Small beginnings: Metal nanoparticle/CNT nanohybrids are synthesized from carbon nanotubes (CNTs) functionalized with an ionic-liquid polymer. The Pt and PtRu nanoparticles with narrow size distribution (average diameter: (1.3+/-0.4) nm for PtRu, (1.9+/-0.5) nm for Pt) are dispersed uniformly on the CNTs (see images) and show good performance in methanol electrooxidation.
Single atomic dispersed M-N-C (M = Fe, Co, Ni, Cu, etc.) composites display excellent performance for catalytic reactions. However, the analysis and understanding of neighboring M-N-C centers at the atomic level are still insufficient. Here, FeCo-N-doped hollow carbon nanocages (FeCo-N-HCN) with neighboring Fe-N 4 -C and Co-N 4 -C dual active centers as efficient catalysts are reported. Spherical aberration-corrected high angle annular darkfield scanning transmission electron microscopy, small area (1 nm 2 ) electron energy loss spectroscopy, and X-ray absorption spectroscopy data analysis and fitting prove the neighboring Fe-N 4 -C and Co-N 4 -C dual active structure in FeCo-N-HCN. Experimental tests and density functional theory calculation results reveal that the FeCo-N-HCN catalyst displays better catalytic activity than Fe single-metal catalyst for oxygen reduction reaction (ORR), which is attributed to the synergistic effect of Fe-N 4 -C and Co-N 4 -C dual active centers reducing the reaction energy barriers for ORR. Although the catalytic performance of the FeCo-N-HCN catalyst is not comparable to the-state-of-art catalysts reported due to the low metal contents (Fe: 1.96 wt% and Co: 1.31 wt%), these results can refresh the understanding of neighboring M-N-C centers at the atomic level and provide guidance for the design of catalysts in the future.
Herein, we reported a special Fe-N-doped double-shelled hollow carbon microsphere (Fe-N-DSC) which was prepared by a facile, in situ polymerization followed by pyrolysis. With porous ferroferric oxide (FeO) hollow microspheres as the templates, where pyrrole monomers were dispersed around the outer surface and prefilled the interior space. By adding hydrochloric acid, Fe ions were released to initiate polymerization of pyrrole on both the outer and inner surfaces of FeO microspheres until they were completely dissolved, resulting in the Fe-containing polypyrrole double-shelled hollow carbon microspheres (Fe-PPY-DSC). The Fe-PPY-DSC was then pyrolyzed to generate the Fe-N-DSC. The FeO hollow microspheres played trifunctional roles, i.e., the template to prepare a double-shelled hollow spherical structure, the initiator (i.e., Fe ions) for the polymerization of pyrrole, and the Fe source for doping. The Fe-N-DSC exhibited a superior catalytic activity for oxygen reduction as comparable to commercial Pt/C catalysts in both alkaline and acidic media. The high catalytic performance was ascribed to the special porous double-shelled hollow spherical structure, which provided more active sites and was beneficial to a high-flux mass transportation.
Due to lots of carboxyl groups introduced uniformly on the carbon nanotube (CNT) surface, platinum-ruthenium nanoparticles were highly dispersed on the 3,4,9,10-perylene tetracarboxylic acid-functionalized CNT surface and showed improved electrochemical properties for methanol electrooxidation.
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