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On the role of zn and Fe doping in nitrogen-carbon electrocatalysts for oxygen reduction

Nano Research 2024年第11期17卷 9564-9572页

作者： Yanan Zou Yuanyuan Su Yongchao Yu Jinliang Luo Xiaomin Kang Jun Zhang Linghan Lan Tianshi Wang Jun Li College of Mechanical Engineering University of South China Hengyang 421001 China Key Laboratory of Low-grade Energy Utilization Technologies and Systems Chongqing University Ministry of Education of China Chongqing 400044 China College of New Energy Zhengzhou University of Light Industry Zhengzhou 450002 China School of Mechanical and Electrical Engineering Guilin University of Electronic Technology Guilin 541004 China

zn is a frequently used and sometimes even an inevitably involved element (when zeolitic imidazolate framework-8 (ZIF-8) is adopted as the precursor) for preparing high-performance Fe-N-C oxygen reduction reaction (ORR) catalysts. However, how the zn element affects the physicochemical architecture of the catalysts, how it enhances the catalytic activity and whether zn atoms serve as the active centers remain unclear. Herein, we proposed a novel route that adopted pyrrole as the precursor and flexibly controlled the addition of exogenous zn and Fe dopants before pyrrole polymerization. In this way, a series of nitrogen-carbon catalysts with or without zn or Fe doping were synthesized. The detailed characterization revealed the role of zn and Fe doping in the catalyst morphology, pore structure, active site configurations, ORR catalytic activity and fuel cell performance. Importantly, the findings revealed that zn doping has little effect on the ORR mechanism and pathway. It enhances ORR activity primarily by increasing the number of active sites via introducing more micro- and meso-pores, rather than by creating new active sites. While Fe doping participated in forming both pores and active site centers. Moreover, the catalyst that co-doped with zn and Fe atoms (zn-FeNC), synthesized via this simple and template-free route we proposed, presented a unique hollow and hierarchical pore structure with highly boosted ORR activity. It exhibited a 40 mV higher E 1/2 value than Pt/C in alkaline media, along with a rapid current response in air-cathode of the direct formate fuel cell. These results are valuable in guiding the synthesis of high-performance Fe-N-C catalysts.

关键词： oxygen reduction reaction Fe-N-C catalysts hollow porous nanocarbon zn doping direct formate fuel cell

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Optimize the thermoelectric performance of CdO ceramics by doping zn

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Chinese Physics B 2017年第10期26卷 428-432页

作者：查欣雨高琳洁白洪昌王江龙王淑芳 Hebei Key Laboratory of Optic-electronic Information and Materials The College of Physics Science and TechnologyHebei University

The thermoelectric performance of CdO ceramics was enhanced by simultaneously optimizing the electrical and thermal transport properties via a small amount of zn doping （≤3%）. The introduction of zn can obviously increase the electrical conductivity of CdO due to the simultaneous increase of carrier concentration and mobility, and eventually results in an improvement in power factor. zn doping is also effective in suppressing the thermal conductivity of CdO because of stronger phonon scatterings from point defects, zn-riched second phase, and grain boundaries. A best ZT of about 0.45 has been achieved in the Cd1-xznxO systems at about 1000 K, which is comparable to the highest values reported for other n-type oxide TE materials.

关键词： thermoelectric properties CdO zn doping power factor thermal conductivity

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Bimetallic site substitution of NiCoP nanoneedles as bifunctional electrocatalyst for boosted water splitting

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Nano Research 2024年第11期17卷 9540-9549页

作者： Ya Gao Yuhui Qiao Xuanrong Li Chengyu Huang Jing Zhang Yirong Wang Xingli Zou Zhonghong Xia Xinxin Yang Xionggang Lu Yufeng Zhao College of Sciences and Institute for Sustainable Energy Shanghai University Shanghai 200444 China School of Materials Science and Engineering Shanghai University Shanghai 200444 China State Key Laboratory of Advanced Special Steel and Shanghai Key Laboratory of Advanced Ferrometallurgy Shanghai University Shanghai 200444 China

The bimetallic nickel-cobalt phosphide (NiCoP) has been confirmed as an efficient electrocatalyst in water splitting. But little attention is paid to the selectivity and affinity of metal sites on hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we report a trace-zn-doping (2.18 wt.%) NiCoP (zn-NiCoP) whereby the nanoparticles self-aggregated to form elongated nanoneedles. We discover that both Co and Ni sites can be replaced by zn. The Co substitution improves HER, while the Ni substitution dramatically reduces the energy barrier of the rate-determining step (*O → *OOH). The negative shift of d-band centers after zn doping ameliorates the intermediate desorption. Therefore, zn-NiCoP demonstrates superior electrocatalytic activity with overpotentials of 48 and 240 mV for HER and OER at 10 and 50 mA·cm^(−2), respectively. The cell voltage with zn-NiCoP as both anode and cathode in water splitting was as low as 1.35 V at 10 mA·cm^(−2).

关键词： zn doping bimetallic phosphides bifunctional electrocatalyst overall water splitting

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Synthesis characterization and improved electrochemical performance of Li2FeSiO4/C as cathode for lithium-ion battery by metal doping

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Progress in Natural Science:Materials International 2019年第2期29卷 111-118页

作者： Ling Li Enshan Han Shunpan Qiao Hui Liu Yake Shi Weiliang Yuan School of Chemical Engineering and Technology Hebei University of Technology

In this paper, Li2FeSi0.98M0.02O4/C（M = Mg, zn, Co, Mn, Ni） was synthesized as cathode material for lithium ion battery by solid-state method. The results show that the materials doped with Mg and zn at the Si-sites have good initial discharge capacity. Then Li2FeSi1-xMxO4/C（M = Mg, zn; x = 0.01, 0.02, 0.03, 0.05） were also synthesized via solid-state method. It is concluded that Li2FeSi0.99Mg0.01O4/C and Li2FeSi0.98zn0.02O4/C have better initial discharge capacity which is 125 mAh/g and 166.2 mAh/g, respectively. The capacity of Li2Fe0.98zn0.02SiO4/C is 157.3 m Ah/g after 10 cycles at 0.1 C, and the capacity retention rate is 94.6%. The Li+diffusion coefficient of Li2FeSi0.98zn0.02O4/C is higher than that of pure phase materials by one order of magnitude. The Li2FeSi0.99Mg0.01O4/C and Li2FeSi0.98zn0.02O4/C were tested by XRD and SEM. XRD patterns indicate that the crystal structure of Li2FeSiO4is not changed after being doped with metal ion at the Si-site. The SEM image indicates that no obvious agglomeration is detected in these materials. Li2FeSi0.98zn0.02O4/C processes better electrochemical performance analyzed by EDS、XPS and FT-IR spectra. The data prove that Si4+is successfully replaced by zn2+in the crystal structure of Li2FeSiO4.

关键词： Li2FeSiO4 Mg zn doping Solid-state method Li-ion battery Electrochemical performance

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Preparation and electrochemical performance of nano-scale Ni(OH)_2 doped with zinc

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Transactions of Nonferrous Metals Society of China 2013年第4期23卷 1033-1038页

作者：赵力刘志豪金雷哈尔滨工业大学化工学院哈尔滨150001

Nano-scale Ni（OH）2 doped with zn was prepared by precipitation transformation method and characterized by XRD and TEM. The electrochemical performance was investigated by cyclic voltammetry （CV） and constant current technology. The measurement results indicate that the lattice parameters of nano-scale Ni（OH）2 are changed and the agglomeration of particles becomes obvious with the increased zn-doped content. Compared with un-doped one, the discharge specific capacities ofnano-scale Ni（OH）2 doped with 10% zn are enhanced by 8% and 6%, respectively, at the discharge rate of 0.2C and 3C. After 110 cycles, the discharge specific capacity of the sample doped with 10% zinc is still above 85% of its initial capacity discharged at 0.2C. Therefore, a suitable zn-doped content is beneficial to improving the discharge performance of nano-scale Ni（OH）2.

关键词： nano-materials nickel hydroxide zn doping electrochemical performance

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