Nitrogen-doped mesoporous carbon is used for sensing Cd(II) and Pb(II), with a detection limit 10 and 25 times lower than the maximum acceptable content for drinking water recommended by the WHO. The work is a collaboration with Prof. Hu and Prof. Yuan (China). The study was published in the journal of RSC Advances. Danfeng Qin, Ruiyu Xu, Hangjia Shena, Xamxikamar Mamat, Le Wanga, Shanshuang Gao, Ying Wanga, Nuerbiya Yalikuna, Thomas Wagberg, Shiguo Zhang, Qunhui yuan, Yongtao Li, Guangzhi Hu. RSC Advances, 7, 36929-36934 (2017) AbstractNitrogen-doped mesoporous carbon (NMC) derived from a single small-molecule protic salt (p-phenylenediamine bisulfate) is used for sensing toxic heavy metal ions. Using Nafion, bismuth and NMC to anchor the glassy carbon electrode surface, the fabricate electrode shows high sensitivity for detecting Cd(II) and Pb(II). The limits of detection (S/N = 3) are estimated to be 0.3 μg L−1 for Cd(II) and 0.4 μg L−1 for Pb(II), respectively, which are 10 and 25 times lower than the maximum acceptable content for drinking water recommended by the WHO. Furthermore, the sensor is successfully used to analyze Cd(II) and Pb(II) in tap-water with high anti-interference capability and good recovery.
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This work was performed in collaboration with Prof. Guangzhi Hu from the University of Chinese Academy of Sciences. Here we report the microwave-assisted synthesis of Mo-doped FeNi3 nanoparticles as excellent oxygen evolution electrocatalyst. Our results were published in the journal of Electrochemistry Communications. Hangjia Shen, Eduardo Gracia-Espino, Le Wang, Dan feng Qin, Sanshuang Gao, Xamxikamar Mamat, Wei Ren, Thomas Wågberg, Guangzhi Hu. Electrochem. Commun. 81, 116-119 (2017) Abstract Oxygen evolution reaction (OER) plays a pivotal role in water-splitting. Here, we report a facile method to synthesize multimetal supported on commercial carbon black via a time-saving microwave process. Crystalline FeNi3 nanoparticles homogeneously doped with Mo are formed via a microwave treatment and activated to metal oxyhydroxide in-situ during cyclic voltammetry test with overpotential of only 280 mV at 10 mA cm− 2 for OER in alkaline electrolyte, outperforming RuO2. Our synthesis methodology is a promising alternative for large-scale production, delivering a valuable contribution to catalyst preparation and electrocatalytic water oxidation research.
We now report a template casting strategy to easily introduce atomically dispersed FeN2 moieties onto the surface of N-doped ordered mesoporous carbon with extraordinary catalytic activity towards ORR. This work was carried out in collaboration with Prof. Guo (College of Engineering, Peking University) and Prof. Hu (Xinjiang Technical Institute of Physics and Chemistry). The results are published in the journal of Nano Energy. H. Shena, E. Gracia-Espino, J. Mac, H. Tang, X. Mamat, T. Wagberg, G. Hua, S. Guoe. Nano Energy, (2017) DOI: 10.1016/j.nanoen.2017.03.027 Abstract Earth-abundant materials with Fe-N-C centers have been identified as promising catalysts for oxygen reduction reaction (ORR), but these alternatives for Pt catalysts are usually the porphyrin-like FeN4 configuration. The density functional theory (DFT) calculations reveal that FeN2 outperforms FeN4 due to its lower interaction with ⁎O2 and ⁎OH intermediates and enhanced electron transport, however, achieving an optimum design of these earth-abundant materials with the enriched FeN2 catalytic centers is still a great challenge. Here, we report an intriguing template casting strategy to introduce a mass of atomically dispersed FeN2 moieties onto the surface of N-doped ordered mesoporous carbon for boosting ORR electrocatalysis. One of unique parts herein is to pre anchor Fe precursor on the surface of template (SBA-15) during catalyst synthesis, preventing Fe from penetrating into the carbon skeleton and facilitating the removal of excessive Fe-based particles during silica elimination by HF etching, resulting in a desirable model structure comprising only highly active atomically dispersed FeN2 sites, as confirmed by high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), extended X-ray absorption fine structure (EXAFS) and Mößbauer spectroscopy analysis. The well-defined structure prompts us to understand the nature of the catalytic active sites, and to demonstrate that the catalyst activity is linearly proportional to the concentration of FeN2 sites. The obtained atomic electrocatalyst exhibits superior electrocatalytic performance for ORR with a more positive half-wave potential than that of Pt/C catalyst. We further establish a kinetic model to predict the ORR activity of these single-atom dispersed catalysts. The present work elaborates on a profound understanding for designing low-cost, highly efficient FeN2-based electrocatalyst for boosting ORR.
Here we study the collapsing and spontaneous twisting of a carbon nanotube by in situ transmission electron microscopy (TEM). This work was developed in close collaboration with the research group of Prof. Zettl from the University of California, Berkeley. Hamid Reza Barzegar, Aiming Yan, Sinisa Coh, Eduardo Gracia-Espino, Claudia Ojeda-Aristizabal, Gabriel Dunn, Marvin L. Cohen, Steven G. Louie, Thomas Wågberg, and Alex Zettl. Nano Res. (2017). doi:10.1007/s12274-016-1380-7 Abstract We study the collapsing and subsequent spontaneous twisting of a carbon nanotube by in situ transmission electron microscopy (TEM). A custom-sized nanotube is first created in the microscope by selectively extracting shells from a parent multi-walled tube. The few-walled, large-diameter daughter nanotube is driven to collapse via mechanical stimulation, after which the ribbon-like collapsed tube spontaneously twists along its long axis. In situ diffraction experiments fully characterize the uncollapsed and collapsed tubes. The experimental observations and associated theoretical analysis indicate that the origin of the twisting is compressive strain.
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Featured publicationsComprehensive Study of an Earth-Abundant Bifunctional 3D Electrode for Efficient Water Electrolysis in Alkaline Medium.
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Catal. Sci. Technol., 2016, 6, 1393-1401 Photocatalytic reduction of CO2 with H2O over modified TiO2 nanofibers: Understanding the reduction pathway.
Nano Res. (2016) 9: 1956. |