices.

关键词： electron cyclotron maser ohmic loss harmonic operation traveling wave interaction

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Studies on the Digital Simulation of Microwave Multichannel Power Synthesis

Studies on the Digital Simulation of Microwave Multichannel ...

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1998 International Conference on Microwave and Millimeter Wave Technology

作者： Hang Kao Wen Xi’ an Navigation Technique Research Insitute

ISBN: (纸本)0780343085

＜正＞In the actual mircowave mullichannel power synthesis system or circuit,especially when a wide frequency band is at work,the system efficiency（i.e the synthesized power efficiency） will be influenced by many factors,such as the amplitude and phase of the branch power source,the standing wave at the port of synthesizer,the branch spacing accurateness,the branch transmission power amplitude,the phase difference and ohmic loss.In the paper,strict computing formulas in relation to these factors are given out,and according to these formulas,the amplitude of the branch power source and the distribution of the value of phase difference in the computer are numerically adapted and the typical three-dimensional efficiency curve and the lowest efficiency curve are given out.

关键词： microwave circuits digital simulation power combiners circuit simulation digital simulation microwave multichannel power synthesis wide frequency band system efficiency branch power source amplitude branch power source phase standing wave synthesizer port branch spacing accurateness branch transmission power amplitude phase difference ohmic loss

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